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).
Calculations for 20 HP chassis gears, including speeds, distances, and various gear ratios.
| Identifier | ExFiles\Box 75\1\ scan0200 | |
| Date | 12th June 1919 | |
| 12.6.19. 20 HP. CHASSIS GEARS X.3481. X.3501 / 4247 Tyres 820 x 120 i.e. 32.250 inches dia. Distance traversed per rev. = 101.2 inches. = 101.2 / (1760 X 36) miles per rev. Back axle ratio = 15/60 = 1/4 = .0016 miles per rev. of road wheel. . . 4 revs of engine give .00160 miles (on top gear). or 1 rev. of engine gives .00040 miles (ditto). . . at engine speed of 1000 R.P.M. car does .4 miles per min. = 24 miles per hour on top gear. Ratio of 2nd. gear is .657. 1st gear is .392. . . M.P.H. at 1000 R.P.M. on top gear is 24 (handwritten over a crossed-out 15.78) on 2nd. gear is 15.78 on 1st. gear is 9.4 Ratio between dynamo and crankshaft speed is 40/25 = 1.6 at 1 M.P.H. engine does 1000/24 R.P.M. = 41.7 R.P.M. on top gr{George Ratcliffe} + 63.5 R.P.M. on 2nd. gea + 106.3 R.P.M. on 3rd gea and dynamo does at the same cor. speed 66.8 R.P.M. on top gear 101.7 R.P.M. on 2nd. gear. 170.2 R.P.M. on 3rd. gear. | ||