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).
Vehicle suspension testing, detailing modifications to springs and the use of weights to improve ride comfort and reduce frame jellying.
| Identifier | Morton\M19\ img113 | |
| Date | 7th February 1931 guessed | |
| -2- safely increase the deflection for load by approx. 50% on the front springs and 25% on the rear. i.e. we use front springs with an initial camber of 4.5" and rear 10.25". The alteration to the front makes a bigger improvement in riding comfort than the rear spring modification. The cars are at the present on the road fitted with these springs :- 38-GW which has been recognised as being considerably more comfortable than with standard springs, 18-EX at present at Le CanadelHenry Royce's French residence and 25-EX. We did not have an opportunity of thoroughly testing 18-EX because the springs only arrived on the eve of the departure date for Le CanadelHenry Royce's French residence, but we understand that it is a good ride but crashes on the buffers excessively on really rough roads. 25-EX whilst in America was fitted with nearly similar springs with beneficial results; on its return to Derby it was fitted with our own low rating springs. As a result of these tests we are proposing to fit this type of spring to the left hand P.II cars for America where the springing question is apparently more acute. 25-EX car whilst being generally a comfortable ride gives the impression of being rather hard. The car does not seem to ride as one solid mass, its gives the impression of being in several pieces, the body appears to flex and too much axle dithering is apparent. This feature is at its worst and appears to coincide with front end frame jellying. It is present but to a lesser degree on 38-GW and 20-EX. With a view to this, this car does not jelly and is fitted with high rating sports type springs. Various tests have been carried out to give an indication of the cause of the trouble. On 25-EX an improvement was effected by stopping the front end from jellying, the only effective method we know of doing this is to clamp a dumbell to the front dumb-irons, the dumbell having weights of 100 lbs at either end, the weights being the same width apart as the front wheel track. A similar dumbell on the rear of the car did not make any appreciable difference. The use of this on 20-EX showed a more marked improve-ment than on 25-EX, the former car is fitted with two spare wheels one on either side on the front of the car, 25-EX has one spare wheel at the rear. It was possible to detect a difference on 20-EX by taking off the spare wheels with the dumbell in position, when the wheels were taken off the riding in this respect was worse. Further tests were carried out on 20-EX to ascertain whether the improvement was due purely to weight distribution or by the effect of the dumbell damping out frame distortion. Firstly the two weights (100 lbs. each) were bolted together | ||