TJ1380.B64"'" ""'""'""■'""'>' Elevator service, 3 1924 015 367 489 "V ^/ Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924015367489 3 4 5 P.M. APPROXIMATE ELEVATOR TRAVEL In Business Buildings ELEVATOR SERVICE BY REGINALD PELHAM BOLTON MEMBER OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS AUTHOR OF *' MOTIVE POWERS AND THEIR PRACTICAL SELECTION " OPERATING CONDITIONS AND PROPORTIONS WITH DIAGRAMS, FORMULAS, AND TABLES FOR PASSENGER TRAVEL, SCHEDULE AND EXPRESS OPERATION, WITH THE RELATION OF THE ELEVATORS TO THE BUILDING, AND PROPORTIONS AND LOADS OF CARS PUBLISHED BY REGINALD PELHAM BOLTON EXPERT MECHANICAL ENGINEER 527 FIFTH AVENUE, NEW YORK CITY 1908 T AY.70 Copyright, 1908,. by Reginald Pelham BoltOn ^11 rights reserved ,.^' P; o.'ip.rtv of ( College of ftr(h'iec.tij"e,j Price, $S-00 CONTENTS CHAPTER PAGE I The Problem of Vertical Transportation . . . 3 II Operating Conditions 13 III Passengers and Operators 16 IV Rating the Work of the Elevator 20 V Computing the Average Work 28 VI Express Service 32 VII The Shape and Size of the Car 37 VIII Load and Speed Combinations 43 IX The Building and its Proportionate Service ... 49 X Examples of the Use of Figure XI 63 XI Definitions of Some Terms Used in Connection with Elevators 66 LIST OF ILLUSTRATIONS FIGURE Approximate Elevator Travel in Business Buildings . . . Frontispiece PAGE I Equalized Elevator Service Showing Proportionate Division of Floors for Local and Express 8 II Elevators and Stairway at 1 68th Street Subway Station . . . .12 III Schedule Service Local Elevator Showing Variations in Traffic within Schedule Time 23 IV Schedule Service Express Showing Variation in Traffic within Schedule Time 25 V Limitations of Passenger Travel, 22 Floors 26 VI Standard Elevator Cars 38 VII Proportion of Maximum and Average Live Loads 41 VIII Division of Elevator Travel 51 IX Atmospheric Conditions in Closed Spaces at One Change of Air per Hour. Ceiling 10 Feet 54 X Occupied Area per Hourly Passenger, Provided by Varying Loads and Landings, on Any Elevator 59 XI Relation of Elevators to Area, Occupants and Floors 71 ELEVATOR SERVICE I THE PROBLEM OF VERTICAL TRANSPORTATION PUBLIC travel in elevators is steadily growing in volume, and the increased number of floors with which the most important classes of buildings are now constructed, has rendered increasingly serious the provision of adequate facil- ities for vertical transportation. This travel has outgrown the extreme capacity of some of the best plants of elevators, and has indicated that, in spite of great power and rapidity of operation, the passenger-carrying capac- ity of an elevator actually decreases after a certain limiting point is reached, a condition which affects all types of elevators, and is the inevitable result of the combination of a certain num- ber of passengers with the number of floors to and from which they are carried. The important relation of elevator service to the success of all classes of buildings, renders it very desirable to determine the cause and character of this limitation, and to ascertain there- from the best service which any elevator, or any combination of elevators, will afford, establishing an average or rated duty which may be adopted as a basis for the service to be expected from an elevator, or from any combination of units in an eleva- tor service. The absence of such a uniform definition of the work of an elevator, has resulted in a confusing variety of proportions, not only in the speed of the machines and in the size of the cars, but in the number of elevators of equal character applied to similar conditions of service. As the work of an elevator is a result of the number of stories ELEVATOR SERVICE composing the height to which it is operated, with a certain limited number of passengers carried to and from these floors, each unit in a set or plant of elevators bears a relation to a cer- tain proportionate segment of the building. For any given area of the site there is, therefore, a corre- sponding number of superimposed floors, which will be related to a certain number of elevators, and any variation of this com- bination should be such as to add or deduct that number of floors which correspond in area to the work afforded by one or more elevator units, which may be added or omitted. The design of a building in which elevator service is of prime importance should, therefore, take into account the relation of the combination of area and height to the number of elevators, and for any area there will be found to be a height or, rather, a number of floors, which will afford the most effective combina- tion with a given elevator service. Thus, in the case of a building in which a suitably propor- tionate plant of elevators already exists, and to which other floors are proposed to be added, each additional elevator con- tributes passenger travel corresponding only to a proportionate increase of floor area, modified by the fact that all the elevators have to travel to a greater number of floors. Assuming a building of twelve stories, with eight local eleva- tors, the addition of one elevator with the extension of the others, corresponds to an increase of i% floors, two elevators corresponding to 3H floors, while the addition of three eleva^rs fits in with an increase of five floors. Without some definition of the best work afforded by each unit of an elevator service, the architect or engineer, confronted with the problem of the number and character of elevators to be installed in a modern building, must depend mainly upon a com- parison with plants installed in other buildings, perhaps of dis- similar character or proportions, in order to reach a decision on VERTICAL TRANSPORTATION this important subject. The disproportion of many such ser- vices to the buildings which they serve is misleading, and may tend to unfortunate conclusions, usually in the direction of re- peating existing errors, or of providing inadequate service. But such comparisons, if a definite scale of duty be available, may be checked with the performance or deficiencies of elevator services under other conditions, and information may thus be gained as to the desirable results to be attained, even from buildings varying greatly in the character and extent of their occupants. Such a scale, it is true, the light of past experience must aid to define, but there is now a sufficiently wide and well- established record of elevator operation to afford a large amount of information as to average duties or performances. In the following system of rating elevator services, the meth- ods have been found to agree with the practical operation of the best existing practice, and to afford, therefore, equally good average results. With this rating, the duty assignable to each elevator unit may be predetermined, each becoming a known quantity instead of a rather vague and uncertain element, and since the develop- ments of great size and extreme heights of buildings are on the increase, such information becomes peculiarly desirable at the present time. Some of the erratic and unrelated combinations of existing elevators and buildings are due to a method which has some- times been adopted, of proportioning the work of one elevator to a fixed proportion of the rented or occupied area, such as twenty-five thousand square feet in a business building. Any such fixed amount, which may suffice under certain conditions of occupancy, and when spread over a certain number of floors, becomes disproportionate when distributed upon a less or a greater number of superimposed floors. In a description of the high office buildings of New York, ELEVATOR SERVICE 1902, Transactions of the Institution of Civil Engineers, Lon- don, I suggested that a basis for the work of elevators under varying conditions was to be found in the relation of each eleva- tor to a graduated floor area per floor served, which proposal has led to the further study and investigation, resulting in the establishment of a ratio, herein presented, between the passen- ger travel due to the operation of the elevator to any number of floors, and the relative area per floor which is thereby served. Such a relation should afford an average operating condition which should provide a capacity for fluctuating travel, and the method laid down, therefore, rates the elevator at an average capacity of travel in both directions, which affords a margin or over-capacity available to meet variations in travel in either direction. In order duly to proportion the number of such rated eleva- tors to a building which they are to serve, some consideration is necessarily applied to the general character of the latter, the probable habits of occupants, and other local conditions. The work of the elevator is that of the carriage of passen- gers, and those passengers are either occupants or visitors. The latter element is irregular, and is less insistent upon immediate carriage than the former. An estimate of probable tenancy, therefore, affords the means of ascertaining the maximum rate of travel which takes place at the time of their arrival and de- parture, and the relation between the elevator passengers and the area of occupancy may thus be established and utilized to reach a clearly defined result. It may be pointed out that the dimensions of the building are related, through the proportionate number of elevators, to the convenience of the service or the number of opportunities which it affords of entering an elevator. Thus, the larger the building, with a proportionate number of elevators, the closer will be the "schedule," or interval between 1:63 VERTICAL TRANSPORTATION departure of cars from the starting floor, and for any given class of building and tenancy a well-proportioned elevator ser- vice will establish a desirably short schedule interval. But as a method of relation between building and elevators, such a basis as a schedule would be open to question, since it is rather a result than a cause of good service. SCHEDULE INTERVALS IN EXISTING BUSINESS BUILDINGS IN NEW YORK CITY EXPRESSES Floors Net Area per Floor Number of Cars Schedule 10-19 17,000 9 17 sec. 11-20 12,000 6 25 sec. 10-19 8,750 • 5 30 sec. 13-25 5,000 4 34 sec. II-18 6,800 3 45 sec. LOCALS COMBINED WITH EXPRESS 10 17,000 9 17 sec. 10 10,900 6 15 sec. 10 8,750 5 24 sec. 10 6,850 5 24 sec. 13 