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).
Investigation into vehicle jolting, suspension, and different tyre pressures.
| Identifier | ExFiles\Box 67a\1\ scan0106 | |
| Date | 25th May 1926 | |
| HS{Lord Ernest Hives - Chair} X8440 To R.{Sir Henry Royce} from CJ. Copy to HS.{Lord Ernest Hives - Chair} Copy to DA.{Bernard Day - Chassis Design} Copy to BY.{R.W. Bailey - Chief Engineer} Copy to F.{Mr Friese} Copy to Rg.{Mr Rowledge} Re Tyres. CJ2/E25/5/26 This morning I received a copy of your confidential memorandum, R1/M24/5/26, concerning tyres. Curiously enough, yesterday, CWB, Hs.{Lord Ernest Hives - Chair}, Da.{Bernard Day - Chassis Design} and EP{G. Eric Platford - Chief Quality Engineer} were investigating the question of suspension and tyres at Derby. Their investigation was mainly directed to the jolting which is felt by the passengers in the car when it is run at about 25 miles an hour over a slightly ridged surface as opposed to a pot-holed surface. This jolting was apparent to some degree in the Silver Ghost without front wheel brakes. It is more apparent in the Silver Ghost with front wheel brakes but not so bad as in the case of the Phantom. Experiments were made yesterday with: a.{Mr Adams} High pressure tyres, which we use as standard at present, pumped up to 80 lbs. b. Medium balloon at 35 lbs. c. The larger balloon at 25 lbs - (in each case on all four wheels respectively) - and it was unanimously agreed that the jerking was not affected by the type of tyre used. The conclusion arrived at was that this jerking originates from the front springs, not from the back springs. It could only be reduced to fairly reasonable proportions by completely slacking off the front shock absorbers. The hydraulic shock absorber has a very much lesser effect than the friction shock absorber in augmenting the intensity of this phenomenon. As regards a road with potholes, it is agreed that the lower the pressure, the less was the shock of the pothole felt. Therefore, everything else being equal, it would be desirable to adopt low pressure tyres. We have been fitting when desired medium pressure tyres on the back wheels of the 40/50 and medium pressure | ||