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 8996 
 
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 Bureau of Mines Information Circular/1985 
 
 Cabs and Canopies for Underground 
 Coal Mining Equipment 
 
 Proceedings: Bureau of Mines Technology Transfer 
 Symposium, Charleston, WV, June 22, 1983 
 
 Compiled by William W. Aljoe 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 
 DD 
 
 C 
 
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 75 
 
 'l^/NES 75TH AV!k^ 
 
Information Circular 8996 , , \ ^ r A a cT^ 
 
 Cabs and Canopies for Underground 
 Coal Mining Equipment 
 
 Proceedings: Bureau of Mines Technology Transfer 
 Symposium, Charleston, WV, June 22, 1983 
 
 Compiled by William W. Aljoe 
 
 UNITED STATES DEPARTMENT OF THE INTERIOR 
 William P. Clark, Secretary 
 
 ^ BUREAU OF MINES 
 
 Robert C. Horton, Director 
 
Library of Congress Cataloging in Publication Data; 
 
 0^ 
 
 ^\4 
 
 ^ 
 
 tl 
 
 Bureau of Mines Technology Transfer Symposium (1983 : 
 Charleston, WV) 
 
 Cabs and canopies for underground coal mining equipment. 
 
 (Information circular ; 8996) 
 
 Includes bibliographical references. 
 
 Supt. of Docs, no.: I 28.27:8996. 
 
 1. Mining machinery— Safety measures— Congresses. 2. Mine 
 railroads- Cars— Safety measures— Congresses. 1. Aljoe, William W. 
 II. Title. III. Series: Information circular (United States. Bureau of 
 Mines) ; 8996. 
 
 TN2&57tJ4~- [TN3451 622s [622'. 2] 84-600210 
 
CONTENTS 
 
 Page 
 
 Abstract 1 
 
 Cabs and canopies for low-coal underground mining equipment , by William W, 
 
 Aljoe 2 
 
 Cost benefit analysis for low-coal cabs and canopies, by K. L. Whitehead 20 
 
 Canopy protection for operators of continuous haulage systems in low-seam- 
 
 helght coal, by R. J. Gunderman and A, J. Kwitowski , 31 
 
 ESD low-coal canopy technology, by Jack Mantel 48 
 
 Cabs and canopies for FMC underground coal mining equipment , by Martin D, 
 
 Wot ring 55 
 
 Cabs and canopies for Joy underground mining equipment, by Gary C. Marshall.,.. 61 
 
 Cabs and canopies for Lee-Norse continuous miners, by E. W. Hiltebeitel 68 
 
 Evaluation of "minimum" and "lowest practical" working heights for safe use of 
 
 canopies , by William W. Aljoe 75 
 
 -^ 
 
 <u 
 
 a. 
 
 
UNIT 
 
 OF MEASURE ABBREVIATIONS USED IN THIS 
 
 REPORT 
 
 deg 
 
 degree in 
 
 inch 
 
 ft 
 
 foot min 
 
 minute 
 
 f t/min 
 
 foot per minute pet 
 
 percent 
 
 h 
 
 hour s 
 
 second 
 
CABS AND CANOPIES FOR UNDERGROUND COAL MINING EQUIPMENT 
 
 Proceedings: Bureau of Mines Technology Transfer Symposium, 
 Charleston, WV, June 11, 1983 
 
 Compiled by William W. Aljoe ^ 
 
 ABSTRACT 
 
 This publication contains eight papers presented at a Bureau of Mines 
 Technology Transfer Symposium in Charleston, WV, on June 22, 1983. 
 Five of the papers describe the results of Bureau-sponsored research on 
 cabs and canopies for low-coal underground mining equipment. The other 
 papers describe the efforts of three underground coal mining equipment 
 manufacturers (FMC, Joy, and Lee-Norse) in the area of cab and canopy 
 design. 
 
 ^Mining engineer, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA, 
 
CABS AND CANOPIES FOR LOW-COAL UNDERGROUND MINING EQUIPMENT 
 
 By William W. Aljoe"" 
 
 ABSTRACT 
 
 This paper reviews the history of 
 Federal cab and canopy regulations, the 
 problems inherent to the use of canopies 
 in low coal, and various technical 
 aspects of cab and canopy design. Each 
 type of underground face equipment 
 
 covered by canopy regulations is examined 
 in terms of the cab and canopy designs 
 presently available. Innovative design 
 features facilitating machine operation 
 in low coal are emphasized. 
 
 HISTORY OF LOW-COAL CANOPY REGULATIONS AND PROBLEMS 
 
 Between 1966 and 1978, 819 fatalities 
 occurred because of roof falls^ in under- 
 ground mines. Over 500 of these involved 
 operators or helpers on the nine major 
 types of self-propelled electric face 
 equipment — continuous miners, shuttle 
 cars, scoops, tractors, ramcars, roof 
 bolters, cutters, face drills, and load- 
 ing machines. This fatality record indi- 
 cated that overhead protection for opera- 
 tors of face equipment would be extremely 
 helpful. Prior to 1972, however, very 
 few machines were equipped with overhead 
 operator protection, and these machines 
 were used almost exclusively in coal 
 seams higher than 72 in. 
 
 Recognition of the potential benefits 
 of overhead protection brought about the 
 enactment of Federal canopy regulations 
 (30 CFR 75-710-1) in 1972. These regula- 
 tions specified the deadline dates by 
 which cabs and/or canopies would be re- 
 quired on the nine types of face equip- 
 ment mentioned above. The requirements 
 applied immediately to machines used in 
 coal seams higher than 72 in; a delayed 
 enforcement schedule was adopted for ma- 
 chines used in lower coal seams. The 
 purpose of this delayed enforcement 
 
 ^Mining engineer, Pittsburgh Research 
 Center, Bureau of Mines, Pittsburgh, PA. 
 
 ^Roof Control Division, Pittsburgh 
 Safety Technology Center, Mine Safety and 
 Health Administration, Pittsburgh, PA. 
 
 schedule was to allow time for develop- 
 ment of cab and canopy technology for 
 low-coal machines. 
 
 The beneficial effects of the cab 
 and canopy regulations were immediately 
 apparent, as canopy "saves" (occasions 
 when the presence of the canopy saved a 
 worker from death or injury) began to 
 occur soon after the regulations were en- 
 acted. In the past 10 years, almost 200 
 canopy "saves" have been reported to the 
 Mine Safety and Health Administration 
 (MSHA) . The actual number of "saves," 
 however, has probably been much greater 
 than this due to underreporting. For ex- 
 ample, mines may have hesitated to report 
 minor roof falls that were deflected by 
 canopies but did not result in signifi- 
 cant injury, property damage, or down- 
 time. On the other hand, some roof falls 
 were so massive that they covered entire 
 machines and required extensive cleanup 
 and rescue efforts to free operators who 
 had been saved by canopies. Witnesses to 
 canopy saves of this type were usually 
 the strongest proponents of Federal can- 
 opy regulations. 
 
 Unfortunately, the presence of cabs and 
 canopies can also cause three serious 
 problems — "roofing," restricted vision, 
 and insufficient space within the opera- 
 tor's compartment. "Roofing" (a colli- 
 sion between the canopy and an overhead 
 obstruction) introduces three potential 
 
hazards: (1) roof supports (bolts, 
 posts, crossbars, etc.) could be damaged, 
 weakening the roof stability of the en- 
 try; (2) ventilation tubing or electric 
 trailing cables hanging from the roof 
 could be broken or dislodged, creating a 
 fire or explosion hazard; and (3) the 
 canopy itself could be knocked off its 
 supports and onto the operator. The ob- 
 vious solution to roofing would be to 
 lower the canopy, but this usually re- 
 sults in the other two problems , re- 
 stricted operator vision and insufficient 
 working space. When these two problems 
 occur, machine operators tend to lean be- 
 yond the confines of their compartments, 
 exposing themselves to collisions with 
 ribs, roof, and other obstacles in the 
 mining section. 
 
 Cab and canopy problems were especially 
 prevalent in low-coal mines for obvious 
 reasons; as stated above, this fact was 
 acknowledged in the delayed enforcement 
 provisions of the 1972 canopy regula- 
 tions. However, the length of time al- 
 lowed for development of low-coal canopy 
 technology proved to be insufficient, and 
 the deadline dates for con^)liance were 
 postponed three times (in 1973, 1976, and 
 1977). The 1977 revision stated that 
 
 canopies would not be required on ma- 
 chines operating in mining heights (mine 
 floor to unfinished roof) lower than 42 
 in, and this exemption for very low coal 
 mines still exists today. 
 
 Mine operators, however, continue to 
 experience numerous canopy problems in 
 coal seams greater than 42 in in height; 
 in fact, these problems still occur in 
 seams as high as 60 in. The main reason 
 for this is that the machines being used 
 in 42- to 60-in coal seams were not de- 
 signed to allow for the everyday use of 
 canopies. Operators' compartments on 
 many existing machines are neither long 
 enough nor wide enough to allow a com- 
 fortable seating position with a low can- 
 opy height. Furthermore, machine con- 
 trols are often arranged such that the 
 operator must sit upright or lean forward 
 to reach them. Unfortunately, anthropo- 
 metric measurements show that the opera- 
 tor must assume at least a semireclining 
 posture to remain seated beneath a canopy 
 that is low enough to prevent roofing. 
 Because of the prevalence of low-coal 
 canopy problems , it became obvious that 
 innovative designs for low-coal machines, 
 cabs, and canopies were needed. 
 
 INNOVATIVE CAB AND CANOPY DESIGNS FOR LOW COAL 
 
 During the past 5 years, numerous at- 
 tempts have been made to develop cab and 
 canopy designs suitable for low-coal min- 
 ing equipment. Many of these designs 
 were originated by the equipment manufac- 
 turers; however, coal company personnel 
 also played an important role in the de- 
 sign process. The remainder of this pa- 
 per discusses the innovative cabs and 
 canopies developed by the mining industry 
 to help alleviate the canopy problems in- 
 herent to low-coal mines. 
 
 CONTINUOUS MINERS 
 
 Continuous miners have historically 
 been involved with more roof fall fatali- 
 ties than any other machine type (except 
 roof bolters, which will be discussed 
 later). Since equipment designers also 
 
 recognized this problem, more design ef- 
 fort has been placed on cabs and canopies 
 for continuous miners than for most other 
 machine types. The need for overhead 
 protection on continuous miners was ob- 
 viously recognized by mine operating 
 personnel; in many cases, problems with 
 canopies were tolerated by continuous 
 miner operators more readily than by 
 operators of other machines. Consequent- 
 ly, continuous miners are the machines on 
 which cabs and canopies have been most 
 successful. 
 
 Figure 1 shows a cab and canopy on a 
 continuous miner designed specifically 
 for low coal seams. The cab and canopy 
 have several innovative low-coal design 
 features: 
 
FIGURE 1. - Split=type floating canopy on continuous miner. 
 
 1, The operator's deck is hinged to 
 the miner frame and "floats" or "slides" 
 along the mine floor during normal opera- 
 tion. This design feature has been 
 utilized on almost all recently devel- 
 oped low-profile continuous miners. The 
 greatest advantage of a "floating" deck 
 versus a "fixed" deck is that no ground 
 clearance is needed; this allows the can- 
 opy top to be lowered by about 6 to 8 in 
 without sacrificing operator headroom. 
 Another advantage of the "floating" deck 
 is that it can drop below the crawler 
 level of the miner when tramming over an 
 undulation, thus decreasing the likeli- 
 hood of canopy roofing. 
 
 2. The canopy top is split into two 
 sections; the upper plate covers the 
 operator's head and torso, while the low- 
 er plate protects the operator's legs and 
 the machine controls. The major advan- 
 tage of this split-type canopy design is 
 that the operator can look through the 
 space between the plates to see in the 
 forward direction. 
 
 3. The controls on this machine were 
 designed to allow the operator to re- 
 cline, thus allowing the canopy to be 
 placed lower than if the operator were 
 forced to sit upright. The tram controls 
 are located in the center of the opera- 
 tor's deck; since the operator straddles 
 them when seated in the deck, they are 
 close at hand at all times. The handles 
 of the other machine controls extend 
 rearward, also placing them within easy 
 reach of the reclining operator. 
 
 Figure 2 shows the same basic cab and 
 canopy design as figure 1; however, the 
 canopy in figure 2 was modified slightly 
 to compensate for the effect of the light 
 mounted on its outside edge. Although 
 this light was needed to achieve compli- 
 ance with mine illumination regulations, 
 it created a problem because the operator 
 was forced to lean outward, far beyond 
 the confines of his compartment, to see 
 down the side of the machine. Since this 
 would have exposed the operator's head to 
 collisions with the roof, rib, or other 
 
FIGURE 2. = Extension welded to outer edge of continuous miner canopy. 
 
 obstructions, the mine mechanics welded 
 an extension plate on the outboard side 
 of the canopy top. This extension made 
 the canopy the widest point on the ma- 
 chine, causing it to strike the roof or 
 rib before the operator's head did. 
 
 Figure 3 shows a cab and canopy as de- 
 signed and installed by coal company 
 maintenance personnel when the miner was 
 rebuilt in the company's central shop. 
 Like the cabs and canopies in figures 1 
 and 2, the operator's deck was designed 
 to "float" on the mine floor. How- 
 ever, this floating deck had another ad- 
 vantage — it was hydraulically adjust- 
 able. A hydraulic jack connected the 
 rear ("floating") end of the deck to the 
 rear bumper of the miner, allowing the 
 operator to selectively raise or lower 
 the deck. The deck is in the raised po- 
 sition in figure 3 because the mine floor 
 in this area was particularly wet and 
 muddy. Another unique feature of this 
 operator compartment was that the con- 
 trols were adjustable; that is, the con- 
 trol handles and valve banks were mounted 
 
 on a pan that could be moved backward and 
 forward to accommodate the reach of both 
 small and large operators. The pan could 
 also be rotated upward to permit the op- 
 erator to enter and leave the cab. The 
 seat back was adjustable also; in figure 
 3, the seat back is in the upright posi- 
 tion, but it could easily be tilted and 
 locked into a reclining position if the 
 operator needed more headroom. Finally, 
 the canopy top itself was hydraulically 
 adjustable, allowing the operator to ei- 
 ther (1) raise it to allow more headroom 
 and vision or (2) lower it to prevent 
 roofing. The hydraulic adjustment capa- 
 bilities of the deck and canopy would be 
 especially helpful in areas where the 
 vertical clearance changed abruptly be- 
 cause the canopy would not always have to 
 be fixed at its lowest setting. 
 
 SHUTTLE CARS 
 
 Some of the cab and canopy design fea- 
 tures used on continuous miners have also 
 been tried on shuttle cars; however, the 
 design problems with shuttle cars have 
 
FIGURE 3. = Hydraulically adjustable continuous miner cab and canopy with adjustable controls. 
 
 been harder to solve because shuttle cars 
 must travel faster, farther, and oftener 
 than continuous miners. Despite these 
 problems, innovative shuttle car design 
 features developed in recent years have 
 allowed the use of canopies in lower coal 
 seams than ever before. For example, 
 canopy roofing occurs less frequently if 
 the operator's compartment is mounted be- 
 tween the tires of the shuttle car rather 
 than at the rear end; consequently, al- 
 most all shuttle cars intended for low- 
 coal use now have center-mounted opera- 
 tors' compartments. Shuttle car seats 
 have also been improved to provide easier 
 machine operation from a reclining posi- 
 tion, a necessity if canopies are to be 
 successful in low coal. 
 
 Figure 4 shows a low-profile, center- 
 driven shuttle car with a "floating" 
 operator's compartment. The major dif- 
 ference between the "floating" compart- 
 ment in figure 4 and the continuous miner 
 conyjartments in figures 1-3 is the means 
 by which it is attached to the machine. 
 Instead of being hinged to the machine 
 frame, the shuttle car operator's deck 
 is connected to the side of the machine 
 through vertical T-shaped guide bars. 
 
 When tramming over rough mine floors, the 
 shuttle car compartment moves straight up 
 and down rather than in an arc. Again 
 the advantage of the "floating" deck is 
 that the canopy can be lowered without 
 sacrificing operator headroom. 
 
 Unfortunately, when mine floors are 
 very wet, rough, or muddy, floating oper- 
 ator compartments experience more prob- 
 lems than compartments with fixed ground 
 clearances. For example, water and mud 
 can enter a floating compartment more 
 easily than when the deck is raised above 
 the mine floor. More importantly, a 
 floating deck is more likely to become 
 "hung up" in a rough or muddy mine floor, 
 reducing the machine's ability to tram. 
 Not surprisingly, these problems are 
 worse for shuttle cars than for continu- 
 ous miners; however, in fair to good bot- 
 tom conditions, floating operator com- 
 partments have been quite successful on 
 both machine types. 
 
 Figure 5 illustrates another problem 
 that occurs when canopies are used on 
 shuttle cars in low coal, regardless of 
 whether the deck floats or is fixed. The 
 presence of sideboards often eliminates 
 
FIGURE 4. = Floating operator's deck on center=clriven shuttle car. 
 
 FIGURE 5. - Operator leaning out of shuttle car cab for better vision. 
 
 operator vision to the opposite side of 
 the entry, and the operator's natural re- 
 action is to lean outward and upward to 
 look over the sideboards. As shown in 
 figure 5, the presence of a canopy makes 
 this process more difficult and danger- 
 ous. Since vision to the opposite side 
 of the entry is almost always negligible 
 on low-coal shuttle cars, the machine and 
 
 compartment should be designed such that 
 the operator can easily see down the side 
 of the machine without leaning out beyond 
 the canopy, 
 
 A novel concept for improving operator 
 vision on shuttle cars is shown in figure 
 6; this experimental operator compartment 
 was built and tested under a Bureau of 
 
FIGURE 6. = Canopy mounted on turntable in center of shuttle car operator's compartment. 
 
 Mines contract,^ The major difference 
 between the compartment in figure 6 and 
 other center-mounted shuttle car compart- 
 ments is that the operator does not 
 change seats when changing tram direc- 
 tions. Instead, the seat is located on a 
 turntable in the center of the compart- 
 ment, and the operator manually rotates 
 the turntable to face forward or back- 
 ward. The improvement in vision results 
 from the use of a split-type canopy de- 
 sign similar to those in figures 1 and 2. 
 In the compartment shown in figure 6, 
 however, the center portion of the canopy 
 
 •^Kopas, P. Design and Development of 
 Protective Canopies for Underground Low 
 Coal 48" and Under (contract HOI 8801 4, 
 Kogen Industries, Inc.). BuMines OFR 
 17-81, 1980, 89 pp.; NTIS PB 81-167533. 
 
 is fixed to the turntable and remains 
 above the operator's head and torso as 
 the seat rotates. The two lower plates 
 are cantilevered from the ends of the cab 
 deck to protect the operator's legs and 
 the machine controls. 
 
 Figure 7 shows how this canopy design 
 improved operator vision; the photogra- 
 pher was seated in the compartment in 
 figure 6 with the canopy in its lowest 
 position. Although vision alongside the 
 machine is not available, it is obvious 
 that the canopy itself does not inhibit 
 vision at all. Furthermore, sideboards 
 were not present on this shuttle car, 
 which greatly improved vision to the op- 
 posite side of the entry. The need for 
 the operator to lean dangerously outward 
 was greatly reduced. 
 
Several innovative cab and canopy de- 
 sign concepts have been used successfully 
 on end-driven shuttle cars. For example, 
 floating operators* decks have been suc- 
 cessful on end-mounted operator compart- 
 ments when good bottom conditions were 
 
 present. However, the most promising cab 
 and canopy concept for end-driven shuttle 
 cars may be the "transverse" or "side- 
 saddle" concept shown in figure 8, It 
 has been accepted and praised by shuttle 
 car operators as a great improvement in 
 
 FIGURE 7. » Improved vision with split-type canopy on shuttle car. 
 
 FIGURE 8. - Side-saddle tram compartment on end-driven shuttle car. 
 
10 
 
 both comfort and vision. In transverse 
 compartments, the operator faces the 
 shuttle car conveyor at all times and 
 merely rotates his or her head to see in 
 the forward or reverse directions; no 
 seat changing is required. The trans- 
 verse seat configuration makes it possi- 
 ble for the operator to see alongside the 
 shuttle car without leaning beyond the 
 protection of the compartment. Extra leg 
 room is provided by building a tunnel be- 
 neath the conveyor discharge boom and 
 placing the tram and brake pedals at the 
 back of the tunnel. More seating width 
 can also be provided with the transverse 
 compartment layout. 
 
 SCOOPS, TRACTORS, AND RAMCARS 
 
 Scoops and tractors are widely used for 
 both coal haulage and cleanup work in low 
 coal because they are smaller, more ver- 
 satile, and less expensive than shuttle 
 cars or continuous haulage equipment. 
 (Ramcars are somewhat similar to scoops 
 in design but are used primarily for coal 
 haulage.) Although scoop and tractor 
 
 operators are only occasionally involved 
 in roof falls, improvements in cab and 
 canopy design are needed for these ma- 
 chines because of the large number of in- 
 juries resulting from collisions with 
 the mine roof and ribs. Most models of 
 scoops and tractors have transverse oper- 
 ator compartments that allow easier vi- 
 sion along the side of the machine, but 
 the compartments are often too small to 
 protect the operator from collisions when 
 she or he reclines. The problem is com- 
 plicated by the presence of relatively 
 simple post-and-plate canopies that se- 
 verely restrict operator vision. These 
 poorly designed canopies increase the po- 
 tential hazard because they introduce 
 another object against which the operator 
 can be crushed. 
 
 Figure 9 shows a properly designed cab 
 and canopy on a scoop; note that the cab 
 deck extends far beyond the side of the 
 scoop, providing both protection and un- 
 restricted vision along its side. Note 
 also that the canopy does not interfere 
 with operator vision when the compartment 
 
 FIGURE 9. - Operator's deck on scoop extended beyond side of machine. 
 
11 
 
 is extended in this manner. This ex- 
 tended type of compartment is even more 
 critical in coal seams lower than 42 in, 
 where canopies are not required, because 
 it eliminates the need for the operator 
 to sit upright, thereby reducing the dan- 
 ger of collisions with the roof. 
 
 Operator ingress and egress is another 
 common problem on existing scoops and 
 tractors. Although the machine design 
 itself contributes to this problem, the 
 presence of a canopy often makes it 
 worse. Figure 10 shows a scoop canopy 
 designed to facilitate ingress and 
 egress; it is mounted on rollers and con- 
 tained within guide rails on the side- 
 walls of the operator's compartment. Be- 
 fore entering the cab, the operator 
 slides the canopy across the machine, 
 creating more room for entry. Once 
 seated, the operator pulls the canopy 
 back into position and locks it in place. 
 