5,300 4 22.5 sec, II 6,700 3 40 sec. LOCALS ONLY 25 7,600 10 18 sec. 24 4,375 6 26.4 sec, 19 3,500 5 27.6 sec. The above list of schedules compiled from actual condi- tions in prominent New York office buildings, indicates that as buildings of equal height vary in area, the relative number of ELEVATOR SERVICE elevators produces a more or less convenient schedule, and where the number of elevators is unduly limited, the ineffective- ness of the service is demonstrated by the extended schedule. The schedule will be that which will result from the propor- tionate number of elevators divided into the average time occu- pied on the round trip of each elevator. The convenience which is provided by the elevators, both as to time and service, in business buildings or portions of build- ings, may be regarded as a direct addition to their real estate value. In applying an elevator service to a building of great height, it is evident that the efficiency of that service, as regards time occupied in travel, may be arranged so as to affect beneficially the relative position at which the upper or more remote portion is placed from the ground. Increase of height places the upper portions of a building at a disadvantage as regards access, and the importance of adequate provision for convenient travel to that part becomes greater as property values advance. Express services have, therefore, come into existence in order to afford the means of reaching an upper portion with the same celerity and frequent opportunity as lower floors. Assume, for instance, a building of twenty-one floors in which a service of elevators is established, the time occupied by which in carrying a traveler to and from its topmost floor is three minutes; assume that the building is raised to thirty-six floors, an addition being thus made of fifteen floors. If an express system of a similar number of elevators is applied to the upper floors, the time occupied by which on a complete trip is also three minutes, this added portion possesses the same aver- age convenience, and is at the same average distance from the street as regards time as the lower portion. If the twenty-one-floor building, therefore, had a certain value due to its position and convenience, the added upper por- VERTICAL TRANSPORTATION tion, provided it be accessible with the same convenience and time, is in an exactly similar position. This involves not only an equality in time-distance, but in passenger capacity. The number of elevators serving such an upper or remote section must be such as will provide for a passenger service per floor fully equal to that of the section below. Since, therefore, the time of each system of travel is affected by the height or, rather, by the number of floors resulting from height, it follows that there is a certain point in the height or number of floors at which such a division must be made. And, further, in order to afford to each section the same con- venience, a similar schedule, or time-interval, must be estab- lished, or, in other words, the same number of elevators must be provided for each section, although the upper section com- prises less floors than the lower section. In Figure I, the divisions at all heights up to thirty-six floors, resulting in equalization of the lower and upper sections of ser- vice, will be found, with the corresponding average time of each, for various speeds of the elevator car. The upper portions of some important buildings have appa- rently been placed at much disadvantage as compared with their lower portion, by an unequal division, resulting in inequality of time-distance, and, consequently, of travel capacity and schedule, partly, perhaps, by the adoption of the view that the superior advantages of light, air, and outlook, which are af- forded by the upper portion, will outweigh the disadvantage of less capacity, convenience, and accessibility. The result in such cases seems to have been that the most active business concerns, who are also the best paying class of tenants, have decided to occupy spaces in lower sections of the building, often at a less rate of rental. As the erection of competing neighbors is likely at any time to deprive the upper sections of any building of much of its advantage of position, the provision of an equal sys- 1:93 ELEVATOR SERVICE tern of access would appear to be dictated by reasonable fore- sight. Finally, in the decision as to the number of elevators to be provided in any building, a reasonable foresight and prudence would seem to require that the subject shall be regarded with a greater degree of liberality than that with which it has been generally treated. The desirability of providing for the growth of a locality and the consequent crowding of a larger tenancy into a building, the always increasing demands of the public for convenience, and especially of the business population for economy in time, are strong arguments in favor of an ample elevator service. This is reinforced by the almost universal complaint of oper- ating engineers that the continuous use of all the elevators in a building leaves no proper opportunity for repairs, except such as can be effected in the limited time and under the disadvan- tageous conditions of night hours. No part of the equipment of a great building causes its oper- ating staff the anxiety which the maintenance of these impor- tant appliances daily brings upon them, especially where an initial deficiency in their number has resulted in the hardest and most difficult duty. The resultant wear and tear is aggravated by the difficulty attendant upon efficient up-keep, and the result is an expense and often a loss of tenants through the incon- venience, far outweighing the cost of additional machines. The adoption of a practice of ascertaining and providing an effective plant, and of deliberately adding thereto an extra, or relief ma- chine, is greatly to be desired. One other consideration remains to be applied to this part of the subject. A high building, and especially the very lofty structures now being developed, places a considerable number of persons in a position where, in case of fire, panic, or emer- gency, they are dependent solely upon the elevator system for CIO] VERTICAL TRANSPORTATION removal or relief. Some thought should, therefore, be devoted to the capacity of the elevators for extricating the occupants within a reasonable space of time. This is especially desirable in buildings occupied as hotels or apartments. In a sixteen-story apartment hotel, the writer planned the elevator capacity to be such as would extricate the estimated number of tenants within a period of ten minutes, and an effec- tive demonstration of the desirability of this capacity was, in one emergency, afforded. A very opposite demonstration was witnessed by the author, in another apartment hotel during a fire, which, though occur- ring upon an upper floor, forced the tenants of floors below, in extreme anxiety and confusion, to the fire-escapes, on account of the incapability of the elevator service to remove them. The point seems to be practically ignored in certain high buildings, in some of which the elevators, running at their ut- most capacity, could not extricate the tenants in half an hour. Stairways in buildings are less effective than elevators, and are liable to be rendered useless on account of smoke and obstruc- tions. The maximum rate at which a body of men can make their way on a high winding stairway is interestingly shown in the accompanying diagram of observations at the i68th Street sta- tion of the Broadway division of the New York subway. A stream of travelers of nearly twice the hourly capacity of the elevators, even when running empty in one direction, over- flowed to the stairway. The capacity of the two elevators, which were excessively crowded, carrying about seventy persons in cars designed for fifty, reached a limit at twenty-four hundred persons per hour, or twelve hundred persons one way per elevator. The rest of the travelers were compelled to take the stairway, which is about ninety feet in height, equal to about eight floors of a busi- ELEVATOR SERVICE ness or hotel building. This in turn reached a capacity of about twenty-two hundred persons per hour, after which the surplus was compelled to await the gradual reduction of the crowd. It is to be noted, that the rate of stair travel would have instantly ceased upon the stumbling and falling of a few persons, such as Figure II ELEVATORS AND STAIRWAY AT 168th STREET SUBWAY STATION Note that full capacity of both elevators is reached at rate of 2400 persons per hour. Observations taken during arrival of crowd to ball -game might be expected to ensue if the travel were taking place under conditions of urgency or panic. It would appear, therefore, that a final index of the suffi- ciency of any elevator system would be its ability to extract the tenants under emergency conditions. ni23 II OPERATING CONDITIONS THE operation of a passenger elevator consists of a series of cycles of motion and rest, in which the car travels from its starting or lowest station, to its upper or top- most station with intervals of rest, returning in the same man- ner to the starting station, there being detained while the pas- sengers who have been brought down make their exit, and others take their place for a new ascent. Such a cycle is, in regular or "schedule" operation, known as a "round trip," and a certain number of these trips compose the hourly work of the elevator. The time occupied by each round trip results from two ele- ments: the operation of the mechanical appliances, or engine, and the operation of the human element, consisting of the pas- sengers and the man controlling the car motion, and of the two, the latter appears to be the larger and less manageable. It will be evident that these features introduce very distinct limitations into the operation of any elevator, and, as will be found to be the case, they bring about an actual reduction of its work after a certain point has been reached. An elevator cannot be regarded as an appliance, the work of which is capable of indefinite expansion by acceleration of its operating mechanism, or by increase of the carrying capacity of its car, for in the first place, practical or physical considera- tions combine to limit the operating speed of