Class T~U 4 kj? 
 
 Book /T^ 
 
 Copyright^ 
 
 COPYRIGHT DEPOSIT. 
 
The Valve-Setter's Guide 
 
THE 
 
 Valve -Setter's Guide 
 
 A TREATISE 
 
 ON THE CONSTRUCTION AND ADJUSTMENT OF THE 
 
 PRINCIPAL VALVE GEARINGS USED ON 
 
 AMERICAN LOCOMOTIVES 
 
 BY 
 
 JAMES KENNEDY 
 
 NEW YORK: 
 
 ANGUS SINCLAIR COMPANY 
 
 114 LIBERTY STREET 
 
 PRICE FIFTY CENTS 
 

 Copyright by the 
 
 ANGUS SINCLAIR COMPANY, 
 
 1 9 10. 
 
 C.CLA25645-4 
 
CONTENTS 
 
 3hapter page 
 
 Preface 7 
 
 I The Steam Engine 9 
 
 II The Slide Valve 12 
 
 III The Link Motion • • 14 
 
 IV Adjusting the Stephenson Valve Gear 18 
 
 V The Walschaerts Valve Gear 27 
 
 VI Variations in Form in the Walschaerts Valve Gear 30 
 
 /I I Construction of the Walschaerts Valve Gear 33 
 
 /III Adjusting the Walschaerts Valve Gear 38 
 
 IX The Baker-Pilliod Valve Gear 42 
 
 X Construction of the Baker-Pilliod Valve Gear 44 
 
 XI Adjusting the Baker-Pilliod Valve Gear 48 
 
 XII The Joy Valve Gear 51 
 
 Note on Setting the Slide Valve of a Stationary Engine. 56 
 
PREFACE 
 
 It would be difficult indeed to write anything particularly new on a 
 subject that has been so much commented on as the valve gearings of steam 
 engines ; but it will be readily admitted that things that are already familiar 
 
 to us may be seen in a new light. It will also be observed that in this age 
 of rapid changes even the steam engine is found to be capable of improve- 
 ment. The recent application of the Walschaerts valve gear to American 
 locomotives, and also the more recent invention of the Baker-Pilliod valve 
 gear has given a new interest to the subject. It is to be hoped the result 
 will be that a greater degree of reliability in the harnessing of steam in 
 locomotive service will be accomplished. It is with the hope of adding 
 something to the general mass of information, especially with a view of 
 being helpful to young railway men, that these articles have been written. 
 
 Other valve gearings claim attention. Many others besides those de- 
 scribed in this little book are in successful operation. Some still in embryo 
 are full of promise. In selecting those that are the most popular forms 
 of locomotive valve gearings in use in America, it is not with the intention 
 of ignoring or belittling other ingenious devices, but with the assurance 
 that a fair knowledge of the organic structure and methods of adjustment 
 
 7 
 
THE VALVE-SETTER'S GUIDE 
 
 of valve gearings commonly in use will readily help the thoughtful mechanic 
 to a more easily acquired knowledge of the mechanism of any valve gear- 
 ing, no matter in what shape the parts may appear. 
 
 Not only so, but as the valve gearing is the most intricate part of the 
 reversible steam engine, so the study of valve gearing is calculated to de- 
 velop the faculty of giving thoughtful attention to the details of all forms of 
 involved mechanism. 
 
 A word may be added in regard to the brevity with which the subject has 
 been treated. In an experience of many years among apprentice machinists 
 and young railway men, I never found it advantageous to pour a mass of 
 tedious information into the ears of listeners however willing they might be 
 to hear. In fact, the more anxious they were to learn the less they needed to 
 be told. A hint in the right direction was generally enough. Many excep- 
 tions arise in practice which can hardly be foreseen in imagination. The in- 
 telligent mechanic or engineer learns much that does not appear in print. 
 Practical experience unfolds the mysteries of all arts. The object of a book 
 of this kind should be to help the beginner to help himself. In the hope of 
 aiding in kindling this noble aspiration these brief articles were written for 
 the pages of Railway and Locomotive Engineering and met with much 
 popular favor, and are now collected in more convenient form in the belief 
 that they may be of further service to railway men. J. K. 
 
 New York, Jan. 1, 1910. 
 
 
 8 
 
THE STEAM ENGINE 
 
 I. THE STEAM ENGINE 
 
 Apart from the many varieties of form 
 in which steam engines are made, there 
 are two general divisons into which they 
 may be classified, those of the condensing 
 and non-condensing engines. The loco- 
 motive and nearly all the factory engines 
 are of the non-condensing type. In this 
 class the steam after it has done its work 
 in moving the piston, is exhausted into 
 the open air. An engine of this kind is 
 readily discerned by the puffing sound of 
 the exhausted steam, each re-percussion 
 indicating the completion of the piston 
 stroke, and sudden release of the pent-up 
 steam, which it may be observed has still 
 much more than sufficient force left in it 
 to overcome the pressure of the atmos- 
 phere. In a condensing engine the steam 
 after passing through the cylinder is ad- 
 mitted into a box or receptacle called a 
 condenser on account of its being cooled 
 by contact with water or with pipes 
 through which cold water is passing. The 
 condensation of the exhausted steam has 
 the effect of producing a partial vacuum 
 in the condenser, which permits the steam 
 being used until it has reached a lower 
 pressure than in a non-condensing engine. 
 Marine engines are mostly of this type, 
 as a constant supply of cold water can 
 readily be obtained. 
 
 It will be remembered that the atmos- 
 
 pheric engine previous to James Watt's 
 invention of the steam engine, was oper- 
 ated by the admission of steam into a 
 vertical cylinder, while the piston was at 
 the upper end of the stroke and when a 
 jet of cold water was admitted into the 
 cylinder, the steam was condensed, thereby 
 producing a vacuum and the weight of 
 the atmosphere acting on the uncovered 
 upper face of the piston was sufficient 
 to press down the piston. Watt con- 
 ceived the idea of condensing the steam 
 in a separate vessel, thereby effecting a 
 great saving and also made the important 
 advance in applying steam alternately to 
 both sides of the piston, thereby creating 
 or inventing an entirely different engine 
 from that of Newcomen. 
 
 The rapid condensation of steam into 
 water renders suitable openings into all 
 steam cylinders a necessity. These open- 
 ings, or cylinder cocks, as they are called, 
 are usually operated by a hand lever 
 which is placed in the open position when 
 starting the engine. This should be care- 
 fully attended to, as water unavoidably 
 gathers in the cylinders while engines 
 are not running, that is if a pressure of 
 steam is in the boiler. 
 
 The most important openings into the 
 cylinder, however, are the ports by which 
 the steam is admitted and that bv which 
 
THE VALVE-SETTER'S GUIDE 
 
 it escapes after its work is accomplished. 
 This leads us to the slide valve, the most 
 common form of valve used in steam en- 
 gines, and although simple in construction 
 it is a most ingenious contrivance for ad- 
 mitting and cutting off the supply of 
 steam at the desired instant of time. The 
 cylinder is so constructed as to form a 
 flat portion on a part of its outer surface 
 on which there are three rectangular 
 openings, the middle being the exhaust 
 port, is wider than the other two, and 
 leads directly from the cylinder face to 
 an opening on which the exhaust pipe 
 may be bolted. The two other ports are 
 the steam ports, one leading to one end 
 of the cylinder and the other to the other 
 end. The slide valve is so constructed 
 as to cover these three openings and is 
 shaped like a hollow rectangular dish 
 with an inner cavity, the edges of the dish 
 forming the face of the valve. This face 
 is carefully fitted so that when the valve 
 is placed in position it forms, in conjunc- 
 tion with the surface of the cylinder, a 
 steam-tight joint. It may be added that 
 in the early days of the steam engine 
 much care was taken in fitting the valve 
 face and valve seat together so that every 
 part of the metals were bearing equally 
 on each other. It was latterly found that 
 the friction incident to the movement of 
 the valve very quickly caused the valve to 
 adjust itself to the valve seat so that a 
 fine bearing at the start is not essential, 
 the bearing being perfected in the course 
 of a few hours' service. 
 
 The slide valve, when in the central 
 position, covers the two steam ports and 
 
 leaves the middle port open in the inner 
 cavity of the valve. If the valve was so 
 constructed as to cover the two steam 
 ports exactly it can be readily perceived 
 that a movement of the valve in either 
 direction would open one of the steam 
 ports leading to the cylinder and open 
 the other steam port to the inner cavity of 
 the valve, thereby opening the communi- 
 cation to the exhaust pipe. A valve so 
 constructed would admit steam during the 
 entire length of the piston stroke, so that 
 when the piston stroke was completed the 
 steam in the cylinder would be at or near 
 
 FIG. i. SLIDE VALVE WITHOUT LAP. 
 
 boiler pressure and when released by the 
 opening of the exhaust port, as already 
 alluded to, the loss of steam at each stroke 
 would be equal to the full capacity of the 
 cylinder and steam spaces. In its primi- 
 tive form the slide valve was constructed 
 in this way and was used on some of the 
 earlier engines of James Watt. Fig. I 
 shows such a valve in the central position. 
 This form of valve had several serious 
 objections. The smallest degree of lost 
 motion had the effect of admitting the 
 steam in a sufficient quantity to obstruct 
 the piston at the end of the stroke. The 
 tendency to create severe pounding was 
 
 10 
 
THE STEAM ENGINE 
 
 very great. The most important draw- 
 back was in the fact, already alluded to, 
 that the steam was released while at full 
 pressure, and no advantage could be taken 
 of the expansive power of steam. Dur- 
 ing Watt's lifetime the pressure of steam 
 as applied to steam engines was extremely 
 low, so that the loss was not so very great 
 as it became when, with the improvement 
 in boiler construction, higher pressures of 
 steam became available. • In the early days 
 of the locomotive fifty pounds pressure of 
 steam per square inch did not admit of 
 much advantage being taken of the ex- 
 pansion of steam in the cylinder. The 
 change of the form of the slide valve was 
 very simple, but very important. It con- 
 sisted merely of lengthening the valve 
 face, so that when the valve stood in the 
 center of the seat the edges of the valve 
 extended a certain distance over the steam 
 ports, as shown in Fig. 2. 
 
 This extension of the valve faces is 
 called outside lap, or simply lap. It has 
 the effect of closing the steam port at a 
 certain distance before the piston reaches 
 
 the end of the stroke, and this point, 
 which with the variations incident to the 
 action of the radial link is a variable 
 point, usually called the point of cut-off. 
 It can be readily understood that when 
 the supply of steam is cut off from the 
 boiler before the piston stroke is com- 
 
 FIGu 2. VALVE WITH OUTSIDE LAP. 
 
 pleted, the piston is moved on its further 
 course by the expansive power of steam, 
 and when the stroke is completed the 
 steam in the cylinder having increased 
 in volume is correspondingly reduced in 
 pressure and when released the loss is not 
 great, as the pressure of the steam is not 
 greatly in excess of the pressure of the 
 atmosphere. 
 
 II 
 
. THE VALVE-SETTER'S GUIDE 
 
 II. THE SLIDE VALVE 
 
 Having described the construction of 
 the slide valve and its relation to the 
 steam ports, and pointed out the advan- 
 tage derived from the face of the valve 
 being made more than sufficient to cover 
 the steam ports, it remains to be stated 
 that the opening and shutting of the 
 steam ports by the movement of the 
 valves is of the utmost importance in the 
 running of the steam engine. It will be 
 readily understood that when the piston 
 is at one or other of the extreme ends of 
 the cylinder and it is intended that it 
 should be moved in the other direction, 
 the steam port should be rapidly opened 
 so that the steam may exert its full pres- 
 sure on the face of the . piston. Many 
 eminent engineers held the opinion that 
 the opening of the port should occur in 
 advance of the arrival of the piston at the 
 end of the stroke. This is what is known 
 as the lead of the valve. It has been the 
 subject of much discussion and is still an 
 open question. At first sight it would ap- 
 pear to be a hindrance to the piston to 
 meet with a pressure of steam working 
 adversely to the direction in which the 
 piston was moving, but when it is borne in 
 mind that even steam at high pressure, 
 moving at a high velocity, requires some 
 small instant of time to move through 
 the intervening space between the steam 
 
 chest and cylinder, and also that the pis- 
 ton itself may be moving at a high speed, 
 it is easy to understand that it may be 
 an advantage to begin to open the valve 
 slightly in advance of the reversing of the 
 movement of the piston. 
 
 This is more readily apparent in the 
 case of engines running at high speeds 
 than otherwise, because the velocity with 
 which the steam moves through a certain 
 space at a certain pressure may be safely 
 called a constant velocity, while the rate 
 of speed at which the valve or the pis- 
 ton travels varies according to the kind 
 of work accomplished. This fact has led 
 to the claim that the increase in the 
 amount of lead in the valve which is 
 caused by the shortening of the travel of 
 the valve in the case of engines equipped 
 with the Stephenson valve gear is an ad- 
 vantage to locomotives running at high 
 speeds when the reverse lever is "hooked 
 up." The action of the steam in striking 
 with sudden force at the beginning of the 
 piston stroke may be likened to what is 
 known as "advancing the spark" in gaso- 
 line engines, which has the effect of in- 
 creasing the velocity of the engine partly 
 from the more complete compression of 
 the inflammable gases, and partly from 
 the fact that the gasoline engine piston 
 receives the full shock of the explosion 
 
 12 
 
THE SLIDE VALVE 
 
 before it has moved any considerable dis- 
 tance from the end of the cylinder. 
 
 The parallel between the action of 
 steam pressure and gasoline explosion, 
 however, is not an exact one. The varia- 
 tion is very great, steam being a constant 
 pressure and gasoline explosion an inter- 
 mittent shock. Increasing the amount of 
 lead in the valve of a steam engine does 
 not by any means increase the speed of 
 the engine. It has the contrary effect, 
 and it is a growing fact that the idea 
 which obtained in many quarters that a 
 locomotive could not run freely unless 
 
 SLIDE VALVE SHOWING LEAD. 
 
 the valves were set with considerable lead 
 is rapidly losing its adherents. This fal- 
 lacy may readily be dispelled by marking 
 the degree of smoothness with which a 
 well-balanced locomotive will run when 
 an opportunity occurs to shut off steam 
 altogether. The alleged shock which a 
 certain amount of lead of the valve is 
 said to overcome is not apparent, and 
 there is undoubtedly a growing opinion 
 that the older methods of having a valve 
 opening of one-eighth of an inch is grad- 
 ually losing ground, and this amount after 
 being cut down to one-sixteenth is now 
 
 reaching the thirty-second mark, and if 
 the present trend of thought continues the 
 so-called lead of the valve will have be- 
 come a minus quantity. 
 
