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 discussing steering geometry, understeer, and the Ackermann angle.
| Identifier | ExFiles\Box 170\3\ img124 | |
| Date | 17th November 1937 | |
| VAUXHALL MOTORS Ltd CONTRACTORS TO THE ADMIRALTY, WAR OFFICE & AIR MINISTRY. LUTON, BEDS. TELEPHONE NUMBER 2600 LUTON TELEGRAMS CAPVAUX, TELEX, LUTON WHEN REPLYING PLEASE QUOTE -> OUR REF. MO/KP YOUR REF. 17th November 1937. Mr. Grylls, Rolls Royce Limited, DERBY. Dear Grylls, I enjoyed having Leslie here on Monday. We have showed him what we could of our very crude set up here. (1). Do you really believe what appears in the Autocar article of November 12th - that "the best arrangement is exactly correct steering"? I would be inclined rather to say that the best arrangement is a straight increase of steering angle from Ackermann to about one degree above Ackermann at .5g. This is based on cars like Olds 6 and 8 which show about this effect and which basically (i.e. as a vehicle on four wheels) have a good sense of direction. The argument for a slight regular definite understeer is roughly :- 1). The self damping effect of understeer on lateral forces such as wind gusts, changes in road camber etc. 2). An allowance for inadvertent changes in load and tyre pressure. 3). An allowance for the fact of decreased cornering power of rear tyres at high traction, which shifts the curve towards oversteer at higher speeds. Do you find that on successively increasing radii of turn the curve of steering angle shifts progress-ively towards oversteer due to increasing rear slip angles? -1- | ||