 The operators' compartments on the 
 scoops in figures 9 and 10 were located 
 at the centers of the machines; fig- 
 ure 11 shows an end-driven scoop with 
 an improved cab and canopy design. 
 
 (Operators' compartments on most tractors 
 are also located at the ends of the ma- 
 chines) . The canopy top on this scoop is 
 hydraulically adjustable, and the hydrau- 
 lic cylinders have been placed to mini- 
 mize interference with operator vision. 
 The back of the seat can be adjusted to 
 allow the operator to recline comfort- 
 ably, as in figure 11, or be raised to 
 peinnit sit-up operation when the mine has 
 sufficient vertical clearance. This is 
 the same basic seat design as on the con- 
 tinuous miner in figure 3; it was also 
 designed by coal company shop personnel. 
 
 ROOF BOLTERS 
 
 Roof bolters are probably the hardest 
 types of machines to describe in terms of 
 cabs and canopies because of the wide 
 variety of roof bolter designs in use to- 
 day. The development of automated tem- 
 porary roof support (ATRS) systems for 
 roof bolters has made the subject of cabs 
 and canopies even more complex. This 
 paper involves only the tramming station 
 of the roof bolter because this is the 
 only location where a complete operator 
 compartment is required. However, some 
 
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 FIGURE 10. ° Sliding canopy top on scoop for easier ingress and egress. 
 
12 
 
 FIGURE IL = Hydraulically adjustable canopy on end=driven scoop. 
 
 type of overhead protection must also be 
 provided at the drilling station — either 
 a canopy, an ATRS, or both. 
 
 Operator compartments on single-head 
 roof bolters can be divided into two 
 basic types: (1) drill-and-tram compart- 
 (2) tram-only compartments, 
 most innovative cabs and 
 existing single-head roof 
 drill-and-tram compartments 
 retrofitted to the machines 
 
 On the compartment in figure 12, this 
 is accomplished by attaching the deck 
 
 ments and 
 Perhaps the 
 canopies on 
 bolters are 
 that were 
 
 (figs. 12-13). These compartments are 
 somewhat similar to the continuous miner 
 compartments in figures 1-3 because they 
 are hinged to the machine frame at one 
 end and "float" on the mine floor at the 
 other. During drilling and bolting, the 
 hydraulic jacks on these cabs and 
 canopies are extended vertically as far 
 as possible, thus wedging the compart- 
 ment between the mine floor and roof. 
 When tramming these bolters between 
 holes or to and from the face areas, 
 the operators can raise the tram decks 
 above the floor to prevent them from 
 hanging up in rough or muddy areas. 
 
 mechanically to the 
 raising the boom, 
 on the compartment 
 double-acting , 
 raised upward 
 
 drilling boom, then 
 
 The hydraulic jacks 
 
 in figure 13 are 
 
 allowing the deck to be 
 
 and suspended from the 
 
 canopy during tramming. The canopy in 
 figure 13 is also hinged to the machine 
 f rame . 
 
 Note also in figure 13 that an extra 
 hydraulic jack is located on the opposite 
 side of the drill head from the opera- 
 tor's compartment. This jack is con- 
 nected to the inboard edge of the canopy 
 through a cantilevered arm that extends 
 across the drilling boom and behind the 
 head. During drilling and bolting, the 
 jack is emplaced against the roof to pro- 
 vide additional roof support; during 
 tramming, the jack is retracted and sus- 
 pended from the cantilevered arm. 
 
 Almost all dual-head roof bolters have 
 tram compartments that are attached rig- 
 idly to the machine at a fixed distance 
 
13 
 
 above the mine floor. Figures 14 and 15 
 show two of the better low-coal tram com- 
 partments on existing dual-head roof 
 bolters. The compartment in figure 14 is 
 
 located between the tramming wheels on 
 the right side of the machine and is 
 large enough to allow the operator to as- 
 sume a reclining position. However, the 
 
 FIGURE 12. - Floating, hydraulically adjustable canopy on single=head roof bolter. 
 
 FIGURE 13. - Extra safety jack attached to floating, hydraulically adjustable canopy on single- 
 head roof bolter. 
 
14 
 
 FIGURE 14. ~ Long tram deck on duaUhead roof bolter permits reclining operation. 
 
 FIGURE 15. - Extended tram deck and hydraulically adjustable canopy on duaUhead roof bolter. 
 
15 
 
 operator often has to lean outward to see 
 down the side of the machine and must 
 turn around and look backward when tram- 
 ming in reverse. The compartment in fig- 
 ure 15 is mounted transversely and is 
 extended beyond the side of the machine 
 to improve operator comfort and vision, 
 and the canopy top is hydraulically ad- 
 justable. The major disadvantage of this 
 tram compartment is that it is located on 
 the rear corner of the machine, which 
 causes the canopy to move farther upward 
 in undulating conditions. 
 
 Figure 16 shows one of the few "float- 
 ing" tram compartments on dual-head roof 
 bolters. This is a rather unique roof 
 bolter because it has two operators' com- 
 partments, both at the front of the ma- 
 chine. The compartment on the left side 
 of the bolter (right side of figure 16) 
 contains controls for both drilling and 
 tramming; the other compartment contains 
 only drilling controls. Unfortunately, 
 this particular machine was designed for 
 medium coal seam heights and does not 
 contain a reclining seat to facilitate 
 canopy use in low coal. 
 
 CONVENTIONAL MINING EQUIPMENT 
 
 In general, the operators' compartments 
 on conventional face equipment — cutters, 
 face drills, and loading machines — were 
 not designed for low-coal canopy use. 
 "Floating" compartments are virtually 
 
 nonexistent, and present compartments are 
 usually too short and narrow. Further- 
 more, substantial machine redesign would 
 probably be needed to provide a suitable 
 low-coal cab and canopy configuration. 
 For this reason, fewer canopies are used 
 on low-coal conventional equipment than 
 on most other machine types. 
 
 Cutters and Face Drills 
 
 Figures 17 and 18 show the typical 
 operator seating positions when canopies 
 are used on cutters (fig, 17) and face 
 drills (fig, 18) in low coal. Obviously, 
 operator comfort and vision are less than 
 adequate. In addition, the machine con- 
 trols were designed to accommodate opera- 
 tors in an upright, seated position; 
 therefore, proper machine operation would 
 be difficult even if the compartments 
 were long enough to allow the operators 
 to recline. Although operator vision 
 could be improved somewhat by installing 
 the two-post, cantilevered canopy shown 
 in figure 19, the basic designs of most 
 cutters and face drills would have to be 
 altered substantially to allow problem- 
 free canopy use in low coal. Fortunate- 
 ly, cutters and face drills move rather 
 slowly and are not often involved in roof 
 falls, so the lack of canopy protection 
 in low coal creates fewer hazards than 
 the lack of canopies on other machine 
 types. 
 
 FIGURE 16. - Dual operator stations at front of dual-head roof bolter. 
 
16 
 
 FIGURE 17o = Operator cramped within tram compartment on cutting machine. 
 
 Loading Machine s 
 
 Figure 20 shows an operator's position 
 while he is seated beneath a canopy on a 
 typical low-coal loader — his legs are 
 crossed, his neck is bent, and his knees 
 nearly touch his chin during "normal" 
 operation. This situation is not sur- 
 prising considering that the overall de- 
 sign of the operator's station on the 
 loading machine has not changed substan- 
 tially in over 20 years. In fact, many 
 of the loaders in use today were origi- 
 nally designed for "walk along" opera- 
 tion, with cabs and canopies added after 
 the machines were built. 
 
 Unlike cutters and face drills, loaders 
 are relatively mobile machines and are 
 frequently involved in roof falls; there- 
 fore, cab and canopy protection in low 
 coal is much more critical. For this 
 reason, loader operators are more toler- 
 ant of "inadequate" cabs and canopies 
 than operators of cutters and face 
 drills. Several coal companies have made 
 
 improvements on existing loader compart- 
 ments while rebuilding the machines 
 (e.g. , widening and/or lengthening the 
 operators' decks). However, substantial 
 machine redesign would be necessary to 
 provide a truly workable low-coal cab and 
 canopy. 
 
 The Bureau of Mines has sponsored one 
 project to achieve an improved cab and 
 canopy design for a loading machine.'* 
 This project is described in more detail 
 on page 48. To install the operator's 
 compartment developed under this program 
 (fig. 21), significant modifications to 
 the loader itself must be made. However, 
 if this compartment is installed, it will 
 represent a substantial improvement over 
 existing loader compartment designs. 
 
 ^Mantel, J. Extension of Cab and Can- 
 opy Technology to Low Coal Seams. Ongo- 
 ing BuMines contract H0387026; for inf., 
 contact J. R. Bartels, TPO, Pittsburgh 
 Research Center, BuMines, Pittsburgh, PA. 
 
17 
 
 FIGURE 18. = Operator cramped within tram compartment on face drill. 
 
 FIGURE 19„ = Mockup of two-post canti levered canopy for cutter and face drill. 
 
18 
 
 FIGURE 20o = Operator cramped within tram compartment of loading machine. 
 
 FIGURE 21o - Mockup of improved loader tram compartment. 
 
19 
 
 SUMMARY AND CONCLUSION 
 
 Coal mining equipment manufacturers 
 have undoubtedly made improvements in 
 low-coal cab and canopy design during the 
 past 5 years. The designs shown here 
 represent a few of the better ideas in- 
 corporated into existing machines, but 
 none is the ultimate answer to low-coal 
 cab and canopy problems . Because of the 
 
 inherent physical constraints of low-coal 
 mines, machine operators will always ex- 
 perience comfort and/or vision problems; 
 however, through equipment redesign and 
 efficient use of existing cab and canopy 
 technology, the severity of these prob- 
 lems can be reduced. 
 
20 
 
 COST BENEFIT ANALYSIS FOR LOW-COAL CABS AND CANOPIES 
 By K. L. Whitehead^ 
 
 INTRODUCTION 
 
 In general, the use of canopies over 
 operators' compartments of underground 
 coal mining equipment has proven to be 
 beneficial as protection against both 
 falling roof rock and the operator's head 
 striking against projections from the 
 roof line. However, experience has shown 
 that in lower working heights, particu- 
 larly 42 in and lower, existing canopy 
 technology can be difficult to apply suc- 
 cessfully. In these low-seam height con- 
 ditions, there is frequently inadequate 
 roof clearance to operate the machines 
 and/or the operator compartments become 
 too cramped and uncomfortable for per- 
 sonnel to function efficiently and safe- 
 ly. Because of these problems, MSHA has, 
 by policy, suspended enforcement of the 
 canopy regulations in seam heights of 
 42 in and lower. As a result, accidents 
 potentially preventable by the use of 
 
 overhead or lateral 
 occurring. 
 
 protection are still 
 
 The Bureau of Mines is, therefore, ini- 
 tiating action on a program to develop 
 technology that will eliminate, or at 
 least minimize, these machine-related ac- 
 cidents. However, the Bureau must decide 
 whether or not to continue a development 
 program for machine-mounted protective 
 devices; establish a program to develop 
 alternate technology such as remote con- 
 trol, robotics, etc.; or fund a program 
 including aspects of both technologies. 
 A final decision on the type of research 
 program to establish must be based on 
 several factors, one of which was the 
 study conducted by Bituminous Coal Re- 
 search (BCR) under the Bureau contract 
 "Cost Benefit Analysis of Low Coal Cabs 
 and Canopies" and summarized herein. 
 
 PROCEDURE USED IN COST-BENEFIT ANALYSIS 
 
 The general procedure used in the anal- 
 ysis was to compare the cost to the coal 
 industry of fitting both old and new min- 
 ing equipment with protective structures 
 to the dollar value assigned to the in- 
 juries and fatalities that could have 
 been prevented by the use of properly de- 
 signed cabs and canopies. In performing 
 this analysis, several assumptions and 
 qualifying statements were used: 
 
 1. For those accidents considered 
 "canopy preventable," the death or injury 
 was assumed to have been prevented, not 
 just reduced in degree of severity. 
 
 2. Even though adequate low-coal can- 
 opy technology is not available, it was 
 assumed that canopies could be success- 
 fully installed on all equipment regard- 
 less of working height. 
 
 3. Philosophically, a dollar value 
 cannot be placed on the death or injury 
 of a worker. However, for purposes of 
 analysis and comparison, a consistent 
 method of assigning dollar values to ac- 
 cidents had to be used. For the purpose 
 of this project, the Accident Cost Indi- 
 cator Model (ACIM) developed by MSHA's 
 Health Safety and Analysis Center (HSAC) 
 in Denver, CO, was selected. 
 
 ^Supervising engineer. Bituminous Coal 
 Research, Monroe vi lie, PA. 
 
 4. The only ACIM accident analyses 
 available to BCR were for the years 
 
1975-78. It was therefore assumed that 
 the average cost calculated for canopy- 
 preventable fatal and lost-time accidents 
 during 1975-78 could be used to calculate 
 a dollar value for preventable accidents 
 occurring in the other years of the anal- 
 ysis period. 
 
 21 
 
 To carry out the analysis, two sets of 
 data had to be developed — the cost to in- 
 stall overhead and lateral protective 
 structures and the benefits realized from 
 the use of these structures. 
 
 COSTS OF INSTALLING CABS AND CANOPIES 
 
 The installation costs were established 
 by requesting equipment manufacturers and 
 rebuild shops to supply estimates of the 
 cost to install these structures on new 
 and rebuilt machines. Cost figures for 
 six different protective structures were 
 requested to reflect equipment designs 
 and accident causes. For example, a roof 
 bolter would require both a tram canopy 
 and a drill-station canopy to protect the 
 operator from roof falls and would also 
 require side protection to guard against 
 injuries from rib rolls or collisions 
 with other equipment. Table 1 summarizes 
 average installation costs by type of ma- 
 chine and protective structure type. A 
 
 comparison of these figures shows that 
 retrofitting is generally more expensive 
 than new installations, indicating that, 
 if possible, the protective structures 
 should be included when a new machine is 
 ordered. 
 
 Calculation of installation costs to 
 the entire industry obviously requires 
 knowing the equipment population. Unfor- 
 tunately, these statistics are not read- 
 ily available, particularly for the peri- 
 od after 1978. Since the analysis was to 
 cover 1971-80, an estimate of equipment 
 population and its distribution with re- 
 spect to seam heights had to be made. 
 
 TABLE 1. - Average estimated installation costs and number of cost estimates 
 received for protective structures on new and rebuilt equipment 
 
 Equipment type 
 
 Tram 
 deck 
 
 Type of protective structure 
 
 Side pro- 
 tection 
 
 Tram 
 canopy 
 
 Drill 
 deck 
 
 Drill 
 canopy 
 
 ATRS 
 
 Number of 
 estimates 
 received 
 
 Continuous miners: 
 
 New. 
 
 Retrofit 
 
 Shuttle cars: 
 
 New 
 
 Retrofit 
 
 Tractors and/or scoops 
 
 New 
 
 Retrofit 
 
 Roof bolters: 
 
 New 
 
 Retrofit 
 
 Cutting machines: 
 
 New 
 
 Retrofit 
 
 Face drills: 
 
 New 
 
 Retrofit 
 
 Loading machines: 
 
 New 
 
 Retrofit 
 
 NAp Not applicable. 
 
 $2,500 
 3,886 
 
 3,100 
 6,471 
 
 15,000 
 19,625 
 
 640 
 1,095 
 
 600 
 1,000 
 
 486 
 48 6 
 
 1,000 
 1,750 
 
 $585 
 1,060 
 
 435 
 765 
 
 278 
 278 
 
 302 
 352 
 
 610 
 1,340 
 
 283 
 453 
 
 455 
 795 
 
 $2,690 
 2,990 
 
 1,568 
 1,897 
 
 1,538 
 1,961 
 
 2,520 
 2,615 
 
 1,300 
 2,270 
 
 945 
 1,378 
 
 1,500 
 2,625 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 $717 
 1,528 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 $4,794 
 4,326 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 $8,816 
 7,866 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 NAp 
 NAp 
 
 12 
 
 10 
 
22 
 
 The procedure used to develop the popu- 
 lation statistics can be summarized as 
 follows: 
 
 1. For 1971-78, the population of con- 
 tinuous miners, cutting machines, mobile 
 loading machines, face drills, and roof 
 drills was based on statistics published 
 in the National Coal Association publica- 
 tion "Coal Data." 
 
 2. Population estimates were made for 
 all equipment types during 1979-80, and 
 for shuttle cars and scoops for 1971-80. 
 These estimates were based on several 
 factors, including — 
 
 a. Coal production by mining meth- 
 od for each year in the period 1971-78. 
 
 b. The productivity or tons mined 
 per cutting machine for continuous and 
 conventional mining. 
 
 c. Equipment ratios 
 period 1971-78. 
 
 used over the 
 
 d. The ratios of shuttle cars and 
 tractors and/or scoops to continuous 
 miners and loading machines based on MSHA 
 equipment compliance data. 
 
 The resulting population data were 
 broken down for each year by equipment 
 type used in seam heights of 42 to 48 in 
 and 42 in and lower (table 2). 
 
 Establishing the industry cost for in- 
 stallation of protective structures re- 
 quired that the population data reflect 
 annual changes in the number of new ma- 
 chines introduced, old machines continu- 
 ing to operate, and machines retired. 
 This provided a means to estimate the 
 annual number of machines requiring in- 
 stallation of either new or retrofit 
 operator-protective structures. An esti- 
 mate of the average machine life for each 
 type of face equipment was developed from 
 data provided by coal companies and re- 
 sulted in estimated machine replacement 
 schedules. Table 3 is an example of the 
 estimated continuous miner replacement 
 schedule for the two seam height ranges 
 of interest. 
 
 The installation costs (table 1) were 
 then applied to the population data (ta- 
 bles 2 and 3) to estimate total costs to 
 the industry (table 4). For the analy- 
 sis, the machines were assumed to require 
 all applicable protective structures 
 (lateral and overhead protection). 
 
 BENEFITS OF CAB AND CANOPY PROTECTION 
 
 The second factor in the analysis, the 
 "benefits," was calculated using accident 
 data obtained from the ACIM file. Since 
 
 data were only available for 1975-78, 
 these had to be used to establish a sta- 
 tistical basis for classifying accidents 
 
 TABLE 2. - Equipment population as a function of seam heights 
 of 43 to 48 and <42 in 
 
 
 Continuous 
 
 Cutting 
 
 Mobile 
 
 Face 
 
 Roof 
 
 Shuttle 
 
 Tractors 
 
 Year 
 
 miners 
 
 machines 
 
 loaders 
 
 drills 
 
 bolters 
 
 cars 
 
 and) 
 
 SCO( 
 
 /or 
 
 
 43-48 
 
 <42 
 
 43-48 
 
 <42 
 
 43-48 
 
 <42 
 
 43-48 
 
 <42 
 
 43-48 
 
 <42 
 
 43-48 
 
 ^42 
 
 3pS 
 
 
 43-48 
 
 <42 
 
 1971 
 
 178 
 
 338 
 
 288 
 
 617 
 
 248 
 
 454 
 
 329 
 
 506 
 
 300 
 
 573 
 
 694 
 
 625 
 
 430 
 
 1,180 
 
 1972 
 
 185 
 
 351 
 
 265 
 
 567 
 
 235 
 
 431 
 
 298 
 
 459 
 
 308 
 
 589 
 
 684 
 
 618 
 
 424 
 
 1,165 
 
 1973 
 
 187 
 
 354 
 
 215 
 
 460 
 
 242 
 
 443 
 
 232 
 
 358 
 
 313 
 
 597 
 
 699 
 
 630 
 
 433 
 
 1,187 
 
 1974 
 
 196 
 
 372 
 
 212 
 
 455 
 
 258 
 
 473 
 
 266 
 
 410 
 
 416 
 
 794 
 
 740 
 
 667 
 
 458 
 
 1,259 
 
 1975 
 
 220 
 
 418 
 
 223 
 
 478 
 
 206 
 
 379 
 
 281 
 
 432 
 
 407 
 
 777 
 
 694 
 
 630 
 
 430 
 
 1,187 
 
 1976 
 
 236 
 
 449 
 
 252 
 
 541 
 
 198 
 
 364 
 
 295 
 
 454 
 
 440 
 
 840 
 
 707 
 
 642 
 
 438 
 
 1,211 
 
 1977 
 
 268 
 
 508 
 
 209 
 
 448 
 
 190 
 
 348 
 
 265 
 
 408 
 
 507 
 
 967 
 
 746 
 
 676 
 
 462 
 
 1,275 
 
 1978 
 
 282 
 
 536 
 
 200 
 
 430 
 
 170 
 
 313 
 
 237 
 
 364 
 
 491 
 
 938 
 
 736 
 
 670 
 
 456 
 
 1,265 
 
 1979 
 
 312 
 
 593 
 
 195 
 
 417 
 
 162 
 
 298 
 
 231 
 
 356 
 
 530 
 
 1,013 
 
 772 
 
 704 
 
 479 
 
 1,327 
 
 1980 
 
 342 
 
 650 
 
 18 6 
 
 399 
 
 151 
 
 277 
 
 221 
 
 341 
 
 570 
 
 1,088 
 
 803 
 
 732 
 
 498 
 
 1,381 
 
23 
 
 TABLE 3. - Continuous miner replacement schedule, 1971-80 
 
 
 Original machines 
 
 
 Replacement machines 
 
 
 New 
 
 
 Total 
 
 Machines 
 
 Year 
 
 (1971 
 
 and older) 
 
 + 
 
 (added 
 
 after 
 
 1971, 
 
 + 
 
 machines 
 
 = 
 
 machines 
 
 retired 
 
 
 
 
 
 but not 
 
 new machines) 
 
 
 
 
 
 
 SEAM HEIGHT < 42 in 
 
 1971 
 
 
 363 
 
 
 
 
 
 
 
 
 363 
 
 40 
 
 1972 
 
 
 323 
 
 + 
 
 
 
 
 
