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).
Technical discussion on shock absorber valve performance, leakage, and design modifications.
| Identifier | ExFiles\Box 55\4\ Scan240 | |
| Date | 13th July 1928 guessed | |
| - 2 - 70 cycles/min. 4" max. allowable stroke (almost entirely at the rear.) All these characteristic movements blend together when car is on road, and because the car is not K² = ab pure bouncing or pure pitching blend off after a time into mixed bouncing and pitching. We have attempted to test shock absorbers for noise and smoothness of action under the conditions roughly of cases A and C above, i.e. 600 cycles 1" stroke and 120 cycles 4" and 6" stroke. We should be very interested to know the results of your tests on characteristic car movements. (2) LEAKING-VALVES I attach prints A-12292-3-4-5 A-12217 A-12180-1 and chart A-12322 showing the approximate relative leakage value, translated from a test of the time taken for a 10-1/2 lb. weight hung on the ball to fall through the full range. NOTE: To use the drilled type effectively we are cutting the bottom of the recess below the H.P. valve exactly .300 below bottom of valve-head, so as to use accurately the dimensions .450, .650, and .850 for the position of the cross-hole. Nadin has mentioned that the slotted valves may mark the aluminum seat. But since the solid valve does not beat down the seat to any noticeable extent we do not see that the existence of the slot should make any difference so long as there are no burrs left on the edge of the slot. We have not found any damage from the slotted valve in a few thousand miles. Actually we have been more worried about the drilled valves because the drilling should spoil the damping action of the valve-stem. But we have not heard any clatter, nor seen any sign of excessive pounding. Actually the worst valve is A-12217, the tightest slotted valve, which gives an audible hiss in the front shock absorber. But this is not loud enough to have caused complaints yet. As you see we are making the valves with a long "nose" for easy extraction. This idea of changeable valves is borrowed from Lovejoy. It fulfils (in a way) your requirement for convenient adjustment with a practical minimum and maximum damping, and also has the advantage that the adjust-ment chosen is always easily determined by inspecting the valves. (Continued) | ||