Road testing and modifications to the 21-EX vehicle, focusing on axle and steering performance.
| Identifier | ExFiles\Box 11\2\ 02-page272 | |
| Date | 13th July 1929 | |
| Hôtel de France, Châteauroux, Indre. To Hs. {Lord Ernest Hives - Chair} From Rm. {William Robotham - Chief Engineer} Re: 21-EX We have now had an opportunity of trying 21-EX with its own axle. We ran it out to Fontainebleau yesterday and to-day came down here with it. On the whole the car behaved remarkably well. Before we changed the axle, we slacked the engine feet off, so there was no compression on the rubber. The result of this was to reduce the vibration on the steering wheel, but it did not appreciably affect the engine roar. This confirms our previous experiments with the rubber engine feet. It also did not make much difference to the steering, which is rather surprising. Before we changed back to 21-EX's original axle, G.W.H. tried the car and agreed that the steering was very much better than with the trials car axle. I think this is due to the fact that the friction in the cross steering tube is very different on the two cars, 12-EX having larger balls. When we refitted its own axle on 21-EX we were able to appreciate that the S.S. axle was not so good as the Phantom axle. The most surprising thing however is that 21-EX steering is really quite good, even with its own axle. It is remarkably selective, quite free from road shocks on bad roads at high speeds, and the only trouble it suffers from is really high-frequency joggles at about 60 to 70 M.P.H. This is largely eliminated by 12-EX's axle. We have not yet got an exact comparison between the two axles, because there is more load on the cross steer tube of 21-EX than there is on 12-EX. Now we are down here, however, we are going to make this precisely the same in every respect, and repeat the test. Testing round Paris is difficult because there is a great deal of traffic. G.W.H. has increased the cross steering tube load on 21-EX since he came down here and made it about 1300 lbs. This is the load we originally fitted to this car, and then altered it because when the steering box was changed it made the steering too heavy. This emphasizes the fact that to get the best out of the steering, the friction in the steering must be reset after the car has done 5000 miles. The pivot lean of this car is also for some reason 3 1/2°. We are reverting to the standard lean of 2 3/4° for further comparisons. The side steering tube has also been altered from standard as explained in G.W.H. 8/7/29. | ||
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).