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).
Speedometer gear ratios and revolutions per mile for the Second Spectre chassis.
| Identifier | ExFiles\Box 59\2\ Scan444 | |
| Date | 6th November 1934 | |
| 56051 By.{R.W. Bailey - Chief Engineer} From Hs{Lord Ernest Hives - Chair}/Wst. Hs{Lord Ernest Hives - Chair}/Wst.5/MA.6.11.34. SPEEDOMETER FOR SECOND SPECTRECodename for Phantom III CHASSIS. We understand that it is proposed to use on this chassis an axle ratio of 4.25 to 1 and a modified speedometer gear drive ratio which gives an overall ratio from the propeller shaft to the speedometer drive of 5. This gives speedometer revs per mile with this gear of 755 and we shall be glad if you will arrange with By/RD. that when the instrument is ordered for this second chassis it will conform to this drive ratio. For your information we have worked out the figures for the SpectreCodename for Phantom III after measuring the actual wheel revs per mile on the road. The figures are as follows :- SpectreCodename for Phantom III I. Using J.3 type gear box. 730 revs per mile. Using correct SpectreCodename for Phantom III gear box. 796 revs per mile. Both these figures are for the 10/37 axle ratio and 18" tyres. Hs{Lord Ernest Hives - Chair}/Wst. | ||