 It may be added that the idea that the 
 increase in the amount of lead of the valve 
 caused by the shortening of the valve 
 travel, in the case of the Stephenson 
 valve gearing, was an advantage, has lost 
 credence largely from the fact that since 
 the rapid introduction of the Wal- 
 schaerts valve gearing, with which many 
 of the new and larger locomotives are 
 equipped, it has been clearly demonstrated 
 that the constant lead maintained by the 
 latter valve gearing at varying amounts 
 of valve travel and speed, is a decided 
 advantage in its favor. Indeed, many 
 experienced engineers do not hesitate to 
 assert that the excessive amount of lead 
 formerly allowed in locomotive practice, 
 and the large increase in that amount oc- 
 casioned by the shortening of the valve 
 travel, was the chief cause of much of the 
 troubles incident to the involved mechan- 
 ism of the Stephenson valve gearing. Be 
 this as it may, the opinion is rapidly tak- 
 ing firm root that the amount of valve 
 opening at the end of the piston stroke 
 should be kept at the lowest possible 
 amount, and that better results in loco- 
 motive and engine running generally could 
 be obtained by having the valve closed 
 at the end of the piston stroke than by 
 having an opening wide enough to admit 
 sufficient steam that cannot do other than 
 counteract the motion of the piston as it 
 approaches the dead center. 
 
 13 
 
THE VALVE-SETTER'S GUIDE. 
 
 III. THE LINK MOTION 
 
 A peculiarly important quality of the 
 steam engine is the fact that it lends itself 
 with ease to perfect control. That mo- 
 tion of such amazing force can be sud- 
 denly stopped and reversed within a brief 
 
 ments are simple enough, and if taken 
 into consideration one by one can be 
 readily understood by the average student 
 in a short time. 
 The invention of the link motion has 
 
 U Valvt 8tm 
 
 BockerSha/t 
 
 a* Central Lint of Motion 
 % 
 
 period of time is one of the most won- 
 derful results of applied science. 
 
 The most common form of reversing 
 gear is what is known as the link motion. 
 The combination of levers and rods and 
 eccentrics and radial link have an involved 
 air of mystery to the young engineer, but 
 a little attention will show that the move- 
 
 been the subject of much controversy, but 
 it is now universally conceded that Mr. 
 William Williams, a young Welchman, a 
 draughtsman employed in the Stephenson 
 Locomotive Works at Newcastle, Eng- 
 land, submitted the first sketch showing the 
 idea of a movable link suspended from 
 the arm of a movable shaft and equipped 
 
 14 
 
THE LINK MOTION 
 
 with means of being attached to two ec- 
 centrics, the movable link being attached 
 to the valve rod, effecting the reversing 
 of the engine and also a variation in the 
 valve travel and consequent variation in 
 the expansive use of steam. It was a 
 masterly invention and the unconscious 
 young inventor, to whom the thought had 
 come as an inspiration, had evidently no 
 comprehension of the momentous impor- 
 tance of the device. It may be said to 
 
 explained his device to some self-seeking 
 shopmates who were not slow to take ad- 
 vantage of his ingenuousness. Claims of 
 improvements were made by others, but 
 the fact is that Mr. Williams' finished in- 
 vention was incapable of any improve- 
 ment. The device was not patented. The 
 Stephensons began applying it to their 
 locomotives in 1842. It came into im- 
 mediate favor and has been the most 
 popular form of valve gearing used on 
 
 &)■ i l *co. fry. 
 
 REPRESENTATION OF THE ANGUS SINCLAIR CO. VALVE MODEL WITH D-SLIDE 
 
 VALVE. 
 
 have completed Watt's wonderful engine. 
 At one stroke the harnessing of the titanic 
 force of steam was completed. Engines 
 could henceforth be run backward or for- 
 ward. Variable expansion, variable speed, 
 with all the delicate varieties in force and 
 velocity, were at once accomplished. 
 
 It is a matter of regret that so little is 
 known of the gifted mechanician. With 
 the frankness of youth he seems to have 
 
 locomotives ever since. In the absence of 
 any legal claim to the invention the device 
 became generally known as the Stephen- 
 son valve gearing or shifting link, the 
 latter name being used in contradistinction 
 to link motions where the link oscillates 
 on a fixed center as in the Walschaerts 
 valve gearing. 
 
 In the excellent model before us, a du- 
 plicate of which can be procured from the 
 
 IS 
 
THE VALVE-SETTER'S GUIDE 
 
 publishers of Railway and Locomotive 
 Engineering, and a drawing of which is 
 reproduced for illustration, it will be noted 
 that the piston is in the middle of the 
 cylinder. Both steam ports are closed, 
 and if it is desired that the engine should 
 be moved forward it will be necessary that 
 the steam be admitted at the front so that 
 the piston should be pressed backwards 
 and so move the wheels forward on the 
 rails. In order to admit the steam to the 
 front end of the cylinder the valve must 
 be moved backward. It will be readily 
 noted that by moving the lever forward 
 on the quadrant the radial link is dropped 
 downward until the upper eccentric rod 
 is in line with the lower end of the rocker. 
 To accommodate itself to this movement 
 the lower end of the rocker has been 
 pushed some distance forward, the upper 
 end of the rocker consequently moving an 
 equal distance backward and carrying with 
 it the slide valve. This has the effect of 
 opening the steam port leading to the 
 front end of the cylinder and the pressure 
 of the steam is admitted to the front face 
 of the piston. 
 
 If, on the other hand, it is desired to 
 move the engine backwards, it will be 
 found that by moving the lever to the 
 back of the quadrant, the link is raised 
 until the lower eccentric is in line with 
 the lower end of the rocker. To admit 
 of this movement the lower end of the 
 rocker is drawn back with the consequent 
 result that the upper end of the rocker 
 has been moved a corresponding distance 
 forward, thereby opening the steam port 
 leading to the back of the cylinder and 
 
 so admitting the steam to the back of the 
 movable piston, which moving forward 
 has the effect of moving the wheels back- 
 ward upon the rails. 
 
 There are several important factors 
 rendering these simple movements pos- 
 sible and wTiich, if carefully observed, will 
 readily impress themselves upon the mem- 
 ory of the attentive student. The first is 
 that with the rocker in perpendicular posi- 
 tion, the valve rod should be of the exact 
 length so that the valve should be in the 
 central positon in regard to the steam 
 ports. Presuming that the piston has 
 moved forward in the cylinder until it 
 has reached the extreme end of the stroke, 
 it is necessary that the valve should be 
 beginning to open the front port in order 
 that the steam may be admitted to the 
 front face of the piston for the purpose 
 of moving the piston backward. At this 
 particular point it is well to turn our 
 attention to the position of the eccentrics 
 and their relation to the driving crank. 
 It will be understood that with the pis- 
 ton at the front end of the cylinder the 
 main crank pin is at the forward center. 
 If the valve was so constructed as to 
 cover the steam ports exactly, the two ec- 
 centrics should be standing with their 
 extreme points at right angles to the main 
 crank pin, the forward eccentric with its 
 extreme point being on the top or above 
 the crank, and the eccentric controlling 
 the backward motion on the bottom or 
 below the crank. 
 
 As previously described, however, the 
 valve in modern use is so constructed that 
 the extreme ends of the valve when in a 
 
 16 
 
THE LINK MOTION 
 
 central position overlap the steam ports. 
 In the modern locomotives this amount 
 of lap extends to three-quarters of an 
 inch, and if to this is added some amount 
 of valve opening it will be readily under- 
 stood that the eccentrics must be moved 
 sufficiently from the position at right 
 angles to the crank to a position nearer 
 to the crank by an amount equal to the 
 lap and lead combined. The effect of this 
 movement toward the crank on the part 
 of the eccentric has the effect of pushing 
 the lower end of the rocker toward the 
 cylinder and consequently drawing the up- 
 per end of the rocker with the valve rod 
 backward a sufficient distance to overcome 
 the lap of the valve. 
 
 It need hardly be stated that the sliding 
 valve alluded to is the common D-shaped 
 valve, but the operations of the outside 
 admission piston valve are identical with 
 the action of the valve described. In the 
 case of an inside admission piston valve 
 a change of the position of the eccentrics 
 in their relation to the main crank is nec- 
 essary, as it will be readily seen that the 
 edge of the valve at the point of admission 
 
 is at the opposite side of the port and 
 the valve also must necessarily travel in 
 the opposition direction to that of the out- 
 side admission valve. The relative merits 
 of the various forms of valves are not 
 pertinent to a general discussion of the 
 link motion. 
 
 It will be observed that the radial link 
 is simply a contrivance for the purpose of 
 detaching one eccentric and placing the 
 other in operation, besides which it has 
 the advantage of varying the amount of 
 travel of the valve, thereby allowing a 
 supply of steam to be admitted for a long 
 cr short space of the piston stroke. This 
 is accomplished by moving the lever 
 toward the center of the quadrant and it 
 will be easily understood that as the ec- 
 centric rod in operation is moved some 
 distance from the end of the rocker it has 
 the effect of shortening the movement of 
 the rocker arm and consequently shorten- 
 ing the stroke of the valve. Such are the 
 chief features of the link motion and with 
 these clearly in mind, other less important 
 details may be readily mastered by the 
 thoughtful student. 
 
 17 
 
ADJUSTING THE STEPHENSON VALVE GEAR 
 
 IV. ADJUSTING THE STEPHENSON VALVE GEAR. 
 
 The importance of correctly adjusting 
 and maintaining the position of the valves 
 cannot be overestimated. Like the valves 
 in the hearts of animals their perfect 
 operation is the very life of the moving 
 force of the machine. The work of ad- 
 justing the mechanism has been absurdly 
 overestimated, and the idea assumed by 
 many that the operation is a difficult one 
 is a gross error. Like other alleged mys- 
 teries that owe their importance to the 
 lack of opportunity of witnessing their 
 true inwardness, familiarity soon begets a 
 spirit of common regard. There is just 
 the same degree of accuracy necessary in 
 adjusting the attachments of the throttle 
 valve. Both are a simple matter of care- 
 ful experiment and exact measurement. 
 In adjusting the ordinary sliding valve it 
 may be said at the outset that there are 
 degrees of proficiency required from the 
 designing of the parts of the gearing to 
 the simple matter of squaring the eccentric 
 rods in a brief roundhouse examination. 
 The working machinist is very safe to 
 assume that the designer's part is correct 
 and he can safely proceed with the adjust- 
 ment of the valve gear, which is generally 
 among the last operations in the building 
 or repairing of a locomotive. 
 
 Assuming that the four eccentrics are 
 loose upon the driving axle of an or- 
 
 dinary 8-wheel locomotive, the best plan 
 is to move the engine until one of the 
 crank pins on the axle to which the ec- 
 centrics are placed is on the forward 
 center, that is the point nearest to the 
 cylinder. We will assume this is on the 
 right side. If the eccentric which is de- 
 signed to move the engine in a forward 
 direction is intended to be next the frame, 
 the eccentric may be promptly put in 
 place somewhere about 85 degs. above 
 the line of the crank pin, the exact po- 
 sition need not be ascertained at this 
 time, the eccentric being temporarily held 
 in place by one or more set screws. The 
 "eccentric intended for the backward mo- 
 tion is placed a simlar distance below the 
 crank pin or center line of the axle. The 
 eccentrics on the other side of the engine 
 can be similarly attached temporarily in 
 their places. Assuming that the links 
 have been already attached to the rockers 
 and the link hangers adjusted to the arms 
 of the lifting shaft, the forward eccentric 
 rod should then be adjusted to the top of 
 the link and the back eccentric rod to the 
 bottom of the link. We are now ready to 
 begin the operation of correctly adjusting 
 the entire gearing, and it may be stated 
 that inasmuch as the preparatory mark- 
 ings of centers and openings are of prime 
 importance, it is proper that the locomo- 
 
ADJUSTING THE STEPHENSON VALVE GEAR 
 
 tive should be levelled. It does not follow 
 that because the engine is new or newly 
 repaired it is exactly level. The tendency 
 is to drop slightly in front, which is gen- 
 erally rectified when the water is placed 
 in the boiler. When the engine is level 
 the rocker should be placed exactly plumb. 
 This can readily be done by moving the 
 reverse lever while a fine line is hung 
 over the rocker end with two small 
 weights attached and the lever stopped at 
 the exact point where the two lines are 
 equidistant from the center of the rocker. 
 The valve rod should then be adjusted 
 so that the valve is exactly in the middle 
 of the valve seat. A neglect of this im- 
 portant point will cause variations in the 
 valve travel that can never be entirely 
 overcome. At this time it should be noted 
 whether the valve yoke is properly ad- 
 justed to suit the thickness of the valve, 
 as in the case of an engine being fre- 
 quently repaired the valves and valve 
 faces wear rapidly and a liner may be 
 necessary under the valve yoke to prevent 
 undue strain upon the valve rod packing 
 as well as a tendency to tilt the valve. 
 
 Before finally attaching the valve rod 
 to the rocker, the best method of marking 
 the exact positon of the valve openings 
 is by a tram reaching from the guide 
 yoke or other fixed part of the engine to 
 a suitable position on the valve rod. 
 Both ends of the tram are sharpened, one 
 end to adjust itself to a center punch 
 mark on the guide yoke, and the other 
 end, which is bent so as to scratch a mark 
 readily on the valve rod. The points 
 marked are necessarily where the valve is 
 
 beginning to open at the front and back 
 steam ports. The marks on the valve rod 
 should be marked lightly with a fine cen- 
 ter punch. The steam chest lid can then 
 be put on the steam chest and any dan- 
 ger of material or articles falling into the 
 steam chest can be entirely avoided. 
 