the mechanical portion, and call for the exercise, on the part of designers, of great ability and judgment ; and in the second place, the time of 1:133 ELEVATOR SERVICE operation is dependent upon the average personal equations of operator and passengers. Consideration is equally required in this connection, for the time consumed by the movements of the operator and the pas- sengers can be considerably affected, beneficially or otherwise, by the combination with an elevator's power and its speed, of a due proportion of travel, desirable proportions of the car and the door-openings, the avoidance of unnecessary weight in the cab, the provision of light and easily-handled doors, and an efficient signal system. The operation of any elevator machine may be considered to be composed of a series of starts, runs, and stops, each occupy- ing an average period of time consumed by the acceleration of the average load to speed, the maintenance of that speed over a certain distance and the reduction from that speed to a state of rest. If the stops be only so far apart that the operations of acceleration and of reduction of speed, cover the distance, then there is no period of time at which the load travels at the attain- able or designed speed. The distances required for the operations of acceleration and retardation with any given power of machine, vary with all loads, and also with the direction of operation. The machine should, therefore, be designed to effect the best results in both of these features with the average live load with which it is in- tended to deal, and thus to afford the best mean speed, inclusive of acceleration and retardation, over the average distance be- tween stops. An examination of operating conditions in a number of good New. York installations, shows that the mean speed over the distance involved in acceleration and retardation is from % to % of the nominal speed, and over ah average distance between the floors, is approximately seventy to eighty per cent, of that speed. An analysis of the operations of acceleration and re- D4n OPERATING CONDITIONS tardation of various types go to show that the average speeds which are attained are less affected by the Hve loads carried than by the distances between stops which those live loads in- volve. The work accomplished by the elevator is thus seen to be de- pendent upon the relative distance apart of'the starts and stops, any increase in the number of which 'detracts from the mean traveling speed. Thus a car which might run w^th a full load from ground to roof at a speed of, say, ten feet per second, would, if the run were made up of a series of stops and starts sixteen feet apart, attain a mean speed of only about six feet per second, though carrying but half of the full load. It may be noted here that the efficiency of higher speed ma- chines falls off at a greater rate than those of lower speed as the distance between stops is decreased, until, at a distance of one floor or, approximately, twelve feet apart, all approach the same speed as that machine which is designed to effect normal acceleration and retardation within that distance. This indicates that inasmuch as the speed of the elevator is affected by the number of stops to be made, there is little advan- tage in the adaptation of high-speed machines to duties where the average service unduly reduces its mean traveling distance. As the stops, commonly and properly referred to as "land- ings," to which both local and express elevators are subject, are made for the landing or reception of the passengers which it carries or receives, and as each passenger must be assumed to require a landing, the mean speed which the car will make upon its round trips is directly dependent upon the average number of persons admitted to the car. The larger the number of pas- sengers and corresponding landings, the less will be the distance between stops and the less will be the mean speed of the car. D53 Ill PASSENGERS AND OPERATORS THE second and larger time element in the cycle of opera- tion of an elevator, is that in which the human beings are concerned, in the control of the car, and in its delay by the ingress and egress of passengers. It will be readily noticeable by any observer that the personal characteristics affecting the time occupied in movement make the latter a variable quantity with operators as well as passen- gers. Operators vary as to the time consumed not only in the phys- ical operation of gate motions, but in mental preparation for action, in the adjustment of action to distance, such as moving the power control in advance of a landing, as well as in their at- tention to passengers' requests, and in their alertness in action upon receipt of signals. Such variations are reduced by training and experience, and as managers have come to appreciate the losses resulting from the practice of overrunning landings, and the dangers due to inexact landings, it may be assumed that such practices need not be considered as part of average efficient operation, and that the personal variation may be covered by a suitable aver- age time to be allotted to the operator's duties. The over haste of some alert and muscular operators intro- duces some apparent gain of time upon the average conditions, but it must be pointed out that elements of danger are intro- duced where time is cut by premature opening and closing of gates and premature starting of cars. Such practices indeed often fail entirely of their purpose, being accompanied by much ni6n PASSENGERS AND OPERATORS overrunning and returning to landings, and, unless all operators in a bank of elevators are of equal agility, the cars get out of schedule and such time as may be gained on the trip by one car is lost in waiting at the starting floor for the others. It is the average of. the operators that maintains the sched- ule, and the average operating efficiency may be improved by the provision of well arranged and accessible levers and door- latches, light-running doors, and the placing of the signal indi- cator in a position to be readily observable. It is unnecessary to do more than refer in a general way to the wide variety of characteristics in that large proportion of the general business population which utilizes the convenience of elevators. Every possible temperament and condition, all ages, and both sexes are included, and upon the movements of the average of all in and out of the car, depends the effective- ness of the elevator to a considerable degree. Fortunately, the general run of city-bred or city resident passengers are habituated to movement in and out of elevator cars, and to the use of signal systems, and thus contribute as much to a general alertness of operation, as the movements of others less accustomed to elevators do to its delay. The time occupied at each landing is dependent upon the co- operation of the operator and the passengers, and of the pas- sengers, one with another. The period which must be taken to represent average conditions, is therefore not the minimum time which may be expected when all personal and operating condi- tions are harmonious, but rather such as will afford a reason- able time for deliberate action on the part of the average pas- sengers. For this determination, widespread observations appear to afford a more secure basis than experiments, which are neces- sarily narrowed to the characteristics of a limited number of people. CI?] ELEVATOR SERVICE Such observations have been made by many persons, and my own have been compared with those of some of the keenest ex- perimenters in elevator operation, also with those of certain building superintendents, car-starters, and op'erators, with the following conclusions. The time occupied on each landing is composed of that nec- essary to open the gate, to admit of the passage, in and out, of the passengers, and to close the gate. In certain cities an inte- rior folding gate has also to be operated, this or the outer gate being sometimes interlocked so that it can be opened only at the point when the car platform is precisely level with the floor. The operation of opening and closing a gate occupies from 1% to three seconds, according to the strength of the oper- ator, the accessibility of the door-latch, ease of gate motion, width of gate opening, and, in certain cases, the additional movement of the interior gate above referred to. The passage of one person in or out of the car will add from one second to as much as five seconds, when conditions are ad- verse, such as an over-crowded car, obtuse passengers, or spe- cial locking devices would bring about. The combined opera- tion, therefore, may vary from 2^ to eight seconds, the majority of my own observations, extending over some years in all classes of buildings, ranging from four to six seconds, and an average of five seconds per passenger entering or leaving the car at a landing represents general conditions. It is to be noted that the operation of the elevator involves an ascent to, and stoppage at the top floor, whether for the pur- pose of a landing or not, and as this stop is affected by the auto- matic limit appliances, which somewhat slow up the car as it nears the upper floor level, and as it may be further assumed that the gate will be opened and closed, a similar amount of time should be allotted to this portion of the trip, whether or no a passenger leaves or enters at that floor. Furthermore, as PASSENGERS AND OPERATORS this top landing is an enforced one, and is not every time made for the purpose of landing or receiving a passenger, the time may be regarded as a separate addition of five seconds to the round-trip operation. The lowest landing, which must also always be made at every round trip, is that at which the passengers are discharged, and a new load of passengers is received, for which purpose the doors are opened and closed. The time occupied by this process is affected by similar condi- tions of alert operation, and of cooperation on the part of pas- sengers as on upper landings ; and it is still more influenced by the proportions of the door-opening through which, at this floor, not merely one or two, but all the passengers must pass both in and out. Heavy doors, narrow entrances, unfavorably shaped cars, and excessive loads in the car, will retard the ingress and egress of passengers at this stage of the work of the elevator. Observations have been made showing that under circum- stances, all of which are favorable, a load of passengers can make their exit at the rate of %o of one second per person, and a new load can enter and take their places in the car at the rate of %o of one second per person, but these figures will be in- creased to double the time when all the circumstances are ad- verse. The conditions are so rarely fully favorable that a conserva- tive average of two seconds per passenger, that is, iVi second for ingress, and % of one second for egress for each person, should be made, and to this should be made, for the operation of opening and closing the gates at the starting floor, an addi- tion of four seconds. 