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).
Causes and remedies for high-speed wobble in specific chassis models, focusing on pivot pins, wheel balance, and tyre pressure.
| Identifier | ExFiles\Box 71\3\ scan0304 | |
| Date | 28th August 1925 | |
| X8950 W/N - Br.{T. E. Bellringer - Repair Manager} (crossed out) C. to By.{R.W. Bailey - Chief Engineer} (crossed out) C. to Hs.{Lord Ernest Hives - Chair} (crossed out) C. to BP. (crossed out) Hm{Capt. W. Hallam - Head Repairs}/NRC{N. R. Chandler}10/EW28.8.25. Re Chassis 123-EM, 16-LM, 103-MC, and 15-MC. You have removed from each of the above chassis two Pivot Pins complete with top and bottom bushes, and we would say without hesitation, that we do not think for a moment that the small amount of slack which exists in these bushes has anything at all to do with the high speed steering wobble, and we trust that you will not scrap any pins and bushes on account of a few thous' clearance between the bush and the pin. The first and most important point to attend to is the accurate balance of the road wheels. These are commonly out of balance owing to the fact that for some reason Dunlops have parted from their original scheme of placing the valve opposite the joint of the tube, and we also find that in some cases covers are out of balance also. A very fair balance may usually be obtained by selecting covers and tubes so that the heavy side of the tube comes opposite to the heavy side of one of the covers. We would say that we are at present preparing studs and washers specially for balancing wheels with S.S. tyres and will send you a supply of these as soon as possible. We also recommend that in cases of high speed wobble the front tyre pressure should be increased to about 50 lbs. We are quite aware that for some time past we have been recommending pressures 30 - 35 lbs for the low speed wobble when f.w.b. are not fitted, but we do not know of a case where low speed wobble has occurred on a four wheel brake car. With regard to slack in the Pivot Pins and Bushes, we would say that if a wobble appears to have been cured by fitting new ones which are rather tight, it can at the best only be a very temporary cure, because the first half thou' of wear would remove friction from this joint just as much as the next five thous', and we really do not think for a moment that replacing pivot pins and bushes has ever been responsible for removing high speed wobble. We think this a coincidence, and that some other factor has been responsible for the wobble not appearing during the test following the fitting of new bushes. Hm{Capt. W. Hallam - Head Repairs}/NRC.{N. R. Chandler} NTDB | ||