 The next operation should be the ascer- 
 taining of the exact dead centers or po- 
 sitions when the crosshead and piston are 
 standing still at each end of the piston 
 stroke. This point should be located very 
 carefully. If the rim of the main driving 
 wheel is near the guide yoke the same 
 tram may suit to locate the center, but 
 generally a longer tram is necessary with 
 both ends bent. The engine may then 
 be moved to a point where the crosshead 
 is about half an inch from the back or 
 forward end of the stroke. A fine center 
 punch mark may be made on the cross- 
 head and guide yoke or guide block as 
 the case may be, and a pair of compasses 
 carefully adjusted to the two points. Ac- 
 companying this adjustment, the tram 
 should be extended from the guide yoke 
 or other point to the rim of the wheel 
 and an arc drawn by the sharp end of 
 the tram. The engine should then be 
 moved over the center until the crosshead 
 returns to the exact point where the com- 
 passes touch the center marks on the 
 crosshead and guide yoke or block. An- 
 other arc or line should be drawn on 
 the wheel rim and a point between those 
 two arc lines is the dead center. It will 
 be noted by those who have time to try 
 the experiment that it is difficult to ob- 
 tain this center mark in a positively cor- 
 
 19 
 
THE VALVE-SETTER'S GUIDE 
 
 rect positon. A repetition of the experi- 
 ment with the crosshead at a greater or 
 lesser distance from the end of the stroke 
 will show a slight variation. This arises 
 from the fact that while the crosshead is 
 moving very slowly near this point the 
 rim of the wheel is moving rapidly, and 
 it may be added that the valve is also 
 moving rapidly at this time. Hence the 
 utmost care should be taken in ascer- 
 taining the dead centers. It is often 
 noted that in looking over the valves, it 
 may be only a few days after the engine 
 has been running, that the exact center, 
 as newly discovered, may show a con- 
 siderable variation in the rim of the 
 wheel. This arises from the lost motion 
 already caused by the incidental wear of 
 the engine bearings, so that old markings 
 on wheel rims instead of being of any 
 value are often misleading. Variations in 
 the dead center marks will also show in 
 marking while the engine is moving for- 
 ward as compared with markings that are 
 made while the engine is running back- 
 ward. 
 
 It is seldom that the wheel rim varia- 
 tions in marking are heeded, but they 
 are of real value if a serious effort is 
 maintained to keep the valves in correct 
 positions. 
 
 Having the valve rods marked and the 
 dead center points located, we now pro- 
 ceed to ascertain the position of the 
 valves. As one at a time is good work, 
 at least for a beginner, we may as well 
 proceed with the right forward. Place 
 the reverse lever in the extreme forward 
 notch and mOve the engine forward' until 
 
 the tram touches the dead center point. 
 Then proceed to make a mark on the 
 valve rod. If you are on the forward 
 center observe if the mark made on the 
 valve rod is near the forward opening 
 mark. Keep in your mind's* eye the lo- 
 cation of the end of the piston stroke 
 and steam port you are working on. 
 Move the engine ahead till you reach the 
 other end of the stroke where it is as- 
 sumed marks have been made on the 
 wheel rim in the same manner as before. 
 With the tram at the center try the tram 
 
 F >l 
 
 F 7\ 
 
 FIG. i. FIRST MARKING. 
 
 on the valve rod and make another 
 scratch. It is not to be expected that 
 the scratches will be equidistant from the 
 marks showing the valve openings. We 
 will suppose that Fig. I is about the 
 location of the scratchings and opening- 
 marks. 
 
 It will be seen at a glance that the valve 
 opening at the front end of the stroke is 
 about three-eighths of an inch, while at 
 the back end there is about one-eighth of 
 an inch of lap, or in other words there 
 is no opening at the back end of the 
 stroke until the valve rod has moved at 
 least one-eighth forward. It will readily 
 be seen that no matter which end of the 
 stroke we are at the valve rod must be 
 moved about a quarter of an inch ahead 
 
 20 
 
ADJUSTING THE STEPHENSON VALVE GEAR 
 
 in order to equalize the opening at both 
 ends of the stroke. Assuming that both 
 ends of the rocker are of equal length, 
 the right forward eccentric rod must be 
 shortened a quarter of an inch. It is not 
 necessary at this time to make the altera- 
 tion perfectly exact, but we shall suppose 
 that the rod is moved and that the open- 
 ing on each end is about a quarter of an 
 inch. Another trial of the tram at both 
 ends should show something resembling 
 Fig. 2. 
 
 We will assume that the amount of 
 opening desired at the end of the stroke 
 is one-eighth of an inch. It will be seen 
 that presuming we are at the front end 
 opening the valve rod must be moved 
 ahead one-eighth, but it must be evident 
 that while moving the eccentric rod would 
 accommodate us at this end of the valve 
 
 r >i 
 
 FIG. 2. ECCENTRIC ROD ADJUSTED. 
 
 stroke, it would have the effect of in- 
 creasing the opening at the other end, as 
 was seen in the previous experiment, it 
 is, therefore, necessary when the eccentric 
 rod has been evenly adjusted that the ec- 
 centric itself should be moved in order to 
 increase or diminish the amount of open- 
 ing at both ends of the valve stroke. In 
 the present instance the eccentric must be 
 moved further away from the crank and 
 approach more nearly to right angles or 
 
 90 degs. from the crank. While the 
 eccentric is being moved, the valve rod 
 should be carefully watched and the ec- 
 centric secured at the desired point, 
 which after experimentally moving the 
 engine and marking the dead centers will 
 show something like Fig. 3. 
 
 Turning our attention to the backward 
 movement of the engine, it is necessary 
 to place the reversing lever in the notch 
 
 F ^1 
 
 1 
 
 FIG. 3. ECCENTRIC ADJUSTED. 
 
 furthest back and proceed with our ex- 
 periments as before. Very likely the dis- 
 crepancies will be greater than what is 
 shown in Fig. 1, but the same methods 
 will bring the desired results, and it will 
 be noted that after having made the nec- 
 essary changes on the backward eccentric 
 rod and eccentric, the effect of the 
 changes, in addition to bringing the open- 
 ings of the valve to the desired amount, 
 will have had the added effect of slightly 
 changing the amount of openings on the 
 forward motion. This is easily explained 
 by the fact that in changing the position, 
 of the eccentric or the length of the ec- 
 centric rod the position of the link is 
 slightly changed, thereby affecting the 
 exact distribution of the motion in a 
 ratio to the amount of change made. 
 There are other disturbing causes that 
 must not be overlooked. The length of 
 
 21 
 
THE VALVE-SETTER'S GUIDE 
 
 the reach rod is an important factor, and 
 while the experiments are going on in 
 regard to adjusting the eccentrics and 
 rods, it is well to observe the amount 
 of clearance that the link block has at 
 each end of the link. It is safe to allow 
 at least a quarter of an inch more clear- 
 ance at the top of the link than at the 
 bottom. In links where the amount of 
 clearance is limited it is perfectly safe 
 that the link block may approach within 
 one-eighth of an inch when the link block 
 is at the bottom of the link, as the 
 tendency of the link is always to drop 
 lower down as the joints begin to wear 
 and as the heat expands the length of the 
 boiler without materially expanding the 
 length of the frames. 
 
 Another important consideration is the 
 fact that while the valves may be care- 
 fully adjusted to open correctly at the 
 -extreme length of the travel of the valve, 
 it does not follow that when the lever 
 is hooked up nearer the center of the 
 •quadrant that the openings retain their 
 exact ratio to each other. The tendency 
 is in addition to increasing the amount 
 t)f opening or lead as it is called, to create 
 variations in the amount of opening at 
 •each end of the valve stroke. In engines 
 that are used with short valve travel, as 
 in light running engines, it is often neces- 
 sary to sacrifice the exact adjustment at 
 the extreme end of the stroke in order 
 that the valve openings may be squared at 
 the point where the engine is called upon 
 to perform most of its work. It need 
 hardly be stated that the same remarks 
 in detail apply to the left side of the en- 
 
 gine, and that in common practice both 
 sides are being adjusted while the engine 
 is being moved or while the wheels are 
 being revolved. 
 
 It has already been noted that an ex- 
 amination of the exact position of the 
 valves after the engine has been running 
 a short time will show more or less varia- 
 tion corresponding in a great degree to 
 the quality of the general workmanship 
 exhibited in the construction or repair of 
 the engine. Repeated examinations and 
 readjustments are invariably necessary. 
 The number and variety of joints through 
 which the motion has to come before 
 reaching the slide valve, renders the re- 
 tention of the exact position of the valve 
 for any length of time a physical im- 
 possibility. 
 
 Assuming that the rods and eccentrics 
 have been carefully adjusted to suit the 
 extreme travel of the slide valves and 
 that it is necessary to adjust the amount 
 of valve opening or travel at some 
 hooked-up point, the common practice is 
 to begin the operation by marking the 
 extreme travel of the crossheads on both 
 front and back end of the stroke. This 
 can be readily done with a pencil marking 
 a line on the guides. It is immaterial at 
 what point we begin, but for simplifying 
 the matter, suppose we begin as formerly 
 at the right front end, and, moving the 
 engine forward until the crosshead has 
 moved six inches from the pencil mark, 
 the valve tram can be used to locate the 
 position of the valve. With the reverse 
 lever in the front notch it will be found 
 that the front steam port is wide open. 
 
 22 
 
ADJUSTING THE STEPHENSON VALVE GEAR 
 
 By drawing back the reverse lever the 
 valve port is gradually closed and when 
 the tram is exactly at the shut point on 
 the valve rod the reverse lever latch 
 should be dropped in the nearest notch 
 and allowed to remain there. It is well 
 to repeat the operation of finding the 
 exact position of the valve by moving 
 the engine a short distance backward and 
 forward again to the point where the tram 
 exactly enters the mark on the valve rod, 
 showing that the steam port is at the clos- 
 ing point. The distance from the extreme 
 front end of the crosshead to the pencil 
 mark on the guide may not be exactly 
 six inches, but this is immaterial. Sup- 
 pose it is 6y 2 ins., this should be marked 
 down with chalk or otherwise and the 
 operation continued on the other side of 
 the engine in the same way and so on 
 until the four separate and distinct dis- 
 tances are discovered and marked down 
 for reference. Suppose the right side 
 shows 6y 2 ins. in front and 5^2 ins. in 
 the back and that the left side shows 
 7 ins. in front and 4^ ins. back. A gen- 
 eral summing up of these distances would 
 show that something near six inches 
 would be the best average that could be 
 obtained. Now if the link saddles are not 
 new and are already bolted in place, the 
 only course open to remedy the variation 
 in the cut-off is to sacrifice the exact ad- 
 justment of the eccentric rods and make 
 such changes in raising one of the tum- 
 bling shaft blocks or lowering one of the 
 rocker boxes as may best meet the com- 
 promise object at which we are darkly 
 aiming. 
 
 Returning to our familiar position on 
 the right front where the distance from 
 the crosshead to the pencil line is 6 l / 2 ins., 
 suppose we stop the engine a little before 
 we reach 6 ins., say 5% ins., and try the 
 valve tram in order to ascertain how far 
 we are from the valve opening mark. It 
 will be found that there is probably y 32 of 
 an inch of a valve opening at this point, 
 and it will readily be seen that if the 
 valve rod has to move forward a short 
 distance in order that the tram will touch 
 the mark as desired the shortening of the 
 forward eccentric rod will have the de- 
 sired effect. After effecting this slight 
 change in the forward eccentric rod the 
 crosshead distance from the pencilled lines 
 on the guide can be again ascertained, 
 and confining ourselves to the right side, 
 suppose the distance at the front end 
 shows 5% ins. and at the back end the 
 distance is 6% ins., it is well to remember 
 that a slight increase of the amount at 
 the back end as measured from the cross- 
 head to the pencilled line is a necessary 
 arrangement in the case of a piston where 
 the piston rod does not extend through 
 the front cylinder head. 
 
 In the case of the ordinary single-ended 
 piston the variation in steam pressure at 
 the different ends of the piston can be 
 readily determined by calculating the area 
 of the piston rod and deducting it from 
 the area of the piston. Suppose the diam- 
 eter of the cylinder is 20 ins., then 20 X 
 20 X 7854 = 314.16 sq. ins., the area of 
 the face of the piston. If the piston rod 
 is 4 ins. in diameter then 4 X 4 X 7854 
 = 12.56 ins., the amount to be deducted 
 
 n 
 
THE VALVE-SETTER'S GUIDE 
 
 from the area of the back end of the pis- 
 ton. This is equal to one twenty-fifth of 
 the entire area, and in any adjustment of 
 the valve gearing this factor of pressure 
 area should be considered. It would be 
 very safe, therefore, to allow the figures 
 to stand that we have already found on 
 the right side and turn our attention to 
 the important variation discovered on the 
 left side. 
 
 In this case where the difference in the 
 measurement of the crosshead from the 
 pencilled lines is much greater it would 
 be inadvisable to adjust the eccentric rod 
 so as to make up the entire difference. If 
 we did so, it would be found that an ex- 
 cessive amount of lead or valve opening 
 would occur at one end of the stroke when 
 the reversing lever was placed at the ex- 
 treme end of the quadrant and there 
 would be no opening at the other end of 
 the stroke. Apart from this involved 
 problem, another one equally important 
 arises from the variation occurring in the 
 amount of the distances at which the 
 cut-off occurs. Even if it were advisable 
 to adjust the eccentric rod to equalize the 
 distribution of the amount of distance 
 traveled by the piston at each end of the 
 cut-off, the total amount at each end 
 would still be greater than the distance 
 already equalized on the right side. Now 
 if we will observe the angle at which the 
 link is hanging as held by the ends of the 
 two eccentric rods it will readily be seen 
 that if the link could be raised or the 
 link block be lowered the effect would be 
 to' move the lower end of the rocker arm 
 towards the eccentrics while the valve rod 
 
 would be moved. a corresponding distance 
 in the opposite direction, thereby effect- 
 ing an earlier closing of the valve. 
 
 There are two methods by which this 
 can be accomplished. A liner can be 
 placed between the rocker box and frame 
 or between the tumbling shaft block and 
 frame. The effect in both cases is alike, 
 although both remedies should be avoided 
 if possible. A third remedy lies in the 
 shortening of the link hanger, but this is 
 a delicate and difficult operation, owing 
 to the brittleness of the ends of the link 
 hanger, and of the three evils the re- 
 adjustment of the height of the rocker 
 box is the best. The exact thickness of 
 the liner can best be discovered by ex- 
 periment. 
 