1:193 IV RATING THE WORK OF THE ELEVATOR HAVING thus ascertained the time occupied in motion of the car, and in the several operations connected with the movement of passengers, it remains to estabHsh the number of the passengers which are to be adopted as the mean working condition. While, of course, at times and under some conditions, cer- tain floors in any building may be more frequented than others, it may be assumed that the distribution of the passengers will average over the several floors, and since these passengers at time of maximum travel are to be assumed to be tenants, whose occupation of the building extends over all floors, each floor receives at some time and returns at some other time, its pro- portion of the total number of occupants. If one floor be more crowded than another, the result would be that the one floor would involve more landings than the other, but this would not affect the mean number of landings required to be made. An allowance of one complete landing to each passenger may be considered liable to vary somewhat by the ingress or egress of more than one person at the same landing of the car, but any assumable gain by this feature is modified by its irreg- ular occurrence, and by the additional movement of other pas- sengers in the car in making way for the larger number enter- ing or leaving. If, therefore, an elevator car be required to receive, in regu- lar operation, a number of persons every trip, equal to the total number of floors which it serves, both up and down, it follows that its mean work must be assumed to involve a landing at 120-2 RATING THE WORK OF THE ELEVATOR every floor, and its traveling speed to be no more than that which it can attain in this Hmited distance. If, however, the number of persons carried per trip be only Vz or %o of the number of floors served, the distance between landings would be doubled, the average speed of the machine would be correspondingly increased, utilizing to better advan- tage the speed of the machine, and the trip would also be short- ened in time by Vz of the time occupied by passengers passing in and out. A further increase in mean speed of travel, and correspond- ing reduction in the round-trip time will be attained by so ar- ranging the work of the elevator that the mean travel will be composed of landings at %o of the total floors up and down, and at this point, with the usual heights from floor to floor, the successive stops will approximately average twenty-four feet apart. This proportioning or rating of the mean work of each trip at a number of passengers coinciding with %o of the total num- ber of floors at which the elevator is arranged to land, agrees with a very generally acceptable practice of designing elevator machines so as to attain with %o of the maximum load in the car, its best results in mean speed in both directions. The time occupied in the travel of the car between floors a certain distance apart, with that occupied in landing at those floors, and loading and unloading the corresponding number of passengers, added to the allowances for the upper landing and for the gate handling at the lowest floor, makes up the total time occupied in the round trip, and, upon the basis of the allowances referred to above, or any other uniformly applied, it will be found that the elevator will, when handling that number of pas- sengers which coincides with %o of the number of the floors which it serves, effect the best combination of up-and-down travel with a minimum expenditure of time. C213 ELEVATOR SERVICE In Figure III, the operation of an elevator serving locally twenty floors above the ground floor, is diagrammatically repre- sented. The horizontal scale is that of time in seconds, reading from left to right, and the vertical scale on the left-hand side is that of the floors, the height of which is assumed to be twelve feet apart. The full lines show the operation of a round trip in which, after having received a load of eight passengers, the car ascends, making eight landings of five seconds each, thus dis- charging its load, then visits the upper landing at an expense of time of five seconds, and descends, making eight landings on the down run, receiving eight passengers, arrives at the ground floor, discharges eight passengers, receives eight new passen- gers, the gate is then closed, and the car is ready for the next trip, the total time occupied being 2.84 minutes. Broken lines are then introduced which show the delay result- ing from increasing the number of passengers on the up trip, successively to numbers corresponding with /4o and %o of the number of floors served, or ten and fourteen persons, each re- sulting in a corresponding delay of the up trip, so that, in order to maintain the convenience afforded by the round-trip time of the fw service, less passengers, in each of the above cases, must be carried on the return half of the trip. At fourteen persons on the up run, or landings equal to %o of the number of floors, only one landing on the down run can be made without delaying the appointed round-trip time, and of course the same result is brought about if the fourteen persons enter on the down run, rendering it necessary for the car to re- ascend with only one landing. If no landing be made on the down run, another may be added to the up run, making approximately y}^ landings out of 10 floors, which, therefore, represents about the point of maximum travel in one direction within the desirable round-trip time. 1:22: Figure III SCHEDULE SERVICE LOCAL ELEVATOR Shqwing variations in traffic witiiin schedule time 7i1t 4 ^ ? &, * P «9 n iS nit \ / T r \ j I- ' > r j 1 1 1 1 \ \ \ V /* \ 1 r 1 \ ) •1 1 / . \ \ i 1 1 1 1 1 \ \ n 9 & T & 3 * 7. i 1 1 / \ ^ 1 ' / / ! 1 1 \ 1 / / r \ \ 1 / 1 / \ \ \ 1 1 1 J / ^,^ E* o sE hr4 IE ft XI lA kTE L. 1 \ \ 1 r / 1 1 r- m ^*> Ufa \ \ \ / 1 1 1 \ UI •J> 1*1 i3> SW f- ■'" k \ 1 \ \ t \ . '\ --- " ,> 1 1 '^ / \ \ /' ^ / f 1 i V Y { i \ \ SL / ./ r 180 ,' /' i \ \ \ \ ^ il* 1 r 7 \ \ \ \ i i \ 1 ! 1 jj \ IX j \ 1 \ I 1 i 60 * N \ La nd ng t 'n ■n ■at b ■^ . «ll '« I «v p A3 ^ < > . TO I 5 20 ZS 2 «SS4O4SS0SSe0 TO 8 SO wo no 120 130' HO ISO 360a«. 1:233 ELEVATOR SERVICE The passenger travel per hour is shown by dotted lines in the center of the figure, the scale of numbers of persons reading upward on the left-hand side of the diagram. This shows that the %o travel produces equalized travel up and down, and thus affords the maximum travel in both directions. Inasmuch as any elevator must be regarded as an appliance for operation in either direction, the basis of %o travel is evi- dently that at which the best all-round results are attainable, affording, as it does, within the same round-trip time, a larger capacity in one direction, up or down, which will meet irregu- larities of visiting travel, or Will deal with the nearly simultane- ous arrival or departure of tenants, at morning, noon, and evening hours, as represented in the frontispiece. Figure IV shows that in the operation of an elevator in the same round-trip time as an "express" machine to the twentieth, thence local to the thirty-fourth floor, a similar limitation of excess travel in one direction occurs at about the same point of %o. Deviation from the round-trip time of the %o travel, does not produce corresponding efficient results in passenger travel. In Figure V are plotted the numbers of passengers carried each way per hour, on a local service of twenty-two floors by an elevator of six hundred feet nominal speed, regardless of any established round-trip time. This confirms the foregoing conclusions, for it will be seen that while the maximum hourly rate of travel may be attained by carrying about fifteen persons each way, making seven land- ings out of ten floors up, and seven landings out of ten floors on the return trip, the service is so accelerated by carrying only nine persons each way, that ninety per cent, of the maximum hourly capacity is then accomplished. Very little is gained, therefore, by departure from the fio service, and much is lost by the inconvenience of slow travel, and by the correspondingly 1:243 Figure IV SCHEDULE SERVICE EXPRESS Showing variation in traffic within schedule time S5 a/> J I fe ^ \ \ / \ \ ' 1 \ / \ 1 V \ I /' \ \ ar / / \ \ / \ , / 1 \ I -"■4 ' r' \ * 2^. 1 / 1 I / ,' \ / 1 \ » ./ I \, 4 /J r"'^ \^ / / \ 1 V ^ E ^5 SE tfl n l- TI\ \% 'El - 1 i / 1 I G- — — — ^ .— :, /

