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 Vauxhall Motors Ltd to S.H. Grylls discussing deceleration, braking tests, and tyre performance.
| Identifier | ExFiles\Box 170\3\ img167 | |
| Date | 8th February 1938 | |
| VAUXHALL MOTORS Ltd CONTRACTORS TO THE ADMIRALTY, WAR OFFICE & AIR MINISTRY LUTON, BEDS. TELEPHONE NUMBER 2600 LUTON. TELEGRAMS CARVAUX. TELEX. LUTON. WHEN REPLYING PLEASE QUOTE -> OUR REF MD/KF YOUR REF. 8th February 1938. S.H. Grylls Esq., Rolls Royce Limited, DERBY. [Handwritten Initials] AFM{Anthony F. Martindale} [Handwritten] Phan Dear Gry{Shadwell Grylls}, I return Koesler & Klaue, herewith, with many thanks. I think they are jumping to conclusions in their first assumptions. Deceleration tests at the Proving Ground frequently show figures as high as .9g. I am perfectly aware that all these tests are subject to a correction for dive of the car which may be of the order of .06. But even this would leave us with a true deceleration of .84g. To get which, with our exceedingly crude methods of apportioning the braking between front and rear, means an optimum brake adhesion which must be close to .9. When the German authors quote the Daimler Benz racing car as a proof of drive coefficients of .88 they appear to be neglecting the "wedging" effect of the rear drive wheels. Attached chart, which deals with acceleration against road traction on front and rear wheel drives, serves to make this clear. At high speeds the wind resistance which probably has a centre of pressure higher than the c.g. will still further compress the rear tyres and relieve the fronts. Bradley & Allen were measuring cornering power of tyres above the skid limit which they arranged rather loosely, by setting the side car wheel over at about 17 degs and entirely neglecting that by so doing the whole | ||