 + 
 
 54 
 
 = 
 
 377 
 
 40 
 
 1973 
 
 
 282 
 
 + 
 
 
 54 
 
 
 + 
 
 45 
 
 ^ 
 
 381 
 
 41 
 
 1974 
 
 
 242 
 
 + 
 
 
 99 
 
 
 + 
 
 59 
 
 = 
 
 400 
 
 40 
 
 1975 
 
 
 202 
 
 + 
 
 
 158 
 
 
 + 
 
 89 
 
 = 
 
 449 
 
 40 
 
 1976 
 
 
 161 
 
 + 
 
 
 247 
 
 
 + 
 
 75 
 
 := 
 
 483 
 
 41 
 
 1977 
 
 
 121 
 
 + 
 
 
 322 
 
 
 + 
 
 103 
 
 = 
 
 546 
 
 40 
 
 1978 
 
 
 81 
 
 + 
 
 
 425 
 
 
 + 
 
 70 
 
 = 
 
 576 
 
 40 
 
 1979 
 
 
 40 
 
 + 
 
 
 495 
 
 
 + 
 
 103 
 
 ^ 
 
 638 
 
 41 
 
 1980 
 
 
 
 
 + 
 
 
 598 
 
 
 + 
 
 101 
 
 = 
 
 699 
 
 40 
 
 
 
 
 
 SEAM HEIGHT 
 
 43 TO 48 
 
 in 
 
 
 
 
 
 1971 
 
 
 153 
 
 
 
 
 
 
 
 
 153 
 
 17 
 
 1972 
 
 
 136 
 
 + 
 
 
 
 
 
 + 
 
 23 
 
 = 
 
 159 
 
 17 
 
 1973 
 
 
 119 
 
 + 
 
 
 23 
 
 
 + 
 
 18 
 
 =s 
 
 160 
 
 17 
 
 1974 
 
 
 102 
 
 + 
 
 
 41 
 
 
 + 
 
 25 
 
 = 
 
 168 
 
 17 
 
 1975 
 
 
 85 
 
 + 
 
 
 66 
 
 
 + 
 
 38 
 
 = 
 
 189 
 
 17 
 
 1976 
 
 
 68 
 
 + 
 
 
 104 
 
 
 + 
 
 30 
 
 = 
 
 202 
 
 17 
 
 1977 
 
 
 51 
 
 + 
 
 
 134 
 
 
 + 
 
 45 
 
 = 
 
 230 
 
 17 
 
 1978 
 
 
 34 
 
 + 
 
 
 179 
 
 
 + 
 
 29 
 
 = 
 
 242 
 
 17 
 
 1979 
 
 
 17 
 
 + 
 
 
 208 
 
 
 + 
 
 42 
 
 = 
 
 267 
 
 17 
 
 1980 
 
 
 
 
 + 
 
 
 250 
 
 
 + 
 
 43 
 
 = 
 
 293 
 
 17 
 
 TABLE 4. - Cost to industry to install cabs and canopies 
 on face equipment, 1971-80^ 
 
 
 Seam height 
 
 Equipment type 
 
 42 in and lower 
 
 43 to 48 in 
 
 
 Retrofit 
 
 New 
 
 Retrofit 
 
 New 
 
 Continuous miners. ••••••••• 
 
 $2,880,768 
 3,033,380 
 1,281,301 
 2,528,130 
 
 27,133,224 
 6,612,292 
 9,278,192 
 
 $4,036,725 
 409,130 
 267,384 
 523,035 
 
 19,203,872 
 2,704.590 
 
 16,562,934 
 
 $764,951 
 
 933,709 
 
 509,647 
 
 869,956 
 
 5,856,928 
 
 3,912,577 
 
 2,825,782 
 
 $1,692,075 
 153,110 
 
 Cutting machines 
 
 Face drills 
 
 13*^ ■'64 
 
 Loading machines 
 
 244.380 
 
 Tractors and/or scoops 
 
 Shuttle cars 
 
 5,633,360 
 2.184.084 
 
 Roof bolters 
 
 6,927,406 
 
 Total 
 
 52,747,287 
 
 43,707,670 
 
 15,673,550 
 
 16,944,879 
 
 Total cost by seam height.. 
 
 $96,454,957 
 
 $32,618,429 
 
 ' Based on 
 shops. 
 
 1981 dollar value as supplied by manufacturers and rebuild 
 
 and assigning dollar values to accidents 
 in other years of the analysis peri- 
 od. This was based on the assumption 
 that the percentage of cab-or-canopy pre- 
 ventable accidents, grouped by seam 
 height and type of equipment involved, 
 did not change significantly from year to 
 year. 
 
 Nonfatal disabling and fatal accidents 
 of all types numbered in the thousands 
 during the 1975-78 period, but certain 
 parameters were established by BCR to 
 limit the accidents included in the anal- 
 ysis to those potentially preventable 
 with overhead or side protective struc- 
 tures. These parameters were — 
 
24 
 
 1. Machine type - the study included 
 only those machines covered under the cab 
 and canopy regulations. 
 
 2. Degree of injury - only fatalities 
 and "lost-day" accidents were included. 
 
 3. Type of accident - only accidents 
 involving haulage operations , face ma- 
 chinery, or falls of roof, rib, or face 
 were included. 
 
 4. Mine worker activity - only such 
 activities as roof bolting-drilling, op- 
 erating shuttle car, operating continuous 
 miner, etc., where a cab or canopy could 
 have been helpful, were included. 
 
 5. Cost of accident - only those acci- 
 dents with costs of at least $1,000 were 
 included. Accidents costing less than 
 $1,000 represented 32 pet of the number 
 of accidents but only 0.5 pet of the to- 
 tal cost. 
 
 Review of the ACIM information resulted 
 in the selection of 616 accidents to be 
 included in the analysis. These were 
 grouped into 11 categories, based on the 
 
 need for tram decks, side protection, 
 overhead protection, and combinations of 
 these structures (table 5). Grouping the 
 accidents in this manner emphasized the 
 type of protective structure that would 
 prevent the most accidents. The 616 ac- 
 cidents were also grouped according to 
 seam height and equipment type, as shown 
 in table 6. 
 
 TABLE 5. - Classification of "cab or 
 canopy preventable" accidents 
 
 Class 
 
 Type of protection required 
 
 1 Tram deck only. 
 
 2. Side protection only. 
 
 3 Tram canopy only . 
 
 4 Tram deck and canopy. 
 
 5 Tram deck and side protection. 
 
 6 Tram deck, side protection, and 
 
 canopy, 
 
 7 Drill station deck only. 
 
 8 Drill station canopy only. 
 
 9 Drill station deck and canopy. 
 
 10 ATRS system only. 
 
 11 ATRS system and drill station 
 
 canopy. 
 
 TABLE 6. - "Cab or canopy preventable" injuries (1975-78), grouped 
 by equipment type, preventability classification, and seam height 
 
 Equipment type 
 
 Preventability classification 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 1 
 
 8 
 
 9 
 
 10 
 
 11 
 
 Total 
 
 
 SEAM HE 
 
 IGHT 
 
 <42 
 
 ! In 
 
 
 
 
 
 
 
 
 Continuous miners 
 
 Cutting machines 
 
 2 
 3 
 1 
 2 
 
 1 
 
 3 
 
 12 
 4 
 1 
 9 
 
 14 
 
 32 
 
 8 
 
 35 
 
 3 
 4 
 45 
 39 
 9 
 
 
 
 
 
 1 
 1 
 
 1 
 
 
 
 
 
 1 
 
 2 
 
 
 1 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 2 
 
 
 
 
 
 
 
 88 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 39 
 
 
 
 
 
 
 
 6 
 
 49 
 8 
 
 Face drills 
 
 5 
 
 Loading machines ......... 
 
 18 
 
 Tractors and/or scoops... 
 Shuttle cars ............. 
 
 61 
 73 
 
 Roof bolters 
 
 156 
 
 Total 
 
 12 
 
 80 
 
 135 
 
 3 
 
 4 
 
 1 
 
 2 
 
 88 
 
 
 
 39 
 
 6 
 
 370 
 
 S 
 
 EAM HEIG 
 
 HT 43 
 
 TO 
 
 48 
 
 in 
 
 
 
 
 
 
 
 Continuous miners 
 
 Cutting machines 
 
 
 
 
 1 
 
 
 2 
 
 10 
 1 
 
 1 
 3 
 5 
 24 
 3 
 
 16 
 1 
 2 
 5 
 17 
 43 
 7 
 
 
 
 
 
 
 1 
 
 
 
 2 
 
 
 1 
 
 1 
 
 1 
 
 1 
 
 
 1 
 
 
 1 
 
 
 
 
 
 
 
 
 
 76 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 15 
 
 
 
 
 
 
 
 5 
 
 27 
 4 
 
 Face drills .............. 
 
 3 
 
 Loading machines 
 
 11 
 
 Tractors and/or scoops... 
 Shuttle cars 
 
 22 
 70 
 
 Roof bolters 
 
 109 
 
 Total 
 
 3 
 
 47 
 
 91 
 
 1 
 
 5 
 
 3 
 
 76 
 
 
 
 
 
 15 
 
 5 
 
 246 
 
25 
 
 Since the cost benefit analysis covered 
 a 10-year period (1971-80), some method 
 had to be developed for estimating the 
 preventable accidents that occurred dur- 
 ing the years not included in the ACIM 
 data, i.e., 1971-74 and 1979-80. The de- 
 velopment of this information was based 
 on (1) the accident-injury reports in 
 the MSHA publications and (2) the assump- 
 tion that the percentage of preventable 
 injuries, grouped by seam height and type 
 of equipment involved, does not change 
 significantly from year to year. The 
 
 estimated number of preventable accidents 
 by year, seam height, and type of equip- 
 ment is summarized in tables 7 through 
 10. Tables 7 and 8 cover nonfatal dis- 
 abling injuries; tables 9 and 10 cover 
 fatalities. 
 
 The cost associated with the accidents 
 was handled in two ways. For 1975-78, 
 the costs calculated by the ACIM system 
 were available and were used as the "ben- 
 efit" for the analysis. For 1971-74 and 
 1979-80, the benefits were calculated 
 
 TABLE 7. - Number of preventable nonfatal injuries in 42-in and 
 lower seam heights, 1971-80 
 
 Equipment type 
 
 1971 
 
 1972 
 
 1973 
 
 1974 
 
 1975 
 
 1976 
 
 1977 
 
 1978 
 
 1979 
 
 1980 
 
 Total 
 
 Continuous miners. 
 
 10 
 
 12 
 
 9 
 
 7 
 
 8 
 
 12 
 
 13 
 
 13 
 
 16 
 
 17 
 
 117 
 
 Cutting machines.. 
 
 2 
 
 2 
 
 2 
 
 1 
 
 
 
 1 
 
 1 
 
 6 
 
 3 
 
 3 
 
 21 
 
 Face drills 
 
 2 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 2 
 
 2 
 
 2 
 
 14 
 
 Loading machines . . 
 
 3 
 
 4 
 
 3 
 
 3 
 
 4 
 
 6 
 
 5 
 
 
 
 5 
 
 5 
 
 38 
 
 Tractors and/or 
 
 
 
 
 
 
 
 
 
 
 
 
 s coops 
 
 10 
 16 
 
 11 
 17 
 
 9 
 16 
 
 7 
 11 
 
 9 
 
 17 
 
 9 
 18 
 
 14 
 19 
 
 12 
 17 
 
 15 
 25 
 
 15 
 25 
 
 111 
 
 Shuttle cars 
 
 181 
 
 Roof bolters 
 
 32 
 
 36 
 
 32 
 
 22 
 
 27 
 
 36 
 
 47 
 
 37 
 
 52 
 
 50 
 
 371 
 
 Total 
 
 75 
 
 83 
 
 72 
 
 52 
 
 66 
 
 83 
 
 100 
 
 87 
 
 118 
 
 117 
 
 853 
 
 TABLE 8. - Number of preventable nonfatal injuries in 43- to 48-in 
 seam heights, 1971-80 
 
 Equipment type 
 
 1971 
 
 1972 
 
 1973 
 
 1974 
 
 1975 
 
 1976 
 
 1977 
 
 1978 
 
 1979 
 
 1980 
 
 Total 
 
 Continuous miners. 
 
 5 
 
 7 
 
 6 
 
 4 
 
 7 
 
 6 
 
 8 
 
 6 
 
 9 
 
 10 
 
 68 
 
 Cutting machines.. 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 2 
 
 
 
 1 
 
 1 
 
 1 
 
 10 
 
 Face drills 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 8 
 
 Loading machines . . 
 
 3 
 
 3 
 
 2 
 
 1 
 
 7 
 
 2 
 
 
 
 1 
 
 4 
 
 3 
 
 26 
 
 Tractors and/or 
 
 
 
 
 
 
 
 
 
 
 
 
 s coops ........... 
 
 3 
 
 5 
 
 4 
 
 3 
 
 3 
 
 5 
 
 5 
 
 6 
 
 7 
 
 7 
 
 48 
 
 Shuttle cars 
 
 15 
 
 17 
 
 14 
 
 11 
 
 18 
 
 15 
 
 25 
 
 10 
 
 24 
 
 24 
 
 173 
 
 Roof bolters 
 
 23 
 
 25 
 
 23 
 
 16 
 
 35 
 
 25 
 
 29 
 
 17 
 
 37 
 
 36 
 
 266 
 
 Total 
 
 51 
 
 58 
 
 51 
 
 37 
 
 71 
 
 56 
 
 68 
 
 42 
 
 83 
 
 82 
 
 599 
 
 TABLE 9. - Number of preventable fatal injuries in 42-in and 
 lower seam heights, 1971-80 
 
 Equipment type 
 
 1971 
 
 1972 
 
 1973 
 
 1974 
 
 1975 
 
 1976 
 
 1977 
 
 1978 
 
 1979 
 
 1980 
 
 Total 
 
 Continuous miners. 
 Cutting machines.. 
 
 Face drills 
 
 Loading machines.. 
 Tractors and/or 
 scoops 
 
 2 
 
 
 
 
 8 
 
 1 
 3 
 
 1 
 
 
 1 
 
 6 
 
 3 
 
 1 
 
 
 
 1 
 
 5 
 
 3 
 
 
 
 
 1 
 
 4 
 
 1 
 2 
 
 
 
 
 1 
 
 5 
 
 1 
 3 
 
 1 
 
 
 1 
 
 4 
 1 
 3 
 
 
 
 
 
 
 2 
 
 
 
 2 
 
 
 
 1 
 
 6 
 
 3 
 
 1 
 
 
 1 
 
 5 
 
 1 
 3 
 
 1 
 
 
 
 
 5 
 
 2 
 
 9 
 
 
 
 7 
 
 50 
 
 Shuttle cars 
 
 Roof bolters 
 
 5 
 25 
 
 Total 
 
 14 
 
 11 
 
 10 
 
 8 
 
 10 
 
 10 
 
 2 
 
 12 
 
 11 
 
 8 
 
 96 
 
26 
 
 TABLE 10. - Number of preventable fatal injuries in 43- to 48-in 
 seam heights, 1971-80 
 
 Equipment type 
 
 1971 
 
 1972 
 
 1973 
 
 1974 
 
 1975 
 
 1976 
 
 1977 
 
 1978 
 
 1979 
 
 1980 
 
 Total 
 
 Continuous miners. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Cutting machines.. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Face drills 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Loading machines.. 
 
 1 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 1 
 
 3 
 
 Tractors and/or 
 
 
 
 
 
 
 
 
 
 
 
 
 scoops. .......... 
 
 
 
 1 
 
 1 
 
 1 
 
 
 
 1 
 
 1 
 
 1 
 
 1 
 
 
 
 7 
 
 Shuttle cars 
 
 
 
 2 
 
 
 
 1 
 
 
 
 1 
 
 1 
 
 
 
 
 
 1 
 
 6 
 
 Roof bolters 
 
 2 
 
 1 
 
 1 
 
 1 
 
 2 
 
 1 
 
 
 
 1 
 
 1 
 
 1 
 
 11 
 
 Total 
 
 3 
 
 4 
 
 2 
 
 3 
 
 2 
 
 4 
 
 2 
 
 2 
 
 2 
 
 3 
 
 27 
 
 TABLE 11. - Estimated benefits paid for injuries preventable 
 with cabs and canopies, 1971-80 
 
 Equipment type 
 
 Seam height 
 
 
 42 in and below 
 
 43 to 48 in 
 
 Total 
 
 Continuous miners 
 
 Cutting machines 
 
 Face drills 
 
 $5,760,969 
 
 234,944 
 
 147,000 
 
 4,677,948 
 
 28,376,958 
 
 6,653,080 
 
 15,624,840 
 
 $1,553,181 
 
 61,500 
 
 119,200 
 
 1,771,500 
 
 5,181,442 
 
 7,066,855 
 
 12,536,535 
 
 $7,314,150 
 296,444 
 266,200 
 
 Loading machines 
 
 Tractors and/or scoops. 
 Shuttle cars 
 
 6,449,448 
 33,558,400 
 13,719,935 
 
 Roof bolters 
 
 27,801,375 
 
 Total 
 
 61,115,739 
 
 28,290,213 
 
 89,405,952 
 
 using the average cost, by machine type, 
 for "fatal" and "nonfatal disability" 
 accidents during 1975-78. For 1971-80, 
 
 the estimated "benefits," by machine type 
 and seam height, are summarized in 
 table 11. 
 
 COST-BENEFIT RATIOS 
 
 The cost-benefit ratio is simply the 
 industry cost to install protective 
 structures divided by the "benefits" — 
 that is, the accident costs that could 
 have been averted by the use of these 
 structures. The calculations were made 
 for two periods — 1971-80 and 1975-78. 
 The calculated ratios, along with the, 
 corresponding cost and benefit values, 
 are summarized in tables 12 and 13. Two 
 analyses were conducted because — 
 
 1. The 4-year study more accurately 
 reflects the "benefit" factor since the 
 values come directly from the ACIM 
 program. 
 
 2. The 10-year study takes into ac- 
 count machine replacement experience, 
 and, therefore, more realistically 
 
 spreads the installation costs over the 
 machine life. The cost-benefit ratios of 
 the 10- and 4-year studies are very simi- 
 lar and show that the loading machine has 
 the most favorable cost-benefit ratio, 
 while the cutting machine has the least 
 favorable. This indicates that from the 
 standpoint of providing maximum personnel 
 protection per dollar spent on protective 
 structures, highest priority should be 
 given to further development of protec- 
 tive structures for loading machines. On 
 the other end of the scale, the cost of 
 protective structures per dollar of ben- 
 efit is so high for cutting machines 
 that continued development of current 
 technology would seem inappropriate 
 and alternate technology should be 
 considered. 
 
27 
 
 TABLE 12. - Cost-benefit ratios for installing cabs and canopies, 1971-80 
 
 Equipment type 
 
 Cost of installing 
 cabs and canopies 
 
 Accident benefits 
 paid 
 
 Cost-benefit 
 ratio 
 
 SEAM HEIGHT <42 in 
 
 Continuous miners ...•..•.••••••• 
 
 $3,679,517 
 
 1,831,122 
 
 823,768 
 
 1,622,960 
 
 24,647,391 
 4,955,788 
 
 13,742,280 
 
 $5,760,969 
 
 234,944 
 
 147,000 
 
 4,677,948 
 
 28,376,958 
 
 6,653,080 
 
 15,264,840 
 
 0.63 
 
 Cutting machines ....* •••••• 
 
 7.79 
 
 Face drills •«••«•••••••••••••••• 
 
 5.60 
 
 Loadinff machines ......•••••••••• 
 
 .34 
 
 Tractors and /or scoods. ...•••.•• 
 
 .86 
 
 Shuttle cars 
 
 .74 
 
 Roof holers 
 
 .90 
 
 Total or average 
 
 51,302,826 
 
 61,115,739 
 
 .83 
 
 SEAM HEIGHT 43 TO 48 in 
 
 
 Continuous miners .....•..•.•••.. 
 
 $1,306,928 
 
 578,095 
 
 340,378 
 
 582,200 
 
 6,111,855 
 
 3,242,904 
 
 5,187,866 
 
 $1,553,181 
 
 61,500 
 
 119,200 
 
 1,771,500 
 
 5,181,442 
 
 7,066,855 
 
 12,536,535 
 
 0.84 
 
 Cuttinff machines •.....•.••...... 
 
 9.40 
 
 Face drills ...*...........•..*.. 
 
 2.85 
 
 Loading machines ................ 
 
 .32 
 
 Tractors and/or scoops .......... 
 
 1.17 
 
 Shuttle cars 
 
 .45 
 
 Roof bolters 
 
 .41 
 
 Total or average 
 
 17,350,228 
 
 28,290,213 
 
 .61 
 
 TABLE 13. - Cost-benefit ratios of installing cabs and canopies, 1975-78 
 
 Equipment type 
 
 Cost of installing 
 cabs and canopies 
 
 Accident benefits 
 paid 
 
 Cost-benefit 
 ratio 
 
 
 SEAM HEIGHT <42 In 
 
 
 
 Continuous miners 
 
 $2,554,859 
 
 1,253,010 
 
 617,763 
 
 1,122,000 
 
 17,947,738 
 4,033,336 
 9,536,577 
 
 $1,982,900 
 89,500 
 52,500 
 1,999,100 
 9,706,000 
 2,645,800' 
 5,598,600 
 
 1.28 
 
 Cutting machines 
 
 14.00 
 
 Face drills 
 
 11.76 
 
 Loading machines 
 
 .56 
 
 Tractors and/or scoops 
 
 1.84 
 
 Shuttle cars 
 
 1.52 
 
 Roof holers 
 
 1.70 
 
 Total or average 
 
 37,065,286 
 
 22,074,400 
 
 1.67 
 
 SEAM HEIGHT 43 TO 48 in 
 
 
 Continuous miners ............... 
 
 $868,792 
 
 455,861 
 
 269,410 
 
 400,646 
 
 4,212,989 
 
 2,546,180 
 
 3,284,567 
 
 $616,700 
 
 24,600 
 
 44,700 
 
 599,100 
 
 2,207,700 
 
 2,429,700 
 
 4,636,500 
 
 1.40 
 
 Cutting machines 
 
 Face drills ..................... 
 
 18.53 
 6.02 
 
 Loading machines •.....••«....•.. 
 
 .66 
 
 Tractors and/or scoops .......... 
 
 1.90 
 
 Shuttle cars 
 
 1.04 
 
 Roof holers 
 
 .70 
 
 Total or average 
 
 12,038,448 
 
 10,559,000 
 
 1.13 
 
 ESTABLISHING RESEARCH PRIORITIES 
 
 The final decision on what technology 
 to pursue and which machine should 
 receive priority should not be based on 
 the cost-benefit ratio alone. Seven fac- 
 tors were identified as relevant to the 
 future direction of the Bureau's cab and 
 
 canopy research program (tables 14-15). 
 These seven factors varied in impor- 
 tance among different machine types; for 
 example, the loading machine had the 
 lowest cost-benefit ratio, so it would 
 be the preferred research target if the 
 
28 
 
 cost-benefit ratio were the only criter- 
 ion used to assign research priorities. 
 However, preventing a fatality or very 
 serious injury would also be a desirable 
 goal; since the tractors and/or scoops 
 were involved in more "canopy prevent- 
 able" fatalities and severe injuries than 
 any other machine type, they would be the 
 preferred target if the Bureau's main 
 goal were to prevent only these types of 
 accidents. Tractors and/or scoops would 
 also be the preferred target if the Bu- 
 reau's goal were to address the most pop- 
 ular low-coal machine; however, the roof 
 bolter would receive highest priority if 
 the machine population trend were consid- 
 ered most important. 
 
