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).
Oversteer and understeer at the GM Proving Ground, spring softness, and a formula for roll stability.
| Identifier | ExFiles\Box 173\4\ img059 | |
| Date | 4th December 1935 | |
| vsa 7 To Sg.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} c. to By.{R.W. Bailey - Chief Engineer} c. to Hdy.{William Hardy} The following is a copy of a memo. received from Hs{Lord Ernest Hives - Chair}/Gry.{Shadwell Grylls} in America, dated 20.11.35 :- "We spent yesterday at the G.M. Proving Ground where Gy. demonstrated various cars that oversteered and understeered. I had hoped to find an answer to your question why a Bentley engine in the Buick would not be a good sports car. However, none of the cars we tried handled like the Bentley but the one that understeered was the least bad. Gy. is convinced that our method of measuring spring deflections give figures about 30% too soft. The SpectreCodename for Phantom III is really about 3" all round. No car out here is stiffer than 9" and hence rolls considerably. He gave us the following formula for roll stability of an orthodox front axle, which should be useful for the low rating experiment on the 20/25. If the springs are sufficiently low rating the shift of the C.G. makes up for the spring stiffness, and the car will stay in the rolled position, no restoring couple existing. α = Fh₁ / (St² + wh₂ - wh₁) R = ROLLING CENTRE S = SPRING RATE t = TRACK. | ||