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 II & III models.
| Identifier | ExFiles\Box 57\1\ Scan073 | |
| Date | 12th February 1925 | |
| X5770 12.2.25. GOSHAWK II & III CHASSIS GEAR RATIOS, ETC. 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 1000 r.p.m. of the engine are :- Goshawk II. Goshawk III. Reverse 4.8 These correspond Reverse 6.4 1st. 6.5 to an effective 1st. 5.5 2nd. 12.6 tyre dia. of 31.4". 2nd. 8.8 3rd. 20.6 (Exact 20.56) 3rd. 13.55 4th. 20.6 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. | Gos.III 1st. | Gos.II 1st. | Gos.III 2nd. | Gos.II 2nd. | Gos.III 3rd. | Gos.II & III 3rd. | 4th. | Dynamo revs. on top gear. -------------------------------------------------------------------------------------------------------------------------------- 10 | 1820 | 1545 | 1136 | 793 | 739 | 487 | - | 730 12 | 2180 | 1850 | 1364 | 950 | 886 | 584 | - | 876 15 | 2730 | 2315 | 1705 | 1189 | 1106 | 730 | - | 1095 20 | - | 3090 | 2272 | 1585 | 1475 | 973 | - | 1460 25 | - | - | 2845 | 1984 | 1847 | 1217 | - | 1825 30 | - | - | - | 2380 | 2215 | 1460 | - | 2190 40 | - | - | - | 3170 | 2950 | 1946 | - | 2919 50 | - | - | - | - | - | 2433 | - | 3649 EFC. | ||