 It need hardly be said that in the case 
 of a new link, or new link saddle, the 
 saddle can be temporarily adjusted and 
 move experimentally to the correct posi- 
 tion. It is usual in describing the exact 
 location of the position of the pin by 
 which the link is suspended to produce an 
 array of figures and selections from the 
 alphabet to illustrate the true position of 
 the point of suspension. The illustrations 
 and formulas are of little use, as is well 
 known to all who have placed the parts 
 of the Stephenson valve gearing in posi- 
 tion, and in spite of the calculations hav- 
 ing been very accurately made by the most 
 accomplished mechanical engineers, there 
 are almost invariably changes to be made 
 in regard to the exact location of the link 
 saddle pin. There are several causes that 
 lead to this involved problem. The angu- 
 lar advance of the main rods, together 
 
 24 
 
ADJUSTING THE STEPHENSON VALVE GEAR 
 
 with the same feature in the eccentric 
 rods, have a singularly conflicting effect 
 on the action that moves the rocker arm. 
 It may be remarked that when the link is 
 suspended exactly by the center of the 
 link the large variation in the cut-off oc- 
 curring under such conditions is caused 
 largely by the angularity of the link 
 caused by the action of the eccentric rod 
 that is not supposed to be in gearing, but 
 is nevertheless affecting in a marked de- 
 gree the action of the eccentric rod that 
 
 down as being among those that are past 
 finding out. The effect of moving the 
 point of link suspension can readily be 
 seen by the most casual observation. In 
 the accompanying illustration showing the 
 Angus Sinclair valve model with piston 
 and reverse lever in the center it will be 
 seen at a glance that by moving the sus- 
 pension point of the link, as can readily 
 be done in the model, either forward or 
 backward, the effect is to raise or lower 
 the link, as the case may be, as the line 
 
 VALVE MODEL WITH PISTON VALVE. 
 
 s in gearing. It is usual to ascribe the 
 variations in the cut-off to the angular 
 advance of the main rod. This would 
 doubtless be true if the eccentrics were 
 set at the same point as the crank is set, 
 Dut as they are set nearly at right angles 
 to the crank the angular advance of the 
 main rod has a corrective effect on the 
 peculiarities of the link motion. 
 
 In common practice it is not necessary 
 o trouble ourselves about these involved 
 problems. They may very safely be set 
 
 of the center of suspension is not in the 
 same plane as the engine frames. In fact, 
 the only points where the link is in a 
 perpendicular position is at the two cen- 
 ters when the piston is at the extreme 
 ends of the stroke. It may be noted that 
 moving the saddle pin backward or for- 
 ward affects the distribution of the cut-off 
 and has the effect of equalizing or dis- 
 torting the points of cut-off according to 
 the direction in which the pin is moved, 
 while moving the link saddle higher or 
 
 25 
 
THE VALVE-SETTER'S GUIDE 
 
 lower upon the link increases or dimin- 
 ishes the distance of the cut-off point 
 from the end of the stroke or pencilled 
 mark. Indeed it may be remarked that in 
 the case of a new saddle it is merely a 
 matter of careful experiment which neces- 
 sarily requires repetition, as the move- 
 ment of the link saddle affects the valve 
 opening at the extreme ends of the stroke 
 so that the reverse lever should be placed 
 in the end notches and the valve openings 
 re-examined after each saddle experiment. 
 It might be added that after the ' for- 
 ward cut-off has been carefully adjusted 
 it does not follow that the backward cut- 
 off will be found to be correct. Other 
 changes and compromises may have to be 
 made, but it should be noted that if we 
 have disposed of the right and left sides 
 of our engine, and have the cut-off ad- 
 justed, say at 6 ins. in the back and S Z A 
 ins. in front, it is not necessary that the 
 same figures should be established as an 
 absolute necessity for the backward mo- 
 tion of the engine. It is enough that the 
 points are equalized to each other, and 
 while the forward and backward motions 
 of the engine can be equalized exactly if 
 there is a new quadrant to be made it 
 
 will be found that where the notches are 
 already made in the quadrant it will be 
 hardly possible to arrange the cut-off 
 points so that they will exactly cor- 
 respond. 
 
 This leads us to observe that which 
 will be noticed, that no matter how care- 
 fully the entire valve gearing may be 
 adjusted it will be found that when the 
 locomotive is overhauled for general re- 
 pairs variations have occurred that seem 
 to the casual observer extremely puzzling. 
 It is common to belittle the orignal con- 
 struction and set down the apparent errors 
 in organic construction to a lack of ability 
 or care in the first adjustment of the 
 mechanism. This is a gross injustice, and 
 if we could only dimly discern the vicissi- 
 tudes through which the mechanism has 
 passed and measure the blows of circum- 
 stance that have fallen upon the multiplex 
 parts of the elastic contrivance we would 
 perhaps recognize the fact that it is re- 
 markable that machinery so involved and 
 so subject to disturbing influences has re- 
 tained such a degree of perfection as it is 
 often found to possess after service so 
 peculiarly exacting and so painfully 
 strenuous. 
 
 26 
 
THE WALSCHAERTS VALVE GEAR 
 
 V. THE WALSCHAERTS VALVE GEAR 
 
 In treating of valve gearing as applied 
 to steam engines generally, it is presumed 
 that it is scarcely necessary to dwell at 
 any great length on the fact that all such 
 gearing is designed with a view to admit 
 steam readily to the reciprocating piston 
 at a time when the steam pressure will be 
 most effectual in moving the piston in the 
 cylinder, which movement is readily con- 
 veyed through a connecting rod attached 
 to the piston at one end, and to a crank 
 at the other end, thereby inducing a turn- 
 ing or revolving motion to a wheel and 
 axle. In the economic use of steam, and 
 incidentally of fuel, it is advisable to shut 
 off the supply of steam as early as possi- 
 ble during the piston stroke, so that the 
 steam admitted to the cylinder at a high 
 degree of pressure may have an oppor- 
 tunity to spend its force before being per- 
 mitted to pass into the outer air. It will 
 be readily understood that in a cylinder 
 two feet in length, if the supply of steam 
 is cut off at a point when the piston has 
 only traveled six inches on its course to- 
 ward the other end of the cylinder, the 
 steam pressure will only amount to one- 
 half of the original pressure when the pis- 
 ton has traveled twelve inches, because 
 the steam will then occupy twice the space, 
 and so on until the piston has reached the 
 end of the stroke, when the pressure will 
 
 be four times less than when admitted. 
 Other causes, which need not now be 
 dwelt upon, will have reduced the pres- 
 sure even more than this, so that steam 
 admitted at 180 lbs. of pressure per square 
 inch at the beginning of the piston stroke 
 will be less than 40 lbs. per square inch 
 by the time the piston stroke is completed. 
 In the early days of the steam engine 
 the necessity for this economical or ex- 
 pansive use of steam, as it is called, was 
 not so great as it is now, for the reason 
 that steam was used at a much lower pres- 
 scure at that time, and the loss of steam 
 at the end of the piston stroke was small 
 in comparison with what it is now, when 
 steam is admitted during the entire length 
 of the stroke. Other causes soon arose 
 calling for a variable supply of steam. 
 With the locomotive the difference in 
 grades to be climbed and in loads to be 
 hauled necessitated an increase and a 
 diminution of the steam pressure, and the 
 brightest minds among steam engineers 
 were early at work on this important 
 problem. As boiler construction improved 
 and higher steam pressures became pos- 
 sible, the necessity for a variable valve 
 motion increased. Egide Walschaerts, a 
 young Belgian engineer, was among the 
 first, and perhaps the most successful, in 
 solving this intricate mechanical problem. 
 
 27 
 
THE VALVE-SETTER'S GUIDE 
 
 Eccentrics were already in use for the 
 simple purpose of reversing the move- 
 ment of the engine. This was accom- 
 plished by having two eccentrics set in 
 such positions that when their rods were 
 in operation on a rocker that moved the 
 valve rod, one rod was adjusted so that 
 it would act in advance of the main crank, 
 while the other, when in operation, would 
 follow the crank. One rod could be lifted 
 off the rocker pin and the other one at- 
 tached by a simple appliance similar to 
 the lifting shaft now in use on locomo- 
 
 eccentric or crank set at right angles to 
 the main crank is the primal necessity in 
 the construction of the Walschaerts gear- 
 ing. It can readily be understood that a 
 connecting rod attached to an eccentric 
 or crank so fixed and so adjusted in point 
 of length that it would reach exactly to 
 the movable valve while the valve was in 
 the central position would, by continuing 
 the movement of the engine, continue to 
 place the valve in the middle of the valve 
 seat when, the piston was at the end of 
 the stroke, and also move the valve to 
 
 WALSCHAERTS 
 
 VARIABLE EXPANSION VALVE MOTION APPLIED TO LOCOMOTIVE 
 98, AT BRUSSELS, BELGIUM, SEPT. 2, 1848. 
 
 tives, the rods being furnished with hooks 
 adapted to catch the rocker pin. 
 
 This reversing contrivance attached to 
 the early locomotives is alluded to in or- 
 der that the condition of the valve gearing 
 at the time that Walschaerts brought his 
 keen intellect and engineering skill to 
 bear upon the problem may be understood. 
 
 The valve then in use, known as the 
 D-slide valve, the steam ports leading to 
 the cylinder and the method of exhaust- 
 ing the steam through the inner cavity 
 of the valve were not in any way affected 
 by the work of the young Belgian en- 
 gineer. The perfect adjustment of an 
 
 the extreme end of its stroke at the mo- 
 ment that the piston w*as in the middle 
 of the cylinder. 
 
 With the piston at either of the extreme 
 ends of the cylinder and the valve in the 
 central position, it would be found that a 
 certain portion of the valve face over- 
 lapped the steam ports and it would be 
 necessary to move the valve a distance 
 equal to the amount of lap in order that 
 the steam might be readily admitted to 
 act on the piston in the early part of its 
 movement towards the other end of the 
 cylinder. The mechanism invented by 
 Walschaerts in moving the valve the re- 
 
 28 
 
THE WALSCHAERTS VALVE GEAR 
 
 quired distance from the center at either 
 end of the piston is one of the cleverest 
 devices in use in steam engineering, and 
 is generally looked upon as the crowning 
 feature of Walschaerts' masterly inven- 
 tion. It should be noted that the overlap- 
 ping of the valve is an essential requisite 
 in the economic use of steam. If the valve 
 exactly covered the ports any movement 
 of the valve would cause an immediate 
 opening of one port at the instant of the 
 closing of the other port. The amount of 
 lap makes a period of closure of the ports 
 possible, and consequently renders the 
 expansive use of steam already alluded 
 to a mechanical possibility. 
 
 This moving of the slide valve toward 
 the desired point is effected by the en- 
 gaging of the valve rod by an intervening 
 combination lever which is connected to 
 the crosshead by a union link, and which 
 will be fully described hereafter. The co- 
 relation between the combination lever 
 and a radius bar driven by an oscillating 
 radial link, which is driven by the eccen- 
 tric rod, becomes the determining factor 
 in moving the valve from the central posi- 
 tion to the point desired. 
 
 The shortening of the valve stroke, 
 
 making it possible to close the supply of 
 steam at any desired point of the piston 
 stroke is effected by the oscillating radial 
 link into which the radial bar attached to 
 the valve rod and cross-head is movable 
 by the lifting shaft, and it will be readily 
 seen that as the radial link suspended 
 centrally oscillates furthest at the extreme 
 ends the radial bar will travel further 
 when near the extreme ends of the imk, 
 and as it is made to approach the center 
 the motion of the bar will be shortened. 
 At the center of the link it will cease 
 moving altogether, and after passing the 
 center it will move in the opposite direc- 
 tion, thus reversing the movement of the 
 engine. The moving of the valve towards 
 the opening point by the use of the cross- 
 head connection, as well as the interven- 
 tion of the oscillating radial link, together 
 with the use of the single eccentric or 
 crank, are three distinct and separate fea- 
 tures of this valve gearing, and these, to- 
 gether with their connections and rela- 
 tion to each other, will be treated in detail 
 in the forthcoming chapters describing 
 the construction and adjustment of this 
 steam-engine attachment, as applied to 
 the locomotive. 
 
 2Q 
 
THE VALVE-SETTER'S GUIDE 
 
 VI. VARIATIONS IN FORM IN THE WALSCHAERTS 
 
 VALVE GEAR 
 
 It will be noted that the construc- 
 tion of the Walschaerts valve gearing 
 as originally applied by the inventor to 
 the locomotives of the Belgian State 
 railways differs somewhat in detail 
 from the forms in which it is now 
 made applicable to twentieth century 
 locomotives. These changes do not in 
 any way affect the organic principles 
 
 being fastened to the eccentric strap, 
 and the other end attached to the lower 
 end of the radial link. This eccentric 
 was set at right angles to the main 
 driving crank, that is while the piston 
 would be at the extreme back end of 
 the cylinder and the main crank pin 
 consequently on the back center, the 
 extreme point of the eccentric would 
 
 WALSCHAERTS' VALVE GEAR, AS APPLIED TO LOCOMOTIVES BY WILLIAM MASON. 
 
 of the device, but are merely matters 
 of convenience made to suit the in- 
 creased size of the engines. Among 
 the changes in form it will be observed 
 that the original method of causing the 
 radial link to oscillate on its central 
 suspension stud was by an eccentric 
 attached to the main axle to which a 
 rod was attached, one end of the rod 
 
 be on the top center, or 90 degrees 
 ahead of the main crank while the en- 
 gine was running forward. It must be 
 borne m mind that the original in- 
 vention was applied to an outside ad- 
 mission D-slide valve. In the case of 
 a modern locomotive equipped with an 
 inside admission piston valve the ec- 
 centric would be set 90 degrees behind 
 
 30 
 
 
VARIATIONS IN FORM IN THE WALSCHAERTS VALVE GEAR 
 
 the main crank, that is on the bottom 
 center. This change of position is 
 made necessary from the fact that an 
 inside admission piston valve must nec- 
 essarily move in the opposite direction 
 from that of the ordinary outside ad- 
 mission slide valve. 
 
 In addition to the change of position 
 in the eccentric there is also a change 
 necessary in the relative positions of 
 the radius bar and valve rod, the out- 
 side admission valve requiring that the 
 valve rod should be attached to the 
 combination lever above the radius bar 
 as in Walschaerts' original design, 
 whereas with an inside admission valve, 
 the valve rod attachment is made be- 
 neath that of the radius bar. The 
 cause and effect of this change of posi- 
 tion will be fully explained hereafter, 
 the present reference being merely the 
 need of calling attention in a general 
 way to some apparent changes in the 
 construction of the valve gearing, 
 which in reality are not changes at all, 
 but simply varying modifications of the 
 same general principles. 
 
