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).
Phantom back axle ratio, comparing 14-tooth and 15-tooth axles for different markets and driving conditions.
| Identifier | ExFiles\Box 66\4\ scan0364 | |
| Date | 10th June 1926 | |
| Hs.{Lord Ernest Hives - Chair} from R.{Sir Henry Royce} C O P Y. c. to BJ. Wor.{Arthur Wormald - General Works Manager} BY.{R.W. Bailey - Chief Engineer} R8/M10.6.26. PHANTOM BACK AXLE RATIO. With reference to the Phantom back axle ratio, rather strangely the car I had in the south of France was fitted with smaller wheels - smaller tyres on 21" wheels, and they were just equivalent to one tooth off the 15-tooth axle. Also Mr. Nadin says that in America the driving is done by avoiding changeing to the 3rd. speed, i.e., most of the traffic work is done on the top gear, and no speeds beyond 60 m.p.h. are used. HS.{Lord Ernest Hives - Chair} also thinks it is very rare for people to demand more than 60 m.p.h. Under the most recent impressions of comparing various cars I have come to the conclusion that we must be able to supply 14-tooth axles, especially for the heavy bodies. I have also learned that the 14-tooth axles were much more generally used than any other type on the Silver Ghost cars. We cannot therefore say that 14-tooth axles are too difficult to get quiet, and from my own personal experience, I do not think our Phantom engine will prove too fussy at the necessary speeds that this back axle will demand. I think therefore we must go on with the 14-tooth axles and have them available for the American trade, and for heavy cars in our own English trade, because undoubtedly the acceleration, power of engine, and performance on top gear, are all definitely improved with this gear ratio over the 15/52. R.{Sir Henry Royce} | ||