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).
Letter providing comments and analysis on shock absorber issues, particularly knocks and leaks.
| Identifier | ExFiles\Box 68\2\ scan0250 | |
| Date | 26th April 1929 | |
| OY 10 Mr. A.{Mr Adams} F.{Mr Friese} Sidgreaves, Rolls-Royce Limited, London, England. Dear Mr. Sidgreaves: April 26th, 1929. cc - Mr. Royce Mr. Hives Mr. Bailey Re SHOCK ABSORBERS - Section 7150/60 With regard to several copies of notes on shock absorbers which we have received recently and for which we thank you, we should like to offer the following comments:- (1) Our principal trouble as regards knock is in the Phantom old type front shock absorbers. The knocks appear to be purely mechanical in the links, the rocking shaft bearings, or the connecting tubes. Spring loaded tubes would undoubtedly help a lot, but might we suggest that connections of the form used at the top of the axle control anchorage, with a spring to hold the pads together would possibly be most satisfactory. Such connections are used by the Gabriel Company on their new hydraulic dampers, by Packard on the cross steering tube, and by several other makers, and appear quite satisfactory. (2) Axle control dampers or rear dampers when fitted with a drilled or slotted valve to give a slight leak (of not more than 1-1/2 thousandths of a square inch) appear to be free from knocks, and we think go very far towards curing jerky low speed riding of which we have no complaints, except the usual few which are traced to neglected road springs. (3) With a slight leak like the above to cushion the jerk during the reversal of motion we appear to find that the movement of the axle on the road can be kept within reasonable limits without distressing vibration being transmitted to the car. Also, since the maximum oil velocity is about twice as high for allowable axle movement as it is for allowable car movement, we find that so long as the leak is not sufficient to allow the car to "pitch" it will not prevent the proper damping out of axle movement, shimmy etc. However we find the dampers very sensitive to small variations in leakage and that an increase of 50% in the leakage at the valve will make a very noticeable change in tendency to pitch, and in the "control of the axles." --continued-- | ||