 With this idea in mind it will be 
 readily understood that the eccentric 
 fulfilled the same purpose in the orig- 
 inal design as the return crank does 
 that in the larger locomotives with the 
 advantage that the crank being at- 
 tached to the outer end of the main 
 crank pin its motion can readily be 
 imparted to the oscillating link by a 
 rod moving in the same plane, thereby 
 avoiding the necessity for extended at- 
 tachments which would be necessary if 
 the eccentric was attached to the main 
 
 axle inside of the engine frames while 
 the oscillating link would necessarily 
 be at some distance outside of the 
 frames. 
 
 Other changes of less importance 
 have occurred, among which is the 
 placing of the lifting shaft above the 
 frames so that the radius bar is hung 
 by a short hanger or suspended by an 
 adjustable sleeve, instead of being sus- 
 tained by a bar from beneath which in 
 the case of the modern locomotive 
 would be of considerable length and 
 add to the degree of unwieldiness of 
 the mechanism. 
 
 Among the first to adopt the Wal- 
 schaerts valve gearing to the expand- 
 ing form of the modern locomotive 
 was William Mason, an American en- 
 gineer. The changes in the position of 
 some of the parts of the mechanism 
 made by him have been closely fol- 
 lowed by subsequent engineers. In his 
 application of the device he not only 
 made the valve rod adjustable by the 
 use of threaded ends on the valve rods 
 on which nuts were movable to equal- 
 ize the position of the valve, but he 
 also applied turn buckles to the ec- 
 centric rods so that the inevitable wear 
 of the return crank bearing could 
 be readily rectified in case of the 
 lengthening or shortening of the rod 
 occasioned by the refitting of the 
 brasses. 
 
 It will be noted that in the modern 
 use of the radial link there is an at- 
 tachment extending beyond and under- 
 neath the bottom of the link. This at- 
 tachment is variable in extent, and is 
 
 31 
 
THE VALVE-SETTER'S GUIDE 
 
 adapted to form a suitable connection 
 for the eccentric rod. The exact loca- 
 tion of the connecting point must be 
 carefully considered by the construc- 
 tor on account of the relation of the 
 amount of throw of the crank to the 
 travel of the valve. In ordinary prac- 
 tice a locomotive with a piston stroke 
 of 28 ins., would have a valve stroke of 
 5^4 ins., while the path of the return 
 crank would describe a circle 12 ins. 
 in diameter. The center of the eccen- 
 tric rod attachment to the link would 
 thus be describing an arc 12 ins. in 
 length while the radius bar being con- 
 siderably nearer the centre of the link 
 would move through a smaller arc 
 which continues to grow smaller if 
 the radius bar is moved towards the 
 centre of the link. 
 In the construction of some kinds of 
 
 locomotives there are two lifting shafts 
 connected by a transmission bar. It will 
 be readily found that variations of this 
 kind are made necessary in order to ac- 
 commodate the location of other parts of 
 the engine, the additional lifting shaft not 
 in any way affecting the action of the 
 valve gearing. 
 
 Such briefly are the principal changes 
 in form which have occurred in Wal- 
 schaerts valve gearing since its orig- 
 inal introduction. These changes illus- 
 trate its ready adaptability to changing 
 conditions and stamp it as one of those 
 few mechanical contrivances that have 
 come to us as nearly perfect as any kind 
 of mechanism involving the changing of 
 circular motion in some parts to linear 
 motion in other parts can. be expected to 
 be, and not surpassed in the fine quality of 
 reliability. 
 
 32 
 
 
CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 
 
 VII. CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 
 
 In view of the fact that the Wal- 
 schaerts valve gearing does not possess 
 that flexibility of adjustment common to 
 shifting link valve gearings, there is 
 greater need for perfect accuracy in con- 
 struction. Not only must the design be 
 carefully laid out, but in fitting up the 
 gearing a degree of exactness must be 
 attained that approaches as nearly as pos- 
 sible to perfection. As a general rule it 
 is very safe to presume that the design, 
 as far as the draftsman's work is con- 
 cerned, is correct, but the same cannot 
 always be said of the machinists' work. 
 Shopmen are well aware that in the proc- 
 ess of hardening the wearing parts 
 of machines there is a tendency to irregu- 
 larities, owing to the variations in the 
 sizes of the parts. This is particularly 
 true in regard to the parts where the 
 greatest degree of exactness is required, 
 and it should be carefully observed that 
 the radial link attachment, extending as 
 it does some distance beyond the link 
 proper, has not moved in one direction 
 or the other during the hardening proc- 
 ess. The application of a turnbuckle or 
 other device to the eccentric rod, although 
 not now used, was a ready corrective to 
 variations of this kind, but it was not a 
 complete remedy, as it will be readily un- 
 derstood that any variation in the paths 
 
 described by the moving parts have some 
 disturbing effect on the constructor's 
 design. 
 
 Errors of this kind are more easily de- 
 tected than remedied, and it may be ac- 
 cepted as a rule that organic defects in 
 the construction of the Walschaerts valve 
 gearing can rarely be altogether reme- 
 died. It is a well-known fact among shop 
 men that in the construction of locomo- 
 tives there is a tendency to what may 
 properly be called dramatic flourishes in 
 the beginning of the building of a loco- 
 motive. The frames and saddle and cyl- 
 inders are bolted together with a degree 
 of rapidity that fills the eye that is 
 pleased with superficial appearances. The 
 exact alignment of the parts, however, is 
 never correct by chance. Whatever is 
 correct in mechanism is always difficult 
 of accomplishment, and it is time well 
 spent to note that the pedestal jaws of 
 the frames are not only exactly square 
 to each other, but that the shoes are also 
 perfectly parallel. It should not be sup- 
 posed that the simple matter of adding 
 or subtracting a certain quantity of met- 
 al to or from the shoes will restore 
 or maintain a just relation of the parts 
 to each other. The least variation in the 
 setting of the frames has the pernicious 
 effect of throwing the bolt holes in the 
 
 33 
 
THE VALVE-SETTER'S GUIDE 
 
 frames out of position, arid braces and 
 guide yokes and rocker boxes are more 
 or less strangers to the truth from the 
 first day of their industrial existence, and 
 no amount of temporary tinkering can 
 •ever bring them back to where they prop- 
 erly belong. This is especially true of 
 the relation of the center of the main 
 driving axles to the various parts of the 
 Walschaerts valve gearing, and it can- 
 not be too strongly instilled into the 
 minds of those who are engaged in this 
 important work that every precaution 
 should be taken to maintain the exact 
 mathematical relation of the parts to 
 which the valve gearing is attached and 
 from which it derives its accuracy of 
 movement. This is the highest kind of 
 constructive work, and to which the work 
 of the draughtsman is merely preliminary. 
 It is a singular circumstance that error 
 multiplies as it proceeds from point to 
 point, and that which is only a small frac- 
 tion at the main axle becomes a consid- 
 erable quantity by the time that it has 
 reached the valve opening. 
 
 In the designing of the Walschaerts 
 valve gearing the length of the piston 
 stroke being given, together with the 
 amount of valve travel and the extent to 
 which the valve overlaps the steam ports, 
 and also the amount of opening or lead 
 which may be deemed necessary, the com- 
 bination lever is designed in such propor- 
 tion as to move the valve the exact 
 amount of lap and lead away from the 
 central position at the time that the pis- 
 ton is at the extreme end of the stroke. 
 The union link and crosshead arm are 
 so constructed that the combination lever 
 
 will be in the perpendicular position when 
 the piston is in the center of the cylinder. 
 The radial link is so constructed that its 
 arc or curve corresponds to the circle de- 
 scribed by the length of the radius bar; 
 that is, measuring from the point to 
 where the radius bar is attached to the 
 combination lever along to the center of 
 the link block. The radius bar should 
 be at least eight times the length of the 
 space in which the link block is designed 
 to travel. The longer the radius bar is 
 the more direct its thrust will be on the 
 valve rod, and consequently less subject 
 to the disturbing and distorting effect of 
 a short angular movement. The length 
 of the link is such as when oscillated by 
 the eccentric rod the radius bar will 
 move the slide valve the desired amount 
 of travel ; that is, when the link block 
 which is attached to the radius bar and 
 moves freely in the link is at either end 
 of the link. 
 
 As we have already stated in the case 
 of engines equipped with the ordinary 
 slide valve or with outside admission pis- 
 ton valves, the radius bar is connected 
 to the combination lever below the valve 
 stem, and in the case of piston valves 
 where the steam is admitted from the in- 
 ner edge of the valve, called inside ad- 
 mission, the connection of the radius bar 
 is above the valve stem. It should be 
 noted that in order to maintain the per- 
 fect equality of the valve travel both in 
 the forward and backward motions the 
 sr-^oension point of the link should be in 
 line with a point between the combina- 
 tion lever's connection with the radius bar 
 and valve rod, the line being drawn 
 
 34 
 
CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 
 
 parallel with the valve rod. The same 
 alignment should be maintained as nearly 
 as possible in regard to the eccentric rod 
 and the center of the driving axle. The 
 point of connection of the eccentric rod 
 with the link should be parallel with the 
 axle centers. In the construction of some 
 classed of locomotives, especially with 
 the largest kind of cylinders, the perfect 
 
 lever, which being attached to the cross- 
 head, maintains the position of the valve 
 with a degree of accuracy rarely equalled 
 by any kind of mechanism where circular 
 motion is changed to linear or recipro- 
 cating motion. 
 
 A working model of the Walschaerts 
 valve gearing is a good aid to a clear 
 understanding of the mechanism, and 
 
 FIG. i. FORWARD GEAR, LINK-BLOCK AT BOTTOM OF LINK. 
 
 alignment of these points would necessi- 
 tate an extra extension of the link arm, 
 which in turn would require an excessive 
 amount of eccentric throw, and hence the 
 point of eccentric rod connection with the 
 link arm is often at some distance above 
 the centre line. The distorting influence 
 of these variations is reduced to a mini- 
 mum by the action of the combination 
 
 readily reveals not only its essential fea- 
 tures and advantages, but shows at a 
 glance some of the seeming contradic- 
 tions to other valve gearings that its ac- 
 tions exhibit. Thus, in Fig. i an illustra- 
 tion of the model before us, it will be 
 rioted that in the forward motion the link 
 block is in the bottom of the link. This 
 is opposite to what occurs in the Stephen- 
 
 35 
 
THE VALVE-SETTER'S GUIDE 
 
 son shifting link, but it will be observed 
 at once that it is the link block and at- 
 tached radius rod that moves, and the 
 action is direct and simple in comparison 
 with a floating link passing through a 
 variable arc, disturbing the exact position 
 of the valve as it passes from point to 
 point. It may be stated here that in 
 Walschaerts' valve gear in the position 
 shown in Fig. i the reverse lever may be 
 moved from one end of the sector or 
 quadrant to the other end without dis- 
 turbing the position of the valve. If the 
 eccentric rod is of the proper length it 
 will be readily proved at either end of 
 the piston stroke by moving the reverse 
 lever and thereby moving the link block 
 in the link. If the valve remains station- 
 ary the rod referred to is of the correct 
 length. If the piston is at the extreme 
 front end of the cylinder and the valve 
 moves forward as the link block rises in 
 the link the eccentric rod is too short. If 
 on the other hand the valve moves back- 
 ward the eccentric rod is too long. The 
 eccentric rod controls the position and 
 motion of the link, and should be so 
 adjusted in point of length that the 
 link block and accompanying radius bar 
 should not disturb the valve when the 
 piston is at the extreme end of the 
 stroke. 
 
 A peculiarity of the gearing may be 
 noted at this point which affects the 
 movement of the valve advantageously. 
 As shown in Fig. i, the eccentric rod is 
 on the bottom center, and when in motion 
 moves the link at a comparatively high 
 rate of speed, the motion of the link be- 
 ing reduced to a minimum as the eccen- 
 
 tric rod passes around what are prop- 
 erly called the dead centers in its cir- 
 cular path. It will thus be seen that at 
 the moment when the eccentric or return 
 crank is at the lowest or highest point 
 of its path the valve, having its motion 
 conveyed to it by the oscillating link, is 
 traveling at its highest velocity. This is 
 at the exact point where the opening of 
 the valve occurs, and coincident with the 
 rapid movement induced by the location 
 of the eccentric or return crank the veloc- 
 ity of the valve travel is further induced 
 by the action of the combination lever, 
 which, acting on the radius bar connec- 
 tion as a fulcrum, has moved the valve 
 in its path the increased distance required 
 to overcome the space occupied by the 
 lap and lead. The opening of the valve, 
 therefore, occurs more rapidly on account 
 of the movement of the combination 
 lever, and if we follow the movement 
 until the middle of the piston stroke has 
 been reached it will be found that there 
 is a diminution of speed not only on ac- 
 count of the return crank passing the 
 dead center, but this pause in the valve's 
 motion is further accentuated by the com- 
 bination lever passing the vertical dead 
 center of its connection to the radius bar 
 and valve rod. This double eccentricity, 
 as has been stated, emphasizes the rapid 
 opening and closing of the steam ports 
 and prolongs the period of full opening. 
 These features are of decided advantage 
 in any kind of valve gearing used in steam 
 engines. 
 
 In overcoming defects in construction 
 the eccentric rod is usually the part in 
 which any change is made. This rod may 
 
 36 
 
CONSTRUCTION OF THE WALSCHAERTS VALVE GEAR 
 
 be lengthened or shortened to correct er- 
 rors in the location of the main axle 
 center or link center. The central po- 
 sition of the valve or the exact amount 
 of opening of the steam port at each end 
 of the piston stroke can readily be ad- 
 justed by lengthening or shortening the 
 valve rod, which is usually fitted with ad- 
 justable threaded nuts. It may be added 
 that the slightest variation of the return 
 crank from its proper position at right 
 angles to the main crank will be readily 
 discovered by comparing the action of 
 the valve as shown in the forward move- 
 ment of the engine with the action and 
 
 position of the valve in the backward 
 movement. Referring again to Fig. I, it 
 will be readily recognized that in the event 
 of the valve showing a greater amount 
 of opening in the forward motion than in 
 the backward motion the variation may 
 be divided by moving the return crank 
 connection the required amount nearer to 
 the main crank, or by moving the point 
 of suspension of the link nearer to the 
 valve; both of these organic changes hav- 
 ing the same effect, neither of these 
 changes should be made except under 
 very pressing conditions, and after re- 
 peated experiment and identical results. 
 
