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).
Valve and shock absorber testing, focusing on leakage times and vehicle pitching issues.
| Identifier | ExFiles\Box 68\2\ scan0245 | |
| Date | 6th May 1929 guessed | |
| - 2 - It was desired to try the effect of changing valves on the right side, but it was found impossible to loosen the valve cap. This is therefore being left until Monday for investigation. Chassis 185-FR: Left Front: 4.0 seconds. Right Front: 5-3/5 seconds. Valve A-12294 was put in the left front, and the leakage time increased to 5-2/5 seconds. It was found on several of the instruments tested, that they were much tighter near the ends of the travel than in the center. This was particularly noticeable on the "rebound" side. This may be a good thing, by giving increased damping for increased amplitudes of movement, but we feel sure that it is only a temporary effect due to internal friction and that uniform friction throughout the range of the instrument would give better results, and render calibration easier. From the above leakage times, it would appear that we are getting a too large variation in instruments; even between two instruments which have had the same amount of running. Our present "standard" leakage time seems to be 6±1 seconds. It is felt that a limit of ±1 second is too great, but that we cannot reduce it with the existing series of valves. To get really consistent times (±1/5 second) we should have valves intermediate to the present series, with cross holes at say .550, .750, and .950 from the head. These, with the ones we already have, should permit of really close and accurate setting. We have received so many complaints of "pitching" that it would seem desirable to instruct the production of 25 each of A-12295 and A-12292 for trial. There were none of these available on Saturday. It may be that setting both front shock absorbers to the same leakage time (6±1 seconds) will cure our trouble. If greater leakage times are required (and it is thought that they will be in some cases) the tighter valves must be used. We do not want to fit solid valve if it can possibly be avoided, as we know that complaints of jerky low speed riding will result. (Heavier oil may be necessary, if the tighter valves do not increase the leakage time sufficiently.) In this connection, it is reported by St.{Capt. P. R. Strong} Marie that pitching is more noticeable on chassis fitted with heavy 7 passenger bodies than on those with light bodies. This has always been so because of the overhang of the rear seat. That is the car actually pitches less than a short car, but the rear passenger feels the pitching more. -continued- | ||