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).
Steering tests investigating wheel wobble at different tyre pressures on chassis 93 NK.
| Identifier | ExFiles\Box 71\4\ scan0298 | |
| Date | 11th July 1925 | |
| X8940 Hotel de France, Chateauroux. Indre. France. GWH.{George W. Hancock - Head Chateauroux}1/Crn.11.7.25. To: "Hs{Lord Ernest Hives - Chair}" From: G.W.Hancock. Re Chassis 93 NK. Further steering tests with wheels approximately 1/2 lb. out of balance. Tyre pressures at 60 lbs. We do not obtain any wobble at our usual speed of 60 m.p.h., but on going up to 66 m.p.h., a slight wobble developes, and keeps on and off up to 69 m.p.h. These wobbles are not at all severe, and the car can easily be kept under control. We consider the steering to be too light with these pressures, the car very easily being deflected out of its course at high speeds. There are no low speed wobbles, and at low speeds the steering is fairly easy. Tyre pressures at 40 lbs. We get slight tendency to wobble at 60 m.p.h. on smooth roads. On a moderately rough road they start at 63 m.p.h., and continue on and off up to 70 m.p.h. The wobbles are worse than what were obtained with front wheels 1/4 lb. out of balance, but are not what we should call violent. The worst period is at 64 m.p.h. Road shocks on steering wheel are definitely more than with tyre pressures at 60 lbs. On the retard, steering wobbles develope up at 66 m.p.h., 60 and 53 m.p.h. One can feel these three distinct periods develope up, but they are not at all violent. Whilst we were testing, it was necessary, on one occasion, to brake hard when we were doing 52 m.p.h., and a violent steering wobble was set up, which lasted until the car speed was brought down to 30 m.p.h. We tried afterwards again and again to reproduce this, but could not obtain it. At low speeds, we obtained the same results as we have obtained previously. Tyre pressures at 30 lbs. No low speed wobbles could be obtained. Steering was very heavy, especially at speeds of 20 m.p.h. and under. At high speeds, steering wobbles commenced at 55 m.p.h., and lasted to 64 m.p.h. They are of about the same intensity as when tyres are 40 lbs. pressure. This is on good surface. On rough roads, they are definitely worse than at 40 lbs. pressure. There are no wobbles over 64 m.p.h. On the retard, the steering developes a severe wobble starting at 58 m.p.h. down to 54 m.p.h. The maximum is at 57 m.p.h. These retard wobbles are much worse than when the tyres are at 40 lbs. pressure. | ||