SHOCK ABSORBERS

Evening Post, Volume CIX, Issue 51, 1 March 1930, Page 27

SHOCK ABSORBERS

TfiE HYDRAULIC TYPE

Now that the iisc.of sonic form, of shock absorber;!;is common practice, on /private carsj motor coaches and even 'goods vehicles, it, is interesting to 're- " view "/the salient features of a type whichis'now very popular, the hydraulic -shock absorber. Hydraulic shock absorb era : have many advantages over those; of. the friction, type, the most important being that they act progressively, owing to the flow of oil following;;, the hydraulic, Jaw and giving little damping, effect for small bumps and greater damping for large bumps. Further, their efficiency is constant and therefore frequent adjustment is unnecessary. Wh'en travelling slowly the load springs require very little control, and if heavily cheeked will cause harshness and discomfort. In this condition the. f.rictional element of a friction type shock absorber is checking at its maximum efficiency, thereby imparting to the springs a chocking which is not required. As the speed, of the car increases, tho impact load on the absorber becomes greater and the efficiency of tho frietional element becomes less, which ia exactly opposite to what is requircdyds it means that at the higher speeds this type of absorber has very little control over the springs. On the other hand, in a hydraulic shock absorber these conditions are reversed, as at slow; speeds:the resistance is very small, but as tho speed and load increase, so tho resistance of the absorber becomes greater, giving smooth riding under all conditions and efficient control of the road springs at high speeds.

A new English shock absorber consists .of a single, vano rotor working in a pressure chamber, this chamber being divided by the reacting block in which is incorporated the> regulation and control of the oil flow. The working chamber is filled with a special oil, the viscosity of which is-very little affected by changes of atmospheric temperature, and the reacting block is provided with a non-return valve,, permitting the oil displaced by the vane, which oscillates ■within the chamber with each movement of the spring, to pass through it to the other side of the upward deflection of the spring, but preventing its return on recoil. This valve being shut, an additional orifice is provided to enable the oil displaced to return through the reacting block, and a tapered screw regulating the sizo tof tliis orifice is fitted so that adequate, control over the recoil checking action is provided.