Wim me ^^^'^ ^bi^ ^s ^^^a^^ aK 



Figure 14.- — In the various hydraulic systems, 

 a pump was required if pressure from water 

 mains was insufficient to operate the elevator 

 directly. There was either a gravity tank on 

 the roof or a pressure tank in the basement. 

 (From Thomas E. Brown, Jr., "The American 

 Passenger Elevator," Engineering Magazine (New 

 York), June 1893, vol. 5, p. 340.) 



The elevator followed, or, at most, kept pace with, 

 the development of higher buildings. 



European elevator development — notwithstanding 

 the number of American rope-geared hydraulic 

 machines sold in Europe in the 10 years or so preceding 

 the Paris fair of 1889 — was confined mainly to varia- 

 tions on the direct plunger type, which was first used 

 in English factories in the 1830's. The plunger eleva- 

 tor (fig. 16), an even closer derivative of the hydraulic 

 press then Armstrong's crane, was nothing more than 

 a platform on the upper end of a vertical plunger 

 that rose from a cylinder as water was forced in. 



There were two reasons for this European practice. 

 The first and most apparent was the rarity of tall 

 buildings. The drilling of a well to receive the 

 cylinder was thus a matter of little difficulty. This 

 well had to be equivalent in depth to the elevator rise. 

 The second reason was an innate European distrust 

 of cable-hung elevator systems in any form, an attitude 

 that will be discussed more fully farther on. 



THE ELECTRIC ELEVATOR 



At the time the Eiffel Tower elevators were under 

 consideration, water under pressure was, from a 

 practical standpoint, the only agent capable of ful- 

 filling the power and control requirements of this 

 particularly severe service. Steam, as previously 

 mentioned, had already been found wanting in 

 several respects. Electricity, on the other hand, 

 seemed to hold promise for almost every field of 

 human endeavor. By 1888 the electric motor had 

 behind it a 10- or 15-year history of active develop- 

 ment. Frank J. Sprague had already placed in 

 successful operation a sizable electric trolley-car 

 system, and was manufacturing motors of up to 20 

 horsepower in commercial quantity. Lighting gen- 

 erators were being produced in sizes far greater. 

 There were, nevertheless, many obstacles preventing 

 the translation of this progress into machinery capable 

 of hauling large groups of people a vertical distance 

 of 1 ,000 feet with unquestionable dependability. 



The first application of electricity to elevator pro- 

 pulsion was an experiment of the distinguished 

 German electrician Werner von Siemens, who, in 

 1880, constructed a car that successfully climbed a 

 rack by means of a motor and worm gearing beneath 

 its deck (figs. 17, 18) — again, the characteristic 

 European distrust of cable suspension. However, the 

 effect of this success on subsequent development was 

 negligible. Significant use of electricity in this field 

 occurred somewhat later, and in a manner parallel 

 to that by which steam was first applied to the ele- 

 vator — the driving of mechanical (belt driven) 

 elevator machines by individual motors. Slightly 

 later came another application of the "conversion" 

 type. This was the simple substitution of electrically 

 driven pumps (fig. 21) for steam pumps in hydraulic 

 installations. It will be recalled that pumps were 

 necessary in cases where water main pressure was 

 insufficient to operate the elevator directly. 



In both of these cases the operational demands on 

 the motor were of course identical to those on the 

 prime movers which they replaced; no reversal of 

 direction was necessary, the speed was constant, and 

 the load was nearly constant. Furthermore, the load 

 could be applied to the motor gradually through 

 automatic relief valves on the pump and in the 

 mechanical machines by slippage as the belt was 

 shifted from the loose to the fast pulleys. The ulti- 

 mate simplicity in control resulted from permitting 

 the motor to run continuously, drawing current only 



14 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



