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).
The chassis gear ratios for the Goshawk 11.
| Identifier | ExFiles\Box 49\2\ Scan050 | |
| Date | 5th December 1921 | |
| X4256 X.4219 - GOSHAWKAero EngineCodename for 20HP Car / Aero Engine after KestrelAero Engine 11. CHASSIS GEAR RATIOS. 5.12.21. X4256 The three back ratios are - 13/60, 14/60, and 15/60. giving ratios of - 1 : 4.285 1 : 4.615 1 : 5 Taking the intermediate back axle ratios, namely, 1 : 4.615, the miles per hour at 1,000 R.P.M. of the engine are - Reverse 4.82 ) 1st. 6.54 ) These correspond to 2nd. 12.7 ) effective tyre diameter 3rd. 20.3 ) of 31.4". With the same intermediate axle ratio, the following table gives the engine revs. and dynamo revs. for various speeds in miles per hour :- M.P.H. Engine Revs. Dynamo revs. 1st. 2nd. 3rd. on top gear. 10 1530 785 493 740 12 1835 942 592 887 15 2300 1176 740 1106 20 3060 1570 987 1476 25 ---- 1960 1233 1845 30 ---- 2350 1478 2215 40 ---- 3140 1962 2955 50 ---- ---- 2465 3690 | ||