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).
The testing and comparison of different shock absorber systems, including adjustable needle valve and Houdaille types.
| Identifier | ExFiles\Box 55\4\ Scan242 | |
| Date | 13th July 1928 guessed | |
| - 4 - We have adopted this practice through finding that instruments set by ball load become impossibly "easy" after a few thousand miles, and that after this distance the mechanical friction of the instrue ment is negligible as compared for example with the inter-leaf friction of the road springs. DIAGRAMS. Your diagrams show very clearly, but probably not at its full value, because of the instantaneous nature of the load, the effect of the valves "popping" due to the increase of pressure-area under the valve when it has lifted. It is encouraging that the "pressure-velocity" shock absorber shows so much less of this and also shows less back pressure on the H.P. side. We tried fitting the shock absorbers with an adjustable needle valve (A-12116 herewith). It was from this that we began to get an idea of the area of orifice required. This made the shock absorber into a pure Houdaille, but with double action. We used these front and rear. It was not a success in the same way that the Houdaille isn't, i.e. although the riding was good on ordinary wavy roads, the slightest bit of a broken surface which could cause the axle to drop suddenly, caused shocks which sounded as though they were pulling the car to pieces (particularly at low speeds.) I mention this because I think the "velocity" effect has got to be kept very moderate to avoid this result. But we should like to have a little more "velocity" effect, I think, if only as an insurance against bad tramping of the front axle. Very truly yours, Maurice Olley r/ | ||