persisted since the days of steam. This was the 

 matter of the drum and its attendant Hmitations. 

 The motor's action being rotatory, the winding drum 

 was the only practical way in which to apply its 

 motive power to hoisting. This single fact shut 

 electricity almost completely out of any large-scale 

 elevator business until after the turn of the century. 

 True, there was a certain amount of development, 

 after about 1887, of the electric worm-drive drum 

 machine for slow-speed, low-rise service (fig. 19). 

 But the first installation of this type that was con- 

 sidered practically successful — in that it was in con- 

 tinuous use for a long period — was not made until 

 1889,' the year in which the Eiffel Tower was com- 

 pleted. 



Pertinent is the one nearly successful attempt which 

 was made to approach the high-rise problem electri- 

 cally. In 1888, Charles R. Pratt, an elevator engineer 

 of Montclair, New Jersey, invented a machine based 

 on the horizontal cylinder rope-geared hydraulic 

 elevator, in which the two sets of sheaves were drawn 

 apart by a screw and traveling nut. The screw was 

 revolved directly by a Sprague motor, the system 

 being known as the Sprague-Pratt. While a number 

 of installations were made, the machine was subject 

 to several serious mechanical faults and passed out of 

 use around 1900. Generally, electricity as a practical 

 workable power for elevators seemed to hold little 

 promise in 1888.* 



' Two machines, by Otis, in the Demarest Building, Fifth 

 Avenue and 33d Street, New York. They were in use for over 

 30 years. 



* Akhough the eventually successful application of electric 

 power to the elevator did not occur until 1904, and therefore 

 goes beyond the chronological scope of this discussion, it was 

 of such importance insofar as current practice is concerned as 

 to be worthy of brief mention. In that year the first gearless 

 traction machine was installed by Otis in a Chicago theatre. 

 As the name implies, the cables were not wrapped on a drum 

 but passed, from the car, over a grooved sheave directly on the 

 motor shaft, the other ends being attached to the counter- 

 weights. The result was a system of beautiful simplicity, 

 capable of any rise and speed with no proportionate increase 

 in the number or size of its parts, and free from any possibility 

 of car or weights being drawn into the machinery. This 

 system is still the only one used for rises of over 100 feet or so. 

 By the time of its introduction, motor controls had been improved 

 to the point of complete practicability. 



Figure i8. — Motor and drive mechanism of 

 Siemens' elevator. (From Alfred R. Urban- 

 itzky, Electricity in the Service of Man, London, 

 1 886, p. 646.) 



PAPER 19: ELEVATOR SYSTEMS OF THE EIFFEL TOWER 

 552119 61 3 



17 



