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).
Steering linkage elasticity, oversteer effects, and the performance of rear stabilizers at high speed.
| Identifier | ExFiles\Box 170\3\ img149 | |
| Date | 21th January 1938 | |
| S.H. Grylls Esq., Rolls-Royce Limited. 21. 1. 38. Curve 2 shows 2 1/2º apparent increased steering angle at .4g at the steering wheel due to elasticity of the steering linkage. We have measured about 3 1/2º excess wind up at .4g on the Ford, which is very soft in its linkage due to transverse drag link and flexible connection of axle to frame. The Pontiac shows no wind up, with new tyres, due to apparently very slight self-centering (neg.caster). Curve 2 is going to double over rather suddenly sooner or later because of the approaching reversal of precession torque like chart (4). This is clearly shown in curve 3, the steering effort curve. In other words, when curve 3 becomes horizontal, curve 2 should be parallel with curve 1. I think I can see a dot at 3.6º and .4g that your boys have not believed. Leslie's chart of 22nd December. Your vertical scales are double ours which confuses me a little. Should guess that curve of Fig. I might embarrass a damn fool on a hard curve at speed just as Olds 6 did when they had a rear stabilizer. Amongst the many things that our methods so far dont explain is the "sudden" effect of rear stabilizer at high speed. It must have something to do with the increased oversteer tendency at speed due to increased rear traction, or possibly due to the increased hopping of the rear end at speed. Even on the assumption of a constant steering angle for a given lateral acceleration at all speeds it is enlightening to plot steering angle against speed for say 100 ft radius flat, 300 ft radius flat, and 800 ft radius banked for 40 m.p.h. I have done this for your rear stabilizer curve on Chart 6, to show that in terms of speed the oversteer effect due to carrying too much of the overturning couple on the rear tyres is fairly sudden. We put down as a rough estimate for a good handling car. Rotary stiffness measured on platform scales, including tyre deflection and at 4 pass.load. -4- | ||