Figure 28. — Plan and section of the Otis system's movable pulley 

 assembly, or chariot. Piston rods are at left. (Adapted from The 

 Engineer (London), July 19, 1889, vol. 68, p. 58.) 



gearing. The cylinders were of the pushing rather 

 than the pulling type used in the Otis system; that 

 is, the pressure was introduced behind the plungers, 

 driving them out. To the ends of the plungers were 

 fixed smooth-faced sheaves, over which were looped 

 heavy quadruple-link pitch chains, one end of each 

 being solidly attached to the machine base. The 

 free ends ran under the cylinder and made another 

 half-wrap around small sprockets keyed to the main 

 drive shaft. As the plungers were forced oiitward, 

 the free ends of the chain moved in the opposite direc- 

 tion, at twice the velocity and linear displacement 

 of the plungers. The drive sprockets were thereby- 

 revolved, driving up the car. Descent was made 

 simply by permitting the cylinders to exhaust, the car 

 dropping of its own weight. The over-all gear or 

 ratio of the system was the multiplication due to the 

 double purchase of the plunger sheaves times the 

 ratio of the chain and drive sprocket diameters: 

 2(12.80/1.97) or about 13:1. To drive the car 



218 feet to the first platform of the Tower the plungers 

 traveled only about 16.5 feet. 



To penetrate the inventive rationale behind this 

 strange machine is not difficult. Aware of the funda- 

 mental dictum of absolute safety before all else, the 

 Roux engineers turned logically to the safest known 

 elevator type — the direct plunger. This type of 

 elevator, being well suited to low rises, formed the 

 main body of European practice at the time, and in 

 this fact lay the further attraction of a systein firmly 

 based on tradition. Since the piers between the 

 ground and first platform could accommodate a 

 straight, although inclined run, the solution might 

 obviously have been to use an inclined, direct plunger. 

 The only difficulty would have been that of drilling 

 a 220-foot, inclined well for the cylinder. While 

 a difficult problem, it would not have been insur- 

 mountable. What then was the reason for using 

 a design vastly more complex? The only reasonable 

 answer that presents itself is that the designers, work- 



PAPER 19: ELEVATOR SYSTEMS OF THE EIFFEL TOWER 



29 