 37 
 
THE VALVE-SETTER'S GUIDE 
 
 VIII. ADJUSTING THE WALSCHAERTS VALVE GEAR 
 
 The operation of adjusting or setting 
 the valves, as it is called, may be most 
 readily begun by connecting all the levers 
 and rods with the exception of the eccen- 
 tric rod which connects the crank pin to 
 the link arm. This admits of the valve 
 being moved backward or forward in or- 
 der to obtain the markings on the valve 
 rod showing the exact points of the valve 
 opening. These markings on the valve rod 
 as well as the markings in the rims of 
 the driving wheels showing the dead cen- 
 ters or points where the piston is at the 
 extreme ends of the stroke, are made in 
 the same manner as the markings on loco- 
 motives equipped with the Stephenson 
 shifting link. The same trams may not 
 suit in both cases as the guide yokes or 
 bearings or other fixed parts upon which 
 a tram may be steadily held vary in their 
 positions according to the location of the 
 parts, but the dimensions and form of a 
 suitable tram will readily suggest itself 
 to an intelligent mechanic. A fine centre 
 punch mark should be made on the valve 
 rod at the exact points where the port 
 edges of the valve are exactly square with 
 the admission port edges of the valve seat. 
 
 The eccentric rods may then be con- 
 nected and the work of moving the driving 
 wheels may be begun. Assuming that the 
 reverse lever is at the extreme end of the 
 
 quadrant in the forward motion, it will 
 be readily seen whether the valve rod is 
 of the proper length, as soon as the two 
 valve rod markings are made when the 
 main rod has reached the dead centres. 
 Whatever variation there may be can 
 readily be rectified by dividing the ap- 
 parent variation by the adjustable nuts 
 usually atached to the valve rod. When 
 the forward motion has been corrected in 
 this manner, suppose the markings on the 
 valve rod should be as shown in Fig. 2, 
 it will readily be seen, apart from the 
 variation observable in the markings in the 
 back motion, that the opening of the 
 valve has to be increased in the case of 
 the forward motion, and diminished in the 
 back motion. Now assuming that the 
 change is to be made on the left side of 
 the engine and that the main rod is on 
 the forward dead center as in Fig. 1, it 
 will be readily observed that in order to 
 increase the opening of the valve it must 
 be moved backwards toward the link. 
 To accomplish this movement the eccentric 
 rod must be shortened, and if it were con- 
 venient to remove the pin connecting the 
 forward end of the eccentric rod from the 
 link arm, allowing the rod to remain in 
 position, and moving the valve the re- 
 quired distance it would be seen by the 
 variation in the edges of the hole in the 
 
 38 
 
ADJUSTING THE WALSCHAERTS VALVE GEAR 
 
 link arm from that of the eccentric rod 
 how much the eccentric rod would require 
 to be shortened. This method, however, is 
 not entirely to be depended upon, as there 
 is a certain amount of lost motion both 
 in the valve and radius rod connections, 
 as well as on the central pivot upon which 
 the link is suspended. These, in addition 
 to the link block would admit of a slight 
 motion backward or forward of the ex- 
 treme point of the link arm without show- 
 ing any motion of the valve. Generally 
 speaking the eccentric will require to be 
 moved or shortened as in the present case 
 between two and three times more than 
 the amount required in the opening of 
 the valve. The exact ratio can be deter- 
 mined by measuring the distance' from 
 the central stud upon which the link oscil- 
 lates to the center of the link block, and 
 supposing this distance to be 8 ins., then 
 measuring the distance from the central 
 stud to the center of the link arm con- 
 nection with the eccentric rod, and sup- 
 posing that to be 20 ins., it will thus be 
 seen that the eccentric rod must be moved 
 two and a half times the amount that we 
 desire to move the valve or increase the 
 opening. So if the increase desired, as in 
 the present instance, should be one-six- 
 teenth, it will require a shortening of the 
 eccentric rod amounting to five-thirty-sec- 
 onds of an inch. 
 
 It may be stated at this point that there 
 is no need of experimenting with the union 
 link. It might be imagined at first glance 
 that by lengthening the union link the 
 opening of the valve could be increased. 
 Any change made in this lever, however, 
 with a view to open the valve at one end 
 
 of the piston stroke, would have the effect 
 of closing the valve a corresponding 
 amount at the other end of the stroke. 
 After rectifying the variation as shown 
 in Fig. 2, as nearly as possible, by shorten- 
 ing the eccentric rod, it may be found 
 that there is still a slight variation be- 
 tween the amounts of openings. This is 
 proof of a slight organic defect probably 
 in the position of the eccentric or return 
 crank, and if the defect does not exceed 
 one thirty-second it is as well to adjust 
 the forward motion as nearly correct as 
 possible and allow whatever variation 
 there may be to remain with the backward 
 
 B 
 
 A 
 
 2H 
 
 1 
 
 FIG. 2. FORWARD MOTION F; BACK- 
 WARD B. 
 
 motion of the engine, which as a rule, is 
 not so frequently in use as the forward 
 motion. 
 
 In the case of adjusting the valve gear- 
 ing of a locomotive equipped with the 
 Stephenson shifting link, it is possible un- 
 der any condition to arrange the eccen- 
 trics and eccentric rods to bring about an 
 exact opening of the valve at the desired 
 point of the piston stroke on either the 
 forward or backward motion of the engine. 
 On an engine equipped with the Wal- 
 schaerts valve gear this is not always the 
 case, but unless the organic defect in the 
 Walschaerts valve gearing is of a serious 
 kind, the gearing may be adjusted so 
 
 39 
 
THE VALVE-SETTER'S GUIDE 
 
 nearly correct that it will likely be in 
 much better condition during its period of 
 service than the shifting link gearing will 
 be after a few weeks' service. In any 
 kind of valve gearing it is well that the 
 point at which the engine will likely do the 
 greatest amount of work, should be most 
 carefully adjusted. In passenger locomo- 
 tives this point is usually with the valve 
 cutting off the supply of steam at some 
 point considerably less than the full stroke. 
 It will generally be found that in the case 
 of the Walschaerts gearing the cut-off 
 point will be nearly correct. In the event 
 of the variation from the exact clos- 
 
 
 1/6 
 
 32 
 
 '6 
 
 FIG. 3. B, BACK; F, FORWARD. 
 
 ing of the valve at each end of the piston 
 showing a more continued opening at the 
 front end, thereby admitting steam a 
 longer period of time, the valve rod may 
 be slightly changed by the adjustable nuts, 
 as it is more desirable to have a slightly 
 prolonged opening in the back of the pis- 
 ton to make up for the space occupied by 
 the piston rod. 
 
 Turning our attention to the right side 
 of the locomotive and proceeding by the 
 same method to mark the valve rod when 
 the crosshead is at the dead centers on the 
 forward and backward motions, we shall 
 presume that the markings are found to 
 be as shown on Fig. 3; it will be ob- 
 
 served that the valve shows an opening of 
 five-sixteenths on the forward motion, 
 while the valve is lapping one thirty-second 
 on the backward motion. We shall as- 
 sume that the central position of the valve 
 on both motions is nearly correct. The 
 position of the link when the main crank is 
 on the dead centers should be carefully 
 noted, and if the link retains its exact po- 
 sition when the engine is on either centres, 
 the eccentric crank position may be as- 
 sumed to be correct. If a variation of the 
 position of the link is observed, it is safe 
 to assume that there is an error in the 
 position of the crank. Placing the engine 
 on the back centre as in Fig. 4, it will be 
 readily seen that the valve must be moved 
 forward in order to obtain the desired 
 amount of opening. As the eccentric rod 
 is now acting indirectly on the valve rod, 
 the eccentric rod must be moved in 
 the opposite direction, and hence the 
 crank connection must be moved a 
 sufficient distance backward or toward the 
 main crank to effect the required change. 
 The exact amount may be ascertained by 
 the same process as used in shortening the 
 eccentric rod on the left side of the en- 
 gine. As the changing of the position is 
 a matter of some difficulty involving the 
 fiting of a new key to hold the eccentric 
 crank in place, it is well to secure the 
 crank temporarily in place and move the 
 engine from centre to centre to ascertain 
 if the desired effect has been obtained. 
 A change of the position of the eccentric 
 crank may involve a slight change in the 
 length of the eccentric rod, and even with 
 the most careful adjustment it is rare in- 
 deed to secure the perfect coincident 
 
 40 
 
ADJUSTING THE WALSCHAERTS VALVE GEAR 
 
 amount of valve opening at each of the 
 four points of admission, and also to ar- 
 range the points of cut-off so that the 
 steam pressure may be most advantageous- 
 ly used in meeting the various require- 
 ments of locomotive service. 
 
 It may be added that the amount of 
 clearance between the link block and link 
 at the extreme ends of the travel of the 
 
 lengthening or shortening the radius rod, 
 but as the length of this rod should co- 
 incide exactly with the arc of the link it is 
 not good practice to change the length of 
 this rod ; that is, if its length be correct. 
 In closing it is well to remember that 
 when locomotive boilers are filled, and all 
 the parts of the engine more or less heated, 
 there is a tendency to slightly distort the 
 
 FIG. 4. WALSCHAERTS VALVE GEAR IN BACK MOTION. 
 
 block should be carefully noted. It is 
 usual to allow a greater amount of clear- 
 ance at the bottom of the link as the 
 tendency of the link block is to approach 
 nearer the bottom of the link as the parts 
 wear. Any marked deviation from an 
 equable centre affects the travel of the 
 valve. Slight variations in the amount of 
 valve opening may also be remedied by 
 
 operations of the valve gearing and it is 
 well that the skilled mechanic should take 
 an opportunity to observe the changes if 
 any, as such tendencies are very often in 
 the direction of magnifying any slight 
 shortcoming from the exact points to be 
 desired, and a final skillful change may be 
 made that may make a nearer approach to 
 perfection. 
 
 41 
 
THE VALVE-SETTER'S GUID] 
 
 IX. THE BAKER-PILLIOD VALVE GEAR 
 
 The twentieth century locomotives have 
 grown to such colossal proportions that 
 the arrangement of the valve gearing 
 outside of the frames has become a 
 primal necessity. The limited space be- 
 tween the frames with the incre'asing 
 size of axles and eccentrics renders it 
 particularly difficult to adjust and ex- 
 amine the Stephenson shifting link gear 
 under such conditions and doubtless this 
 was the chief cause that called the Wal- 
 schaerts valve gearing into prominent use 
 in American locomotive service. As we 
 have endeavored to show in the pre- 
 ceding chapters the Walschaerts gearing 
 
 has several advantages over that of the 
 shifting link. It also has its drawbacks, 
 which in these days of rapid construction 
 and hard usage are not far to seek. It 
 is not to be wondered at therefore that in 
 the atmosphere of American enterprise 
 many clever mechanicians have been at 
 work devising means of actuating and 
 controlling the valve gear of the modern 
 locomotive. Perhaps the most successful 
 attempt in the present century in this 
 direction has been the combination known 
 as the Baker-Pilliod valve gear. The de- 
 vice resembles the Walschaerts gearing 
 in several features. It has the eccentric 
 
 THE BAKER-PILLIOD VALVE 'GEAR. 
 42 
 
THE BAKER-PILLIOD VALVE GEAR 
 
 crank attached to the main crank pin, 
 and a combination lever deriving its mo- 
 tion from the crosshead. With these two 
 factors in the motion the resemblance 
 ceases, the chief variation being the ab- 
 sence of the radial link. As is well 
 known the movement of a radial link 
 whether shifting or fixed is a source of 
 error in all motions. These errors are 
 caused by the slipping of the link-block 
 and are especially marked in the case of 
 the shifting link as it travels through a 
 longer arc than is usual in the case of 
 links oscillating upon a fixed center. 
 
 In view of this fact, it will be readily 
 understood that if the motion of a slid- 
 ing valve can be perfectly controlled and 
 
 the length of stroke varied without the 
 intervention of a radial link, a real gain 
 in the economical use of steam will be 
 made. The best proof of this is shown in 
 the use of the Corliss valve on stationary 
 engines. This kind of valve gearing with 
 its delicate governor and complex mech- 
 anism is not suited for the incessant vi- 
 brations and distorting strains of loco- 
 motive service. The ideal valve gearing 
 for a locomotive must have the element 
 of rigidity in a marked degree, and at the 
 same time possess that flexibility of 
 adaptation essential to the various re- 
 quirements of the service. The best use 
 of steam pressure is possible only when 
 under perfect control. 
 
 43 
 
THE VALVE-SETTER'S GUIDE 
 
 X. CONSTRUCTION OF THE BAKER-PILLIOD VALVE GEAR 
 
 Coming to the valve gearing under 
 consideration it will be observed that 
 there are a number of rods in addition 
 to those we have alluded to, besides lev- 
 ers and bell cranks and brackets which 
 in appearance form a complex combina- 
 tion, but which when followed one by 
 
 gree of rapidity toward the center and 
 diminishes in velocity toward the ends of 
 its stroke. The same irregular linear 
 movement is made by the eccentric rod, 
 and in Fig. i it will be seen that the 
 crosshead is near the center of its stroke, 
 the swiftest part of its motion, while the 
 
 FIG. i. OUTLINE OF BAKER-PILLIOD VALVE GEAR. 
 
 one lead from the circular movement of 
 the eccentric crank and the reciprocating 
 movement of the crosshead to the sim- 
 ple reciprocating motion imparted to the 
 valve rod. It will be readily understood 
 that neither of these primary movements 
 are regular in their linear velocity, the 
 crosshead travels with an increasing de- 
 
 eccentric crank which is set at right 
 angles to the main crank is experiencing 
 its slowest movement. The union link 
 attached to the crosshead and the eccen- 
 tric rod are attached to the separate ends 
 of a bell crank. The end of the bell 
 crank attached to the eccentric rod de- 
 scribes a circle or ellipse, according to 
 
 44 
 
CONSTRUCTION OF THE BAKER-PILLIOD VALVE GEAR 
 
 the relative proportions of the arms of 
 the bell crank, but always at irregular 
 velocity. This varying motion is con- 
 veyed by a coupling and hanger to an- 
 other bell crank, the lower end of which 
 is attached to the valve rod, which in 
 turn is attached to the valve rod cross- 
 head to which the valve stem is attached 
 
 REACH ROD 
 
 REVERSING 
 SHAFT 
 
 increasing rapidity and closes with a 
 speed equal to that of the piston. 
 
