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).
Letter from Dunlop discussing tyre cushioning capacity, cornering forces, and the effects of rim width and inflation pressure.
| Identifier | ExFiles\Box 157\2\ scan0083 | |
| Date | 27th November 1936 | |
| 1332 DUNLOP RUBBER CO.,LTD. TELEGRAPHIC ADDRESS: 'DUNLOPS PHONE, BIRMINGHAM'. TELEPHONE: BIRMINGHAM CENTRAL 4108 (P.B.E.) EXTENSION No. 232 YOUR REF: OUR REF: LJL/FJ/BG. FORT DUNLOP ERDINGTON BIRMINGHAM November 27th, 1936. Messrs Rolls Royce Ltd., DERBY. For the attention of Mr G.H. Grylls. Dear Sir, We are sending you, as promised, curves showing the vertical deflection rate (cushioning capacity) of the 6.00/16 tyres fitted to the various rims on which cornering forces were measured. You will see that there is a steady decrease in cushioning capacity with increase in rim width, the percentage decrease being of the same order as the percentage increase in cornering force. You will also see that the effect of inflation pressure on cushioning capacity is much greater than its effect on cornering force. Thus the increase in cushioning capacity when the pressure is decreased from 30 lbs/in. to 20 lbs/in. is of the order of 30% whereas the corresponding decrease in cornering force at low slip angles is only approx. 15%. We have not yet completed the tests on the India and Dunlop covers as we have been delayed due to difficulty in getting a suitable 17" wheel, but we hope to let you have the results in the near future. We have been considering your query regarding a tyre which will not lose cornering power when run in an inclined position, and although we have no information on this point, we think that tests could be made if a front axle could be suitably modified. The car we have been using for our tests is a 1935 Hillman Wizard, but unfortunately as this car is used for other purposes, we cannot spare the front axle for a modification which would obviously take a fair amount of time. In view of your previous offer to loan us an axle in connection with these investigations, and having regard to the difficulties mentioned above, we were wondering if you could modify an axle on one of your experimental cars so that it could have various degrees of camber at one end and then we could arrange for one or more of our technical men to come to Derby with the necessary equipment to make the measurements there. | ||