 Therefore, the seven different machine 
 types considered in this analysis were 
 ranked for each of the seven factors 
 that could influence Bureau research pri- 
 orities. Tables 16 and 17 show the re- 
 sults of this ranking procedure; for each 
 factor, the machine type demanding the 
 greatest amount of attention was ranked 
 number 1, and the type demanding least 
 attention was ranked number 7. Note that 
 tables 14 and 16 cover machines in seam 
 heights of 42 in or less; tables 15 and 
 
 17 show the rankings obtained for ma- 
 chines in 43- to 48-in seams. An overall 
 "average" ranking was then calculated for 
 each equipment type, with the low numbers 
 again corresponding to the machine de- 
 serving the highest priority. 
 
 In addition, each factor was ranked ac- 
 cording to its importance in the overall 
 analysis (bottom row of tables 16 and 
 17). The ranking of the factors was not 
 included in the calculation of the over- 
 all average but could be used to estab- 
 lish priority for two or more machines 
 with the same or very similar ranking. 
 For example, in 42-in and lower seams, 
 the "average ranking" criterion would 
 give continuous miners, tractors and/or 
 scoops, and bolting machines equal prior- 
 ity. However, considering only the top- 
 ranked factor, preventable fatal injury 
 population, tractors and/or scoops would 
 be the top-priority machines. The analy- 
 sis for 43- to 48-in seams identified the 
 roof bolter as the top-priority machine 
 according to the "average ranking" cri- 
 terion; again, tractors and/or scoops 
 ranked first in terms of preventable fa- 
 tal injuries. 
 
 CONCLUSIONS AND RECOMMENDATIONS 
 
 The final decision to continue or dis- 
 continue cab and canopy development for 
 any face-equipment type will depend on 
 (1) the cost-benefit ratios considered 
 to be the lower and upper limits for 
 justifying the expenditures required 
 to continue cab and canopy development 
 and (2) the ranking given the seven pa- 
 rameters used to prioritize, by equip- 
 ment type, the need for development of 
 operator-protection technology. Since 
 decisions on these two items may depend 
 on factors not considered in this 
 analysis, only the following general 
 recommedations for the continued develop- 
 ment of cab and canopy technology can be 
 made: 
 
 1. There is an immediate need to de- 
 velop some type of operator-protection 
 
 technology, particularly for continuous 
 miners, tractors and/or scoops, and roof 
 bolters in seam heights of 48 in and 
 lower. 
 
 2. In seams 42 in and lower, the high- 
 er cost-benefit ratio values generally 
 indicate that future cab and canopy de- 
 velopment is marginally justified. In 
 view of past experience with attempts to 
 use canopies in these seam heights, BCR 
 recommends consideration of alternate 
 technologies. 
 
 3. For 43- to 48-in coal seams, where 
 canopies have been used successfully, the 
 cost-benefit ratio values indicate that 
 further development of canopy technology 
 is warranted. 
 
29 
 
 
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31 
 
 CANOPY PROTECTION FOR OPERATORS OF CONTINUOUS HAULAGE SYSTEMS 
 
 IN LOW-SEAM-HEIGHT COAL 
 
 By R, J. Gunderman^ and A, J. Kwitowski2 
 
 ABSTRACT 
 
 Placing an operator of a mobile contin- 
 uous haulage conveying system under a 
 protective canopy was investigated using 
 the latest technology for both canopies 
 and floating compartments. Investiga- 
 tions first considered how to position 
 the operator in the low compartments and 
 included unobtrusive observation of human 
 subjects repositioning themselves when 
 confined to the compartment. Locations 
 for such a compartment on the crawler- 
 mounted machine were considered using 
 both small-scale and full-scale mockups. 
 
 A floating operator compartment was de- 
 signed in conjunction with the new design 
 
 for an improved machine. Evaluation of 
 the compartment for human factors was 
 made at the manufacturer's facility prior 
 to installing the machine in an under- 
 ground coal mine. Subjects representing 
 the male 5th, 50th, and 95th percentile 
 sizes were used along with photographic 
 techniques for recording data. 
 
 Operation of the new machine with oper- 
 ator compartment in a coal mine with seam 
 heights typically between 40 and 46 in 
 was monitored for 10 months. The practi- 
 cal feasibility of this operator protec- 
 tion was adequately demonstrated for coal 
 seams as low as 40 in. 
 
 INTRODUCTION 
 
 This program was one of several ini- 
 tiated by the Bureau of Mines to investi- 
 gate the applicability of canopies and 
 cabs to coal mining machines operating in 
 seam heights below 48 in. A study con- 
 tract was awarded to the Jeffrey Mining 
 Machinery Division, Dresser Industries, 
 Inc. , to investigate the feasibility of 
 placing the operator of a model 506C-5 
 double-bridge carrier, shown in figure 1, 
 under a protective canopy. This crawler- 
 mounted carrier supports a bridge con- 
 veyor on the inby end (seen to the left 
 of the operator) , which is linked to 
 the discharge boom of the continuous min- 
 ing machine. A similar bridge conveyor 
 links between the carrier and the pan 
 line. If there are more than three en- 
 tries, a second bridge carrier and an 
 additional bridge conveyor may be added 
 to lengthen the reach. The operator of 
 
 ^Consultant; formerly project manager, 
 Jeffrey Mining Machinery Division, 
 Dresser Industries, Inc., Columbus, OH. 
 
 ^civil engineer, Pittsburgh Research 
 Center, Bureau of Mines, Pittsburgh, PA. 
 
 the double-bridge carrier maneuvers the 
 machine to follow movements of the mining 
 machine and controls operation of the 
 conveyor. This machine is used in seam 
 heights as low as 28 in. 
 
 The inby bridge conveyor is supported 
 on a carriage or dolly that rides on the 
 receiving conveyor of the double-bridge 
 carrier. This carriage, which is free 
 to move approximately 6 1/2 ft, provides 
 flexibility for small movements of the 
 continuous miner. The operator of the 
 double-bridge carrier must move the car- 
 rier to assure that the carriage is ade- 
 quately positioned to allow movement of 
 the continuous miner in either direction. 
 
 Using technology and ideas applied in 
 previous Bureau of Mines contracts as 
 well as concepts developed by manufac- 
 turers and coal companies, the feasibil- 
 ity of a protective operator compartment 
 was investigated. As shown in figure 1, 
 the controls on the 506C-5 are on the 
 side (or fender) , and the operator usual- 
 ly squats or kneels next to the machine. 
 
32 
 
 FIGURE 1. = Operator at controls of 506C=5 double-bridge carrier. 
 
 This gives the operator good visibility 
 and mobility. However, this position is 
 vulnerable in the event of a roof fall or 
 if the bridge carrier is inadvertently 
 
 pushed by the mining machine, which could 
 possibly pinch the operator against a 
 rib. 
 
 ACKNOWLEDGMENT 
 
 The work described in this paper was 
 performed under Bureau of Mines contract 
 H03870273 to the Jeffrey Mining Machinery 
 Division, Dresser Industries, Inc., Co- 
 lumbus, OH. The in-mine evaluation was 
 
 performed under a cooperative agree- 
 ment between the Solar Fuel Co., Somer- 
 set, PA and the Jeffrey Mining Machinery 
 Division. 
 
 PRELIMINARY DESIGN 
 
 All possible operating positions for 
 the human body were considered because 
 of the severe space restrictions in low 
 seams. Studies were conducted on six 
 subjects to evaluate each one's response 
 to postures within the confines of a 
 compartment 30 in high, 24 in wide, and 
 
 ^Gunderrnan, R. J. Canopy Technology 
 for Low Seam Continuous Haulage. Final 
 Report USBM Contract No. H0387027, Feb. 
 1980, 72 pp.; for inf., contact A. J. 
 Kwitowski, TPO, Pittsburgh Research Cen- 
 ter, BuMines, Pittsburgh, PA. 
 
 70 in long. A video camera recorded 
 their positions and movements on tape for 
 later analysis. Each subject was told 
 to position himself in the compartment 
 and to go through simulated functions 
 of operating controls and observing both 
 inby and outby operation for periods of 
 1 h. These subjects tried lying down, 
 squatting, sitting cross legged, sit- 
 ting in a very reclined position, etc. , 
 and needed frequent postural relief. 
 The consensus favored the reclined seat 
 position. 
 
33 
 
 Required dimensions for an operator 
 compartment were thus determined to be 
 approximately 5-1/2 ft long and at least 
 2 ft wide in the shoulder area, A de- 
 tailed consideration of the 506C-5 bridge 
 carrier showed that there was no possi- 
 bility of locating such an operator com- 
 partment on that machine. However, Jef- 
 frey was starting design of a new bridge 
 carrier with increased haulage capacity 
 and greater tram speed. Effort was then 
 directed at locating an operator compart- 
 ment on the new machine so that the re- 
 sulting design would allow adding the 
 compartment, if desired. Fender-mounted 
 controls would be retained in the stan- 
 dard design because of mine operator 
 preference, especially in seam heights 
 less than 36 in. 
 
 Many potential locations for the com- 
 partment on the machine were examined 
 using a small-scale model. Because of 
 the requirement for frequent ingress and 
 egress, along with maintaining a proper- 
 ly located machine center of gravity. 
 
 the side-rear compartment position was 
 preferred. 
 
 A full-scale mockup was constructed 
 from cardboard and wood (fig, 2), Only 
 significant portions of the bridge car- 
 rier were Included in the mockup since 
 it was used primarily to determine opera- 
 tor fit, functional movement, and visi- 
 bility. The canopy on the mockup and 
 the items inside the operator compartment 
 were moved until satisfactory locations 
 were established empirically. Figure 3 
 shows a 50th percentile operator in the 
 mockup. 
 
 Results from the mockup evaluation 
 showed feasibility with canopy heights 
 adjustable between 30 to 42 in above the 
 floor. Depending upon seam conditions 
 and undulations , a bridge carrier of this 
 type could operate in seams from 48 to 36 
 in high. Jeffrey agreed to constrain the 
 design of the new machine to allow for 
 this compartment as an option. 
 
 OPERATOR COMPARTMENT DESIGN 
 
 Considerable effort went into the de- 
 sign of the operator compartment and at- 
 tachment to the bridge carrier. Also, 
 the controls of the new bridge carrier 
 were relocated to the right side of the 
 machine instead of the left side because 
 the operator of the continuous mining ma- 
 chine is on the right side. The result- 
 ing design is shown in figure 4. 
 
 The newly designed machine is 9 in 
 wider and almost 4 ft longer than the 
 506C-5 in order to accommodate the com- 
 partment and the fact that the outby 
 conveyor must swing as much as ±90°. 
 This also required longer crawler 
 tracks. Therefore, the compartment has 
 to float on the floor in order not to im- 
 pede mobility. 
 
 The operator compartment is attached to 
 the main frame by two pivots with hori- 
 zontal axes. Figure 5 is a closeup of 
 this attachment taken during tests for 
 mobility. The compartment side of the 
 
 pivots consists of steel collars that 
 slide vertically on the two front canopy 
 support posts. This slide travel is lim- 
 ited to 8 in by the support members at 
 the bottom and fixed collars on top. 
 Angular movement of the compartment is 
 limited with respect to the discharge 
 conveyor in the upward direction by a 
 stop on the conveyor and in the downward 
 direction by a link chain. 
 
 Selection of an operator seat was lim- 
 ited by the practical factor of avail- 
 bility. In this case a seat was selected 
 that has a seat unit separate from the 
 back rest. A new adjustable seat mount 
 was designed using data from the func- 
 tional mockup evaluation. A single lever 
 on the seat back retracts dual pins that 
 engage in holes in the seat mount. This 
 provides positions reclining from the 
 vertical of 25°, 34°, 43°, 51°, or 60°. 
 A similar arrangement allows separate 
 adjustment of the seat cushion to angles 
 from the horizontal of 10°, 20°, or 
 
34 
 
 FIGURE 2. = Looking down on the mockup from the receiving end. 
 
35 
 
 FIGURE 3o - Operator seated in the mockup. 
 
 FIGURE 4. - Completed operator compartment on new machine. 
 
36 
 
 FIGURE 5. - Attachment of compartment to mainframe. 
 
 30°. The adjustment holes are Indicated 
 by arrows in figure 6. The mount with 
 the seat slides forvard and back on the 
 track bar shown in figure 7. A clevis 
 pin through holes in the seat mount al- 
 lows nine fore and aft position selec- 
 tions in 1-in increments. 
 
 Arm rests that tilt back for ingress 
 and egress were provided. However, the 
 left arm rest was deleted when it was 
 
 found to interfere with both arm movement 
 and other items in the compartment. 
 
 As noted in figure 1, the operator 
 kneeling and facing the machine only has 
 to turn 90° to see either inby or outby 
 operation. Unfortunately, there is not 
 enough room in the entries to place a 
 compartment so that the operator faces 
 the machine the same as with the 506C-6. 
 The compromise in the new design is to 
 
37 
 
 FIGURE 6. - Seat adjustment. 
 
 FIGURE 7. = Seat fore-aft adjustment track. 
 
38 
 
 place the operator at a small angle (19°) 
 with respect to the longitudinal axis of 
 the machine. This angle helps consider- 
 ably when turning the head to see the 
 outby transfer point. Most operators, 
 sitting in the reclining position, roll 
 the body slightly off the seat when turn- 
 ing to see outby. 
 
 Four posts are used to support the can- 
 opy because of the size and loads. The 
 posts telescope, and each is adjustable 
 with a pin for canopy heights from 30 to 
 42.5 in in 2.5-in steps. During the com- 
 partment design phase, the Solar Fuel Co. 
 became interested in this program and 
 agreed to an in-mine evaluation of the 
 machine at its mine No. 9. Because the 
 seam heights there have considerable var- 
 iation, as well as undulations, they de- 
 sired a method to change canopy height 
 without the need for extra equipment, 
 such as a jack. Two hydraulic lift cyl- 
 inders were added, one at the left rear 
 as shown in figure 8 and the other at the 
 opposite corner. A small pump with oil 
 
 FIGURE 8. - Operating the canopy adjusting pump 
 and flow valve. 
 
 reservoir and a reversing valve comprise 
 the rest of the canopy raise system. The 
 pump is operated by stroking the handle, 
 and the flow direction is set by the 
 valve. The first step in adjusting the 
 canopy height is to pump up the circuit 
 to lift the weight of the canopy off the 
 four pins so that they may be removed. 
 The four adjustment pins must all be re- 
 placed for the desired height setting be- 
 fore the operator enters the compartment. 
 Figure 9 shows, left to right, the sup- 
 port post, raise cylinder, flow direction 
 valve, and hydraulic pump. 
 
 Both the electrical and hydraulic con- 
 trols are located to the left of the 
 operator so as not to impede ingress and 
 egress. Figure 10 is a side view of the 
 operator compartment taken during the in- 
 mine evaluation. Note that the arm rest 
 is tilted back. The handhold on the com- 
 partment floor adjacent to the seat aids 
 the operator during ingress and egress. 
 
 Operator visibility in order to safely 
 and comfortably accomplish all functions 
 was a major concern. This was investi- 
 gated using the full-scale mockup shown 
 in figure 2. Markers indicating the 
 height above the floor were placed at 
 four locations — the inby end of the 
 bridge conveyor loading boom, the inby 
 ends of both the right and left crawlers, 
 and the outby end of the conveyor dis- 
 charge boom. Data were collected for 
 each size operator in the mockup with 
 canopy heights of 30, 32, 34, and 36 in, 
 and at each key direction from his eye 
 location. Higher canopy settings were 
 considered to be no problem, so data were 
 not collected for these. Visibility at 
 the loading boom, discharge boom, and 
 near-side (left) crawler positions for 
 the minimum canopy height was 17, 25, and 
 25 in respectively. The minimum visible 
 height across from the operator and in 
 front of the right crawler ranged from 24 
 to 35 in. As the canopy was raised, so 
 also was the operator's head, which gave 
 a lower minimum visible height. 
 
39 
 
 FIGURE 9. = Canopy adjusting system. 
 
 FIGURE 10. - Side view of operator compartment. 
 
40 
 
 Variations in the highest visible 
 height were relatively small. These var- 
 iations were dependent upon how the oper- 
 ator positioned the seat, both in angle 
 
 and in fore-aft direction. The highest 
 visible measurements ranged from 38 to 50 
 in at the four aforementioned positions. 
 
 EVALUATION PRIOR TO SHIPMENT 
 
 These visibility measurements were 
 repeated for the actual machine before 
 shipment to the mine. As shown in figure 
 11, the operator compartment was located 
 on the right rather than the left side 
 (fig, 2) of the machine. A camera was 
 positioned at the operator eye location, 
 and pictures were taken of the visibility 
 of the inby loading boom position. With 
 the canopy set at 30 in above the floor 
 (fig, 12), the limits of visibility were 
 34 to 47 in. When the canopy was raised 
 to 35 in (fig, 13) , the visibility range 
 was 23 to 56 in; at a canopy height of 40 
 in (fig, 14) , the visibility range was 22 
 to 75 in. 
 
 When the operator looks back at the 
 bridge carrier outby transfer point, the 
 angles are limited. However, the opera- 
 tor does not have to see over a large 
 vertical angle, as long as the coal flow- 
 ing across the transfer point is within 
 the visible angle. In figure 15 the lim- 
 its are 14 to 34 in with the canopy at 30 
 in. In this case the discharge end boom 
 was lowered to the floor. The boom can 
 
 be raised 7° or lowered 6° with respect 
 to the mainframe, but if the seam height 
 requires the canopy at 30 in, it is not 
 likely that the boom would be raised more 
 than 12 in from the conditions shown in 
 figure 15, 
 
 Another visibility consideration is to- 
 ward the general outby direction when 
 tramming the system outby. In this case, 
 the operator will usually turn in the 
 opposite direction, as when observing the 
 outby conveyor transfer. There is very 
 little visibility obscuration in that di- 
 rection. However, as shown in figure 16, 
 the operator has to strain somewhat even 
 with the canopy at 35 in. 
 
 In general, the visibility is reason- 
 able at most canopy heights, except for 
 30 in. If the operator size is not much 
 over the 50th percentile rank and the 
 mine conditions are good, then operation 
 with the canopy at 30 in should be possi- 
 ble. Table 1 summarizes the visibility 
 data collected with subjects in the ma- 
 chine before shipment to the mine. 
 
 FIGURE 11. - New machine ready for human 
 factors evaluation. 
 
 FIGURE 12. 
 opy height. 
 
 Looking forward under 30=in can- 
 
41 
 
 FIGURE 13. - Looking forward under 35-in can- FIGURE 14. - Looking forward under 40-in can- 
 
 opy height. opy height. 
 
 FIGURE 15. = Looking at outby transfer point 
 under 30-in canopy height. 
 
 FIGURE 16. - Operator under 35=in canopy 
 tramming outby. 
 
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 Canopy heights at 35 in or more appear 
 reasonable on this particular mobile 
 bridge carrier. The effective window is 
 large enough for good visibility angles. 
 A perspective on this window may be ob- 
 tained from figure 17, which is a photo- 
 graph looking at the 5th percentile oper- 
 ator in the compartment with the canopy 
 set at 35 in. 
 
 A large operator finds the compartment 
 a tight fit, as shown in figure 18. This 
 
 subject's favorite position for his legs 
 was crossed and on the floor. In this 
 scene, the canopy height is 40 in and the 
 backrest angle is 34° from the vertical. 
 Another view of this operator position is 
 shown in figure 19. Note that he uses 
 the headrest to support his shoulders 
 rather than his head. 
 
 Control operation is primarily with the 
 left hand. As shown in figure 20, there 
 are four levers located in a console on 
 
 FIGURE 17. - Looking at operator under 35-in can- 
 opy from inby end of loading boom. 
 
 FIGURE 18.= Large=s ize operator with legs crossed. 
 
 FIGURE 19. - Large^size operator supporting 
 shoulders with headrest. 
 
 FIGURE 20. - Closeup of controls in compartment. 
 
44 
 
 the floor of the compartment to the left 
 of the operator. These levers work hy- 
 draulic levers on the mainframe in front 
 of the operator through cables. The two 
 upper levers are for the left and right 
 tram. Pushing them forward moves the ma- 
 chine inby, and pushing them rearward re- 
 verses the tram. 
 
 There are two lower controls on this 
 console that work the receiving and 
 the discharge conveyor booms. The left 
 control raises the discharge conveyor 
 when it is pushed up and lowers it when 
 pushed down. The receiving conveyor 
 
 works similarly with the right control 
 lever. 
 
 The electrical controls, also shown in 
 figure 20, are all located within the en- 
 closure mounted high on the left wall of 
 the operator compartment. This was an 
 existing control box used on another ma- 
 chine which had already been approved by 
 MSHA. The fire extinguisher is located 
 below the electrical control case, and 
 the actuator knob is visible just above 
 the backrest. Note that the panic bar 
 must be operated either with the left 
 shoulder or a hand. 
 
 IN-MINE EVALUATION 
 
 The in-mlne evaluation was conducted 
 through the cooperation of the Solar Fuel 
 Co. at its mine No. 9 near Somerset, PA. 
 Seam height at this mine generally ranges 
 from 40 to 46 in but frequently pinches 
 down much lower. Entries and crosscuts 
 are 20 ft wide. Moisture, roof, and 
 floor conditions were fair. 
 
 The new bridge carrier (Jeffrey model 
 5010) with operator compartment was sub- 
 stituted on an operating section for a 
 Jeffrey model 506C-5 bridge carrier. The 
 new machine was installed early in Octo- 
 ber 1981, and the evaluation was planned 
 to last 3 months. This time was extended 
 for various reasons, including unrelated 
 interruptions to the mining operation. 
 The bridge carrier with operator compart- 
 ment was removed from the mine in October 
 1982 and was delivered to the Bureau's 
 Pittsburgh Research Center. 
 
 In the section area, the mine operator 
 first tried the 35-in canopy setting 
 but settled on 37.5 in soon afterwards. 
 As can be seen in figure 21, there was 
 little clearance between the canopy and 
 the roof when the height was set at 37.5 
 in. During the in-mine operation, the 
 compartment floated well on the floor 
 through the action of the slides and piv- 
 ots. As a result, the canopy-to-roof 
 clearance could be nominally as low as 6 
 in. 
 
