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).
The testing of a low-geared back axle to improve acceleration and performance.
| Identifier | Morton\M22\ img040 | |
| Date | 12th February 1920 | |
| To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. c. to Bn.{W.O. Bentley / Mr Barrington} c. to E.{Mr Elliott - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} c. to EP.{G. Eric Platford - Chief Quality Engineer} Handwritten: X.3056 Handwritten: 49 GB Hs{Lord Ernest Hives - Chair}3/LG12.2.20. X.2631. - RE LOW GEARED BACK AXLE. X.3056. X.3545. We are running on 49-GB an axle with a 15 toothed pinion with a crown wheel with 52 teeth which gives us a ratio of 3.47 to 1 instead of 3.25 to 1 which is the present standard. We find that the car fitted with this low geared back axle is a distinct improvement as regards acceleration and speed over ordinary roads. The axle we are running is very bad for silence. We have cut 3 sets of these gears; the set on the car is the best of the three. Sometime ago we asked that some Gleason Bevels should be obtained from America to give this lower gear reduction. We think it is worth while doing all we know of to obtain quiet low geared back axles for further tests. Now we are using the oversize tyres, the present car has a gear ratio higher than we had on the standard cars before the war. The improvement in HP. on the present cars is only apparent at the higher engine speeds so to take full advantage of it we ought to use a lower geared back axle. As soon as the weather is suitable, we will endeavour to make a comparative test with the lowered geared back axle compared with the present standard. On a 200 mile run 49-GB averaged 14.5 M.P.G. average speed 33 M.P.H. Hs.{Lord Ernest Hives - Chair} | ||