tJ Tt as ■r V :j 5 -lO ' 20 SO -40 JO 60 7*^ SO so ^OO no 120 1»0 140 ISO !60 sec.l [1253 ELEVATOR SERVICE lengthened "schedule" interval between the departure of cars. When carrying more than the number of persons corre- sponding to seven floors out of ten each way, the reduction in the distance between landings actually results in a less number being carried per hour, as shown by the right-hand portion of the curve. Figure V LIMITATIONS OF PASSENGER TRAVEL, 22 FLOORS .f/.lllir f^ ze? Z7 ZZ fitr-fyi'A Therefore, if the work of an elevator be so settled and pro- portioned as to compel it to carry so many persons per average trip as to correspond with seven landings out of ten, then it possesses no margin of passenger-carrying capacity beyond its pre-defined duty, but will actually fall off in its work, if, by any means, more than its designed capacity should temporarily be imposed upon it. But if its work be planned to correspond with, say, four landings out of ten, then it will possess the capacity to 1:263 RATING THE WORK OF THE ELEVATOR carry an additional number of passengers per hour of ten per cent., and an excess capacity, as showjn in Figures III and IV, in one direction only, of about eighty per cent. Conversely, if its work should fall off to a considerable ex- tent, the hourly passenger duty would still be near the point of efficient operation. These results, agreeing as they do with good economical practical operation, may, therefore, be considered to establish the fact that the mean work to be assumed and assigned to any elevator should' be an average passenger travel each way per trip, of that number of persons which corresponds to Yio of the number of floors served, which is the basis herein adopted as the standard, or Bolton rating of the work of a passenger elevator. n273 V COMPUTING THE AVERAGE WORK THE relation of the number of passengers per trip to the floors which are served being thus established, the com- putation of the time of each round trip, the resulting travel, the schedule-interval, and the relation to the building, become ascertainable. In the following computations the notations are made as follows : NOTATIONS A Occupied area per floor of the building in square feet. a Occupied area per elevator, in square feet. c Occupied area per car per floor in square feet. Occupied area per passenger or occupant in square feet. n Number of elevators. / Floors served by the elevator, always above the ground floor. t Traveling time, or time occupied by the motion of the car, in minutes. / Loading and unloading time in minutes. s Mean speed between average landings in feet per second. i Schedule or interval between starts of the elevator. r Round-trip time of a local elevator in minutes. e Floors run past by an express elevator. d Time of the express distance in minutes. R Total round-trip time of an express elevator, in minutes. p Passengers per hour, in each direction. h Total height of the local floors served, in feet. COMPUTING THE AVERAGE WORK The percentage of fio of landings to floors affords an ap- proxinlate distance between stops of twenty-four feet, and at such a distance the mean speeds of elevator cars in feet per sec- ond may be taken to be as follows : Nominal speed 600 5(X) 400 300 Mean speed in feet per second y.S3 6.33 5.33 4.33 The number of feet from ground to top floor and back again, divided by the above-stated rates, gives the time in seconds occupied by the actual travel or motion of the car. The addition for landing time is at the rate of five seconds for each stop up and down, the number of such landings being %o of the total number of floors served in each direction. For ingress and egress of passengers at the ground floor iVi seconds is allowed for each passenger entering^nd % of one second for each leaving, or one second average, ixtth ways. An addition of nine seconds is made for the visit to the top floor, and the gate handling at the ground floor. These items may be then reduced' to the simple formulas be- low by which any round-trip time is found for elevators of dif- ferent nominal speeds, as follows : ,,0! - " For a 600-ft. elevator r^/x.i345+.'i5. For a 500-ft. elevator r=/x.i4^2 + .is For a 400-ft. elevator r=/x.i55o + .i5 For a 300- ft. elevator r=/x.iy22 + .i$ And to ascertain the passenger travel per hour, up or down, on the %o proportion of passengers to floors served, r in which r= the time of the round trip m minutes. /= the number of floors served. /> = passengers per hour each way. n293 ELEVATOR SERVICE ROUND TRIPS AND PASSENGERS CARRIED IN EACH DIRECTION Average floor height 12 feet. 600-Ft. Machine 500- Ft. Machine 400- Ft. Machine 1.1 a. S„-s 2.. boo h |g ji ill Trips Hoi Passen Pi ^ t^ 1^ 22 3-II 19.3 169.8 3-30 18.2 160.0 3-56 16.8 148.3 21 2.98 20.1 169.4 3-15 19.0 ■159.8 3-41 17.6 148.0 20 2.'84 21. 1 169.0 3.01 19.9 159-3 3-25 18.5 147-7 19 2.71 22.1 168.5 2.87 20.9 158.9 3.10 19-3 147-3 18 2.57 23.3 168.0 273 22.0 158.4 2.94 20.4 146.9 —17 2.44 24.6 167.4 2.58 23.2 157-9 2.79 21.5 146.5 m6 2.30 26.1 166.8 2.44 24.6 157-3 2.63 22.8 146.0 15 2.17 27.6 166.0 2.30 26.1 156.7 2.48 24.2 145-5 14 2.03 29.5 165.2 2.15 27.9 156.0 2.32 25.6 144.8 13 1.90 31.6 164.3 2.01 29.8 155.1 2.17 27.6 144. 1 12 1.76 34.1 163.2 1.87 32.1 154.2 2.01 29.8 143-3 II 1.63 36.8 162.0 1.72 34-9 153-1 1.86 32.2 142.3 10 1.50 40.0 160.5 1.58 38.0 151.7 1.70 35-3 141. 2 9 1.36 44.1 158.7 1.44 41.6 150.2 1-55 38.7 139.8 8 1.23 48.8 156.6 1.30 46.2 .148.2 1-39 43-1 1 38. 1 It might seem, from a cursory examination of the results of these computations, that as the number of floors is increased, a corresponding increase in hourly passenger travel per eleva- tor is obtained. But it will be seen, on examination of the fig- uires of passenger travel in the foregoing tabulation, that the increment is not directly proportionate to the increase in the number of floors served, but is a gradually decreasing quantity. COMPUTING THE AVERAGE WORK It will also be observed that the number of trips per hour de- creases at a decreasing rate. Where business conditions, therefore, render the time of travel of major importance, or where the convenience of the number of trips per hour is an element of value, the gain in pas- senger travel, due to a greater number of floors served, is found to be insufficient compensation for the loss of round trips and of time which is involved. This conclusion very interestingly co- incides with practical experience in operation under city condi- tions, by which it is found that when about fifteen to seventeen floors of local service is exceeded, it becomes desirable to effect a division of the building into local and express services. CsO VI EXPRESS SERVICE AN express elevator is one of which the first landing at l\ which it is caused to stop is removed a considerable ■^ -*- number of floors above the ground level. It must, therefore, have an addition made for the time occu- pied on this extra run, but in all other respects, it will be similar to a local machine serving the number of floors at which it stops.. The distance thus added to the local service by the express run^ is that between the first floor above the ground, and the floor at which the express first stops. It may be considered as a straight run at express speed, since the operations of accel- eration and of 'retardation are already included in the local service with which it is combined. The average load which the express car is to be assumed to be carrying, is that due to the number of persons, correspond- ing to Yio of the number of floors which will be locally served by it, including the first floor at which it stops. For express elevators a nominal speed of six hundred feet per minute is usually adopted. The time added by the express run on assumed heights of floors of twelve feet may be conveniently found by the follow- ing formula : e = Tiumber of floors which are passed by the express car d= time of travel in minutes in both directions y = the number of floors served by the express, which includes the first floor at which it stops. 1:323 EXPRESS SERVICE For nominal speeds of ... . 600 ft. 500 ft. d= e X.034 e X.042 The result (rf) is to be added to the round-trip time (r) of any floors which the express serves locally, i.e., the floor at which it first stops and all above it. So, then, the express round- trip time (i?) becomes: R = d+r and the express passenger traffic per hour becomes : ^ d+r R Express service is, of course, mainly due to the demand of the public for such convenience as shall bring the upper por- tion of the building within as short a time-distance of the ground as possible. It is not necessary to repeat the reasons which have brought about' this demand, which were dealt with in the first section of this work, and it is more to the point to ascertain just when a division of a building should be adopted, and where that divi- sion should be located. The table of round-trip times of local machines at five-hun- dred-foot speed, will show that at a height of seventeen floors, the trip occupies over 2% minutes, and while there are some buildings as high as twenty- four floors which are running a lo- cal service at a time per trip extending to about 3% minutes, such a service cannot be considered as one that is fully desirable in the interests of the rentable value of the property. It will be found, therefore, that a division of high buildings has been very generally adopted when they reach sixteen stor- ies in height, and from that point upward such a division must be regarded as accepted practice. 1:3311 ■ ELEVATOR SERVICE It is interesting to ascertain just what the subdivision at this point effects. The local service to the sixteenth floor above the ground floor of a five-hundred-foot machine, requires 2.44 minutes for a round trip, or 24%o round trips per hour, making 157.3 land- ings each way per hour, corresponding to that number of pas- sengers in each direction. For an express service, a faster ma- chine, nominally six hundred feet, may be assumed. The first and rather natural suggestion is to effect the divi- sion at the middle floor, or at the eighth above the ground floor. The local service of eight floors would then be made in a round trip of 1.30 minute, while the upper section, running ex- press to the eighth, and thence local to the sixteenth or nine floors, would require 1.60 minute, evidently placing the upper tier of floors in a less advantageous condition than the lower, though cutting down the round-trip time of the lower service by nearly fifty per cent. By a division at the ninth, the time for the lower tier of nine floors would become 1.44 minute, and for the upper eight floors 1.50 minute, making practically equal service between the two sections of the building. A division at the tenth floor makes the lower service of ten floors 1.58 minute, and the upper tier of seven floors 1.40 min- ute, throwing the balance the other way, and affording the up- per section better facilities than the lower. By adopting, therefore, that division which will most nearly produce a balance in time of service, the two sections of the building receive an equal amount of convenience, and it may be asserted that the upper section is brought as near to the street as the lower. By the tables and formulae here presented, these times for any height are readily ascertainable, but for greater conven- ience they have been compared and the best result tabulated in 1:343 EXPRESS SERVICE Figure I, page 8, giving the equalized