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 of performance characteristics between 14-tooth and 15-tooth axles on early Phantom cars.
| Identifier | ExFiles\Box 49\2\ Scan209 | |
| Date | 1st July 1926 | |
| To PN{Mr Northey}, from Hs.{Lord Ernest Hives - Chair} C. [illegible] Dept. X4299 HS{Lord Ernest Hives - Chair}2/LGS.7.26. Replying to PN{Mr Northey}14/DN25.6.26. X8420 The 14-tooth axles were tested on the early Phantom experimental cars. Sales ran and criticised 44-PK fitted with the 14-tooth axle; it was sent to them later fitted with a 15-tooth axle. The report was that the car was much better with the 15-tooth axle fitted. Since then however we think we have improved the Phantom so that the disadvantages which were then noticed with the 14-tooth axle may not now be so objectionable. Replying to your questions :- (a) Definite information is given on this point in the experimental technical information file under 'Petrol Consumption Tests'. From our experience we expect a Phantom which does approx. 13 m.p.g. with the 15-tooth axle would do between 12 and 12½ m.p.g. with the 14-tooth axle. (b) It is very difficult to estimate this. The engine runs approximately 7% faster with the 14-tooth axle compared with the 15-tooth. There must be a more wear and tear; a great deal depends upon how the car is driven. We should not expect the difference to be serious. (c) This again is a difficult matter to fix a value for. It depends on the type of body and the speed at which the car is run. It would be unreliable to take the results of one car. Our own impression is that the short runs with the 14-tooth axle would be more [strikethrough]lively[/strikethrough], but if one was travelling long distances at relatively high speeds, one would prefer the 15-tooth. (d) Effect on maximum speed. This is shewn in the technical information file on 'Car Performance'. Depending on the type of body, we should expect the maximum speed to be reduced 2 or 3 m.p.h. We should like to point out that if we could reduce the weight of the car by 3 cwts. this should give us the approximate improvement in acceleration which we obtained when we changed from the 15-tooth axle to the 14-tooth axle. As regards the difficulty to produce contd :- | ||