This independent suspension system which has been designed by Moulton Development Limited and British Leyland Motor corporation and is manufactured by Dunlop Suspension Division of Coventry England, is an improvement over the hydrolastic suspension.

Hydragas suspension consists of an integral spring and damper unit at each wheel. An inert gas like nitrogen is used in this units for springing, while the weight of the car is supported by water based fluid under pressure. The units are interconnected front and rear and the whole system is hermetically sealed.

Hydragas unit :-

The hydrolysis unit consists mainly of two chambers the nitrogen filled spherical chamber and the displacer chamber, the former being welded over the latter. The two chambers are connected by means of carefully designed holes covered by rubber compression blocks. These holes are meant for controlling the fluid flow between the two chambers and provide the required damping. The displacer chamber is hermetically sealed at its lower end. There is a butyl separator in the upper chamber. The volume above the separator is filled with nitrogen at 1725 KPa and is sealed for life. It provides the requisite springing. The fluid is filled in the space between the separator and the rubber diaphragm.

Suspension installation :-

Hydragas unit operates with a leverage of 4 to 5:1 to reduce the unit size. The rear suspension installation is rubber mounted at its end. The load from the unit passes through the shroud and onto a pin which acts as the pivot about which the trailing arm turns. The opposing load from the piston via the knuckle joint onto the arm, is fed through two dual concentric bushes and from there to the pivot pin. The reaction on the unit, of a similar magnitude as wheel load, is taken on the body by a rubber pad acting directly on the spherical chamber.

The front suspension units are mounted vertically with the piston acting on the upper support arm through a knuckle joint.

Working :-

The working of Hydragas suspension system will be discussed here from the following consideration :-

(i) Pitching :- In pitching the closure of the front suspension causes the tapered piston to displace fluid from the front unit through the interconnecting pipe to the rear unit. As the diaphragm rolls between the tapered piston and the tapered skirt the effective area of the front unit increases and the rear decreases causing a righting force.

(ii) Bounce :- In bounce (both front and rear wheels over a bump) the closure of front and rear suspension units together causes the fluid pressure to rise in the gas springs compress.

(iii) Rolling :- In case of a Hydragas, car rolling for instance, to the right, both units on the right side of the car closes and both units on the left side open. The movement of the front and rear suspension units together causes the fluid pressure to rise in the right hand side and fall in the left hand side, giving rise to a force opposing rolling.