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).
Comparative test report on rear axle gear ratios (11/50 vs 12/50) for 25 HP high compression cars.
| Identifier | ExFiles\Box 102\4\ scan0051 | |
| Date | 7th February 1930 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/AJL. (Held up). c. to Sg.{Arthur F. Sidgreaves - MD} Mor. c. to L. Da.{Bernard Day - Chassis Design} c. to Ry. PH. X5350. Hs{Lord Ernest Hives - Chair}/AJL.1.7.2.30. ********************** [Handwritten] X5350 X5771 X488 X1725 REAR AXLE GEAR RATIO FOR 25 HP. HIGH COMPRESSION CARS. -------------------- We have carried out a series of comparative tests on two high compression (5.25:1) 25 HP. cars, 12-G4 and 17-G4., one fitted with 12/50 axle gears and the other with the present standard 11/50 gears. These two cars when fitted with 12/50 axle gears, and when loaded up to exactly the same weight, gave an identical road performance as regards acceleration, hill climbing etc. The results obtained from side by side tests 11/50 versus 12/50 axle ratio are as follows:- SIDE BY SIDE ACCELERATION. ----------------------- From 10 m.p.h. 11/50 gets away easily. " 20 m.p.h. 11/50 " " " 30 m.p.h. 11/50 gets away. " 40 m.p.h. 11/50 still just superior. " 50 m.p.h. both cars the same. Above 50 m.p.h. the 12/50 ratio is superior, its superiority increasing with the increase of speed; the maximum speed increase appears to be 3 to 4 m.p.h. HILL CLIMBING TESTS. ------------------ These were carried out on our two standard test hills Ticknall and Piston Hill. The conditions were nearly ideal. | ||