Calculation sheet detailing the fan speed of the Goshawk engine at a specific road speed.
| Identifier | ExFiles\Box 75\3\ scan0039 | |
| Date | 5th February 1925 | |
| EFC. {E. Fowler Clarke - Electrical Engineer} X.1017. 5.2.25. GOSHAWK(Aero Engine)(Codename for 20HP Car / Aero Engine after Kestrel(Aero Engine)) FAN SPEED. Engine speed 60 m.p.h. = 2,920 r.p.m. Ratio of engine pulley to fan pulley = 1 : 1.316. ... Fan speed at 60 m.p.h. = 3,840 r.p.m. (Assuming 11/50 axle ratio and effective tyre diameter of 31.4".) HEW. | ||
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).