 Visibility for the operator was fairly 
 good with the canopy at 37.5 in. A pro- 
 tective metal mesh, angled inward, was 
 added to the top of the compartment wall 
 to assure that the operator did not reach 
 beyond that wall and become pinched by 
 the relative movements between the com- 
 partment and the discharge conveyor. 
 This mesh did not significantly block 
 visibility toward the opposite side of 
 the machine. 
 
 As stated earlier, the discharge con- 
 veyor may be raised several inches. Fig- 
 ure 22 is a view from the left front of 
 the machine with the conveyor raised to 
 the roof. While this conveyor would ob- 
 scure vision directly across the machine, 
 it does not otherwise affect operation. 
 The conveyor would normally be lower when 
 tramming the machine, and the operator 
 would be able to see through the mesh and 
 across the machine. 
 
 Four different operators of the double- 
 bridge carrier were observed during 
 the in-mine evaluation. One male opera- 
 tor was in the 50th percentile size 
 range, and two other males were somewhat 
 smaller. The other operator was female 
 and was slightly larger than a 50th per- 
 centile female. 
 
 Operator indoctrination occurred quick- 
 ly, although it took the operators some 
 
45 
 
 FIGURE 21. - Clearance under roof with canopy at 37.5 in. 
 
 time to get over the restless reaction 
 that resulted from confinement within the 
 compartment. Inability to directly see 
 the inby conveyor carriage was the big- 
 gest problem. The movement between stops 
 on the new machine is only 5 ft, which 
 means that the operator must be even more 
 skillful in moving the bridge carrier to 
 avoid banging the carriage against the 
 stops as a result of continuous miner 
 movement. The operator seated in the 
 conqjartment can only see the top of this 
 carriage. 
 
 Each operator had different preferences 
 on positions within the compartment. Re- 
 positioning was frequent in order to re- 
 tain reasonable comfort. There was a 
 tendency toward operator inattention 
 since the workload within the compartment 
 was small. Operator personnel were en- 
 couraged to get out of the compartment 
 frequently when not running coal and to 
 do spillage cleanup, machine inspection, 
 etc, , in order to overcome boredom. 
 
 The attitude of the operators varied as 
 they became more familiar with the new 
 compartment. At first, they did not like 
 the concept and were very uneasy because 
 they could not move around as they did 
 before and because visibility was now re- 
 stricted. After familiarization for a 
 few weeks, the operators expressed satis- 
 faction with the compartment. However, 
 the satisfaction did not last long as 
 boredom set in and their personal per- 
 formance tended to deteriorate. The 
 operator workload was subsequently ad- 
 justed by having the operators leave the 
 compartment when not running coal and 
 perform duties including spillage cleanup 
 and machine lubrication. Ultimately, the 
 operators accepted the operator compart- 
 ment as a compromise from the older ma- 
 chine with fender-mounted controls. 
 
 Difficult mining conditions, due to 
 incursions of stone into the coal seam, 
 precluded a good measure of the ef- 
 fect that the addition of an operator 
 
46 
 
 FIGURE 22o - Looking at compartment from left side with conveyor raised. 
 
 compartment on the double-bridge carrier data collected that the production rate 
 had on coal production. It appears from is unchanged, 
 
 CONCLUSIONS 
 
 The program objective of investigating 
 the feasibility of providing operator operating position, 
 protection on crawler-mounted continuous 
 haulage systems was achieved. These 
 findings are summarized as follows: 
 
 6. A reclining seat provides the best 
 
 7, Operator repositioning within the 
 compartment occurs frequently. 
 
 1, Adding operator protection requires 
 considerable compromise. 
 
 8, The operators always set the can- 
 opy to the highest tolerable setting. 
 
 2. An operator compartment is reason- 
 able for seam heights as low as 40 in, 
 
 3. Operation in seam heights as low as 
 36 in is questionable and should be eval- 
 uated in-mine, 
 
 4. Adding an operator compartment re- 
 quired redesign of the machine, 
 
 5. The floating concept using slides 
 and pivots works well. 
 
 9, Line of sight to the continuous 
 mining machine operator is more frequent- 
 ly obscured, 
 
 10, Operators react mostly on the ba- 
 sis of familiarity with running condi- 
 tions and seldom use signals, 
 
 11, Noted shortcomings with the com- 
 partment include — 
 
47 
 
 Inattention due to minimal 
 activity. 
 
 Limited visibility requires ex- 
 tra care when tramming. 
 
 It is recommended that the double- 
 bridge carrier with operator compartment 
 be further evaluated under in-mine condi- 
 tions where the mining height is typical- 
 ly 36 in. 
 
 Large operators are not practi- 
 cal at lowest canopy setting. 
 
48 
 
 ESD LOW-COAL CANOPY TECHNOLOGY 
 By Jack Mantel^ 
 
 INTRODUCTION 
 
 This paper highlights the work per- 
 formed by ESD Corp. under Bureau of Mines 
 contract H0387026, Development and As- 
 sessment of New and Existing Canopy Tech- 
 nology to Lower Coal Seams . 
 
 While cab and canopy technology is well 
 established for coal mines with working 
 heights of over 48 in, technological ad- 
 vances are needed for use of cabs and 
 canopies in lower working heights. Ac- 
 cording to the February 1975 issue of 
 Coal Mining and Processing, many mining 
 fatalities caused by rib and roof fail- 
 ures could be avoided through use of cabs 
 and canopies. Figure 1 shows the effect 
 on reported fatalities of the 1969 Fed- 
 eral Mine Health and Safety Act, which 
 required substantially constructed cabs 
 and canopies on all self-propelled elec- 
 tric face equipment in underground coal 
 
 ^ ESD Corp., San Jose, CA. 
 
 mines. 2 These statistics emphasize the 
 importance of improving upon the state of 
 the art in low-coal canopy technology. 
 
 Four of the programs conducted by ESD 
 for the Bureau of Mines included develop- 
 ment of cabs or canopies: 
 
 o Inherently Safe Mining Systems. 
 
 o Development of a Dual-Boom, Semiau- 
 tomated Roof Bolter. 
 
 o Fabrication and Evaluation of Opti- 
 mized Operator Compartments. 
 
 o Development and Assessment of New 
 and Existing Technology to Lower Coal 
 Seams . 
 
 ^Coal Mining and Processing, February 
 1975. 
 
 20 
 
 -i en 
 
 100 
 
 < UJ 
 
 
 8t 
 
 80 
 
 IJ_ -J 
 
 
 o< 
 
 60 
 
 q: 5 
 
 
 Lu u: 
 
 
 ^ UJ 
 
 40 
 
 Z) — 
 
 20 
 
 
 
 /%^ V 
 
 '%<9 '%5 
 
 /Sx. fS^^ <9> 
 
 
 
 / 
 
 FIGURE 1. - Coal mine fatalities, 1966-74. 
 
49 
 
 The objective of our current program 
 was to develop two transverse-mounted 
 canopies, one to be used on an FMC 6L 
 shuttle car, and one to be used on a Joy 
 14BU10-11A loader. As shown in figure 2, 
 an operator sitting in a transverse- 
 mounted canopy faces in a direction 90° 
 to the direction of travel. The shuttle 
 
 car canopy (fig. 3) was to be used in 
 working heights of 42 to 48 in, and the 
 loader canopy (fig. 4) was to be used in 
 working heights as low as 42 in. This 
 paper emphasizes work performed on the 
 shuttle car canopy, because evaluations 
 have been conducted of its performance in 
 an underground mine. 
 
 CONCEPT DEVELOPMENT 
 
 ESD's initial program work was an in- 
 vestigation of the state of the art in 
 canopy technology to establish design 
 needs. On the basis of this investiga- 
 tion, concept drawings were prepared, and 
 various concepts for shuttle car and 
 
 loader canopies were compared and evalu- 
 ated by BCR, the Bureau of Mines, MSHA, 
 and mining equipment manufacturers. 
 Wooden mockups were made of the selected 
 shuttle car and loader canopy concepts: 
 
 FIGURE 2. - Mockup of transverse-mounted canopy for shuttle car. 
 
50 
 
 FIGURE 3. - Transverse shuttle car canopy layout. 
 
 o A transverse-mounted, floor-riding 
 canopy for an FMC 6L shuttle car. 
 
 o A transverse-mounted canopy 
 Joy 14BU10-11A loading machine. 
 
 for 
 
 Mockups of seats and other equipment 
 were installed in these canopies. Three 
 seating configurations were considered. 
 The first configuration, with the opera- 
 tor seated in a cross-legged position, 
 was considered uncomfortable. The sec- 
 ond configuration, which offered a seat 
 which swivelled 35° from side to side, 
 was not considered compatible with the 
 transverse-mounting concept. The third 
 configuration, which had a sling seat 
 which pivoted slightly either forward or 
 backward for adjustment and seated the 
 operator with his legs slightly bent and 
 his feet and lower legs in a tunnel ex- 
 tending below the car body, was consid- 
 ered the most comfortable and responsive 
 to transverse canopy requirements. 
 
 The mockups were evaluated on the basis 
 of the following criteria: 
 
 o Suitability for operators ranging 
 from a 5th percentile female to a 95th 
 percentile male. 
 
 o Maximum inside dimensions. 
 
 o Reach envelopes for 
 placement. 
 
 control 
 
 o Seat design, 
 
 o Vision. 
 
 o Ease of ingress and egress. 
 
 o Operator comfort. 
 
 Recommendations resulting from this 
 evaluation were incorporated into the 
 canopy design. 
 
51 
 
 FIGURE 4. - Transverse loader canopy layout. 
 SHUTTLE CAR CANOPY DESIGN 
 
 ESD's shuttle car canopy, shown in fig- 
 ure 5 on FMC 6L shuttle car, has the fol- 
 lowing design features: 
 
 Transverse Mounting . — Seating the op- 
 erator in a position facing at 90° to the 
 direction of shuttle car travel elimi- 
 nates the need for the operator to change 
 seats when changing from inby to outby 
 tram and thus leave the protective can- 
 opy. Also, the canopy provides better 
 protection from rib bursts or ribbing 
 than conventional canopies. 
 
 Floor Riding . — Allowing the canopy to 
 ride on the mine floor reduces the hazard 
 of roofing associated with end mounted 
 canopies. The canopy bottom is flat and 
 curved upward on all four edges , giving 
 it a sled contour to facilitate moving 
 over the mine floor. This sled contour 
 also keeps material on the mine floor 
 from entering the canopy. 
 
 Canopy float (floor-riding capability) 
 has been provided by the addition of 
 
 vertically mounted channels on the inby 
 and outby sides of the canopy, which 
 interface with guide roller assemblies 
 mounted to the car body sides. Two guide 
 roller brackets interface with each chan- 
 nel to guide the canopy as it rides up 
 and down over the floor. 
 
 Pivoting Operator Seat . — The operator's 
 seat is composed of heavy canvas fabric 
 18 in wide and supported by a pivoting 
 strong back. The fabric forms a sling 
 which is adjusted by pivoting the strong 
 back forward, positioning the operator up 
 and forward, or pivoting it backward, po- 
 sitioning the operator down and back. 
 The operator sits with his legs slightly 
 bent and with his feet and approximately 
 8 to 10 in of his lower leg in the tunnel 
 area (fig. 3). This tunnel extends below 
 the car body and conveyor boom and houses 
 the brake master cylinder and operating 
 pedal and the tram switch and foot actu- 
 ation pedal. The operator's left foot 
 actuates the brake pedal, and the tram 
 switch is actuated by a pedal that pivots 
 
52 
 
 FIGURE 5. - Transverse operator compartment on FMC 6L shuttle car. 
 
 about a vertical centerline. The shuttle 
 car moves in the direction of tram pedal 
 rotation. 
 
 Easily Reached Controls . — All controls 
 are within easy reach of the operator 
 while in his normal sitting position. 
 
 Improved Operator Vision . — Because of 
 the transverse mounting of the canopy, 
 the operator can see both inby and outby 
 without leaving the canopy and changing 
 seats. He also has roof-to-floor vision 
 without extending his head outside the 
 canopy. 
 
 SHUTTLE CAR REWORK 
 
 To provide room for the canopy tunnel 
 and its upward movement, the following 
 car body rework was performed: 
 
 1. The car body was notched to provide 
 clearance for the canopy tunnel and its 
 upward movement. 
 
 2. An extension was added to the outby 
 side of the outby fender to keep mud from 
 being thrown into the cab by the wheel. 
 
 3. Doubler plates were added to com- 
 pensate for loss of car body strength due 
 to notching. 
 
 Rework was performed on the conveyor 
 boom as follows: 
 
 2. The conveyor side plate bottom edge 
 was cut out on the canopy mount side to 
 accommodate the canopy tunnel and its up- 
 ward movement. 
 
 3. The space for the conveyor flight 
 return support was reduced by raising the 
 conveyor return guiding side plates. 
 
 4. Cable troughs were mounted to the 
 side surfaces of the conveyor vertical 
 plate. These channels doubled as guides 
 for the conveyor flights and were added 
 to clean coal from a valley that was cre- 
 ated in the conveyor top plate when it 
 was raised. 
 
 1. The top plate of the conveyor was 
 raised approximately 3 in over that used 
 in the standard FMC 6L design. 
 
53 
 
 UNDERGROUND EVALUATION OF THE SHUTTLE CAR CANOPY 
 
 An evaluation of the shuttle car canopy 
 was successfully performed at a Virginia 
 Crews Coal Co. (VCCC) mine. VCCC is a 
 drift entry coal mining operation with 
 seven mines, all located in a 5-square- 
 mile area in West Virginia. VCCC oper- 
 ating personnel and management were 
 extremely cooperative throughout the 
 evaluation process. 
 
 The evaluation site was a conventional 
 mining operation with a seam height aver- 
 aging 52 in. The roof in this mine is 
 bolted, and the floor is relatively dry 
 and pitching at approximately 4 pet. 
 Working height is approximately 48 in. 
 During the evaluation, a Goodman loader 
 was used to retrieve the coal at the face 
 and load either the shuttle car or a 
 scoop. The load was then trammed to the 
 feeder-breaker. Some ribbing of the can- 
 opy occurred, especially when tramming at 
 an intersection. Time for a complete cy- 
 cle was approximately 4 min, with 40 s 
 each utilized in loading and unloading. 
 
 Initial reaction to the shuttle car 
 canopy was mostly favorable. The follow- 
 ing comments were particularly positive: 
 
 o Smooth ride. 
 
 o Comfortable seat. 
 
 o Roomy canopy . 
 
 o Easy ingress and egress. 
 
 o Good vision inby and outby. 
 
 o Easy orientation to steering. 
 
 o No difficulty with pivoted, foot- 
 operated tram switch. 
 
 o No change in sitting position re- 
 quired when changing between inby and 
 outby tram. 
 
 The following were recommended for 
 improvement: 
 
 o Seat sling adjustment. 
 
 o Coal entering the canopy at floor 
 level on the entry side when moving into 
 position to unload at the breaker. This 
 problem was corrected by adding 6-in-high 
 plate on the entry side. 
 
 o Coal entering by the opening in 
 front of the operator. This problem was 
 corrected by adding an expanded metal 
 shield over the opening. 
 
 Figure 6 shows the shuttle car compart- 
 ment after these improvements were made. 
 
 RECOMMENDATIONS FOR FUTURE WORK 
 
 Floor-riding canopies offer the most 
 effective use of available head room 
 space, and development of this concept 
 should be continued. For lower working 
 heights, efforts should be made to extend 
 the tunnel farther under the shuttle car 
 body. The operator would then be in a 
 layback position, and more of his legs 
 would protrude into the tunnel. A de- 
 crease of 10 in in canopy height could be 
 achieved. 
 
 An evaluation site for the loader can- 
 opy shown in figure 4 has not yet been 
 located. This loader canopy was designed 
 
 for use in 39-in headroom. Its suspen- 
 sion system, as designed, consists of 
 captured pivot pins on top, a horizontal- 
 ly mounted adjustable spring suspension 
 on the bottom, and a shock-absorbing ra- 
 dius arm. This suspension system permits 
 upward, downward, or sideways movement of 
 the canopy when roofing or ribbing. This 
 resiliency minimizes damage to the struc- 
 ture and loader attach points and mini- 
 mizes impact on the operator. This load- 
 er canopy offers significant improvements 
 over the state of the art in low-coal 
 canopy technology. 
 
54 
 
 FIGURE 6. - Final configuration of shuttle car compartment. 
 
55 
 
 CABS AND CANOPIES FOR FMC UNDERGROUND COAL MINING EQUIPMENT 
 
 By Martin D, Wotringl 
 
 ABSTRACT 
 
 A low-seam canopy has been developed 
 by FMC Corp. to be used on scoops and 
 shuttle rams. It also can be adapted to 
 other equipment. A midseam roof bolter 
 has been developed with built-in canopy 
 protection. This machine features the 
 
 operator compartment in the center of the 
 machine where tramming and bolting can 
 be done under the protection of the can- 
 opy. Cabs and canopies used on other 
 roof bolters and shuttle cars are also 
 discussed. 
 
 INTRODUCTION 
 
 The 1969 Coal Mine Health and Safety 
 Act required the installation of can- 
 opies on face equipment. Initially, many 
 coal miners were opposed to these cano- 
 pies, which were being retrofitted on 
 existing underground equipment. As more 
 and more lives were saved, most of this 
 opposition vanished. However, operators 
 of equipment used in very low seams still 
 
 experienced canopy problems , so MSHA sub- 
 sequently revised the canopy regulations 
 to exclude all machines used in mining 
 heights under 42 in. Equipment manu- 
 facturers, rebuild facilities, and coal 
 miners have since tried many different 
 methods of developing protection for the 
 operators. 
 
 ROOF BOLTERS 
 
 Figure 1 shows the standard cab and 
 canopy configuration on a model 300 roof 
 
 ^Lead engineer, roof bolters, FMC 
 Corp., Mining Equipment Division, Fair- 
 mont, WV. 
 
 bolter. The canopy covers a tramming 
 deck on the side of the machine and the 
 drilling station at the front. The orig- 
 inal operator's deck was lengthened and 
 widened to allow the operator's position 
 to be lower, and the tram valve was 
 
 FIGURE 1. - Standard cab and canopy on model 300 roof bolter. 
 
56 
 
 placed outside the deck to allow more 
 room for the operator. The canopy in 
 figure 1 was designed to work in seam 
 heights from 34 in up. 
 
 Figure 2 shows "floating" aperator's 
 deck with a canopy on a model 3000 roof 
 bolter. This deck was located beside the 
 drill boom where the operator can tram 
 the machine as well as install the bolt. 
 The "floating" deck allowed the machine 
 to be built in a lower package. This ma- 
 chine was intended for use in seams 32 in 
 and up. 
 
 The cab and canopy configuration on the 
 model 370 roof bolter (fig. 3) positions 
 the operator in the center of the unit. 
 Tramming and bolting are done under the 
 protection of the canopy. This machine 
 is intended for use in coal seams 6 ft 
 and up. 
 
 Dual-head roof bolter models are avail- 
 able with canopies over the drill station 
 similar to the canopies on the single- 
 head bolter in figure 1 and the opera- 
 tor's deck (fig. 4). These canopies are 
 basically designed for 42 in and above. 
 
 SHUTTLE CARS, SCOOPS, AND SHUTTLE RAMS 
 
 The canopy for the center-driven model 
 5L (fig. 5) has four posts, which can be 
 mechanically or hydraulically operated. 
 The canopy for the end-driven model lOL 
 shuttle car (fig. 6) has only three 
 posts, to provide better operator vision. 
 These machines are intended for use in 
 seams of 42 in and up. 
 
 A "low-coal canopy" designed for scoops 
 and shuttle-rams is mounted in a track 
 which allows it to roll from over the 
 operator (fig. 7) to a position over 
 the frame of the machine (fig. 8). 
 By sliding the canopy back over the ma- 
 chine frame, entering and exiting the 
 
 operator's deck is made easier. This 
 canopy is mechanically adjustable, locks 
 open or closed, and is easily installed 
 on other equipment. 
 
 Another protective feature used on 
 scoops and shuttle rams in low coal is a 
 "glancer." When the coal seam is so low 
 that the operator cannot look over the 
 top of the machine, the operator will 
 lean out of the deck and look along the 
 side of the machine. As a form of pro- 
 tection from the ribs, the "glancer" is 
 added to the outer edge of the operator's 
 deck. 
 
57 
 
 FIGURE 2. - Floating operator compartment on model 3000 roof bolter. 
 
 FIGURE 3. - Model 370 roof bolter with central operator platform and canopy. 
 
58 
 
 1^^ 
 
 t 
 
 FIGURE 4. » Tram compartment on dual-head roof bolter (model 3510). 
 
 FIGURE 5. - Model 5L shuttle car with center-mounted cab and canopy. 
 
59 
 
 FIGURE 6. = End-driven shuttle car (model lOL) with three-post canopy. 
 
 FIGURE 7. - Low-cool scoop with sliding canopy in closed position. 
 
60 
 
 FIGURE 8. - Low-coal scoop with sliding canopy in open position. 
 
61 
 
 CABS AND CANOPIES FOR JOY UNDERGROUND MINING EQUIPMENT 
 By Gary C. Marshall'' 
 
 INTRODUCTION 
 
 In early 1971, the first operator's 
 protective canopies were designed for Joy 
 mining equipment. Since then, more than 
 370 different cab and canopy designs have 
 been produced. Many more were on the 
 drawing board but never reached produc- 
 tion. More than 5,000 cabs and canopies 
 have been shipped to Joy's customers over 
 the past 10 years. This paper shows the 
 evolutionary process in developing cabs 
 and canopies on Joy underground mining 
 machines. 
 
 Joy's first protective canopies were 
 fabricated from plate and pipe such that 
 
 the top structures were reinforced with 
 ribs , making them much deeper than pres- 
 ent designs, which use flat plate tops 
 without ribs. The early structures (fig. 
 1) were very strong, but visibility was 
 adversely affected and extra headspace 
 was used by the pipes or ribs. This is 
 not a serious problem when operating in 
 high seams; however, many machines oper- 
 ating in seam heights of less than 5 ft 
 required lower compartments with thinner 
 canopy sections. Reinforcing ribs were 
 still used, and adjustable height columns 
 became popular. 
 
