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).
10,000-mile test of shock absorbers, detailing faults with the replenishing ball valve.
| Identifier | ExFiles\Box 182\M19\ img212 | |
| Date | 24th July 1931 | |
| ORIGINAL X.235 X.7520. To H.{Arthur M. Hanbury - Head Complaints} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c. to Hy.{Tom Haldenby - Plant Engineer} Ha/Rm.{William Robotham - Chief Engineer}2/WJ.24.7.31. 10,000 MILE TEST SHOCK ABSORBERS. We have received the following report from Hancock today, with reference to the rear shock absorbers on 25-HX.:- "We have dismantled the rear shock dampers today. We found upon testing these dampers that a definite fault had arisen. We found that when the lever was moved upwards fairly quickly, and then the motion reversed quickly, we obtain a free movement of the lever from 1" to 1.1/2" without any load taking place. We could obtain this feature with every test." During my visit to Derby I had a conversation with Mr. Brock who informed me that during his investigations he had come across a similar phenomenon, and that the trouble is caused by the replenishing ball valve not operating correctly due to the seating becoming hammered by the motion of the ball. We examined this features in our dampers and found that the seating had become severely hammered. We therefore, without interfering in any way with any of the other mechanism of the dampers, dressed the seating of the ball release valve up, making the ball have a knife edge seat. This definitely cured the loss of movement above mentioned". We think that this may be a partial explanation of why this car has not been holding the road well. We have come across this trouble before and mentioned it to Da.{Bernard Day - Chassis Design} in our Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}5/LG 4.12.28., but we have had no evidence that it was a frequent source of trouble in customers hands. We think, however, that now we have put the high pressure load up to 115 lbs. ball pin load to deal with the low rating springs, that we have increased the tendency of this ball to hammer on its seat, and consequently we shall have to do something to prevent the cause of the trouble. We have recently had a case brought to our notice on production. The cast iron ends fitted to the damper in France deal with the low pressure replenishing valve and therefore it is only the high pressure replenishing valve that we have to consider. Six months ago we reduced the lift on these ball valves to .025 to reduce any tendency to hammer. This is about the minimum lift at which the valve will operate satisfactorily. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||