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 Maurice Olley discussing vehicle roll stiffness, oversteer/understeer, and stability, with comparisons to competitor cars.
| Identifier | ExFiles\Box 170\3\ img150 | |
| Date | 21th January 1938 | |
| S.H. Grylls Esq., Rolls-Royce Limited. 21. 1. 38. (1). Total. 345-450 lbs feet per degree per 2000 lbs of car wt. 450 is definitely on the stiff side. 345 is pretty soft though 1937 Chrysler 6 & 8 Studebaker 6 & 8 and Packard 6 & 8 are all below this limit. Olds 6 is 428 lbs ft/deg (short) ton. (2). Front rotary stiffness should be 1.8 (max) to 1.2 (min) times the rear rotary stiffness. I think 1.8 is too high (too much understeer). Olds 6 is 1.23, i.e. front rotary stiffness is 55% of the total. This means that on curves, about 42% to 50% of the total overturning couple is carried on the front tyres. If, as you say, you want to make a car definitely oversteer when pushed to the limit, then perhaps your curves for no stabilizer shown in Fig.2 of your chart of Leslie's note are about right, in other words you should try a careful balance between front and rear stabilizers till you get this curve coupled with adequate roll stability. (This is what Olds did). But I doubt very much that you do want ultimate oversteer, even for safety on Alpine passes. When the rear end drifts the front slip angle increases and the front end soon follows it. When the front end drifts it reduces all slip angles and corrects itself. What I think one needs is what Olds have done, to get as straight a steering curve as possible right up to the limit and then have the thing in doubt which way to turn. (Like sketched line on chart 6). With two stabilizers it is possible to get this, and you will find this, with adequate stability will give you the maximum controllable speed on the skid pad. Yours, Maurice Olley MAURICE OLLEY. | ||