division of any build- ing to heights, corresponding with thirty ^six floors, with com- bination of five-hundred-foot, or six-hundred-foot locals, with six-hundred-foot expresses. The division will, in any case, require more elevators than would be the case with an entirely local service, as, notwith- standing the increased speed of the two shortened services, the passenger capacity of each is less -than that of a local serving floors to the full height, though the convenience is, of course, greatly increased. Thus for the i6 stories, 2 local elevators carry hourly each way, 157 persons x 2, or 314 while the express, 9 to 16, carries 128 and its companion, local to 9 150 The local machine and its companion express machine carry 278 Thus the local and express combination together carries about ninety per cent, of the capacity of two long-rtm locals, but at about sixty per cent, of the time of the latter, so that a meas- ure of the cost of the convenience of an express system may be stated as an addition of about ten per cent, more elevators, for a gain of about forty per cent, in time. The division of buildings into two tiers will extend only so far as the desirable maximum time occupied by the local eleva- tors. At sixteen floors, this part of the system has again reached the point of a ■2j^-minute service, and at twenty-two floors, even with the use of a six-hundred-foot machine, has passed the three-minute mark. This number of floors corresponds with an express system reaching to the thirty-eighth floor, and this may, therefore, be regarded as the limit of an effective two-tier division of high buildings. 1:353 ELEVATOR SERVICE Beyond that point, a further subdivision becomes necessary, and a three-tier arrangement of floors must be considered. The same course of extension of floors and of time follows, until the lowest of the three sections again reaches the twenty- two-floor point, corresponding, in this case, with a total height of forty-five floors, when a fourth division will be required, ex- piring, in turn, at the fifty-second floor. To afford in any express service an equality of convenience in the subdivided portions of the building, an equal number of cars should be provided for such service, with a round-trip time as nearly as possible equal. Naturally, the equality in the number of each class of eleva- tors is to be varied, if the area of the building be not equal at all heights, as in the case of "tower" buildings. 1:363 it VII THE SHAPE AND SIZE OF THE CAR THERE are, naturally, conditions of the design of any building which are liable to affect the size of elevator hoistways, and thereby to«^redetermiric the' practica- ble size of the car. Exigencies of space brought about by the shape of the building plot, and necessary disposition of columns, have frequently rendered it necessary to adopt a car for a ser- vice to which it is not well adapted. For similar reasons, many unsuitable and undesirable shapes have been adopted, which tend to restrict the free movement of passengers, and so to limit the effective work of the elevator. Of these, the narrow and deep car, the car with narrow en- trance and wide rear, the car with central pilasters, need only to be named to be readily appreciated as unsuitable for rapid and convenient work. Much can be gained by the adoption of an ample width with shallow depth whereby the passengers at the rear are not hindered from egress by a number standing in front of them. These proportions also admit of wide door- ' openings, rendering ingress and egress as free as possible. It may, therefore, be unhesitatingly assumed that for effec- tive service and rapid schedules, the proper shape of the car will be an element of importance, and unless it be desirably pro- portioned, the car will have a restricting effect upon the travel. Naturally, the same remark applies to the use of unduly heavy doors, and of inaccessible and sluggish door-fastenings. The size of the car is based upon the number of its human occupants, all of whom occupy a standing position, but all of whom, except the operator, must make a complete turn around l37l Figure VI STANDARD ELEVATOR GARS ^ ^Mafch wheft vsrheat AfaeAine fsusffd ^ ^ ' ^ yHafch when Cotm^rtnfei ti Af /is in 3aeA ^ ^ ^ ^Hafch whe/i f^erf/ca/ AfacA/fte/6 ifsed ^ K P ;^ HaA:A ¥^ief7 Coanrerw^ /^ Af/s m 3ac/r <. ^ •SgQ-/^ -*A 1:383 THE SHAPE AND SIZE OF THE GAR at some time between their entrance and exit. The free space required for such a rotation is found to be, for an adult, 2.2 square feet, but, since much of the travel is composed of young people of immature proportions, practice has settled down to an allowance of two square feet per average traveler. It would be very desirable if the space allotted to the oper- ator could be not only theoretically increased, but practically re- served to his use, since his arm movements in handling controls with the one hand, and in reaching across the door-opening with the other, clearly involve, for rapid and secure operation, a free- dom of movement. The area required for these purposes is an addition of 1.8 square feet to his standing space. Unfortunately, the tendency of the public to crowd into any vehicle makes it possible for this space also to be occupied by passengers, whose presence and weight must, therefore, be taken into account in the maximum load that may be on some occasions imposed upon the apparatus. The average weight of the units composing public traffic has been well established at about one hundred and forty to one hundred and fifty pounds per passenger, which corresponds, therefore, to a live load of seventy to seventy-five pounds per square foot of interior car space or platform area, the latter figure being commonly adopted. It has already been shown that for any given number of floors served by an elevator, a maximum of travel is reached when the average number of persons carried each way corre- sponds to about %o of the number of those floors, without re- gard to the round-trip time or the schedule; or a maximum in one direction is reached when a total of between %o to %o is carried one way only within the established round-trip time, and that beyond this number, the elevator is delayed and the number of passengers carried falls off. It would logically follow, therefore, that for any given num- 1:393 ELEVATOR SERVICE ber of floods served by a car its interior dimensions should be such as will accommodate, at the rate of one hundred and fifty pounds per two square feet, or seventy-five pounds per square foot, no more than the number of persons corresponding to %o of the floors which it serves. If this be exceeded, then the capability of the car to carry a larger number may be made use of, with the result of delaying and reducing the traffic. It would, however, be expecting too much and would add to the already confusing variety of the proportions of elevator cars, to demand that such a practice be rigidly followed, and it appears that. the practical conditions can be sufficiently met by the adoption of a few standard sizes, see Fig. VI, such as will carry the traffic related to certain floor heights within a moder- ate variation of their full capacity. Figure VII affords information as to the proportion which the average traffic at any floor, on the Bolton rating, will bear to the/ maximum carrying capacity of cars of various sizes, up to forty-eight square feet net interior area of cab. The upper scale gives the corresponding live load in the car, including the operator, at seventy-five pounds per square foot of area. Thus a car, the size of which has been fixed at, say, forty-two square feet interior area of the cab, is found to carry a maxi- mum of .3150 pounds, and at forty per cent, of that load, it is carrying an amount of 1260 pounds, equal to 7.4 passengers and an operator, which is near the average load of a nineteen- floor service. At twenty-two floors, the rated service affords 8.8 passengers and the operator, or 1470 pounds, which provides a load of 46^ per cent, of the maximum capacity each trip, and inversely, if it be serving less than nineteen floors, less than forty per cent, of the capacity would be utilized per average trip. r-^ aoffjs ^JVKe-z3 fiMttooSSSSSS^'SSS- S ^^'irXUKiC >47- /*2 00^.9 S \ \ i. \ 1 1 \ ! S \ o — s- s- 5- s- ? r 1 / \ / /^ > 4 \ \ > \ o z O > a r ! ;; ,8!! o O r S . 3 i? > H A > f z 3 \ % \ \ \ \ % K K / /* / /5 / » / 1 / A / / / / / / / i / 1 / / / I / / / / 1 / / / A / / / / / / » / / / / / / / / / / / / 1 / / / / / / / / / A / / / / / { / / / / / / / / /^ / / / / / / y ^ / / / / / / / y \ / / / / / / / y y / / / / / / / / y ^ i ,/ / / / / / / / y y y / / / / / / y y y y ■ / / / / / / / y y y y 1 t / / / / / y /■ y y^ y I / / / / / / \y ^ y y y / / / y / / ^ y ^ y ^ ^ / / / / / / / y ^ ^ ^ / / / / \/ y y ^ y ^ y / / / / A / y y y /■ y^ / V / / y / / y y ^ y .