 In regard to the reversing gear it may 
 be shown more clearly by referring to 
 Fig. 2, which represents a skeleton sketch 
 of the Baker-Pilliod valve gear, shaded, 
 and which we have purposely distorted 
 to show more clearly the movable and 
 fixed parts of the gearing. It will be ob- 
 served that the continuance of the ec- 
 centric arm after passing the two bell 
 
 CROSSHEAD CONNECTION 
 
 FIG. 2. PURPOSELY DISTORTED SKELETON SKETCH OF GEAR. 
 
 and held in place by adjustable nuts. The 
 result of the two initial motions con- 
 veyed through this double system of bell 
 cranks is such that the valve travels as 
 fast as the piston at the beginning of its 
 stroke and by the time that the piston has 
 moved about one-twentieth of its stroke 
 the valve is wide open and the valve then 
 moves very slowly during the period 
 while the piston is traveling with increas- 
 ing rapidity during the first half of its 
 stroke. As the piston approaches the 
 release point the valve again travels with 
 
 cranks already described is attached to 
 a hanger G, at the point F. This hanger 
 is suspended from the upper end of a 
 radius yoke J, which is attached to a 
 fixed point at K. The point F therefore 
 swings about the point H. This radius 
 yoke J is suitably attached to the gear 
 reach rod which is connected to the re- 
 versing shaft. Assuming that the piston 
 and slide valve and reverse lever are all 
 in the central position, it can be seen 
 that in the event of the reach rod being 
 moved to the front end of the quadrant, 
 
 45 
 
THE VALVE-SETTER'S GUIDE 
 
 the lower arm of the reversing shaft will 
 be drawn backward, carrying w T ith it the 
 radius yoke, which hangs from the top of 
 the reverse yoke. This backward move- 
 ment of the radius yoke has the effect of 
 lowering the hanger G, so that the point 
 F will be considerably lowered, carrying 
 with it the point N of the second cell 
 crank and consequently drawing the valve 
 rod backward and opening the front 
 steam port. 
 
 If on the other hand the reverse lever 
 is drawn backward to the back end of the 
 quadrant the radius yoke will be moved 
 forward, carrying with it the hanger G, 
 and raising the point F, the effect being 
 to raise the bell crank at N, which 
 moves on the fixed point P. Thus the 
 lower part of the bell crank at Q will be 
 moved forward, carrying with it the valve 
 rod and opening the back steam port in 
 the cylinder, thereby inducing a back- 
 ward motion of the engine. This de- 
 scription presumes an outside admission 
 valve with the main rod at the lower or 
 bottom center. 
 
 Having thus shown the action of the 
 radius yoke on the second bell crank and 
 its effect on the valve rod, it can be 
 readily imagined that the placing of the 
 reversing lever at any of the intervening 
 spaces between the center of a quad- 
 rant and its extreme ends, have their 
 relative effect on the position of the bell 
 crank and the corresponding effect on 
 the motion of the valve rod. 
 
 It will thus be seen that there are a 
 large number of joints through which the 
 motion must necessarily pass from the 
 
 main crank pin and crosshead connection 
 before the movement reaches the slide 
 valve. This is one of the drawbacks in 
 the Stephenson shifting link, and it is one 
 of the chief merits of the Walschaerts 
 valve gearing that the crosshead connec- 
 tion is immediately attached with only 
 one joint between the combination lever 
 and valve stem. There is this particular 
 advantage, however, in the Baker-Pilliod 
 gear, that the parts lend themselves read- 
 ily to massiveness and rigidity of con- 
 struction which is impossible in the case 
 of the Stephenson shifting link gear and 
 is only partially so in the case of the 
 Walschaerts gearing. 
 
 The diagram Fig. 3 shows the shape 
 of the distorted elliptical path of point 
 L, and the portions of the ellipse passed 
 over by the point L for port openings 
 and for lap and lead. The same letters 
 that are used in Fig. 2 are used in Fig. 
 3. The ellipse marked Y is the path fol- 
 lowed by point L when in forward gear, 
 and the ellipse X is that followed in 
 backward gear. The curves in Fig. 3 
 marked 1, 1, is that followed by the point 
 F in full forward gear, the curve 2, 2 is 
 that followed when the reverse lever is 
 in the center, and curve 3, 3 is that for 
 full backward gear. 
 
 It may be added that the lead or open- 
 ing of the valve at the end of the piston 
 stroke is an unvarying or constant quan- 
 tity, so that the length of the valve stroke 
 or point of cut-off of steam supply does 
 not in any way affect the exact amount of 
 opening at the beginning of each piston 
 stroke, while the degree of rapidity with 
 
 46 
 
CONSTRUCTION OF THE BAKER-PILLIOD VALVE GEAR 
 
 FIG. 3. DIAGRAM OF MOVEMENTS OF PARTS OF BAKER-PILLIOD GEAR, 
 
 which the valve opens during the early sired point of cut-off is not surpassed by 
 part of the piston stroke or the rapidity any kind of valve gearing applied to lo- 
 with which the valve closes at the de- comotives. 
 
 47 
 
THE VALVE-SETTER'S GUIDE 
 
 XL ADJUSTING THE BAKER-PILLIOD VALVE GEAR 
 
 In the adjustment of the gearing it may 
 be noted that it is essential that the pro- 
 portions of the various parts be correctly 
 designed by following a precise formula, 
 aided, if possible, by an adjustable model. 
 The setting of the valves, in the same 
 sense of the words as is used in the care 
 of the Stephenson gearing, would be an 
 idle experiment. This is one of the 
 advantages of the Baker-Pilliod gearing 
 that when properly constructed and ad- 
 justed to the locomotive the valve gearing 
 passes outside of the pale of the con- 
 stant consideration of the engineer or 
 mechanic, and while liable, of course, to 
 a certain amount of wear and possible 
 fracture, it is not subject to those erratic 
 variations so peculiar to some forms of 
 valve gearing. Generally speaking, the 
 eccentric rod is the only part that may 
 occasion a renewal of adjustment, as the 
 wear of the bearings at the main crank or 
 in the main driving boxes may occasion 
 a slight variation in point of length of 
 the eccentric rod. The gear reach rod 
 and eccentric arm as well as the valve 
 rod are all fitted with means for adjust- 
 ment in regard to length, so that the 
 equalization of the travel of the valve 
 can be readily effected in the original as- 
 sembling of the parts. 
 
 The amount of lead or opening of the 
 
 valve at the beginning of the piston stroke 
 can be increased or diminished by 
 lengthening or shortening the lower arm 
 of the bell crank. It can be readily seen 
 that by lengthening the arm of the bell 
 crank attached to the valve rod connection 
 that an increase in the length of the 
 valve stroke will be made, and this in- 
 crease will be added to the amount of 
 valve opening at the end of the piston 
 stroke. A corresponding decrease will 
 occur in the case of shortening the bell 
 crank arm. These organic changes are 
 rarely necessary, and it is questionable 
 whether in the instance of a change in 
 the amount of valve opening being neces- 
 sary it would not be advisable to make 
 a slight change in the length of the com- 
 bination lever. It will be readily noted 
 that by shortening or lengthening that 
 lever the stroke of the valve would be af- 
 fected in a lesser degree. 
 
 The exact position of the eccentric crank 
 in relation to the main crank is a vari- 
 able point to the designer, and is adapted 
 by him to suit the requirements of the 
 valve gear construction. In the case of 
 an inside admission valve, the return or 
 eccentric crank follows the main crank 
 when the engine is running forward. In 
 the case of an outside admission valve, 
 the eccentric crank is set a corresponding 
 
 48 
 
ADJUSTING THE BAKER-PILLIOD VALVE GEAR 
 
 distance ahead of the main crank. The 
 length of the eccentric crank is also a 
 variable quantity to the designer. The 
 eccentric crank used in the case of an 
 inside admission valve being longer than 
 that used in the case of an engine equipped 
 with a valve having outside admission. 
 The necessity for this variation is appa- 
 rent when it is observed that the angle 
 of inclination of the eccentric rod is an 
 ascending one towards the lifter bar and 
 bell crank. These necessary variations 
 
 of hardened pins and bushings affords an 
 opportunity of retaining the action of the 
 gearing with a degree ^of accuracy which 
 leaves little or nothing to be desired in 
 the ready application of means for the 
 maintenance of the wearing parts. This 
 is a marked advance over the use of slid- 
 ing blocks and cumbrous rockers which 
 cannot be overestimated and reflects much 
 credit on the practical ingenuity of the 
 accomplished inventors. 
 It need hardly be stated lhat the gear- 
 
 FIG. i. BAKER-PILLIOD VALVE GEAR ARRANGED FOR INSIDE ADMISSION. 
 
 will be readily observed in comparing the 
 illustration of the different positions of 
 the eccentric crank, as shown in Fig. i, 
 which displays the arrangement of the 
 eccentric crank and lifter bar adapted 
 to an inside, admission valve, with that 
 of Fig. 4, which shows the parts arranged 
 from an outside admission valve. 
 
 An admirable feature of the gearing 
 is the fact that all the connections are 
 mechanically positive and the exchange 
 
 ing is capable of many changes in organic 
 structure and is readily adaptable to any 
 length of valve stroke. In its present 
 form as applied to a large number of 
 American locomotives the throw of the 
 eccentric crank is such as describes a cir- 
 cle of seven inches in diameter producing 
 a valve travel when in full gear of six 
 inches. This could be easily increased 
 or diminished to suit the requirements of 
 any size or design of locomotive. The 
 
 49 
 
THE VALVE-SETTER'S GUIDE 
 
 equable motion of the eccentric rod trav- 
 eling as it does in parallel precludes the 
 •possibility of any of that peculiar varia- 
 tion in motion incident to all movements 
 where circular motion is changed into 
 linear motion and which is such a disturb- 
 ing factor in the action of the Stephenson 
 
 7?e*e/ Toe? 
 
 and which prevents the 'motion of the 
 valve gearing from having a distorting ef- 
 fect on the frames, and adds much to their 
 necessary rigidity. 
 
 In brief assuming that the design of the 
 valve gearing is correct, the adjustment 
 of the parts is a matter comparatively 
 
 FIG. 4. BAKER-PILLIOD VALVE GEAR ARRANGED FOR OUTSIDE ADMISSION. 
 
 shifting link motion, and is not alto- 
 gether absent in the Walschaerts valve 
 gearing. This regularity of movement is 
 fully and completely secured by the car- 
 riage of the gearing, which is almost en- 
 tirely supported in a substantial, chan- 
 neled cradle set between the guide yoke 
 and a cross tie extending over the frames, 
 
 easy of accomplishment, while the com- 
 pleted, clever contrivance, when once ad- 
 justed, has the rare quality of retaining 
 that degree of accuracy which approaches 
 as near to perfection as can be expected 
 in the strenuous segregation of diverse 
 forces that have their being in locomotive 
 service. 
 
 / 
 
 50 
 
THE JOY VALVE GEAR 
 
 XII. THE JOY VALVE GEAR 
 
 In Dr. Angus Sinclair's monumental 
 work "Development of the Locomotive 
 Engine," there are about fifty different 
 types of locomotive valve gearing de- 
 scribed and illustrated, and, while many 
 of these are merely variations of two 
 distinct types, all of them bear evidences 
 of a high order of mechanical ingenuity, 
 and it would seem as if the problem of 
 steam distribution is one that has engaged 
 the attention of the brightest minds in 
 the realm of steam engineering and that 
 the complete solution of the problem, like 
 the squaring of the circle, is one that 
 eludes and ever will elude the seeker 
 after perfection. Even the survival of 
 the fittest is often hindered by ignorance 
 and prejudice, and it is marvelous with 
 what tenacity the mechanical mind will 
 cleave to established institutions. It may 
 be remarked that the most successful in- 
 ventions and variations in locomotive 
 engine valve gearing have been made by 
 skilled mechanicians whose experience in 
 actual work has sharpened their intellects 
 and in many cases rendered the applica- 
 tion of their theories comparatively easy 
 by giving an opportunity in the locations 
 where they were employed to test the 
 merits of their devices. 
 
 David Joy, an English locomotive 
 superintendent, patented a valve motion 
 
 in 1879. Although belonging to the radial 
 gear variety of valve motions, it has sev- 
 eral features distinctively its own. It 
 has neither eccentric nor crank, the valve 
 deriving its movement from a system of 
 levers connected with the main rod and 
 varied by the application of a sliding 
 link. 
 
 The motion for the valve is taken di- 
 rectly from the connecting rod and by 
 utilizing independently the backward and 
 forward action of the rod, due to the 
 reciprocating motion of the piston, and 
 combining this with the vibrating action 
 of the rod up and down, a movement re- 
 sults which is used to actuate the valves 
 of engines having any combination of lap 
 and lead, and giving an almost mathe- 
 matically correct cut-off for both sides of 
 the piston for forward and backward mo- 
 tion, and for all points of expansion in- 
 termediately. The action of the gear may 
 be understood by reference to the engrav- 
 ings, Figs. 1, 2, 3 and 4, which are respec- 
 tively an elevation, plan, a transverse 
 section on XY of Fig. 1 looking forward, 
 and modified arrangement of the gear. 
 
 From a point, A, Fig. 1, in the con- 
 necting rod, motion is imparted to a 
 vibrating link, B, constrained at its lower 
 end, H, to move vertically by the radius 
 rod, C, which is pivoted at I. From a 
 
 Si 
 
THE VALVE-SETTER'S GUIDE 
 
 point, D, on this vibrating link, B, hori- 
 zontal motion is communicated to the 
 lower end of a lever, E, from the upper 
 end of which lever the motion is trans- 
 mitted to the valve spindle by the rod- G. 
 The center or fulcrum, F, of the lever E, 
 partakes also of the vertical movement of 
 the connecting rod to an extent equal to 
 the amount of its vibration at the point 
 A; the center F is for this purpose car- 
 
 crum, F, of the lever, E, is represented in 
 Fig. i. The shaft, L, and the links can 
 be partially rotated on the center of the 
 former, so that the slots in the links will 
 be inclined over to either side of a verti- 
 cal position, as shown at W and X. This 
 is done by means of an ordinary reverse 
 lever connected to the upper arm, M, 
 attached to the shaft, L. When the links 
 are thus inclined, the vertical movement 
 
 FIG. i. ELEVATION OF JOY'S VALVE GEAR. 
 
 ried vertically in blocks which slide in 
 slots in the links JK, which are curved to 
 a radius equal to the length of the rod G, 
 connecting the lever F to the valve 
 spindle. These links are attached to a 
 shaft, L, Figs. 2 and 3, corresponding to 
 the ordinary lifting shaft of a link mo- 
 tion. The center of this shaft corre- 
 sponds to the position in which the ful- 
 
 of the lever, E, causes the blocks in the 
 links and the center, F, to traverse a path 
 inclined to a vertical center line; and to 
 diverge from it to either side. The 
 center, F, therefore, has a horizontal 
 movement, the extent of which depends 
 upon the degree of inclination of the 
 links, and the direction of whicji is gor- 
 erned by their position. 
 
