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).
Investigation into wheel wobble, focusing on the effects of tire pressure, speed, and engine mounts.
| Identifier | ExFiles\Box 170\3\ img047 | |
| Date | 14th July 1933 guessed | |
| -18- kingpins, are not within practical possibilities. Tire Pressures. We attempted to find the effect of changing tire pressure from 20 to 35 lbs. The effect, if any, is not marked. It appears to be worse at the higher pressure. The effect on frequency is small. Speed. From road tests it appears possible to run through a wobble and that it will not occur above a certain speed. On road and drums ordinary 300 cycle wobble is worst at 20 m.p.h. The 'extraordinary' 190 cycle wobble starts about 6 m.p.h. and increases in violence up to 20 p.m.h. We have run no faster. On the road without a tie-rod, by increasing the moment of inertia of the right hand wheel and box assembly about 120% it is possible to run through a very slow and feeble wobble at 6 m.p.h. and subsequently to operate the car at any speed without trouble. The 190 cycle wobble is probably the worst danger that the driver will meet in the event of a broken steering gear, since it appears quite capable of turning the car over at any speed above 10 m.p.h. Engine Mount etc. Although generally speaking the frame does not shake and twist in wobble as much as it does in shimmy, the engine mount is profoundly important. In the case of the 1934 Chevrolet Master the engine shook considerably in the 300 cycle wobble, blocking the engine against the steering column stopped the engine movement but greatly increased the violence of the wobble. Removing the block was followed by five or six extremely powerful swings of the engine, which appeared to act as a harmonic balancer, since it immediately stopped the wobble. This happened with the greatest regularity, and the wobble had to be restarted each time. On the other hand in the case of the TT Job (with 1935 engine mount) blocking the engine causes the wobble to decrease and (if the caster excitation is not too great) will make the wobble die out entirely. The different | ||