AIRCRAFT PROPULSION — TAYLOR 



285 



Figure 17. — Reduction gears of Renault Type 12 Kh engine. 



cedes, and the 220-hp. Hispano-Suiza. These were soon followed by 

 the RoUs-Koyce "Eagle" with planetary gears. By 1920, most large 

 European engines were geared. 



The general use of gearing was much later in the United States. 

 Actually, gearing was eliminated for the Curtiss D-12 in 1924 in order 

 to save 25 pomids weight ! 



By 1930 it was evident to all that large engines should be geared to 

 allow of optimmn performance. Pratt and Wliitney used an internal 

 gear in 1931, and both Wright Aeronautical and Pratt and "Wliitney 

 adopted the Farman planetary gear (fig. 18) for use in the DC-3 in 

 1933. From that time on, propeller reduction gears became an inte- 

 gral part of all large airplane engines, planetaiy spur gears (pi. 25, 

 fig. 2) being standard for radials, and plain two-element spur gears 

 for Vee engines (fig. 17) . 



