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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).
Analysis of factors causing vehicle wobble, including tire pressure, frame stiffness, and wheel overhang.

Identifier  ExFiles\Box 170\3\  img066
Date  17th June 1935
  
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wobble excitation. Actually careful check on three cars fails to show definite result. Wobble was produced with drums running in either direction, and the amount of wobble for a given actual caster offset was the same (as near as we could measure, for the same caster whether the weight was leading or trailing). We think the reason for this is that the rocking motion of the car is highly damped.

2. Tire pressure. The effect is not great and at present is not predictable.

3. Frame stiffness. Within small limits increased stiffness of frame-body assembly appears to reduce the tendency of wobble.

4. Wheel overhang. Change in overhang from the centre of the wheel-plane to the kingpin probably affects wobble, and also the overhang from the tire contact centre to the line of the kingpin. We have no certain figures on this. Directional shocks due to bumps are reduced as the overhang is reduced, but self-energised wobble is certainly not prevented by making the overhang zero.

5. The rate and internal damping of the front springs, etc. must affect wobble to some extent. We think that within limits, the effect is small.


M.{Mr Moon / Mr Moore} Olley

June 17, 1935.
  
  


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