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 back axle and chassis gear ratios for the Goshawk II model.
| Identifier | ExFiles\Box 75\1\ scan0181 | |
| Date | 8th December 1923 | |
| Sp{Mr Spinney} X3426 8.12.23. X.4219 - GOSHAWK II CHASSIS GEAR RATIOS. The two back axle ratios are now 11/50 12/50 giving ratios of 1 : 4.545 1 : 4.167 Taking the low back axle ratio, namely, 1 : 4.545, the miles per hour at 1,000 r.p.m. of the engine are :- Reverse 4.90 ) 1st. 6.65 ) These correspond to an 2nd. 12.9 ) effective tyre dia. 3rd. 20.6 ) of 31.4". With the same low 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 1510 774 486 729 12 1810 928 583 875 15 2265 1159 729 1090 20 3020 1546 973 1454 25 -- 1930 1215 1819 30 -- 2315 1458 2185 40 -- 3093 1934 2910 50 -- -- 2410 3640 EPC. | ||