From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
And comparing various fan drive ratios for different engines and models.
| Identifier | ExFiles\Box 113\5\ scan0152 | |
| Date | 31th October 1940 | |
| To Rm.{William Robotham - Chief Engineer} FAN DRIVE RATIOS. ----------- On B-V the ratio is 0.8, and on cast iron engines 1.1. This latter figure is identical with the 1938 Buick, which we copied. A large fan rotating slowly is quiter than a small fan running fast while a water pump should be driven fast in order to reduce its size. Therefore when both water pump and fan are mounted on the same pulley it is a case of getting the last compromise. Our present set up seems a reasonable compromise. Below are some representative examples :- 1937 Buick "8" 1.28 1937 Olds "6" 1.06 1937 Old's "8" 1.1 Vauxhall "25" 1.2 1938 Buick "8" 1.1 Studebaker 0.935 B - V 0.8 B-60 & 80 1.1 Rm{William Robotham - Chief Engineer}/Clm.{D. D. Clapham} | ||