Figure lo. — Components of the steam passen- 

 ger elevator at the time of its peak development 

 and use (1876). (From The First One Hundred 

 ^ Tears, Otis Elevator Company, 1953.) 



cables invariably were wound on a drum. The travel 

 or rise of the car was therefore limited by the cable 

 capacity of the winding drum. As building heights 

 increased, drums became necessarily longer and 

 larger until they grew so cumbersome as to impose a 

 serious limitation upon further upward growth. A 

 drum machine rarely could be used for a lift of more 

 than 150 feet.^ 



Another organic difficulty existing in drum machines 

 was the dangerous possibility of the car — or the 

 counterweight, whose cables often wound on the 

 drum — being drawn past the normal top limit and into 

 the upper supporting works. Only safety stops could 

 prevent such an occurrence if the operator failed 

 to stop the car at the top or bottom of the shaft, and 

 even these were not always effective. Hydraulic 

 machines were not susceptible to this danger, the 

 piston or plunger being arrested by the ends of the 

 cylinder at the extremes of travel. 



THE HYDRAULIC ELEVATOR 



The rope-geared hydraulic elevator, which was 

 eventually to become known as the "standard of the 

 industry," is generally thought to have evolved 

 directly from an invention of the English engineer 

 Sir William Armstrong (1810-1900) of ordnance fame. 

 In 1846 he developed a water-powered crane, utilizing 

 the hydraulic head available from a reservoir on a 

 hill 200 feet above. 



The system was not basically different from the 

 simple hydraulic press so well known at the time. 

 Water, admitted to a horizontal cylinder, displaced a 

 piston and rod to which a sheave was attached. 

 Around the sheave passed a loop of chain, one end of 

 which was fixed, the other running over guide sheaves 

 and terminating at the crane arm with a lifting hook. 

 As the piston was pressed into the cylinder, the free 

 end of the chain was drawn up at triple the piston 

 speed, raising the load. The effect was simply that 



5 A notable exception was the elevator in the Washington 

 Monument. Installed in 1880 for raising materials during 

 the structure's final period of erection and afterwards con- 

 verted to passenger service, it was for many years the highest- 

 rise elevator in the world (about 500 feet), and was certainly 

 among the slowest, having a speed of 50 feet per minute. 



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