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 springing and shock absorber performance of the Phantom II chassis.
| Identifier | ExFiles\Box 16\7\ Scan203 | |
| Date | 18th February 1929 | |
| P/W "SE" copy "MGM" " Hs{Lord Ernest Hives - Chair}" +7410. Pel/RJ.18/II/29. Concerning the springing of Phantom II Chassis Further to my adverse criticism of the springing of 25-WJ (Paris Trials Car) under certain conditions, I can now say definitely that, judging by the riding qualities of the three cars which have passed through Sèvres, there is room for improvement. Since my report on 25-WJ, we have received a request from the owner of 7-WJ (ex-Hooper's Paris Show Car) to weaken the springs, as the riding is uncomfortable and harsh over cobbles at slow speeds. Chassis 34-WJ (Embericos), fitted with a Weymann Sports Inside Drive, which I tried last week, has this trouble more pronounced than the others, and as this complete car is considerably lighter than the two others, it automatically confirms the theory I have formed, that the trouble emanates from the rear shock-absorbers. Firstly, at anything over 20 M.P.H. the springing of these cars leaves very little to be desired, but in the lower range, over indifferent roads especially cobble stones and shallow pot holes, one gets the impression of riding in a car with the axles lashed too tightly to the chassis. In other words, one feels to be riding on the shock-absorbers. For the moment, I do not think it is necessary to decrease the resistance of the shock absorber on the rebound, but possibly we may have to increase this, but I feel that if we could reduce the resistance of the shock-absorber on the lower pressure stroke, one would get better results. I almost feel one would like to reduce this to a minimum to enable the minor shocks to be absorbed by the flexibility of the springs. I feel that if one could so design our shock-absorbers as to permit a sort of relay action, or progressive resistance according to the force of the shock applied, one would get better results. Under the present circumstances, the trouble is less pronounced as the sprung weight is increased, which coincides with the theory of the resistance on the lower pressure stroke of the shock-absorber being too great for the weight to be carried, hence the light Weymann Sports car is harsher than the Hooper's Enclosed Drive. I have taken buffer clearances of these cars with 4 passengers and full petrol tank. They read as follows:- ....... | ||