 CONTINUOUS MINERS 
 
 It is difficult to predict exactly how 
 much clearance is required between a 
 continuous miner canopy top and the low- 
 est objects on a mine roof. For exam- 
 ple, continuous miners tip up and down 
 on their center of gravity when moving 
 over an undulating floor, causing some 
 unexpected problems. A typical miner 
 with a 44-in-high, fixed canopy requires 
 15 in of clearance to operate on a trans- 
 ition from level ground to a 10° down- 
 slope in a 59-in-high seam. However, 
 figure 2 shows that the same miner needs 
 22 in of vertical clearance to oper- 
 ate on a change from level to a 15° 
 slope, so the seam height must increase 
 to 66 in to keep the canopy from strik- 
 ing the mine roof. Lowering the can- 
 opy height does not change the clear- 
 ance requirements, but it does permit 
 working in a lower seam. If the canopy 
 height in figure 2 is lowered to 33 in, 
 a 10° slope can still be safely traversed 
 if the seam height is 48 in (15-in verti- 
 cal clearance required). The 15° slope 
 can be negotiated (22-in required clear- 
 ance) if the minimum seam height is 55 in 
 and the canopy height is 33 in. 
 
 ^ Joy Manufacturing Co., Franklin, PA. 
 
 Early Joy cabs and canopies for contin- 
 uous miners were usually rigid box struc- 
 tures surrounding the operators. Some- 
 times adjustable columns were used to 
 provide easy height changes as the mining 
 conditions varied. When the fixed can- 
 opies were "roofed" owing to rolls and 
 bumps in the floor, as in figure 2, de- 
 signers proposed floating compartments. 
 Joy believes that floating compartments 
 provide the best features for low seams. 
 The canopies on Joy's floating compart- 
 ments have either three or four adjust- 
 able columns and solid plate tops for 
 good visibility and maximum safety. Some 
 operator cabs have side, or rib, protec- 
 tion for high-seam mining applications. 
 Others have MSHA-approved face lighting 
 systems. 
 
 In very low-seam heights, a split-level 
 top on a floating compartment provides 
 good visibility on a lower height machine 
 such as the 14CM miner shown in figure 3. 
 The canopy top in figure 3 is vertically 
 adjustable in three different positions. 
 Joy's lowest continuous miner, the 15CM 
 (fig. 4) , has a 23-in-high chassis and a 
 30-in-high operator's compartment (fig. 
 5). Since most 15CM miners are operated 
 
62 
 
 FIGURE 1. - Rib-reinforced canopy on Joy shuttle car. 
 
 55" 
 
 ^Center of gravity 
 
 Center of gravity 
 FIGURE 2. - Upward movement of continuous miner canopy in undulating conditions. 
 
63 
 
 FIGURE 3. = Floating cab and split-level canopy on model 14CM continuous miner. 
 
 FIGURE 4. - Overall viev/ of model 15CM continuous miner. 
 
64 
 
 FIGURE 5. - Operator compartment on model 15CM continuous miner. 
 
 FIGURE 6. - Wooden mockup used to design continuous miner cabs. 
 
65 
 
 by remote control and do not have opera- 
 tors riding on the miner, Joy developed 
 the compartment in figure 5 specifically 
 for particular customers. Fitting the 
 operator, the controls, and all other 
 necessary items within a 30-in cab height 
 was a very difficult design job. 
 
 Full-scale wooden models (fig. 6) are 
 essential to producing successful, inno- 
 vative cabs and canopies, especially for 
 lower height designs. The wide vari- 
 ety of controls and options require the 
 use of mockups to evaluate the loca- 
 tions for each device. Product managers. 
 
 designers, field engineers, and customers 
 all have an input into the detailed de- 
 sign process. Many months of work are 
 required before an actual compartment is 
 built, but the result is a sound enclo- 
 sure with a high chance of success. 
 
 Joy also manufactures continuous mining 
 machines with integral roof bolters and 
 temporary roof support (TRS) cylinders. 
 The TRS safety posts are set against the 
 mine roof before a bolter operator pro- 
 ceeds to the drilling-bolting area just 
 in front of the miner operator. 
 
 SHUTTLE CARS 
 
 Most of Joy's shuttle car cabs and can- 
 opies have the unobstructed flat plate 
 tops. Figure 7 shows the cab and canopy 
 on an end-driven shuttle car, and figure 
 8 shows a center-driven machine. The ex- 
 panded metal screen next to the conveyor 
 side of the compartment in figure 7 pre- 
 vents spillage on the operator and keeps 
 the operator from inadvertently squeez- 
 ing an arm or finger between the elevat- 
 ing conveyor and the canopy top. Over 
 the years, pin-adjustable canopy posts 
 have replaced screw-adjustable and fixed 
 columns because the screws were diffi- 
 cult to operate if the posts were bent 
 or the screws became corroded. Joy's 
 most popular shuttle car canopies today 
 
 provide for pin adjustments in 2- and 
 4-in increments. 
 
 Floating compartments have been devel- 
 oped for shuttle cars operating in lower 
 seams. Figures 9-11 show recently de- 
 signed floating compartments on center- 
 driven 21SC shuttle cars. Several of 
 Joy's customers are operating floating 
 units like these, and more cars are on 
 order. The floating decks have well- 
 rounded, beveled bottom edges to prevent 
 plowing of the mine floor while tramming. 
 Smooth, positive cab mounting slides are 
 needed so the compartment floats freely 
 without binding. 
 
 SUMMARY 
 
 Compared to the last decade, it 
 is doubtful that Joy will produce as 
 many new cab and canopy designs dur- 
 ing the next 10 years. However, it is 
 
 anticipated that improvements in opera- 
 tor's controls, comfort, visibility, and 
 safety will continue. 
 
66 
 
 FIGURE 7. - End-mounted cab and canopy on Joy shuttle car. 
 
 -FIGURE 8. - Center-mounted cab and canopy on Joy shuttle car. 
 
 <% .t»i««»<~3«WS?'W».«^5«^®«SS«M?!-«^^«S^ 
 
 FIGURE 9. - Prototype floating cab on center-driven shuttle car. 
 
67 
 
 FIGURE 10. = Modified floating cab on center-driven shuttle car (side view). 
 
 FIGURE 11. - Modified floating cab on center-driven shuttle car (end view). 
 
68 
 
 CABS AND CANOPIES FOR LEE-NORSE CONTINUOUS MINERS 
 By E. W. Hiltebeitell 
 
 INTRODUCTION 
 
 The design of a cab or canopy for a 
 continuous miner is subject to many out- 
 side influences in addition to the seam 
 height to be considered. In the ideal 
 case, the operator's area is considered 
 from the inception of the machine design. 
 In the case of the Lee-Norse LN 800 con- 
 tinuous miner, it was possible to begin 
 cab design essentially at the beginning 
 of the machine design, starting with con- 
 sultation of outside sources and human 
 factors specialists. The initial design 
 
 sketches developed into mockups and later 
 into prototype machines and finally into 
 the production design being sold today. 
 The results of this development have af- 
 fected many other designs in Lee-Norse 
 continuous miners. This paper reviews 
 the process that was used on the LN 800 
 and shows how a design can evolve over 
 the course of a long development pro- 
 gram. It also discusses some of the cab 
 and canopy developments for low-height 
 miners. 
 
 DESIGN PROCESS 
 
 The design process of the operator's 
 area for the LN 800 began with the deci- 
 sion to improve the cab early in the ma- 
 chine design process. Such a decision 
 must be accepted by management and shown 
 to offer a true market advantage. The 
 earlier the cab design is started, the 
 more likely that a good design will be 
 developed. One of the factors is choos- 
 ing space for the operators before it has 
 been allocated to other components or de- 
 vices on the machine. This space must be 
 determined by considering other machine 
 parameters, including the length of the 
 machine, the width of the machine, height 
 restrictions, and type of machine in- 
 volved — in this case, a continuous miner 
 (fig, 1), One important factor in a con- 
 tinuous miner is the distance from the 
 operator to the face, or the front of the 
 machine. This effectively determines the 
 safe and legal depth of cut and has a di- 
 rect effect on productivity and safety 
 since a deeper cut allows more continuous 
 operation before place change. The major 
 consideration, however, is operator size. 
 The cab should be designed to be compati- 
 ble with the size range from 5th percen- 
 tile females (smaller individuals) to 
 
 ^Product design engineer^ 
 Company, Pittsburgh, PA, 
 
 Lee-Norse 
 
 95th percentile males. If such consider- 
 ations are used, the cab should be com- 
 fortable for 90 pet of the population 
 using the machine. 
 
 The next decision involves the general 
 design approach. For example, the cab 
 could be designed completely in-house, it 
 could be totally subcontracted to outside 
 consultants or specialist organizations, 
 or a combined approach could be used. 
 The combined approach can offer the best 
 of both worlds; however, it requires di- 
 plomacy, tact, and careful consideration 
 of the relations between the manufac- 
 turer's staff and the consultant's staff, 
 In-house design can be quicker and less 
 costly, if staff is available. Outside 
 design avoids "tunnel vision" or the "not 
 invented here" syndrome, but usually 
 costs more in initial cash outlay. If 
 consultants are to be used, the selection 
 process is extremely important. The con- 
 tract should be definite about the time 
 frame for the work, the work to be done, 
 and the acceptable form of the final re- 
 port or design. 
 
 For the design of the LN 800 cab, we 
 chose the combined approach, Phillip 
 Stevens Associates of Skaneateles, NY, 
 was chosen since they had a number of 
 
69 
 
 Cab 
 
 PLAN VIEW 
 
 \ 
 \ 
 
 
 1 
 
 
 K 
 
 \ 
 
 
 1 
 
 / 
 
 Canopy 
 
 59.8 
 50.8' 
 
 63.5" 
 
 ^^^^^^^^^^;^^^^^^^^^^^^^^^^^^^^^^^^^^%^^^^^;^^^^ 
 
 397' 
 
 ELEVATION 
 FIGURE 1. - Layout drawing of LN 800 continuous miner. 
 
 successful design and human factor proj- 
 ects for Ingersoll-Rand Corp. In the 
 initial meetings with Phillip Stevens 
 Associates, Lee-Norse attempted to define 
 the space available, the specific compo- 
 nents that could not be changed (and the 
 reasons they could not be changed) , the 
 functional controls desired, and the best 
 available machine layout at the time. As 
 the machine and compartment designs pro- 
 gressed, further meetings were held 
 to clarify and combine ideas from both 
 parties. A certain amount of redesign 
 occurred on both sides at this stage. 
 
 After a firm paper design was estab- 
 lished, a mockup was the next step. 
 Mockups are excellent for design reviews, 
 but they can be expensive and difficult 
 to transport. The mockup was substan- 
 tially constructed to allow people to 
 "try it on for size." Figures 2 through 
 5 show how 50th and 95th percentile size 
 
 male operators fit within the operator's 
 area with the canopy in the low and high 
 positions. The mockup was reworked in 
 the process of design and proved to be an 
 effective way to make good decisions on 
 the prototype design features. 
 
 Prototype construction was the next 
 step taken on the LN 800. After final 
 mockup acceptance and completion of de- 
 tail drawings, two prototype machines 
 were built (fig. 6). During the process 
 of prototype construction, the consultant 
 reviewed the prototype and commented on 
 areas of improvement or difficulties not 
 identified in the mockup stage. The pro- 
 totype was then field-tested, and com- 
 ments from the operators on the equipment 
 were noted and evaluated as impartially 
 as possible. The consultants reviewed 
 the underground operation of the proto- 
 type after the operators of the machine 
 had a chance to familiarize themselves 
 
70 
 
 FIGURE 2. - Cab mockup - 50th percentile operator with canopy in low position. 
 
 FIGURE 3. - Cab mockup - 95th percentile operator with canopy in low position. 
 
71 
 
 FIGURE 4. - Cab mockup - 50th percentile 
 operator with canopy in high position. 
 
 FIGURE 5. - Cab mockup - 95th percentile 
 operator with canopy in high position. 
 
 FIGURE 6. - Prototype cab and canopy on LN 800 continuous miner. 
 
72 
 
 with the new machine and its operation. 
 These evaluations were followed by rework 
 of the prototype as required. The final 
 stage of the prototype design reflected 
 a value analysis , considering the advan- 
 tages of the human-engineered design ver- 
 sus its cost. 
 
 At this point the design was ready 
 for production. The LN 800 compartment 
 
 design process also affected other ma- 
 chines in the product line. It was 
 very difficult to measure productivity 
 increases or safety improvements rela- 
 tive to the new design of the LN 800 
 operator's area; however, the qualita- 
 tive results showed in positive com- 
 ments from the owners and operators of 
 the equipment. 
 
 PROBLEM AREAS 
 
 Potential pitfalls to the design ap- 
 proach described here include human fac- 
 tors data, which are most often taken 
 from samples of the military and there- 
 fore represent a younger sample than 
 the general population; this sample is 
 also in above-average physical condition. 
 One must also consider additional width 
 and motion restrictions due to cap lamps, 
 self -rescuers , and other belt-mounted 
 equipment. Hand and foot access must be 
 designed for gloved hands and heavy 
 boots, and simplicity in design is es- 
 sential. It is particularly difficult 
 to maintain simplicity in low machines 
 and still provide good human factors 
 over a wide range of operator shapes and 
 sizes. 
 
 Another area of difficulty is spare 
 controls. Many human factor specialists 
 recommend different-length handles and/ 
 or different-shaped knobs to provide tac- 
 tile sensation of machine operation. 
 This requires the mine to stock more 
 spare parts. Even if the parts are 
 stocked, the wrong spare knob or handle 
 can easily be installed by mine mechan- 
 ics, creating the potential for serious 
 errors. In addition, electrical enclo- 
 sure designs must be finalized in the 
 initial machine design stages owing to 
 the time involved in X/P certification by 
 MSHA. Finally, even in long-term pro- 
 grams such as the LN 800, only a limited 
 time is available for review, testing, 
 and redesign. 
 
 DESIGN FEATURES 
 
 Figure 7 shows a closeup of the LN 800 
 operator area. One of its advantages is 
 the single control lever for the convey- 
 or; it moves right or left to swing the 
 conveyor tail section and moves up and 
 down to lift or lower the conveyor. The 
 separation of the tram controls from the 
 hydraulic controls is designed to in- 
 crease safety. There is a logical se- 
 quence to the pushbutton station; start- 
 ing at the trailing cable entry end of 
 the station, the operator proceeds for- 
 ward on the machine for the normal start- 
 ing sequence. The start buttons are 
 
 recessed to prevent accidental tripping. 
 The stop buttons are covered with plates 
 or paddles such that a slap of the hand 
 stops the machine in an emergency. This 
 effectively acts as a backup for the 
 emergency stop and makes the stop mech- 
 anism easier to locate. Finally, the 
 entire seat assembly swings out to allow 
 access to control panels, circuit break- 
 ers , and the miner water system without 
 major disassembly of the machine. The 
 seat itself is vertically adjustable, has 
 lateral and lumbar support , and includes 
 a self -draining design. 
 
 CURRENT LOW-COAL DESIGNS 
 
 The operator compartment on the Lee- 
 Norse 285 miner (fig. 8) has a floating 
 cab that doubles as a stabilizer shoe to 
 allow a wider, deeper operator's area 
 
 than the previous design with a separate 
 stab shoe. The Lee-Norse 245 miner has a 
 similar floating cab. The seating posi- 
 tion is more comfortable in the floating 
 
73 
 
 FIGURE 7. - Closeup of LN 800 operator area. 
 
 FIGURE 8. - Floating cab and canopy on low-coal continuous miner. 
 
74 
 
 1 1 
 
 1 m 
 
 iP 
 
 
 1 
 
 
 I 
 
 I 
 
 FIGURE 9. - Redesigned controls for low»coal continuous miner. 
 
 cab, and the visibility is improved. The 
 floating cab can be mechanically locked 
 in a position clear of the ground, and 
 the canopy height can be adjusted inde- 
 pendently in the front and the rear 
 of the compartment. We are currently 
 
 reviewing this design to move the con- 
 trols closer to the operator so that they 
 move with the cab, rather than being 
 mounted on the fender and fixed relative 
 to the cab position (fig. 9). 
 
75 
 
 EVALUATION OF "MINIMUM" AND "LOWEST PRACTICAL" WORKING HEIGHTS 
 
 FOR SAFE USE OF CANOPIES 
 
 by William W, Aljoe 
 
 ABSTRACT 
 
 This paper outlines an analytical ap- 
 proach to determining the "minimum work- 
 ing heights" and "lowest practical work- 
 ing heights" necessary to allow the safe 
 use of canopies on underground coal min- 
 ing equipment. Each element of the work- 
 ing height (mine floor to nearest over- 
 head obstruction) is discussed in some 
 detail, emphasizing the variability of 
 the numerical values assigned to each 
 
 element. The effects of machine type, 
 machine frame height, and mine conditions 
 on the working heights attainable with 
 canopies are reviewed. With state-of- 
 the-art cab and canopy technology, these 
 variables will frequently prevent the 
 safe use of canopies in low coal seams 
 without extensive modifications to exist- 
 ing equipment. 
 
 INTRODUCTION 
 
 Roof falls have historically been one 
 of the most frequent causes of fatalities 
 in underground coal mines. Preventing 
 injuries and deaths from such falls is a 
 difficult technological challenge, but 
 progress is being made through a variety 
 of engineering advancements. For exam- 
 ple, the life-saving potential of proper- 
 ly designed and constructed cabs or cano- 
 pies on self-propelled face equipment has 
 been demonstrated in numerous instances 
 when operators escaped serious injuries 
 from roof falls, some so massive that the 
 machine was buried. Unfortunately, a 
 number of technical problems remain un- 
 solved in the design of functional opera- 
 tor compartments for mining equipment 
 working in low coal seams. 
 
 Three principal problems are associ- 
 ated with the use of canopies on low-coal 
 equipment: "roofing" of the canopy dur- 
 ing travel over uneven floors, limited 
 vision of the machine operator, and se- 
 verely cramped operator compartments. 
 Design changes to minimize any of these 
 problems usually worsen the impact of at 
 least one of the other two. If an opera- 
 tor is uncomfortable or has restricted 
 vision, he or she tends to operate the 
 
 ^Mining engineer, Pittsburgh Research 
 Center, Bureau of Mines, Pittsburgh, PA. 
 
 machine in an unsafe manner, such as 
 leaning beyond the protection of his can- 
 opy or machine frame. Because many ex- 
 isting cabs and canopies were not de- 
 signed to compensate for this, numerous 
 injuries to miners have occurred from 
 collisions with the ribs, roofs, or other 
 objects in the mining section. 
 
 At present, Federal regulations require 
 protective operator compartments in sec- 
 tions having a minimum mining height 
 of 42 in. However, extensive review of 
 field data indicated that this require- 
 ment could have better addressed the 
 uniqueness among mining sections and the 
 seriousness of operational problems with 
 existing canopies in working heights be- 
 tween 42 and 54 in. In numerous cases, 
 low working heights prohibited the con- 
 sistent use of canopies despite sub- 
 stantial efforts by coal companies to 
 achieve compliance with canopy regula- 
 tions through innovative cab and canopy 
 design concepts. Often, these designs 
 were unsuccessful because only complete 
 machine redesign or machine replacement 
 would have allowed safe, efficient opera- 
 tion with a canopy. 
 
 This paper describes the results of 
 approximately 3 years of research, spon- 
 sored principally by the Bureau of Mines, 
 
76 
 
 to document the application of cabs 
 and canopies in low-coal mines. Most 
 of this research was performed by Bitu- 
 minous Coal Research, Inc., Monroeville, 
 PA, under Bureau contract. ^ This paper 
 describes a procedure that can be used, 
 if the machine, operator's compartment. 
 
 and canopy have been designed specifical- 
 ly for low coal, to define the "minimum" 
 and "practical" working heights at which 
 canopies could be used without roofing 
 and without restricting operator comfort 
 or vision. 
 
 THE MINIMUM WORKING HEIGHT WITH A CANOPY - WHAT DOES IT MEAN? 
 
 The working height of the underground 
 mining section is probably the most cri- 
 tical factor governing the successful use 
 of canopies. First, it is very Important 
 to note that the term "working height" 
 used here is not the same as the "mining 
 height" contained in MSHA canopy regula- 
 tions. Mining height as defined by MSHA 
 is the total extracted height, from the 
 mine floor to the unfinished roof; the 
 minimum working height of a mining sec- 
 tion is defined as the distance from tine 
 mine floor to the lowest ovevhead olo- 
 stvuetion on the section, if the obstruc- 
 tion is not the result of poor mining 
 practices. In some cases this obstruc- 
 tion can be the mine roof itself, but it 
 is usually a roof support device, machine 
 trailing cable, or ventilation tubing 
 suspended from the roof. Thus, the mini- 
 mum working height will always be less 
 than or equal to the minimum mining 
 height, and the mining height at any lo- 
 cation is equal to the working height 
 
 plus the height (thickness) of the over- 
 head obstruction at that point. 
 
 Two other clarifications must be made 
 about the meaning of the "minimum working 
 height." First, it must be assumed that 
 the machine frame or objects on top of 
 the machine will not interfere prohibi- 
 tively with operator vision. Second, the 
 mine floor must be fairly level, with no 
 sharp undulations. Because these condi- 
 tions exist only rarely in actual prac- 
 tice, a "lowest practical working height" 
 with a canopy, usually larger than the 
 minimum working height, must also be de- 
 fined. Later in this paper, procedures 
 for quantifying the lowest practical 
 working height are given; these take into 
 account the actual machine frame height 
 and degree of mine floor undulation. 
 However, let us first examine how the 
 minimum working height under ideal condi- 
 tions can be determined. 
 
 PRODECURES FOR QUANTIFYING THE MINIMUM WORKING HEIGHT 
 
 The first step toward quantifying the 
 minimum working height with a canopy 
 would be to divide the available vertical 
 clearance into seven segments as shown in 
 figure 1. The segments are defined as 
 follows: (i) mine floor to bottom of cab 
 deck, (2) thickness of deck and opera- 
 tor's seat, (3) top of seat to opera- 
 tor's eye level, (4) eye level to top of 
 miner's cap, (5) cap to underside of can- 
 opy» (^) canopy thickness, and i?) clear- 
 ance between canopy and lowest overhead 
 obstruction, 
 
 ^Bituminous Coal Research, Inc. "Ad- 
 vancement of Cab and Canopy Design and 
 Use in Coal Mines," Ongoing BuMines con- 
 tract No. J0199055. 
 
