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).
Explanation of the principles of spring oscillation and the benefits of two-way shock absorbers, specifically the Hartford type.
| Identifier | ExFiles\Box 51\4\ Scan035 | |
| Date | 10th February 1922 guessed | |
| 5. It will be evident from the foregoing explanation of spring oscillation that no device which does not absorb energy from the spring can be a Shock Absorber in the sense of damping out oscillations. Any cushion spring or auxiliary spring merely changes the elasticity of the spring support of the car; that is an elliptical spring, plus an auxiliary spring of any kind is still really a simple spring and can, in fact, be exactly duplicated by one spring having the elasticity of the two springs combined. It may be that for some special conditions it is desirable to change the elasticity of the springs of an automobile, and auxiliary springs can be used to advantage for this purpose, but in general, the car manufacturers have obtained about the right elasticity in their springs and the addition of auxiliary springs will make the springs too flexible and produce excessive oscillation. It will be realised that in order to be really effective and efficient the Shock Absorber must operate in two directions as its principal object is to reduce the peaks of the curves on both sides of the neutral line and to flatten out the curve as rapidly as possible. The one way Shock Absorber only applies friction when the spring is expanding and since the friction acts only for half the time it would be necessary to make the friction twice as great for a one way Shock Absorber, as for a two way such as the Hartford. Again if we consider what happens when the car drops off a slight elevation, a road has as many hollows as bumps, all the advantage is in favour of the two way Shock Absorber. In this case the bump that causes discomfort to the passengers and possible injury to the car due to the body or frame hitting the axle, is not controlled by the one way Shock Absorber at all as it has no effect in this direction. One way Shock Absorbers are necessarily more complicated than the two way type, they require greater pressure and consequently are subject to more wear and strain; they do not protect the spring against breakage, they do not counteract the inertia of the unsprung weight of the axles, not do they prevent rolling or side-sway. The Hartford Two-Way Shock Absorbers have been designed to fulfil all these conditions. They regulate the spring action on both compression and expansion and absorb the energy stored in the spring by friction, which can be easily and quickly adjusted to any desired value and it is interesting here to note that the pressure required to effectively control the springs is comparatively small when compared with the load carried by the springs and is generally in about the region of 3% to 4% only, and their effect is only to stiffen the spring by a practically negligible amount. T. B. Andre & Co. Ltd., 5, Dering Street, New Bond Street, London. W.1. | ||