HYDRO ELASTIC SUSPENSION SYSTEM

The main component of the hydraulic suspension is the displacer unit, which is attached to the individual wheels of the vehicle. The displacer unit consists of two chambers. Chamber A is just above the flexible diaphragm and the other B is above the separating member and connected by the other displacers by a hose pipe. The stem is usually connected to the lower link of the double wishbone. 

The diaphragm is connected with the piston and bears the wheel load. The fluid in chamber A can all the time pass into the chamber B through the bleed holes provided in the separating member. When the pressure of liquid in B rises sufficiently above that in A, then the rubber flap valve which is loaded by the spring will open downwards thus allowing the fluid to pass from B to A through the holes. Similarly to pass the fluid from A to B the damper valve functions accordingly. The fluid in B acts on the under side of the rubber element and through the   hose pipe is transmitted to the other wheel unit. The Canister Displacer unit in Hydraulic suspension is provided at the outside of the rubber element, while the pot member at inside. The canister is fixed to the body structure of the vehicle.

PLASTIC SUSPENSION SYSTEM

This suspension is similar to the compression type rubber spring but here plastic is used instead of rubber. It consists of a metallic cylindrical container which is fixed with the chassis. Inside the container there are two centering rings, one is located at the lower end of the cylinder and the other at the top position inside the cylinder. A suspension shaft is provided, which is fixed to the axle of the vehicle and is free to slide the plastic rings. The shaft has side supports at the upper and the bottom centering ring.

Plastic rings are provided above and below the upper centering ring. These plastic rings absorb the vertical dynamic loads. The plastic rings are supported on a disc in the shaft and when the suspension is in rebound position, the disc seats on the bottom centering ring. The centering rings are located in the container with help of the circular pressed steel plates and sleeve assemblies. When the vibrations in the axle is transmitted to the spring shaft due to the road irregularities, then the plastic rings will be compressed or and elongated and the sleeve assembly, carrying the centering ring and surrounding the plastic rings will move up or down in the cylinder. A flexible gaiter is provided at the bottom to prevent the system from dust or other foreign particles. The main advantage of this system are light weight, silent operation, simple construction, less maintenance, low wear cost, better cornering characteristics and less chances of sudden collapse. 

TORSION BAR SPRINGS

A torsion bar spring, usually called as a torsion bar is a spring steel rod that uses its torsional elasticity to resist twisting and takes only the shear stresses. One end of the torsion bar is anchored to the frame or other structural member of the body and the other end to a component that is subjected to torsional load.

The amount of energy stored per unit weight of material is nearly the same as that of the coil spring. Torsion bar is oftenly used with the independent suspension. As shown in the figure, the bar is fixed at one end to the frame, while the other end is fixed to the end of the wheel arm and supported in the bearing. The other end of the wheel arm is connected to the wheel hub. When the wheel strikes a bump, it start vibrating up and down, thus exerting torque on the torsion bar, which acts as a spring.

Torsion bar is lighter as compared to the leaf springs and so it occupies less space. As the torsion tubes are much stiffer than the bars, it is preferred. The main disadvantage of the torsion bar is that it does not take the braking or driving thrust so that additional linkages has to be provided for this purposes. The second disadvantage is that the absence of friction force to damp out the vibrations and hence additional dampers are to be provided.

COIL SPRING SUSPENSION SYSTEM

The coil springs are generally used with independent suspension. Since the energy stored per unit volume of the coil spring is almost double that of the leaf springs, they can be accommodated in restricted space. The coil springs are made from rods of special spring steel formed into the shape of a coil. When a load acts on the spring, the entire spring rod is twisted as the spring contracts to absorb the energy.

Progressive coil spring: If a coil spring is made from a rod of spring steel having uniform diameter, the entire spring will flex uniformly in proportion to changes in load. This restricts the application of this type of spring for the wide range of loading. However, if a spring rod having a constantly changing diameter is used, the ends of the springs will have a smaller spring rate than the center, thus varying the spring index under different loading conditions. Thus the spring ends will contract and absorb light loads and the center part of the spring will allow a wide range of loading. The progressive springs can be made by using unequal pitch spring (low pitch at the ends and high pitch at the middle), conical spring or by providing the helper coil springs with the main spring like in the case of leaf spring.