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).
High-speed steering wobbles, comparing 6' and 6.75' tyres and the effect of wheel inertia.
| Identifier | ExFiles\Box 29\1\ Scan238 | |
| Date | 23th August 1926 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to BJ. Wor.{Arthur Wormald - General Works Manager} c. to E.{Mr Elliott - Chief Engineer} Da.{Bernard Day - Chassis Design} c. to Ey. OY. x457 Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}5/T23.8.26. HIGH SPEED STEERING WOBBLES. With reference to the 6.75" tyres having a greater tendency to promote high speed wobbles than the 6" tyres. It will be remembered that some time ago we carried out a comparison of fitting a mass of 50 lbs. round the brake drums and a similar mass in the form of a brass band at the tyre radius (Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG4.9.26). Further tests on these lines have shewn us that when the moment of inertia of the wheel is increased in this manner, without altering the transverse moment of inertia of the axle, the tendency to high speed wobble is definitely reduced, in other words the gyroscopic action of the wheels resists the axle criss-cross movement. This may therefore be a possible explanation of the recent results obtained in France. The 6" and 6.75" Dunlop tyres are both 6-ply. They both fit on 21" rims. The 6.75" tyre, however, has considerably more rotational moment of inertia than the 6" tyre. This may reduce its tendency to high speed wobble. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||