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THE ULTIMATE IN PERFORMANCEAND COMFORT

Done by:

Pallav Sharma117/09

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Introduction

Principle of operation

Why nitro shock absorber

How foaming affects

How it works

Analysing different designs

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Shock absorber is an asssembly mainly to control

spring and suspension movement.

It is basically a hydraulic damping mechanism forcontrolling spring vibrations.

They isolate the spring vibrations by absorbing some

disturbing energy themselves and their performance

directly affects the comfortability, dynamic load of the

wheel.

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Schematic Diagram of the Interior of a Shock

AbsorberSpring

It controls spring movements in both directions: when

the spring is compressed and when it is extended, the

amount of resistance needed in each direction is

determined by the type of vehicle, the type ofsuspension.

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The damping mechanism of a shock absorber is

viscous damping.

So fluids viscosity plays an important role in

its effectiveness.

The damping force is

opposite to the direction of

velocity and the orifice size

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Springs alone cannot provide a satisfactorily smooth

ride.

Oscillating motion of the spring causes the wheel to

rebound or bounce up and down as bump is

encountered.

Shock absorbers prevent these spring

Oscillations. Conventional type of shock absorbers has the

drawback as it causes foaming of the fluid.

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Foaming is fundamental root problem of air

contamination .

Foaming is characterised by the formation of

relatively large air bubbles on the surface of fluid.

Causing factors are suddenly falling pressure or rising

temperature,viscosity of the working fluid.

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Entertained bubble formation can increase the

compressibility of fluid and affect its hydraulic

control mechanisms.

Foam affects performance because it can be

compressed while fluid cannot.

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It like spring also has two cycles-compression and

Extension cycle.

Compression cycle

During the compression strokeor downward movement, some

fluid flows through the piston

from chamber B to chamber A

and some through the compression

valve into the reserve tube.

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Extension cycle

As the piston and rod move upward toward the top of

the pressure tube,the volume of chamber A is reducedand thus is at a higher pressure than chamber B.

Because of this higher pressure,

fluid flows down through the

piston's 3-stage extension valve into

chamber B.

Fluid then flows from the reserve tube into chamber

B, keeping the pressure tube full.

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The shock absorber designs commonly in use today

are :

Gas Charged Twin Tube Designs

Mono-Tube Designs.

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The twin tube design has an inner

tube known as the working or

pressure tube and an outer tubeknown as thereserve tube.

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Rod Guide: Therod guide keeps the rod in line with

the pressure tube and allows the piston to move freely

in.

Seal: Thesealkeeps the hydraulic oil inside andcontamination out.

Compression valve: The base valve located at the

bottom of the pressure tube is called acompression

valve. It controls fluid movement during thecompression cycle.

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The design of twin tube gas charged shock

absorbers solves many of today's ride controlproblems by adding a low pressure charge of

nitrogen gas in the reserve tube. The pressure of

the nitrogen in the reserve tube varies from 100 to

150 psi, depending on the amount of fluid in thereserve tube. The gas serves several important

functions to improve the ride control

characteristics of a shock.

The prime function of gas charging is to

minimize aeration of the hydraulic fluid

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Improves handling by reducing roll, sway and dive

Reduces aeration offering a greater range of control

over a wider variety of road conditions as comparedto non-gas units

Reduced fade - shocks can lose damping capability as

they heat up during use. Gas charged shocks could cutthis loss of performance, called fade

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Disadvantages:Can only be mounted in one direction

Current Uses:Original equipment on many domesticpassenger car, SUV and light truck applications

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These are high-pressure gas

shocks with only one tube, the

pressure tube. Inside the pressure

tube there are two pistons: adividing piston and a working

piston.

The pressure tube of the mono-

tube design is larger than a twin

tube design.

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The working piston and rod are very similar to the

twin tube shock design. The difference in actual

application is that a mono-tube shock absorber can be

mounted upside down or right side up and will workeither way.

A free-floating dividing piston travels in the lower

end of the pressure tube, separating the gas charge andthe oil.

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The area below the dividing piston is pressurized to

about 360 psi with nitrogen gas. This high gas

pressure helps support some of the vehicle's weight.

During operation, the dividing piston moves up and

down as the piston rod moves in and out of the shock

absorber, keeping the pressure tube full all times.

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Can be mounted upside down, reducing the unsprung

weight.

Mono-tube shocks are a significant component, along

with the spring, in supporting vehicle weight.

Disadvantages A dent in the pressure tube will destroy the unit.

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In the current scenario of automobile industry the

need for vehicles which provides smooth and

comfort ride is growing. Nitro shock absorbers

are designed to be ultimate in performance andcomfort. In a country like ours whose roads are not

up to world standards the need for automotive

components like nitro shocks are necessary. It

goes without saying that if the right choice is made

the improvements in vehicles ride and handling

can be shocking.

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