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).
Chassis gear ratios and corresponding engine revolutions for a 40/50 HP model.
| Identifier | ExFiles\Box 49\2\ Scan172 | |
| Date | 12th November 1923 guessed | |
| X.3457 40/50 HP. CHASSIS GEAR RATIOS ETC. The three back axle ratios are now - 14/52 15/52 16/52 giving ratios of - 1 : 3.714 1 : 3.467 1 : 3.250 Taking the most normal ratio 15/52, the miles per hour at 1000 r.p.m. of the engine are :- Reverse 8.43 1st. 8.43 2nd. 12.93 3rd. 19.33 4th. 28.74 These correspond to an effective tyre dia. of 33.5". With the same axle ratio, the following table gives the engine revs. and dynamo revs. for various speeds in miles per hour :- Engine revs. M.P.H. 1st. 2nd. 3rd. 4th. 1 1/4 engine revs. on top gear. 10 1187 773 517 348 522 12 1423 927 620 418 627 15 1780 1160 776 522 783 20 2374 1546 1034 696 1044 25 2968 1933 1290 870 1305 30 -- 2319 1551 1044 1566 35 -- 2706 1810 1218 1827 40 -- 3092 2068 1392 2088 45 -- -- 2325 1566 2349 50 -- -- 2585 1740 2610 55 -- -- 2844 1914 2871 60 -- -- 3102 2088 3132 EFC./HEW. | ||