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).
Comparison report on 12/50 and 11/50 axle ratios with hill climb test results and recommendations.
| Identifier | ExFiles\Box 113\2\ scan0159 | |
| Date | 7th February 1930 | |
| -2- HS{Lord Ernest Hives - Chair}/AJL1/MJ.7.2.30Contd. dry roads and no appreciable wind. The tests were carried out on these hills side by side. TICKNALL HILL. 12/50 axle. Time for hill - 67.5 secs. 11/50 axle. " " " - 65 secs. This does not appear to be a very big difference but represents a difference of 125 to 150 yards between the two cars at the end of the test. The improved low speed acceleration of the 11/50 car is very marked. PISTERN HILL. This is essentially a low speed test and demonstrates the greatest difference noticeable between the two cars. 12/50 axle. Time for hill - 96 secs. (The car will only just climb on top gear.) 11/50 axle. Time for hill - 69 secs. GENERAL. When the two cars are driven over ordinary roads, one behind the other, it is very noticeable that the 11/50 car leaves the 12/50 every time during acceleration etc. It is very seldom that the high speed superiority of the 12/50 ratio is useful under English road conditions. Our opinion is that the 11/50 axle ratio should remain as standard for the high compression - 25 HP. car, and the 12/50 be listed as an alternative for very light sports bodies on for Continental use. It would be fatal to use the 12/50 ratio on heavy bodied town carriages. The presence of the engine is certainly felt more, and is slightly more fussy, when using the 11/50 ratio but even so, with the rubber engine mounting the car is smoother and less noisy than the present standard 4.75:1 compression 25 HP. car. Hs{Lord Ernest Hives - Chair}/AJL. | ||