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).
Problem of high-speed wobbles and the benefits of hydraulic shock dampers over friction types.
| Identifier | ExFiles\Box 29\1\ Scan228 | |
| Date | 15th June 1926 | |
| To BJ. from Hs.{Lord Ernest Hives - Chair} +457 Hs{Lord Ernest Hives - Chair}1/LG15.6.26. HYDRAULIC SHOCK DAMPERS. X235 Answering your BJ3/E14.6.26. We had a case of high speed wobbles occurring on a car in customers hands on one of the original 20 HP. without front wheel brakes. This was proved to be due to the exceptional out of balance of the wheels and tyres. With the 20 HP. cars fitted with front wheel brakes, we can produce a wobble on any car when the wheels are out-of-balance. This will occur with the present standard front shock absorbers fitted. They will occur very much more readily if no shock dampers are fitted. They are practically eliminated when hydraulic shock dampers are fitted. There is however definitely less danger of high speed wobbles on the 20 HP. than on the Phantom. It is for this reason that we recommend fitting medium pressure tyres on the 20 HP. but do not recommend fitting them on the Phantom until we are in a position to fit hydraulic dampers. We can at any time demonstrate that high speed wobbles are dormant on the 20 HP. and can be produced by fixing wheels which are out-of-balance. The degree of out of balance has to be greater than in the case of the Phantom. It should be remembered however that the hydraulic damper has advantages apart from high speed wobbles. The feature of the hydraulic damper is that it will cover a wider range of conditions than the present standard friction type. It is a well known characteristic that when riding over bad roads at high speeds, a considerable amount of damping is beneficial, whereas, if the car is run at low speeds with the same amount of friction, it will ride like a truck. With the hydraulic dampers on the front, we consider that we can cover the range of carriage work in England, and high speed touring in France. We have never been able to do this with the friction type shock dampers. CWB. when he ran a 20 HP. car 2000 miles in France reported - see report CWB12/LH{Mr Haworth}22.9.25 :- "The question of shock dampers affects the springing very greatly and as the days proceeded, I gradually tightened these up more and more, with improved results. The trouble was, however, that the amount of friction became gradually reduced during the days run, and it would be necessary in order to maintain them in a given condition, to adjust them about every 200 miles, which is not considered at all satisfactory". contd :- | ||