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).
The variation of self-centring torque and slip angle between new and worn tyres.
| Identifier | ExFiles\Box 158\1\ scan0216 | |
| Date | 27th September 1938 | |
| -2- Rm{William Robotham - Chief Engineer}/PJH.1/JH.27.9.38. The results obtained are shown on graphs No. 2 and 3. As can be seen there is a 40% increase of self centring torque with a completely worn tyre. Also, the slip angle of the worn tyre is 20% less than that of the new tyre. The effect of castor angle is shown on graph 3. It is surprising that, even with the comparatively large castor angle of 3½°, a worn tyre accounts for no less than 70% of the total self centring torque. The large variation of self centring between new and worn tyres is a serious disadvantage and it is desirable to reduce this variation as much as possible. We have little hope of reducing the torque of the worn tyre so the best line of attack would appear to be to increase that of the new tyre. The castor angle could then be reduced to produce the same nett result. Rm{William Robotham - Chief Engineer}/PJH. | ||