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).
Letter from G. Temple providing information and advice on wheel wobble and tramp issues.
| Identifier | ExFiles\Box 153\4\ scan0007 | |
| Date | 4th October 1939 | |
| 1300 E/SGH.{Sir Stanley Hooker} Rm{William Robotham - Chief Engineer}/Gry.{Shadwell Grylls}1/JH.4.10.39. Letter from G.{Mr Griffiths - Chief Accountant / Mr Gnapp} Temple. The only good literature on the subject is a confidential internal General Motors Report of which we have a copy. To make another copy of this would be very expensive and take a long time. I don't much like lending ours but it is visible here. The following information may suffice - (1) Low speed wobble more probable than high speed tramp. (2) Resonant speed of wobble determined by usual relation of wheel inertia round king pin and stiffnes of steering control. To measure the latter, lock the wheel or rudder and measure stiffness from the other end. (3) Avoid this resonant speed being near to any other such as rocking of aeroplane, stiffness of wheel mounting etc. (4) To tune (2) add or subtract sponge in the steering control. If wheel is not steered alter stiffnes of whatever keeps it straight. Low speed wobbles can be damped by frictions which is usual practice on cars. (5) Increased"precessiontorque" (natural self-centring of a tyre running at a slip angle) makes wobbles worse. Also increased pivot lean. Americans now use negative pivot leans as precession torque of soft large section tyres is considerable and goes up 50% for a worn tyre. Presume this trouble is a wobble and not wandering due to oversteer (see Olley's paper to the I.A.E. about 2 years ago) Let me know if you want any more. Rm{William Robotham - Chief Engineer} /Gry.{Shadwell Grylls} | ||