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.

LEAF SPRING SUSPENSION SYSTEM IN AUTOMOBILES

Leaf springs are made up of a number of curved bands of spring steel called leaves sticking together in order from shortest to longest. This stack of leaves is fastened together at the center with a center bolt or U- bolt to prevent the longitudinal movement. Similarly sometimes the leaves are made with pips or projections at the bottom and recess at the top surface. The leaves are arranged in such a way that the projection of the upper spring should mesh in the recess of the lower spring. Also to keep the leaves from slipping out of place, they are held at several places with the clips. Both ends of the longest or main leaves are bent to form spring eyes, used to attach the spring to the frame. To adjust the variations in length of the master leaf while the vehicle move across the road irregularities, one end of the spring is connected to the fame through a shackle and the other end is mounted directly on the frame with a pin. For the front suspension, it is a usual practice to provide the shackle in the front side of the spring to reduce the wheel wobble.

Generally, the longer a leaf spring, the softer it will be. Also the more leaves in a leaf spring, the greater the load they will withstand. But on the other hand as the spring will become firmer, the riding comfort will suffer.

The curvature of each leaf is called a nip. As the nip of the leaf is greater, shorter the leaf will be. Each leaf curves sharply than the one above the stack. When the center bolt is tightened, the leaves flatten somewhat and causing the ends of the leaves to press very lightly against one other.

The suitable steels that have been used for the manufacture of leaf springs are chrome-vanadium steel        (C-0.46%, Cr-1.4%, Va-0.18%), silico-manganese steel (C-0.52%, Si-1.95%, Mn-1.05%) and carbon steel (C-0.55%, Mn-0.6%, Si-0.2%).

Programmable speed limiter

Programmable speed limiter

Ford Motor Co. has introduced new technology called MyKey that includes a speed limiter setting for the engine of certain models. MyKey can be programmed to limit the top road speed of the Focus model to a maximum of 80 mph.

They say it will curb road racing, but to be honest, I can’t recall if I’ve ever seen a Focus doing 80 mph. Oh well, it’s a start.

A practical application for the MyKey is that it can be programmed to sound warnings to the driver when the car reaches 45, 55 and 65 mph.

MyKey encourages seat-belt usage by chiming frequent reminders and by muting the vehicle’s stereo until the seat belt is engaged. That’s practical. It won’t let drivers play the stereo until they’re buckled up.

MyKey also limits the volume of the stereo to 44 percent of its total volume to encourage the driver to pay attention to the road instead of the latest CD from My Chemical Romance.

The programmable technology will come standard on 2010 and newer Ford Focus models and will soon be standard on other Ford, Lincoln and Mercury models, officials announced on Monday, Oct. 6.

About half the people surveyed during testing said they would allow their teens to use the family car more often if the vehicle were equipped with MyKey technology.

Initially, 67 percent of the teens surveyed didn’t like the idea of having this technology limit their driving habits, but that number dropped to 36 percent if using it meant they could borrow the car more often.

It’s a step in the right direction. What they really need is for technology – or at least a driver education course – that teaches teens more about sharing the road with large trucks.