 52 
 
THE JOY VALVE GEAR 
 
 The forward or backward motion of 
 the engine is governed by giving the slots 
 this inclined position on one or other 
 side of the vertical center line; and the 
 amount of expansion depends on the 
 amount of the inclination, the exactly 
 central or vertical position being "mid- 
 gear." In that position steam is admitted 
 at each end of the stroke to the amount 
 only of the lead; and this is done exactly 
 equally on each side of the center line, 
 the amount of lead being constant for 
 forward and backward motion, and for 
 all degrees of expansion. Thus when the 
 crank is set at the end of the stroke 
 
 described by the lower end, D, of the 
 lever, E, and this would give an unequal 
 port and unequal cut-off for the two ends 
 of the stroke. But this error is corrected 
 by attaching the lower end, D, of the 
 lever, E, to the vibrating link, B; for 
 while the point A in the connecting rod 
 is performing a nearly true ellipse, the 
 point D in the vibrating link B is moving 
 in a figure, DOPQ, Fig. i, like an ellipse 
 bulged out on the lower side, and this 
 irregularity is so set as to be equal in 
 amount to the versed-sine of the arc 
 described by the lower end, D, of the 
 lever, E, thus correcting the above error, 
 
 FIG. 2. PLAN OF THE JOY VALVE GEAR. 
 
 either way, the center, F, of the valve 
 lever coincides with the center of the slot, 
 and, therefore, the slot may be moved 
 over from forward to backward gear 
 without affecting the valve at all. 
 
 It will be seen at a glance that if the 
 lower end, D, of the lever, E, were at- 
 tached directly to the point, A, on the 
 connecting rod, it would travel in the 
 path of the ellipse, AN, represented by 
 dotted lines, and there would be imparted 
 to the center, F, of that lever, an unequal 
 vibration above and below the center of 
 the links, JK. The extent of inequality 
 would be twice the versed-sine of the arc 
 
 and giving an equal travel to the center, 
 F, of the lever above and below the cen- 
 ter of the slot. At the same time the 
 error introduced by the movement of the 
 end of the valve-rod, G, is corrected by 
 curving the slots or links, JK, to a radius 
 equal to the length of G. 
 
 Referring again to the equalizing of the 
 traverse of the center, F, of the lever, 
 E, in the slot, JK, the unequal traverse 
 may be either under corrected or over 
 corrected by shifting the point D in the 
 vibrating link, B, near to or further from 
 A ; by this means a later point of cut-off 
 may be given to either end of the cylinder 
 
 53 
 
THE VALVE-SETTER'S GUIDE 
 
 at will, and the engine may thus have 
 more steam admitted to one side of the 
 piston than to the other, if required. The 
 same thing may be done for the lead. By 
 altering the position of the crank for 
 which the lever center, F, coincides with 
 the center of the slots, JK, an increased 
 or diminished lead may be given. The 
 central positions and exact connections 
 
 FIG. 3. SECTION OF GEAR. 
 
 are, however, in all cases standard and 
 equal. 
 
 Hitherto the center, F, of the lever, E, 
 which gives motion to the valve spindle, 
 has been described as carried in curved 
 slots. This plan is given as the most 
 simple to manufacture, but if preferred 
 the center, F, may be carried by a radius 
 rod so that its vibration will make the 
 center, F, of the lever, E, describe identi- 
 cally the same arc as if moving in the 
 slots JK. 
 
 In locomotives with small wheels the 
 link, C, may come so low down as to be 
 in danger of being knocked off. For such 
 cases, and for others when it may be 
 considered desirable, Mr. Joy proposed 
 the plan shown in Fig. 4, in which the 
 link, B, is cut off at the center, D, and is 
 connected at that point by a rod, S, to a 
 crank, T, on the end of the crankpin. The 
 movement of the valve produced by this 
 mechanism is almost identical with the 
 other. 
 
 The Joy valve gearing has met with 
 considerable favor on a few of the British 
 railways, notably on the Great Western 
 Railway of England. This railroad, con- 
 structed by the justly celebrated engineer, 
 Brunei, is among the best built and main- 
 tained railways in the world. The long, 
 straight stretches of flat lands over which 
 most of the road passes form an excellent 
 opportunity for fine roadbeds, and conse- 
 quently the locomotives are comparatively 
 free from those vibratory oscillations 
 which are a severe test on the rigidity of 
 almost all forms of valve gearing. It 
 will be readily observed that any vertical 
 disturbance on the main rods of locomo- 
 tives equipped with the Joy valve gear 
 would have a particularly distorting effect 
 on the gearing, and this is the cause of 
 the very limited use to which the gearing 
 has been put on American railroads. As 
 roadbeds improve, the gearing may come 
 into more popular favor. It unquestion- 
 ably takes its place among the leading 
 devices used in steam distribution. Like 
 the Corliss valve gearing and others of 
 real merit, the Joy valve gearing has 
 
 54 
 
THE JOY VALVE GEAR 
 
 advantages peculiarly its own, but its conditions which we are not likely to 
 best work can only be done under reach for many years to come. 
 
 ~t~ 
 
 FIG. 4. JOY'S GEAR MODIFIED SO AS TO RAISE PARTS FROM TRACK. 
 
 55 
 
THE VALVE-SETTER'S GUIDE 
 
 NOTE ON SETTING THE SLIDE VALVE OF A STATIONARY 
 
 ENGINE 
 
 The valve rod connections being prop- 
 erly adjusted, place the crank on the 
 dead center and move the eccentric around 
 on the axle, in the direction in which the 
 engine is intended to run, until the valve 
 begins to open at the same end at which 
 the piston is then placed, or would be if it 
 was attached to the crosshead. Then 
 fasten the eccentric on the axle. It is 
 usually held by one or two set screws. 
 Next turn the engine, in the direction in- 
 tended to be run, until the crank pin is on 
 the opposite center, and if the opening of 
 the valve at the other port is the equal to 
 the opening of the first, it proves that 
 the valve is correctly set. The lead or 
 opening, need not exceed one thirty-second 
 of an inch for engines of less than twenty 
 horse power, but may be increased in the 
 case of larger engines. 
 
 In determining the proper length of the 
 valve rod, the eccentric may be left loose 
 on the axle and after being connected to 
 the valve rod the eccentric may be readily 
 moved around on the axle and the extreme 
 points of the travel of the valve marked 
 on the steam chest or valve face. If the 
 points of travel are at equal distances 
 from the ports the length of the valve 
 rod is correct. If the distances are un- 
 
 equal, the valve rod should be lengthened 
 or shortened, as the case may require, half 
 the amount of the variation. The ex- 
 periment of turning the eccentric around 
 on the axle should be repeated and care 
 should be taken that the valve rod is ex- 
 actly the required length. 
 
 A good method of finding the dead 
 centers of stationary engines is by using 
 a surface gauge which may be set con- 
 veniently on the bed-plate of the engine 
 and the pointer adjusted to the center 
 of the shaft. The engine can then be 
 turned until the center of the crank cor- 
 responds to the height of the pointer. In 
 the absence of a surface gauge, a bent 
 rod of iron, pointed, or a thin board or 
 other convenient device adapted for point- 
 ing to the center of the shaft, may be 
 used. Where the bed-plate of the engine 
 cannot be utilized the dead centers can 
 readily be found by markings on the 
 crosshead and rim of the wheel when 
 near the center and moving the engine 
 slowly and carefully, catching with a 
 tram or compass the same mark on the 
 crosshead after it has passed the center. 
 The crosshead need not be moved more 
 than a quarter of an inch backward and 
 forward. Meanwhile the rim of the wheel 
 
 56 
 
NOTE ON SETTING THE SLIDE VALVE OF A STATIONARY ENGINE. 
 
 will have moved a considerable distance 
 and a point exactly between the two mark- 
 ings on the rim of the wheel will be the 
 dead center. This operation was more 
 fully described in our article on the ad- 
 justment of the Stephenson shifting link 
 gear. 
 
 A direct acting engine, so called be- 
 cause of the eccentric acting on the valve 
 rod without the intervention of a rocker, 
 requires that the eccentric should be set 
 ahead of the crank, the exact amount de- 
 pending upon the lap of the valve and the 
 amount of lead or opening allowed at the 
 beginning of the stroke. In the case of an 
 engine equipped with a rocker, which is 
 an indirect acting engine, the eccentric 
 follows the crank pin at a corresponding 
 distance. 
 
 It need hardly be reiterated that the 
 exact relation of the eccentric to the 
 crank, as well as the correct adjustment 
 and careful maintenance of all the parts 
 of the valve gearing is of the utmost im- 
 portance in all kinds of steam engines. 
 The exact location of the valve at the 
 end of the piston strokes should be occa- 
 sionally ascertained with a view to make 
 corrections if necessary. In all changes 
 it is well to note carefully that the valve 
 moves evenly and freely on the valve 
 seat. The tendency to twist the valve 
 rod in blacksmithing operations is very 
 great, and a hasty or careless adjustment 
 of any part of the valve gearing, and es- 
 pecially of the valve rod, is almost certain 
 to be fraught with the most pernicious 
 consequences. 
 
 The tendency among engineers to med- 
 
 dle with the valve motion is happily pass- 
 ing away. A growth in technical educa- 
 tion has hushed the cry for more lead. 
 One would think that common sense 
 would suggest to any intelligent mechanic 
 the fact that a large quantity of steam ad- 
 mitted into the end of the cylinder 
 toward which the piston was moving .could 
 not be other than a hindrance to the pis- 
 ton, but so rooted was this mistaken 
 idea in the minds of many enginemen 
 that the exploded fallacy still lingers in 
 the minds of some. 
 
 It could not be expected in this brief 
 article to describe the endless variety of 
 forms in which the valve gearing of sta- 
 tionary engines appear. As we have pre- 
 viously stated, a knowledge of the ele- 
 mentary principles that govern the rela- 
 tion of the valve and piston of all recip- 
 rocating engines will naturally lead the 
 intelligent mechanic or engineer to a 
 ready understanding of any kind of valve 
 motion that may come to his attention. 
 The introduction of what are known as 
 inside admission piston valves on many 
 locomotives as well as on stationary en- 
 gines does not present any new problem 
 to those already familiar with the opera- 
 tions of the older sliding valve. The lo- 
 cation of the eccentric on the axle may 
 readily be found by experiment. In the 
 case of an inside admission valve with a 
 rocker operating between the valve rod 
 and eccentric rod, the location of the 
 eccentric on the axle is identical with 
 that of a direct acting engine, equipped 
 with an outside admission valve. In 
 brief, with the proper adjustment of the 
 
 57 
 
THE VALVE-SETTER'S GUIDE 
 
 valve rod, as has been already stated, merely in the direction of making 
 
 and with the crank pin in either center, the adjustment of the gearing as near. 
 
 the mechanism may be moved until the an approach to perfection as is pos- 
 
 valve begins to open at the proper port, sible in a complex and rapidly moving 
 
 and it will be found that the succeeding engine exerting forces of variable magni- 
 
 operations that may be necessary are tude. 
 
 58 
 
^o locomotive 
 
 Has long held the reputation of being 
 
 The Most Interesting Paper Published 
 
 It is the best kind of a paper 
 FOR BUSY RAILROAD MEN TO READ 
 
 The paper gives in a succinct form 
 
 ALL THE RAILROAD NEWS 
 
 of the month, besides current personal notes and attractive technical 
 information. 
 
 Discussion of railroad subjects by 
 
 PRACTICAL RAILROAD MEN 
 
 is a most interesting feature. 
 
 The Air Brake Department and the Electrical Department are 
 edited by experts while the Question and Answer Department gives 
 correct answers to every question asked. 
 
 THE PAPER IS ADAPTED TO GIVE USEFUL 
 INFORMATION TO 
 
 EVERY CLASS OF RAILROAD MEN 
 
 Sample Copies on Application 
 TWO DOLLARS PER ANNUM. 
 
 Published monthly by the 
 
 ANGUS SINCLAIR CO., 114 Liberty Street, NEW YORK 
 
 50 
 
THE ANGUS SINCLAIR COMPANY'S 
 STEPHENSON VALVE MOTION MODEL 
 
 SEE PAGES 15 and 25 
 
 29 inches long, 11 inches high, cylinders 3^4 x 4^ inches, 
 throw of eccentrics 1 inch, length of link slot A 1 /* inches. 
 
 EVERY PART MADE OF METAL. 
 
 EVERY PART ADJUSTABLE. 
 
 Price, $15.00, or twenty-five subscriptions to Railway and Loco- 
 motive Engineering at $2.00 each. 
 
 Is unquestionably the finest model of its kind ever placed 
 within the reach of railroad men. 
 
 Valve setting can be learned much more readily on this model 
 than on the locomotive itself. All the parts are visible. All the 
 parts are readily adjustable. The subject can be studied during 
 leisure hours. 
 
 D slide valves or piston valves may be used, the parts being 
 interchangeable. 
 
 A thorough knowledge of the valve motion in locomotives is 
 indispensable to Engineers and first-class Machinists. An accom- 
 plished valve setter outranks his brother engineers or shopmates 
 and is in line for sure promotion. Firemen and apprentices should 
 study it. Hundreds are already in use in Railway Clubs and 
 Schools. It has become an essential educational factor in the train- 
 ing of the Twentieth Century Railway Man. 
 
 Sole Manufacturers and Proprietors, 
 
 ANGUS SINCLAIR COMPANY 
 
 114 LIBERTY ST., NEW YORK 
 
 6o 
 
KB 3 JgjQ 
 
One copy del. to Cat. Div. 
 
 Ivlv