 Using available anthropometric data and 
 state-of-the-art technology for mining 
 machines, operator's compartments, and 
 canopies, a minimum value can be assigned 
 to each of these segments. Their sum is 
 equal to the minimum working height with 
 the canopy. However, the operator's 
 size, machine type, machine model, and 
 operator compartment design all have very 
 important effects on the values assigned 
 to each segment. In fact, completely new 
 or radically different equipment technol- 
 ogy could reduce these values substan- 
 tially. It may be helpful, therefore, to 
 consider how the minimum working height 
 could be calculated for an existing ma- 
 chine - a continuous miner with a very 
 low frame. 
 
77 
 
 7~-^ 
 
 Extra header 
 ( 2 in thick) 
 
 Bump 
 (2 in high) 
 
 V7Z7777. 
 
 FIGURE 1. - Breakdown of minimum working height with canopies. 
 
 Figure 1 was drawn to simulate a con- 
 tinuous miner operator within the com- 
 partment (sketch not to scale) ; let us 
 start at the ground and work upward. Be- 
 cause nearly all models of low-profile 
 continuous miners can be equipped with 
 "floating" cabs which slide along the 
 mine floor in nonundulating conditions, 
 the minimum value of segment 1 of figure 
 1 would be zero. 
 
 Segment 2 of figure 1 consists of two 
 elements — the cab deck and the opera- 
 tor's seat. The floating deck must be 
 strong enough to withstand abrasion from 
 the mine floor. If high-strength, heat- 
 treated steel is used, the deck can 
 be as thin as 1/2 in. However, mild 
 steel is a much more common and inexpen- 
 sive deck material; for practical pur- 
 poses, a minimum deck thickness of 1 in 
 (mild steel) is assumed here. 
 
 The thickness of a seat or pad, when 
 compressed by the weight of the operator, 
 can also be as small as 1/2 in. In many 
 cases, however, a higher seat is needed. 
 For example, mud and water often spill 
 into floating decks; if the seat were 
 only 1/2 in above the cab deck, the oper- 
 ator would have to spend most of his or 
 her time cleaning out the compartment. 
 Even on a slow-moving machine like a 
 continuous miner, a thicker seat pad is 
 
 often needed to cushion the operator when 
 tramming over rough mine floors. The 
 minimum seat thickness assumed in this 
 example is 2 in. 
 
 A realistic minimum value of segment 2 
 in figure 1 would thus be 3 in — 1 in for 
 the deck, and 2 in for the seat pad. 
 Theoretically, this value could be lower 
 (approximately 1 in); however, as subse- 
 quent discussion will show, this reduced 
 deck and seat thickness will not usually 
 result in a substantial reduction of the 
 minimum working height with a canopy. 
 
 Segment Z is perhaps the most critical 
 and controversial component of the mini- 
 mum working height. The distance from 
 the operator's seat to his or her eyes is 
 governed by the operator's size and the 
 internal configuration of the operator 
 compartment. According to anthropometric 
 data supplied by SAE,^ the seat-to-eye 
 height would be approximately 23 in for 
 both small (5th percentile female) and 
 large (95th percentile male) machine op- 
 erators if the operator can recline with- 
 in the compartment. However, when a 
 "sit-up" position must be utilized to run 
 
 ^Society of Automative Engineers. "De- 
 velopment of SAE Guidelines for Under- 
 ground Operator Compartments." Ongoing 
 BuMines contract No. H0308110. 
 
78 
 
 the machine effectively, the required 
 seat-to-eye height can be as much as 29 
 to 33 in for small and large operators, 
 respectively. Obviously, the minimum 
 working height with a canopy must also 
 increase. To maximize the use of cano- 
 pies in low coal, the operator's compart- 
 ment must be designed to minimize the 
 required seat-to-eye height. 
 
 Most continuous miners in use today do 
 not have compartments that allow the op- 
 erator to recline (seat-to-eye height 23 
 in). However, some presently available 
 models do contain reclining seats , and 
 compartments that provide at least a 
 semireclining operator position can be 
 retrofitted to other models. For the 
 purpose of defining the minimim working 
 height attainable with canopies on con- 
 tinuous miners, it will be assumed that 
 segment 3 of figure 1 can be reduced to 
 23 in. 
 
 The distance from the operator's eyes 
 to the top of his or her cap, segment 4 
 of figure 1, is approximately 6.5 in for 
 both small and large operators. This 
 value agrees with SAE anthropometric data 
 and a survey of high-coal cab and canopy 
 design done by Bendix.^ 
 
 Segment 5 of figure 1 represents the 
 "bounce space" required between the top 
 of the operator's cap and the underside 
 of the canopy. Based on numerous obser- 
 vations of continuous miners in opera- 
 tion, a value of 1.5 in was chosen; this 
 was also the value selected by Bendix in 
 the study mentioned above. 
 
 Canopy thickness, segment 6 in figure 
 1, is governed by its design and the 
 strength of the material used. Solid- 
 plate canopies are thinner than canopies 
 made of structural steel tubing; if high- 
 strength steel plate is used, it can be 
 
 "^Farrar, R., R. Champney, and L. Wein- 
 er. Survey on Protective Canopy Design, 
 (contract H0242020, Bendix Corp.). Bu- 
 Mines OFR 50-76, 1976, 163 pp.; NTIS PB 
 251-67 2/AS. 
 
 as thin as 1/2 in. As with cab decks, 
 however, mild steel plate is much more 
 common and inexpensive, so a minimum can- 
 opy thickness of 1 in (mild steel plate) 
 is assumed here. Although canopy thick- 
 ness does not usually have a substantial 
 effect on the minimum working height with 
 the canopy, the overall design of the 
 canopy top can be very important. 
 
 Because the minimum working height with 
 a canopy must be chosen so that canopy 
 roofing does not occur, segment 7 of fig- 
 ure 1 must be defined very clearly. This 
 segment represents the minimum vertical 
 clearance required between the canopy top 
 and the nearest overhead obstruction nor- 
 mally present in a flat coal mining sec- 
 tion. Although this value is essentially 
 arbitrary, it was chosen to be 4 in on 
 the basis of observations of continuous 
 miners in level seam conditions. This 
 clearance is needed partly to overcome 
 obstructions on the mine floor and part- 
 ly to account for unexpected overhead 
 obstructions. 
 
 Even in flat , nonundulating coal mines 
 where good housekeeping practices are 
 followed, debris or an obstacle of some 
 type will usually be present on the floor 
 of the mining section. When the continu- 
 ous miner trams over an obstacle, such as 
 a pile of loose coal or a large rock, the 
 machine and canopy will rise temporarily. 
 If this occurs at the same spot in the 
 mining section where an object protrudes 
 below the level normally occupied by the 
 lowest obstruction (e.g., a header board 
 or trailing cable hanging beneath the 
 bottom of required roof bolts), the local 
 vertical clearance could be substantially 
 less than the working height (mine floor 
 to roof bolt) normally present on the 
 section. To prevent the canopy from 
 roofing, the maximum height of the canopy 
 above the mine floor should be at least 4 
 in less than the working height normally 
 present. 
 
 Adding the values assigned to segments 
 1 through 7 of figure 1 yields the mini- 
 mum working height needed to allow the 
 
79 
 
 safe use of canopies on continuous 
 miners: 
 
 Segment in 
 
 1 — ^Mine floor to cab deck 0.0 
 
 2 — Deck and seat thickness 3.0 , 
 
 S — Seat-to-eye height 23.0 
 
 4 — Eye-to-cap height 6.5 
 
 5 — Cap-to-canopy height 
 
 ("bounce space") 1.5 
 
 6 — Canopy thickness 1.0 
 
 7 — Clearance above canopy 4.0 
 
 Total 39.0 
 
 EFFECT OF MACHINE TYPE AND MINE FLOOR CONDITIONS 
 
 Remember that the preceding example 
 dealt with an ideal canopy installation — 
 a slow-moving, low-profile machine with a 
 properly designed operator compartment in 
 a flat, dry, well-kept mining section. 
 However, table 1 shows that the "minimum" 
 working height needed to allow the safe 
 use of canopies is different for differ- 
 ent machine types. Also, "imperfect" 
 conditions will increase the minimum 
 working height with the canopy, and the 
 
 effects of machine type and mining condi- 
 tions can be quantified by reviewing the 
 seven segments of figure 1. 
 
 SEGMENT 1 - MINE FLOOR TO CAB DECK 
 
 In the previous example, special care 
 was taken not to use the term "ground 
 clearance" when referring to this dis- 
 tance. The ground clearance of a float- 
 ing cab deck is zero, while the ground 
 
 TABLE 1 . - Breakdown of minimum working heights with canopies , inches 
 
 
 Machine type 
 
 Segments of working 
 height (fig. 1) 
 
 Contin- 
 uous 
 miners 
 
 Shut- 
 tle 
 cars 
 
 Scoops 
 and 
 tractors 
 
 Roof 
 bolters , 
 single- 
 head' 
 
 Roof 
 bolters, 
 dual- 
 head' 
 
 Cutters 
 and 
 face 
 drills 
 
 Loading 
 machines 
 
 1 — Mine floor to cab deck. 
 2 — Deck and seat thickness 
 
 2 — Seat-to-eye height 
 
 4 — Eye-to-cap height 
 
 5 — Cap-to-canopy height... 
 
 6 — Canopy thickness 
 
 7 — Clearance above canopy. 
 
 20.0 
 
 3.0 
 
 ^23.0 
 
 6.5 
 
 71.5 
 1.0 
 4.0 
 
 20.0 
 
 3.0 
 
 ^23.0 
 
 6.5 
 
 83.0 
 1.0 
 4.0 
 
 ^6.0 
 
 3.0 
 
 514.0 
 
 6.5 
 
 83.0 
 1.0 
 4.0 
 
 20.0 
 
 3.0 
 
 423.0 
 
 6.5 
 
 71.5 
 1.0 
 4.0 
 
 20.0 
 
 3.0 
 
 ^23.0 
 
 6.5 
 
 71.5 
 1.0 
 4.0 
 
 20.0 
 
 3.0 
 
 629.0 
 
 6.5 
 
 71.5 
 1.0 
 4.0 
 
 20.0 
 3.0 
 629.0 
 6.5 
 71.5 
 1.0 
 4.0 
 
 Minimum working height 
 (sum of elements 1 
 through 7) 
 
 39.0 
 
 40.5 
 
 37.5 
 
 39.0 
 
 39.0 
 
 45.0 
 
 45.0 
 
 '"Tram-only" or "drill-and-tram" compartment. 
 
 2Floating compartment; if unworkable or unavailable, use ground clearance of opera- 
 tor's compartment. 
 
 ■^Floating compartment not available; use ground clearance of operator's compartment 
 (6 in normal) . 
 
 ^Reclining operator position; add 6 to 10 in for sit-up position. 
 
 ^Lie-down operator position; add 9 in for reclining, 15 to 19 in for sit-up 
 position. 
 
 6 Sit-up operator position; small operator. 
 
 7 Slow-moving machines - tram speed 50 to 200 ft/min. 
 
 8Fast-moving machines - tram speed 350 to 450 ft/min. 
 
80 
 
 clearance of the frame of the continuous 
 miner is commonly 6 in or more to prevent 
 it from becoming hung up in the mine 
 bottom. In broken, irregular, or muddy 
 bottom conditions , hangup problems often 
 become so severe that the deck must^be 
 suspended above the mine floor at all 
 times. The value of segment 1 of figure 
 1 would not be zero if adverse bottom 
 conditions prevail; it could be as large 
 as the ground clearance of the machine 
 f rame . 
 
 Although floating operator compartments 
 are available for several models of shut- 
 tle cars, they must travel faster, far- 
 ther, and more often than continuous 
 miners, and they are much more suscepti- 
 ble to hangup problems. As a result, the 
 coal industry has not used floating com- 
 partments on shuttle cars nearly as often 
 as on continuous miners. When calculat- 
 ing the minimum working height with a 
 canopy on a shuttle car, the value of 
 segment 1 of figure 1 will often be equal 
 to the ground clearance of its main 
 frame. However, this distance can be as 
 low as zero if very good mine floor con- 
 ditions exist. 
 
 Although conceptual designs of floating 
 cab decks have been developed for conven- 
 tional equipment — cutters, face drills, 
 and loaders — equipment manufacturers do 
 not usually offer them as either "stan- 
 dard" or "optional" items on new low- 
 profile machines. Substantial modifica- 
 tions or complete machine redesign would 
 be needed to incorporate floating decks 
 on most existing models of conventional 
 equipment. Conceptual designs of float- 
 ing cab decks have not been developed for 
 scoops, tractors, and ramcars; substan- 
 tial machine redesign would be needed. 
 
 therefore, be the ground clearance of the 
 machine, although new machine technology 
 could lead to the development of mine- 
 worthy floating compartments. 
 
 Assigning a minimum mine-floor-to-cab- 
 deck distance to roof bolters is espe- 
 cially difficult because there is really 
 no such thing as a "typical" roof bolting 
 machine. Single-head and dual-head bolt- 
 ers must be treated differently; some 
 models require the operator to walk 
 alongside the bolter when tramming, while 
 others have tram compartments similar to 
 those on the machine types previously 
 mentioned. Also, for the purpose of spe- 
 cifying a minimum working height with a 
 canopy, only the tram function of the 
 roof bolter can be considered. Because 
 the operator must often drill and bolt 
 while sitting or kneeling directly on the 
 mine floor, the operator position shown 
 in figure 1 would not apply to the tasks 
 of drilling and bolting. 
 
 Floating tram compartments are present- 
 ly available for some models of single- 
 head bolters whose drilling, bolting, and 
 tramming functions are performed from the 
 same compartment at the front of the ma- 
 chine, near the drill head. For these 
 machines the minimum mine-floor-to-cab- 
 deck distance would be zero. Some mod- 
 els of dual-head roof bolters also have 
 floating compartments. However, many 
 models of single-head bolters and almost 
 all models of dual-head bolters have sep- 
 arate tram compartments, whose ground 
 clearance is usually equal to the ground 
 clearance of the machine. For these ma- 
 chines, the ground clearance of the frame 
 of the roof bolter would often be a rea- 
 sonable estimate of the value of segment 
 1 of figure 1. 
 
 Consequently, the mine-floor-to-cab- 
 deck distance will not usually be zero 
 for scoops, tractors, and ramcars. The 
 ground clearance of the fixed deck need 
 not be as large as the ground clearance 
 of the machine frame, but many manufac- 
 turers will make these two clearances 
 equal. A reasonable estimate of the 
 value of segment 1 of figure 1 would. 
 
 In summary, the minimum distance re- 
 quired between the mine floor and the 
 bottom of the tram deck can range from 
 zero to the ground clearance of the ma- 
 chine frame, depending on machine type, 
 model, and mine floor conditions. Each 
 individual mine-machine combination must 
 be examined carefully to determine how 
 large this distance must be. 
 
81 
 
 SEaiENT 2 - DECK AND SEAT THICKNESS 
 
 As explained in the previous example 
 of the continuous miner, machine design 
 and mine floor conditions can affect 
 the minimum thickness of the deck, and 
 seat. However, the 3-in combined thick- 
 ness assumed in that example represents 
 a reasonable tradeoff between the best 
 and worst deck material, floor condi- 
 tions, and riding comfort. For practical 
 purposes , a nominal 3-in deck and seat 
 thickness can be used when calculating 
 the minimum working height with a canopy, 
 
 SEGMENT S - SEAT-TO-EYE-HEIGHT 
 
 The variable nature of this distance on 
 a continuous miner was discussed in the 
 previous example. Theoretically, the 23- 
 in seat-to-eye height also represents the 
 minimum height attainable on other types 
 of electric face equipment. However, 
 compartments on most existing low-profile 
 machines were designed for sit-up opera- 
 tion; these must be modified to provide 
 the minimum possible (23-in) seat-to-eye 
 height. In many cases such modifications 
 would be difficult or unfeasible because 
 of original machine design, and the mini- 
 mum seat-to-eye height would be 29 in, 
 even for the smallest operators. Almost 
 all cutters, face drills, and loaders 
 presently require operators to sit up- 
 right at all times. 
 
 types , the long axis of the operator' s 
 body is parallel to the travel direction, 
 and the attempt to look forward from the 
 lie-down position would result in exces- 
 sive head and neck strain. Changing 
 seats or turning around to face the oppo- 
 site tram direction would also be ex- 
 tremely difficult. Therefore, the lie- 
 down operator position and 14-in seat- 
 to-eye height are applicable only to 
 scoops and tractors with transverse 
 compartments. 
 
 Unfortunately, only a few models of 
 scoops and tractors have been designed to 
 accommodate operators in the lie-down po- 
 sition. Substantial modifications would 
 be needed on most models to provide ade- 
 quate leg room while allowing the opera- 
 tor to remain protected by the compart- 
 ment. Even if such modifications are 
 made, the resulting compartment configur- 
 ation could place the operator's eyes far 
 below the top of the machine frame, pro- 
 hibiting vision to the opposite side of 
 the entry, 
 
 SEGMENT 4 - EYE-TO-CAP HEIGHT 
 
 No significant type-to-type or model- 
 to-model variations exist for this dis- 
 tance; a minimum value of 6.5 in can be 
 used in all cases. 
 
 SEGMENT 5 - CAP-TO-CANOPY "BOUNCE SPACE" 
 
 Some models of scoops and tractors , 
 however, can be modified to allow machine 
 operation from a "lie-down" position. 
 SAE anthropometric data^ indicate the 
 minimum operator seat-to-eye height in 
 the lie-down position would be approxi- 
 mately 14 in for both small and large 
 persons. In the transverse or "side- 
 saddle" compartments characteristic of 
 scoops and tractors, the long axis of the 
 operator's body (head to toe) is perpen- 
 dicular to the direction of machine trav- 
 el, and the operator needs only to rotate 
 his or her head to see alongside the ma- 
 chine in the forward and reverse direc- 
 tions. On almost all other machine 
 
 ^Work cited in footnote 3. 
 
 When traveling over mine floors of 
 equal roughness, the operators of fast- 
 moving machines — shuttle cars, scoops, 
 and tractors — will need approximately 
 twice as much "bounce space" as opera- 
 tors of slow-moving machines — continuous 
 miners, cutters, face drills, loaders, 
 and roof bolters. Therefore, the values 
 assigned to segment 5 of figure 1 would 
 be 3,0 and 1.5 in, respectively. 
 
 SEGMENT 6 - CANOPY THICKNESS 
 
 The same statements made about deck 
 thickness apply to canopy thickness; most 
 existing low-coal canopies are made of 
 1-in-thick mild steel rather than 1/2-in- 
 thick high-strength steel. For practical 
 
82 
 
 purposes, 1 in should be allowed for can- 
 opy thickness when calculating the mini- 
 mum working height with a canopy on ex- 
 isting equipment. 
 
 SEGMENT 7 - CLEARANCE ABOVE CANOPY 
 
 The value of this dimension on con- 
 tinuous miners — 4 in — applies equally to 
 all machine types and models as long as 
 large-scale mine floor undulations are 
 not present. As will be shown later in 
 this paper, machine type and model do 
 have significant effects on the clearance 
 required above the canopy when mine floor 
 undulations occur. 
 
 SUMMARY 
 
 if mineworthy 
 developed. 
 
 floating decks can be 
 
 2. The deck and seat thickness of 3 
 in can be reduced to about 1 in if high- 
 strength steel and minimal seat padding 
 are used. Conversely, some machine oper- 
 ators may insist upon higher seats if mud 
 and water spillage are excessive, and 
 more seat padding or suspension may be 
 needed to cushion the operator against 
 rough rides. 
 
 3. The required seat-to-eye height is 
 governed by the control configuration and 
 interior dimensions of the operator's 
 compartment. Substantial type-to-type 
 and model-to-model variations exist. 
 
 Table 1 summarizes the values to be as- 
 signed to segments 1 through 7 of figure 
 1 when calculating the minimum working 
 heights attainable with canopies on ex- 
 isting equipment. As noted in table 1, 
 many of these values can be either higher 
 or lower because — 
 
 1. Floating cab decks may or may not 
 be available or feasible on existing 
 machines. If a floating deck is not 
 commercially available for a particular 
 equipment type, a nominal compartment 
 ground clearance of 6 in is listed in ta- 
 ble 1. However, the actual ground clear- 
 ance of the fixed deck can be lower than 
 6 in, and it could be reduced to zero 
 
 4. "Bounce space" between the opera- 
 tor's cap and the canopy depends on ma- 
 chine tram speed. 
 
 5. Canopy thickness can be reduced if 
 stronger steel is used; however, if steel 
 tubing is used for the canopy, its thick- 
 ness will be greater than 1 in. 
 
 6. Required clearance above the canopy 
 in a flat coal seam depends on the number 
 and height of unexpected obstructions on 
 the mine roof and floor; these will vary 
 greatly from mine to mine, from section 
 to section in a mine, and within the same 
 mining section. 
 
 LOWEST PRACTICAL WORKING HEIGHTS WITH CANOPIES 
 
 The ideal conditions needed to achieve 
 the minimum working heights with canopies 
 listed in table 1 — flat, nonundulating 
 seams and equipment that does not ob- 
 struct operator vision — will not be pres- 
 ent on most mining sections in operation 
 today. Therefore, we should define the 
 "lowest practical working height" with 
 canopies, again using state-of-the-art 
 technology, to take into account the ad- 
 verse effects of mine floor undulations 
 and visual obstructions caused by the 
 canopy and machine frame. 
 
 EFFECTS OF MACHINE FRAME HEIGHT 
 
 The machine frame almost always ob- 
 structs vision in low coal. Operators 
 frequently lean outward to see alongside 
 their machines because this is the only 
 vision available when clearance between 
 the frame and the mine roof is limited, 
 even when a canopy is not present. The 
 canopy introduces yet another visual ob- 
 struction, one that many machine opera- 
 tors consider "unnecessary" and "danger- 
 ous." The following paragraphs describe 
 
83 
 
 a simple procedure for calculating the 
 lowest practical working height with a 
 canopy from the machine frame height. 
 
 When defining a relationship between 
 the machine frame height and the lowest 
 practical working height at which a can- 
 opy can be used, one critical factor must 
 be specified — the vertical distance be- 
 tween the top of the machine frame and 
 the operator's eye level. A wide range 
 of opinions was received regarding the 
 distance needed to assure "adequate" op- 
 erator vision. For example, in the Ben- 
 dix canopy survey^ equipment manufactur- 
 ers recommended that the operator's eyes 
 be placed 3 to 8 in above the machine 
 frame. Conversely, the fact that low- 
 coal equipment operators can often run 
 their machines using solely "down-the- 
 side" vision has been used as evidence 
 that their eyes can be at any level below 
 the top of the main frame. Considerable 
 disagreement will continue to exist no 
 matter what frame-to-eye level distance 
 is chosen; however, for simplicity, it 
 is assumed here that the operator's eyes 
 must be at the same level as the top of 
 the machine frame to assure adequate vi- 
 sion. Using this assumption and the pro- 
 cedures described earlier in this ar- 
 ticle, the "lowest practical working 
 height" with canopies can be determined 
 directly from the machine frame height. 
 