\ / / / / y ^ y / / / / y ^ ^ y / /. ^. y ^ y^ '^ ^ ^ ^ > ^ 5 Ay^fMqs U'^/G^r i I \ ' i ' i i a \ I •a UO ELEVATOR SERVICE Its maximum capacity, however, being 3150 pounds, it would carry a maximum trafiftc of that weight, which, deducting the operator, is 3000 pounds, or twice the rated load of a twenty- four-floor service, which corresponds to %o one way on that number of floors. Beyond this, it could not handle further travel, so that its extreme effective travel capacity is at a twenty- four-floor service. Such a car, therefore, would be adaptable to services of nineteen floors up to twenty-two floors, and might serve twenty-three or twenty-four floors, were such a number desirable. Extending the study, we find that a car of 32.5 square feet area, having a maximum load of 2437 pounds, reaches a similar limitation at a nineteen-flopr service, and would be carrying forty per cent, of its full load, with the rated service of fourteen floors, while the range of a car of twenty-six square feet is fif- teen floors and eleven floors, and that of a car of twenty-one square feet, eleven floors and seven, respectively. These four sizes are therefore found to cover the range of floor services from seven to twenty-two, the latter being con- sidered the highest number for efficient local. service, and they have, therefore, been adopted as standard cars, the det3,ils of which are given, with dimensions, in Figure IX, showing their proportions of cab interior and exterior, gate opening, and least clearances required in hoistways. The conditions under which other areas of car will operate on the rated loads of various floor services, can be observed in Figure VII. 1:423 VIII LOAD AND SPEED COMBINATIONS IEGAL restrictions as to the speed of the motion of the car are established in certain locaHties, such as is the case — « in Manhattan, where a curious and not very comprehen- sible difference is drawn between local and express elevators, the former of which are limited to a speed not exceeding four hundred feet per minute, while the same elevator, if operated over an "express" or non-stopping distance of eighty feet, is permitted a car-speed of six hundred feet per minute. The speeds thus referred to are such as are commonly used to designate the speed of the elevator car with a predefined load, known as its speed-load, and by no means indicate that the actual speeds under all conditions are within the nominal figure, nor, on the other hand, that the mean operating speed is of that amount. Such as they are, however, these definitions have come into general use, as descriptions of the relative- speed capacities of elevators, but, unless the load to be thus carried bear some rela- tion to that which the elevator will be called upon to lift in the floor service to which it is to be applied, such a nominal speed may be misleading as an indication of the work which will result. Thus such legal restrictions as that referred to, which do not define the conditions under which the restricted speed is to be attained, become impractical and inoperative, and are indeed Us 3 ELEVATOR SERVICE unnecessary, since the conjunctions of loads and speeds are brought about by physical and economical causes, which also fix their limitation. A regard for reasonable economy in operation requires that the moving parts of an elevator combination shall be so bal- anced as to leave the least practicable amount of dead weight to be Hfted. The unbalanced portion of the mass is desirably reduced to that necessary to effect the descent of the car at a suitable speed, when it has no passengers in it, and inversely, on 'the up motion, to aid by the action of gravity in bringing the car to rest within a suitable and safe distance. In the electrical form of operation, the empty car may be, and generally is, overbalanced to the ex- tent of the average load, and the descent of the empty car is ef- fected by lifting the counterweight. Unbalanced weight, over and above that which performs these functions, is undesirable and unnecessary, both on the score of the power which is required to set and maintain it in motion, and on account of the tendency which it affords toward undue speeds on the down motion, so that an adjustment is sought by the elevator constructor which will bring about the combination of proper upward stopping distance, and moderate downward speed, with the least unnecessary unbalanced dead weight. When so adjusted, the distances are defined within which the car will come to a stop after the power is cut off, and the desirable combination is readily seen to be such as will, even with an express machine, admit of secure and controllable starts and stops within the short distance between one floor and the next. The same result must be brought about in the descending mo- tion without shock to the occupants of the car, and it is to be noted, that while the arrest of the car can be, and is, effected in 1:443 LOAD AND SPEED COMBINATIONS this direction by mechanical means, such as by brakes, or by confining or reversing the source of power, the distance within which such a stop can be made is somewhat affected by the fact that counterweights, ropes, and other moving mechanism which are rising as th^ car is descending, are arrested by the action of gravity. The same general conditions, therefore, properly ap- ply to stopping distances and time decupled in attaining and retarding motion, in both directions of car travel, and in greater or less degree with various types of machines. The most important feature of the power of the motive mech- anism is that which produces the acceleration of the working loads from a state of rest to the designed speed, because the normal work calls for successive starts from a state of rest to speed, and a reduction of that speed to rest, all within limited distances. It must be borne in mind that by determining upon any size of car and, incidentally too, by undue weights involved in the design of the cab, the operating conditions of the elevator ma- chine are thereby affected. The car may be crowded with per- sons to its full capacity and corresponding weight, and the machine must be capable of lifting that load. But that load is decided merely by the area of the car platform, and, if the car be unduly large, may demand so great a power on the part of the machine as to unnecessarily aflfect the speed and economy of the machine with other loads. The capacity to lift the maximum load is often regarded as merely a test of the ability of the machine to lift a certain load which its car is large enough to receive, and the speed with which this is done is regarded as unimportant, but if that maxi- mum load be properly related to the number of floors to be served, then the power of the machine to lift that load, at as high a speed as practicable (with due regard for economical operation with other loads) becomes a valuable feature in Us: ELEVATOR SERVICE facilitating travel, particularly in connection with express ser- vice. The load which may have to be operated at the nominal speed is that due to the travel in one direction or the number of pas- sengers corresponding to %o of the number of floors served, in addition to the operator, or (.7/+ i) X 150 lbs. being the so-called "speed-load" of the machine. This combination is that which should result in the nominal or stated rate of travel, and is generally understood as being at- tained on a flying run in the upward direction only. If the machine be an express, the speed at which the car will operate over the express distance becomes of interest, and the norrnal load, which it will be called upon to lift and lower over the express distance, will be that number of persons correspond- ing to Yio of the number of floors served, plus the operator. But as it will be required at times to operate over this dis- tance when carrying the heaviest travel in one direction, it should be capable of lifting that load at express speed. Ex- press operation therefore involves lifting the speed-load, but it should also be capable of descending with the operator only, at about the same speed. The working conditions by which the passenger travel is mainly affected is the mean speed between the average or rated stops which on floor-heights of from twelve to fifteen feet are approximately from twenty-four feet to thirty feet apart. This mean speed is directly dependent upon the time occupied by the machine in accelerating the car and mean load to the cor- responding speed, and in retarding the traveling car and mean load from that speed to rest, in both directions, up and down. The average load carried on the rated operation is that due 1:463 LOAD AND SPEED COMBINATIONS to liftings from the ground floor the number of persons cor- responding to %o of the number of floors served, gradually dis- tributing them on those floors, and on the return trip gradually receiving a similar number, so that the mean load of all the short runs is one half the rated number of passengers plus the operator. The elevator will, however, at certain times be temporarily occupied in lifting, distributing, or in receiving and lowering, the heaviest one-vyay travel, under which conditions it is still desirable that it should maintain the service within the same round trip time. It will be proper, therefore, that its propor- tions should provide for the handling in the up-direction, of the heavier load over the shorter distances. The mean of this load will be about (.4/+1 ) ^ 150 lbs., and the f average distance in feet between the stops, will be — x floor- height. The conditions of operation should be planned so that, while aiifording the power tQ lift the speed-load covering the busy one-way travel, the best economy of the apparatus should be developed in the carriage of the rated load, or average pas- senger travel. The following list of loads resulting from the application of the four standard sizes of car to their respective numbers of floors served affords information which will aid the elevator constructor to bring ^bout the best combination of Iqad-speed and mean-speed, with proper economy in power consumption. 1:471 "i-S ELEVATOR SERVICE STANDARD CARS AVERAGE TRAVEL AND LOAD CONDITIONS ey, Car Proportions Designed Loads Average Conditions Area Sq.Ft Length WidtK Ft. Ft Gross Load Speed Load Passengers One Way Rated Live Loads Mean in Lbs. , Rated 22 42 7'-o" 6'-o" 3000 2500 15-4 8.8 1470 810 21 14 7 8.4 1410 780 20 14 8.0 1350 750 19 13 3 7.6 1290 720 18 33 6'-6" 5'-o" 2500 2000 12 6 7.2 1230 690 -17 — II 9 6.8 1 1 70 660 16 - II 2 6.4 I no 630 15 . 