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).
Performance of hydraulic shock absorbers, specifically addressing back pressure and jerking issues.
| Identifier | ExFiles\Box 28\1\ Scan126 | |
| Date | 28th June 1928 | |
| OY2.R.6.28.28 Mr-Rowbotham +832 June 28th, 1928. Will you please reply to the above queries? cc - Mr. Burton Mr. Beaver Mr. Ainsworth TO: Mr. Nadin FROM: Mr. Olley RE SHOCK ABSORBERS - SECTION 7150/60 As July 11/28 Hs.{Lord Ernest Hives - Chair} Rm{William Robotham - Chief Engineer}2.LG18.6.28 has just arrived with indicator diagrams of the hydraulic dampers. I see that Hs.{Lord Ernest Hives - Chair} did not send you a copy but probably you have seen the results. (1) The existence of back pressure during the L.P. stroke suggests setting to nominally equal loadings up and down which we were rapidly coming to from the "feel" of the car on the road. (2) The "pop-valve" effect on both H.P. and L.P. valves is very marked and considering the instantaneous nature of the load and the damping which must exist in the indicator itself, is probably much greater than the diagrams show. We think that from our results on the "active test rig" and the road, this effect is responsible for the jerking at low speeds. (3) Could you persuade Rm.{William Robotham - Chief Engineer} to take diagrams with leaking valves, say A-12293, (drilled with cross hole .450 from head) and with A-12306 (one .047 slot)? This would be of extraordinary use to us just now, as it would show the extent to which the leaking valve destroys the effectiveness of the instrument under various conditions, and would show whether we are running any risk in using them. (4) Could you also ask Rm.{William Robotham - Chief Engineer} to try to eliminate the pop valve effect by using valves with a knife-edge seat? (I doubt whether it is possible to get rid of it entirely without a leak in the valve, but certainly the H.P. valve, which is small with a wide seat must be very bad for "popping".) (5) From Rm{William Robotham - Chief Engineer}'s. remarks about the destruction of the low speed shock absorber action if a speck of dirt lodges on the L.P. valve seat, he obviously does not believe any leakage is desirable. We should agree if it were made possible to get rid of clicking and jerking at low speeds without it. (6) I notice that Rm.{William Robotham - Chief Engineer} is going to determine "typical" actions of the instruments on the road. In this connection the conditions of the tests do not seem to represent anything like the conditions which actually occur on the car. (Continued) | ||