 Referring again to figure and table 1, 
 segments 1 through 3 define the minimum 
 distance between the mine floor and the 
 operator's eye level. Since it is as- 
 sumed the machine frame will not obstruct 
 operator vision if it is below eye level, 
 the lowest practical working height with 
 a canopy will not be governed by the ma- 
 chine frame height if it is less than the 
 sum of segments 1 through S, For such 
 low-frame machines, the lowest practical 
 working height in a flat coal seam will 
 be equal to the minimum working height 
 listed in table 1; operator headroom 
 rather than vision will be the limiting 
 factor. 
 
 ^ork cited in footnote 4. 
 
 The first four columns of table 2 show 
 how the machine type, compartment ground 
 clearance, and operator seating position 
 combine to determine the minimum machine 
 frame height to be considered in the 
 analysis of the lowest practical working 
 height with a canopy. For example, if 
 the operator compartment on a continuous 
 miner forces a 95th percentile size male 
 to assume an upright position (33 in from 
 seat to eyes), the minimum frame height 
 to be considered will be 36 in (33 in + 3 
 in deck and seat thickness) despite the 
 compartment's ability to float on the 
 mine floor. On the other hand, scoops 
 and tractors with frames as low as 23 in 
 can be considered because the operator's 
 ability to lie down (if modifications to 
 the compartment are made) places his or 
 her eyes at this height despite the nomi- 
 nal 6-in compartment ground clearance. 
 If the actual machine frame height is 
 greater than the minimum applicable 
 height given by table 2, it is assumed 
 that segment 1,2, or 3 of table 1 would 
 be increased to place the operator's eyes 
 at the same level as the frame. 
 
 The fifth column of table 2 shows 
 how the lowest practical working height 
 with a canopy in a flat coal seam is 
 calculated from the machine frame 
 height. The sum of segments 4 through 7 
 in figure 1 and table 1 is the required 
 vertical clearance between the machine 
 frame (eye level) and the nearest over- 
 head obstruction. This clearance is 14.5 
 in for fast-moving machines and 13.0 
 in for slow-moving machines because the 
 need for operator headroom increases 
 with tram speed. Thus, in level seams, 
 one of the two formulas listed in the 
 fifth column of table 2 can be used to 
 calculate the lowest practical working 
 height. 
 
 Note that if the lowest practical work- 
 ing height were calculated with the re- 
 quirement that the operator's eyes be 
 placed at a certain level above the top 
 of the machine frame, for example, 3 in, 
 the result would be the same as if the 
 formulas listed in table 2 were used. 
 
84 
 
 TABLE 2. - Formulas for calculating "lowest practical work heights" 
 with canopies in flat coal seams 
 
 
 Compart- 
 
 
 Minimum appl- 
 
 Formula for 
 
 
 ment 
 
 
 cable frame 
 
 lowest prac- 
 
 Machine type 
 
 ground 
 
 Operator seating 
 
 height , 
 
 tical work- 
 
 
 clear- 
 
 position^ and size 
 
 ground 
 
 ing height, 
 
 
 ance, 
 
 
 clearance 
 
 frame height 
 
 
 in 
 
 
 plus — 
 
 plus — 
 
 Continuous miners... 
 
 0-6 
 
 Reclining - 5th pet female 
 
 and 95th pet male. 
 Sitting - 5th pet female 
 Sitting -95th pet male.. 
 
 26 in 
 
 32 in 
 36 in 
 
 13 in 
 
 Shuttle cars 
 
 0-6 
 
 Reclining - 5th pet female 
 
 and 95th pet male. 
 Sitting - 5th pet female 
 Sitting -95th pet male.. 
 
 26 in 
 
 32 in 
 36 in 
 
 14.5 in 
 
 Roof bolters,^ cut- 
 
 0-6 
 
 Reclining - 5th pet female 
 
 26 in 
 
 13 in 
 
 ters, face drills, 
 
 
 and 95th pet male. 
 
 
 
 and loading 
 
 
 Sitting - 5th pet female 
 
 32 in 
 
 ' 
 
 machines . 
 
 
 Sitting -95th pet male.. 
 
 36 in 
 
 
 Scoops and tractors. 
 
 63 
 
 Lying - 5th pet female 
 
 and 95th pet male. 
 Reclining - 5th pet female 
 
 and 95th pet male. 
 Sitting - 5th pet female 
 Sitting -95th pet male.. 
 
 17 in 
 
 26 in 
 
 32 in 
 36 in 
 
 14.5 in 
 
 'Modifications to 
 lying-down positions. 
 
 ^Tram canopy only. 
 
 ^Floating operator 
 or less than 6 in. 
 
 operator compartments may be necessary to allow reclining and 
 "Pet" indicates percentile in entries in this column. 
 
 compartments unavailable; actual ground clearance may be more 
 
 Although the minimum applicable frame 
 height would be 3 in lower than listed in 
 table 2, the numerical value added to the 
 frame height to obtain the lowest practi- 
 cal working height would be 3 in greater 
 (16.0 in or 17.5 in versus 13.0 in or 
 14.5 in). On the other hand, if the op- 
 erator's eyes are allowed to remain below 
 the level of the machine frame, the low- 
 est practical working height with a can- 
 opy would be equal to the minimum working 
 height listed in table 1. The minimum 
 applicable frame height in this ease 
 would be equal to the minimum working 
 height minus 4 in to allow for rough bot- 
 tom conditions which may cause the frame 
 itself to hit the roof. 
 
 EFFECTS OF MINE FLOOR UNDULATIONS 
 
 Until this point , it was assumed that 
 mine floor undulations (abrupt changes in 
 eoalbed elevation) were not prevalent. 
 However, all mine floors undulate to some 
 degree, and both the miaehine frame and 
 the canopy will experience some amount of 
 upward or downward movement , or excur- 
 sion, when tramming through the undula- 
 tion. The amount of canopy excursion 
 must be added to either the minimum work- 
 ing height (table 1) or the lowest prac- 
 tical working height in a flat coal seam 
 (table 2) to obtain the lowest practical 
 working height with a canopy in undulat- 
 ing conditions. 
 
85 
 
 Overall canopy excursion can be cal- 
 culated geometrically and depends on 
 three major factors: (1) the location 
 of the operator's compartment and can- 
 opy on the machine, (2) the degree of 
 change in the slope of the coalbed floor 
 (degree of undulation) , and (3) the de- 
 sign of the cab and canopy. Floating 
 operator compartments can reduce canopy 
 excursion somewhat but cannot always 
 eliminate it. Figures 2 through 7 illus- 
 trate canopy excursion and show how it 
 can be calculated. 
 
 Canopy Excursion on 
 End-Driven Equipment 
 
 Figures 2 and 3 are scale drawings of a 
 typical continuous miner tramming over a 
 "severe" undulation — an abrupt 6° change 
 in the slope of the mine floor. When the 
 miner is in the position shown in figure 
 2, the maximum amount of vertical canopy 
 excursion is taking place because its 
 center of gravity (pivot point) has just 
 crossed the undulation point. The maxi- 
 mum possible excursion E is equal to D 
 
 Distance from machine pivot 
 point to canopy, D 
 
 '^m\wiim^im^jj^m\^ii^\^^m^mm\mm 
 
 Undulation 
 point 
 
 Angle of 
 
 mine floor 
 
 undulation, 0- 
 
 "Upward canopy excursion; E 
 
 FIGURE 2. - Upward canopy excursion on end-driven equipment. 
 
 Maximum downward 
 canopy excursion = 9' 
 
 Cab -canopy hinge 
 point 
 
 Machine pivot point 
 and undulation point 
 
 FIGURE 3. - Canopy excursion reduction with floating operator compartment. 
 
86 
 
 (sin 0), where D is the distance from the 
 machine's center of gravity to the point 
 on the canopy being considered, in this 
 case the rear edge, and is the degree 
 of mine floor undulation. In figure 2, D 
 equals 140 in and is 6° , so E equals 
 14.6 in. 
 
 If the operator's compartment and can- 
 opy cannot float downward below the orig- 
 inal level of the crawlers of the miner, 
 as in figure 2, the lowest practical 
 working height with a canopy would be 
 14.6 in greater than indicated in table 1 
 or 2, and the rear end of the canopy 
 would "roof out" first. However, as 
 shown in figure 3, floating operator com- 
 partments on continuous miners are usual- 
 ly hinged at the end closest to the cut- 
 ting heads, with the rear end free to 
 float downward until stopped mechanical- 
 ly, in this case by the rear bumper of 
 the miner. The amount of downward canopy 
 movement depends on (1) the location of 
 the front and rear ends of the canopy 
 with respect to the hinge point and 
 (2) the distance below the crawler at 
 which the deck is downstopped. To show 
 how this downward movement can be calcu- 
 lated, let us examine figure 3. 
 
 Figure 3 shows the full-down position 
 of the operator's compartment — note that 
 the deck is not resting on the mine 
 floor. The distance between the downstop 
 block and the rear bumper of the miner 
 when the deck is in the level position 
 (fig. 2) represents the maximum downward 
 excursion of the rear end of the canopy, 
 in this case 9 in. Subtracting this val- 
 ue from the 14.6 in of initial upward 
 canopy excursion yields an overall upward 
 excursion of 5.6 in at the rear end of 
 the canopy. 
 
 Now the excursion of the front end of 
 the canopy must be examined. The angle 
 through which the canopy rotates when it 
 floats downward is the same at both its 
 front and rear ends, and the amount of 
 downward movement at the front end de- 
 pends on its horizontal distance from the 
 hinge. From geometry, the downward ex- 
 cursion was found to be 2.1 in, using 
 compartment dimensions provided by the 
 
 manufacturer. Subtracting this downward 
 movement from the 10-in upward excursion 
 of the front end [from the formula E 
 = (D) (sin 0) at D = 96 in] yields a to- 
 tal canopy excursion of 7.9 in. Thus, if 
 the front and rear ends of the canopy 
 were at the same level before the 6° 
 undulation was encountered, the front 
 end would strike the roof or roof sup- 
 ports first (7.9 in versus 5.6 in overall 
 excursion) . 
 
 Note in table 1 that the minimum work- 
 ing height for canopy-equipped continuous 
 miners in level conditions was found to 
 be 39.0 in. The lowest practical working 
 height with the canopy on the miner in 
 figures 2 and 3 can now be calculated: 
 
 in 
 
 Minimum working height in level 
 conditions (table 1) 39.0 
 
 Maximum upward canopy excursion 
 (fig. 3) 7.9 
 
 Total 46.9 
 
 Although figures 2 and 3 show a 
 crawler-driven continuous miner, the pro- 
 cedure used to calculate canopy excursion 
 would be the same for any wheel-driven 
 machine whose operator's compartment is 
 at the front or rear end. Several models 
 of shuttle cars, roof bolters, scoops, 
 and tractors fall into this category. 
 Because the maximum canopy excursion will 
 take place when the axle closest to the 
 operator's compartment crosses the undu- 
 lation point, the distance D depicted in 
 figures 2 and 3 would be the distance 
 from the end of the canopy to the axle of 
 the nearest wheel. Also, if the opera- 
 tor's compartment can float downward at 
 both ends, instead of being hinged, the 
 amount of downward movement would be the 
 same at both ends of the operator's com- 
 partment, and the end of the canopy far- 
 thest from the axle would roof out first. 
 
 In general, the procedure for determin- 
 ing the lowest practical working height 
 with canopies on end-driven equipment can 
 be summarized as follows: 
 
87 
 
 1. Find the potential upward excur- 
 sion from the formula E = (D) (sin 0) for 
 the actual slope change angle and pivot- 
 point-to-canopy distance, 
 
 2. Use actual compartment geometry to 
 calculate the maximum excursion reduction 
 possible, as in figure 3. 
 
 3. Add the difference of items 1 
 and 2 to the height obtained from ta- 
 ble 1 or table 2 for the machine under 
 consideration. 
 
 The resultant distance is the working 
 height that must be provided to keep the 
 canopy from roofing when undulating mine 
 floor conditions prevail. The same pro- 
 cedure can be used to calculate the 
 "lowest practical working height" with 
 the machine itself , simply by adding the 
 maximum upward excursion of the machine 
 frame (usually near its rear end) to the 
 original machine frame height. 
 
 Canopy Excursion on 
 Center-Driven Equipment 
 
 Figures 4 through 7 illustrate canopy 
 excursion as it would occur on a shut- 
 tle car whose operator's compartment is 
 located between the tramming wheels. 
 Most low-profile shuttle cars fall into 
 this category, along with cutters, face 
 drills, and many models of roof bolters. 
 
 Canopy excursion on center-driven 
 equipment is different from that on end- 
 driven equipment in three important ways. 
 First, the a&ntev portion of the canopy 
 on a center-driven machine will experi- 
 ence greater upward excursion than either 
 the front or rear end. Second, the 
 wheelbase of a center-driven vehicle is 
 the critical dimension governing the 
 overall canopy excursion. Finally, both 
 upward and downward mine floor slope 
 changes can cause upward canopy excur- 
 sion on center-driven machines. There- 
 fore, four individual mine-machine-canopy 
 configurations are shown in figures 4 
 through 7 to describe all situations 
 where canopy roofing can occur. 
 
 Figure 4 shows a center-driven shuttle 
 car whose deck is fixed at 6 in above the 
 mine floor, tramming over an upward undu- 
 lation. This situation represents the 
 maximum upward excursion possible with a 
 center-mounted canopy and illustrates 
 most clearly the geometrical relationship 
 between the cab, canopy, machine, and 
 mine floor. Note first the enlarged 
 sketch of the transition area around the 
 point of coalbed slope change (undulation 
 point). The maximum canopy excursion (E) 
 occurs when the wheels of the shuttle car 
 straddle the undulation point and the 
 upward projection of the undulation point 
 bisects the wheelbase. From geometry, it 
 can be seen that E = (w/2) sin (0/2), 
 where E is the upward canopy excursion, w 
 is the wheelbase of the machine, and is 
 the angle of mine floor undulation. 
 
 Applying this formula to the shuttle 
 car in figure 4 (w = 120 in, 0=6°) 
 yields a canopy excursion of 3,14 in. 
 Note also that the center portion of the 
 canopy is closest to the mine roof, which 
 has been drawn parallel to the mine floor 
 in figure 4, 
 
 The lowest practical working height 
 with a canopy on this shuttle car can now 
 be calculated (the minimum working height 
 is 46,5 in because 6 in of compartment 
 ground clearance is added to the sum of 
 segments 2 through 7 of table 1): 
 
 in 
 
 Minimum working height 46, 5 
 
 Overall canopy excursion 
 (fig. 4) 3,1 
 
 Total 49,6 
 
 Figure 5 shows a slightly different 
 shuttle car, this one with a floating 
 compartment, as it trams over an upward 
 mine floor undulation. The formula for 
 calculating the potential upward canopy 
 excursion is the same as in figure 4, 
 E = (w/2) sin (0/2), However, the over- 
 all canopy excursion would be equal to 
 
88 
 
 -w=l20"- 
 
 ^^^^^^i^mmMimmm^mm 
 
 "^^^^^mrmrm 
 
 Direction 
 
 ^mum 
 
 Transition 
 area 
 
 ■Undulation 
 point 
 
 Closeup of transition area 
 (exaggerated) 
 
 
 E=3.I4 
 
 FIGURE 4. - Upward canopy excursion on center-driven equipment (shuttle cor). 
 
 -w = 96'- 
 
 "^^^^^^^^^^^^^^^^^^^^^^^^^ 
 
 Direction 
 
 Upward excursion negated by 
 tree-floating deck 
 
 Undulation 
 point 
 
 0=6" 
 
 FIGURE 5. - Center-driven shuttle cor with floating operator compartment - upward undulation. 
 
 zero if the cab deck were allowed to 
 float downward far enough to negate the 
 upward movement. Then the lowest practi- 
 cal working height with a canopy would be 
 40.5 in, the same as in table 1, 
 
 Figure 6 shows the same shuttle car as 
 in figure 5, this time tramming across a 
 downward mine floor undulation. However, 
 instead of floating downward into open 
 space, as in figure 5, the compartment 
 in figure 6 will be pushed upward by the 
 mine floor as the shuttle car crosses the 
 
 undulation point. The maximum canopy ex- 
 cursion occurs when the undulation point 
 contacts the midpoint of the deck and is 
 calculated from the formula E = (w/2) sin 
 (G/2). 
 
 Figure 7 shows a shuttle car whose 
 operator's compartment is fixed at 6 
 in above the mine floor, tramming across 
 a downward mine floor undulation. The 
 compartment ground clearance enables it 
 to pass over the undulation point as 
 though the floor were level. The canopy 
 
89 
 
 No excursion reduction possible 
 
 Undulation 
 point 
 
 of travel 
 
 FIGURE 6. - Center-driven shuttle car with floating operator compartment - downward undulation. 
 
 Ground clearance negates upward 
 canopy excursion 
 
 Undulation 
 point 
 
 of travel 
 
 FIGURE 7. - Center-driven shuttle car with fixed operator compartment -> downward undulation. 
 
 excursion in this situation would be neg- 
 ligible, and the lowest practical working 
 height with a canopy would be the same as 
 the height found in table 1 or 2. 
 
 Summar y 
 
 Table 3 lists the range of canopy ex- 
 cursions that can be expected when "se- 
 vere" mine floor undulations of 6° are 
 encountered. The values in the right- 
 hand column of table 3 were obtained 
 from the formulas (D) (sin 0) and (w/2) 
 sin (0/2) , for end-driven and center- 
 driven equipment, respectively. Obvi- 
 ously, end-mounted canopies will almost 
 always experience more excursion than 
 center-mounted canopies because the undu- 
 lation angle is halved in the latter 
 calculation, 
 
 A wide range of potential canopy ex- 
 cursions exists for continuous miners 
 for two reasons: (1) Different models 
 
 TABLE 3, - Typical values of canopy 
 excursion' 
 
 Canopy 
 Machine type excursion,^ 
 
 in 
 Continuous miners, all 
 
 end-driven 6-15 
 
 Shuttle cars, center-driven, 3- 4 
 Shuttle cars, end-driven,,,, 6- 8 
 Scoops and tractors, center- 
 driven , 2- 3 
 
 Scoops and tractors, end- 
 driven 6- 8 
 
 Roof bolters - single- and 
 
 dual-head, center-driven,,, 2- 3 
 Roof bolters - single- and 
 
 dual-head, end-driven 6- 8 
 
 Cutters, face drills, and 
 loaders, all center-driv en, 2- 3 
 ' Severe mine floor undulations assumed; 
 slope change = 6° , 
 
 ^Excursion determined by machine model, 
 compartment location, and design of cab 
 and canopy. 
 
90 
 
 of continuous miners can have signifi- 
 cantly different pivot-point-to-canopy 
 distances, and (2) the design of the 
 hinged, floating cab and canopy has an 
 important effect on the amount of excur- 
 sion reduction attainable. Cab and can- 
 opy design is also very important when 
 calculating canopy excursion on any end- 
 driven machine. 
 
 Excursions of center-mounted canopies 
 do not vary greatly from machine to ma- 
 
 chine because wheelbases do not vary as 
 much as pivot-point-to-canopy distances. 
 Also, figures 6 and 7 show that floating 
 compartments experience move canopy ex- 
 cursion than fixed compartments when 
 downward mine floor undulations are en- 
 countered. Therefore, the only advantage 
 of using floating operator compartments 
 on center-driven machines is that they 
 eliminate the initial compartment ground 
 clearance, segment 1 of figure 1 and 
 table 1. 
 
 COMPLIANCE WITH MSHA CANOPY REGULATIONS 
 
 As stated earlier, present MSHA regula- 
 tions require the use of canopies on all 
 face equipment when the minimum mining 
 height on the section is 42 in or great- 
 er. However, even though the minimum 
 working heights with canopies listed 
 in table 1 are less than 42 in for some 
 equipment types, there are several rea- 
 sons why compliance may be difficult or 
 impossible in low-coal situations: 
 
 1. The thickness of required roof sup- 
 ports or other roof-mounted obstruc- 
 tions must be added to the minimum work- 
 ing height to obtain the minimum mining 
 height. In mines where planks, cross- 
 bars, or rails are needed for extra roof 
 support, the minimum mining height (mine 
 floor to unfinished roof) needed to allow 
 the safe use of a canopy will almost al- 
 ways be greater than 42 in. 
 
 2. Floating operator compartments are 
 not presently available for all equipment 
 types and models. Minimization of com- 
 partment ground clearance is essential to 
 the increased used of canopies in mining 
 heights close to 42 in. 
 
 3. The need for equipment operators to 
 assume upright positions makes it physi- 
 cally impossible for them to remain be- 
 neath a canopy without discomfort when 
 the mining height is limited to 42 in. 
 This problem cannot be resolved until 
 compartments are designed to allow pro- 
 tected machine operation from a reclining 
 or lying down position. 
 
 4. Canopy excursion due to mine floor 
 undulations can cause roofing to 
 
 occur in mining heights much greater than 
 42 in. 
 
 5. The heights listed in tables 1 and 
 2 were based mostly on static human body 
 and equipment dimensions rather than 
 dynamic work procedures. The effects 
 of the machine frame, the canopy, and 
 machine-mounted obstructions as the ma- 
 chine is operated will be very different 
 from machine to machine. Each operator's 
 willingness to tolerate constraints to 
 his comfort and vision will also be 
 different. 
 
 6. In many mines, the mining height 
 fluctuates above and below 42 in very 
 frequently. When the mining height is 
 below 42 in, canopies are not required, 
 so machine operators usually remove them 
 to improve comfort and vision. \ However, 
 these machines would be "out of compli- 
 ance" when the mining height rises above 
 42 in. Canopies are often very heavy, 
 cumbersome, and time-consuming to install 
 and remove, especially in the confined 
 quarters of low coal seams. Therefore, 
 both the mine operator and the workers on 
 the mining section tend to be reluctant 
 to reinstall canopies that have just been 
 removed, if they know that in the near 
 future the mining height will again fall 
 below 42 in. 
 
 In conclusion, it is obvious that low- 
 coal canopy problems are very complex 
 and can be resolved only if the exact 
 machine, mine conditions, and equipment 
 operator involved with the problem are 
 defined. 
 
 I 
 
 SU.S. CPO: 1981-505-019/5083 
 
 INT.-BU.OF MINES, PGH., PA. 27751 
 
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