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).
Performance comparison between a 20.G.IV model and Mr. Bernard Hopps' car, analysing the impact of weight and axle ratio.
| Identifier | ExFiles\Box 107\1\ scan0118 | |
| Date | 15th June 1932 | |
| W/S. to Cx.{Major Len W. Cox - Advertising Manager} from Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson} Hs{Lord Ernest Hives - Chair}/Rn.{Mr Robinson}1/KT.15.6.32. Re. Mr. Bernard Hopps. G.L.R. 50. With reference to Cxl/KW.14.6.32. We do not expect the synchromesh 20/25's to have very much better acceleration than the previous series of 20/25's up to 40 m.p.h. when the cars are the same overall weight. The attached curves which are more accurate and reliable than acceleration curves, illustrate this point. The gain in performance with the synchromesh unit is above 40 m.p.h. You yourself had a demonstration of this when you tried 20.G.IV. against your trials car (Sg{Arthur F. Sidgreaves - MD}3/E17.12.31.) The reason Mr. Hopps was able to beat 20.G.IV. with his old car is - (1) Weight. As far as we can ascertain Mr. Hopps car weighs 31.5 cwt. 20.G.IV. weighs 35.7 cwt or 13% heavier, and therefore, with the same B.H.P. available, will have 13% less acceleration at low speeds. (2) Axle Ratio. 20.G.IV. axle ratio is 3¼% higher than standard and the 18" X 16" tyre, rolling dia. 4¾% smaller. Net result 4% higher gear ratio. From these figures, for the same B.H.P we expect the acceleration of 20.G.IV. to be 13 + 4 or 17% worse than Mr. Hopps existing car at low speeds. The effect of the weight can be easily reproduced by putting three passengers - besides the driver - in Mr. Hopps's car and comparing it with 20.G.IV., driver only. We have always been impressed with Mr. Hopp's body, as being exceedingly light and yet quite comfortable. With regard to the maximum speed, we expect 20.G.IV. to lap Brooklands at 72 - 73 m.p.h. This | ||