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).
Back axle ratios for covered cars, including specific weight-to-ratio recommendations.
| Identifier | ExFiles\Box 49\1\ Scan220 | |
| Date | 5th October 1920 | |
| R.R. 255a (100 T) (S.H. 159, 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 X3457 Extract from E1/G8.10.20. RE VISIT OF MESSRS. HIVES & DAY TO WEST WITTERINGHenry Royce's home town Z.1698. TUESDAY 5th OCTOBER. 1920. X.3832. X.3457. BACK AXLE RATIO - BUZZARD AND GENERAL. Referring to the back axle, Mr. Royce stated that he thought we ought to have a heavier and stronger axle of lower gear ratio for covered cars, and he fixed up the following table of weights and ratios, shewing how he thought the ratio should vary with the weight:- 2 tons - 3 to 1 ratio. 2.25 tons - 3.25 to 1 ratio. 2.5 tons - 3.5 to 1 ratio. 2.75 tons - 3.75 to 1 ratio. 3 tons - 4 to 1 ratio. It will be noticed that the ratio does not vary in direct proportion to the weight, but the reason for this is that it would not be practicable and productive of the best all-round results, to fit a 4.5 to 1 axle to the three tonner, which would be in proportion to a 3 to 1 axle for the two tonner. Mr. Royce wishes to know what our competitors gears ratios (both change speed and back axle) and displacement per ton mile are. Mr. Hives should send to West WitteringHenry Royce's home town blue prints of charts shewing power required to climb hills of various gradients. Mr. Royce thought that the crown wheel on our new axles should not be less than 13" in diameter for the larger ratios. The present Buzzard axle should be allowed to go on as started, but it should be kept in mind that we want 1" on the big wheel for covered cars. | ||