10 5 6.0 1050 600 14 26 6'-o" 4'-4" 2000 1600 9 8 5-6 990 570 13 V 9 I 5-2 930 540 12 8 4 4.8 870 510 II 7 7 4.4 810 480 10 21 5 -0" 4'-2" 1500 1200 7 4.0 75° 450 9 6 3 3-6 690 420 8 5 6 3-2 630 390 7 4 9 2.8 570 360 US] IX THE BUILDING AND ITS PROPORTIONATE SERVICE HAVING arrived at a basis on which to compute the aver- age and maximum travel to be afforded by elevators at different numbers of floors, there remains to be de- cided, What number of such elevators shall be provided in the building? The effect of height has been already taken into account in the round-trip time, and the delivery and receipt of passengers has been distributed on the floors composing that height to the best advantage. How much of the building shall now be allotted to each ele- vator ? The answer may be found in the proportion of the cubical contents of the occupied portion of the building, which is oc- cupied by these passengers. For practical purposes it may be assumed that the modern building of twelve-foot floors will have a clear height from floor to ceiling of about ten feet, so that the question nets down to the cubical contents divided by ten, or, in other words, to the area of floor space related to the passengers. It has been found by observation that it is the tenants or oc- cupants of the building who form the heaviest degree of travel at any one time, and if their travel be provided for, the visiting, or transient travel will be sufficiently covered. The tenants, 1:493 ELEVATOR SERVICE consisting largely of employes, having regular hours of begin- ning and ceasing their work, naturally arrive and depart within a limited period, while the visiting traffic is spread over a num- ber of hours. Figure VIII illustrates this point in a business building, and it might be varied as to the particular hours involved in special travel to suit hotels and other classes of building. The average tenant travel occurs four times per diem, at which time little, if any, visiting travel is present. These ten- ant travelers who are, as has been stated, employes, are anxious to reach their destination with the least possible margin of time between their arrival on the ground floor and arrival at the place of their employment. This travel is, therefore, insistent, recurrent, and regardless of crowding. It is by observation found to spread over about % of an hour in one direction, 'either up or down, according to the time of day, i.e., on arrival, at lunch hours, on departure, and it constitutes the maximum hourly rate of traffic to which the elevator must be able to ac- commodate itself. Obviously, if the building be provided with elevator capacity at the Mo rating, to handle its entire tenancy in one hour, the oc- cupants can be carried in one direction only, at the %o to %o one- way rate, or in about % of the time. That it can be handled effectively by a sufficiency of elevators of that proportion, is shown by daily practice in certain well- served buildings. The problem of the relation of the size of the building to the number of elevators consists, therefore, in the relation of the rated hourly passenger capacity to the total number of occu- pants. And if we first ascertain what is the occupied area above the ground or street floor which the elevator is to serve, a matter which is readily settled by reference to the plans, we have only Figure VIII DIVISION OF ELEVATOR TRAVEL ■♦■ I r i > r — dr 0/ / ^.-"'--x -^ -Ha V .'**• |R I »^ /fM /^>JN. k fN\t.PM /a AT. \«^-R.TL T-c-crr t^i=i occt/RA-n-r . 6 » 7 a O 9 O 1 o » o i; O 11 O li K» M o ■* o i; o 1 O 1 K> C )0 20 2 o a 10 a lO 2 !S a So 16 \ 15 V 14 \ V -li \ M>U1MUM la N V 11 s N 1o \ ■N 9 School S ' f ' — 6 e CCMCRAL . * TBNCriKMTS BWAf4BSS ■urkRlMCS OCHOOia IMSriTUTIONS HeSPlTALA feet, is afforded by one hundred and four square feet of floor space to each occupant. This indicates the desirable limit of occupancy in any modern structure of the nature and conditions of a business building, and agrees, it is interesting to note, with the proportion of space to occupant which has been ascertained to exist in the busiest office buildings of New York City. This comparison of certain natural causes bringing about a 1:543 THE BUILDING— PROPORTIONATE SERVICE relation between occupant and space may be regarded as an in- dex toward the settlement of the relation under any unknown conditions, in which it is sought to establish the proportionate elevator travel. The probabilities of occupants consenting to be crowded into less space, under modern conditions of business, are not great. Tenants who find their space close or stuffy soon make a change, or are compelled, by the difficulty of retaining efficient labor, to add to the space occupied. Business offices, with which schedule operation has mainly to deal, are, by reason of the large space occupied by furniture, and by the restrictions on the penetration of light, limited in the number of occupants of a given interior space. Brokers' offices are, by observation, found to be the most closely occupied, but, even with this class, the area per occupant does not increase the average of such buildings beyond the re- lation of one hundred square feet to the occupant. One of the largest of New York down-town office buildings, which has very little unrented space at any time, and is, in large part, occupied by busy shipping, railroad, and engineering bu- reaus employing a considerable number of clerks and drafts- men, is found to have a normal tenancy of twenty-two hundred persons on fifteen stories above the ground floor. The floor heights average nearly 12% feet, with a net ceiling height of eleven feet. The rented or occupied portion of the fifteen floors is 2,475,000 cubic feet, or 225,000 square feet, a proportion of one person to one hundred and twelve square feet. A recent lease brought into the building an additional staff of nearly two hun- dred and fifty employes in one section, making the total popula- tion twenty-four hundred and fifty persons, and bringing the relation of occupant to area to one hundred and one square feet. With the ceiling height of eleven feet, the cubical space per oc- cupant thus became eleven hundred and ten cubic feet, which ELEVATOR SERVICE would have corresponded to one hundred and ten square feet, with a ten-foot ceiling. Analysis of the operating conditions in existing buildings develops variations in relation, which would be misleading were it assumable that in each instance the existing number of eleva- tors and number of floors served, were the most suitable and uniform. But such is not the case. Several such instances could be cited, where the elevators are deficient in number, and more, in which the division of the local and express service is set at such a point as to present very wide divergence between the times of travel and passenger capacity, while others suffer by the inefficient position of the elevators in the building, whereby certain elevators become of reduced effect. The application to the conditions of these buildings of the Bolton rating and scale of travel, affords, however, a means of testing the effectiveness, uniformity, and relation of such exist- ing combinations of elevators and buildings, and in examples, to which it has been applied for this purpose, the method af- forded a very correct index of the desirable number of eleva- tors, agreeing with those already installed in certain buildings of known sufficiency of service, but requiring more elevators in instances of well-defined insufficiency, even indicating the lack of relation in number of floors, their area, and the elevator systems. The rated hourly passenger capacity of any existing elevator is ascertained as follows, when round-trip time, nominal speed, and floor heights are known. 6o(r-- — +-i5 Locals /> = — •2 r or 6o(ji-- — +-is + d) h-xpresses p = ■2R [:56n THE BUILDING— PROPORTIONATE SERVICE where p ~ passengers each way per hour r = round-trip time in minutes— locals R - round-trip time in minutes— expresses h = total height of local floors served, in feet d = time over express distance in minutes s = mean speed in feet per second, and s for nominal speeds of 600 500 400 ft. per min. may be assumed to be . . 7.33 6.33 5.33 ft. per sec. From an analysis 6f the operating conditions in a variety of New York and Chicago business buildings, where efficient elevator service is expected, a number of indications have been gathered as f oUo^vs : SQUARE FEET OF OCCUPIED FLOOR AREA PER OCCUPANT Under Where re- When In buildings, or portions of buildings, the moved from occupying occupied by busiest main center isolated conditions of business positions Stockbrokers, Exchange firms . . . 100 no 115 Shipping, Railroads, and wherever many employes, or draftsmen, are employed 105 115 120 Lawyers, also where small offices are laid out, or where tenants are al- lowed to rent desk-room .... no 120 130 City departments, public offices, large Insurance and Surety offices with numerous employes 115 127 ^35 Banks, large business corporations, where hours of arrival are not co- incident 120 133 142 Real estate, general business agencies, hours of arrival scattered . . . 125 140 150 1:573 ELEVATOR SERVICE Allowance can be made for a certain proportion of unrented and unoccupied area, except in crowded localities. A restaurant at the top of a building divides the lunch-hour travel, and does not, therefore, always add to the work at that time. A club, or an exclusive restaurant at the top of a building which the tenants' employes do not patronize, on the contrary, adds travel to the lunch-hour work, especially where an elevator is specially assigned to the use of a club or restaurant at that time. Toilet-rooms grouped on a single floor, add to visiting or transient travel, and, in certain buildings, add to and confuse the arriving travel in the mornings. A basement or mezzanine landing on certain cars in a sched- ule, or to which the cars are liable to be called, causes irregular- ity in operation. In certain buildings in Chicago and in some cases, in New York City, the down travel at lunch hour, and at the evening departure hour, is facilitated by placing the car starter on the top floor. Rate of rental by itself would not form a reliable index of occupancy, since location, light, and other conveniences have effects upon the amount obtainable. With these suggestions the decision as to the building's rate of occupancy is left to the judgment and decision of those who are in possession of information as to its location, purpose, and character, only urging the desirability of a wise prevision in the direction of liberality. The decision may be facilitated by reference to Figure X, from which is to be learned the effect of variations in the relation between the passenger and the occupied area, upon the elevator service. If a certain area per passenger has been indi- cated by certain known conditions, the relation with the rated cssn Figure X OCCUPIED AREA PER HOURLY PASSENGER Provided by varying loads and landings, on any elevator /^oportion o/d La/7 a '/'nffs mae/sf>er Tn'f, tonoora. ■? ^ ^lo ^0 ^0 %7 ^M 1 1 I 1 1 1 1 y ^ ^ " / / ^ no / /> ^ ^ ^ / / y ^ "^ ^ / / / ^ ^ 1 / / / ^ ^ ^ fZO y^fl / / / y y ■^ / / / / ^ ^ {40- / / / / ^ ^ / / / / ^ y / / / / X y -ISO t5 / / / / y / - ■^ / / / / / / ^ y / / / I / y y ,/- y^io i7ei ' 1 f / / / / y X ^ ^ / / y / / / y' itifi 1 1 / / / / / / /' -m / / / / / _z / 1 7f •) Mi 9< 1 1 1 % 7/to «/ > 10 ™ ^^ o r H o 2 vn O o C H T1 O O S3 I HI ^ ^ ^ I! ^^ -^ ^C(7/c (9f /fa/G3 of occ^p/ec/ /frc^ /x^r Ze/?a/?/- (^r ^rCify/>a/7/: CONSERVATION 1987 tll '^'