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).
Improving ride comfort through tyre selection, suspension adjustments, and axle ratios.
| Identifier | ExFiles\Box 183\M22\ img069 | |
| Date | 26th September 1920 | |
| Contd. -2- What has been said of roads can also be said of tyres. Pleasant riding cannot be obtained without Pneumatic tyres, and these must be allowed to deflect with the load. Moreover, like the springing of the car, their resiliency should be damped, or they will bounce like a tennis ball. Now recently the alterations in the manufacture of America tyres by adopting (1) cord constructions, (2) resilient rubber (3) higher air pressure, and (4) increased sizes of tyres have made these tyres like English Palmer cord tyres, with which we could never obtain really nice motor travelling. The result is that what is best with softer and more damped tyres is not permissible with the harder less damped tyres, and hence we are called upon to provide more damping friction in the springing of the car. The way to do this most economically is to return to the thin leaf springs, because to obtain sufficient damping in shock dampers puts too much work upon them, and they cannot be made to last without excessive weight, whereas as supplementary to the friction within the springs they are useful and satisfactory. I do not believe it is so impossible to get a supply of rear springs of pre-war type for the comparatively small number of cars complained about, and to fit shock dampers to all other cars at a very early date. I have agreed that Platford should go to U.S.A. and see if our conclusions are correct, and that the cars are working under the correct conditions. One certainly imagines that the lighter cars are the ones to give the most trouble, and that in many cases it may be found that the springs are too stiff for the load as I imagined was the case with 6.EX. X.3483. The Ferodo interleaves certainly make the springs more silent and are to be recommend if they continue to stand up to the work. They have been recently used on 1.EX so far with success, although with thick plates and sheared ends, which are not so suitable for such interleaves. There is the difficulty in their use, of adding considerably to the thickness of the spring; this we shall hear about later. X.3545. X.3457. Regarding the ratio of the back axle, so far my experience points, as I suggested previously, that the present ratio is best all-round for light open cars weighing about two tons for high speed drivers, and that the lower gear should at present be used only on covered cars of 2.5 tons and over, and for people who never go fast, otherwise, wear and tear of tyres and engine and petrol consumption is decidedly worse with the lower geared axle. There is also a retarding effect when closing the throttle, which is slightly too manifest to be pleasant. Contd. | ||