NITRO SHOCK ABSORBERS ABSTRACT
In the present scenario of automobile industry manufacturers are trying to produce comfortable and safe vehicles veh icles which the consumers con sumers are looking for. A shock absorber is a damping element of the vehicle suspension, and its performance directly affects the comfortability, comfortability, dynamic load of the wheel and dynamic stroke of the suspension. The conventional type of shock absorbers has got g ot the main drawback that it causes foaming of the fluid at high speeds of operation. This results in a decrease of the damping forces and a loss of spring control. The gas filled shock absorbers are designed to reduce foaming of the oil and provide a smooth ride for a long period.
CONTENTS
Page No.
INTRO!"TION
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INTRODUCTION
%or a smooth and comfortable ride the disturbing forces should be eliminated or reduced considerably by using some devices. &hock absorbers are such devices which isolate the vibrations by absorbing some disturbing energy themselves. Of the many types telescopic shocks are widely used which has got the draw back that the flow of oil in the cylinder can cause foam of oil and air to form. These limit the optimum throughout of the flow in the valves. as shocks represent an advance over traditional shocks. Nitrogen filled gas shock absorbers are the results of years of e7tensive research and development with top flight shock design engineers. They are designed for both lowered and stock vehicles to provide shock absorbers that would out perform anything on the market today. Nitro shock absorbers are high 8uality, nitrogen filled shocks designed and gas charged specifically for each vehicle application. The addition of nitrogen under pressure limits the foaming effect and increases efficiency.
NEED FOR SHOCK S HOCK ABSORBERS
&prings alone cannot provide a satisfactorily smooth ride. Therefore an additional device called a 9shock absorber: is used with each spring. "onsider the ac tion of a coil spring. The spring is under an initial load provided by the weight of the vehicle. This gives the spring an original amount of compression. 2hen the wheel passes over a bump, the spring becomes further compressed. After the bump is passed the spring attempts to return to its original position. 'owever it over rides its original position and e7pands too much. This behaviour causes the vehicle frame to be thrown upward. 'aving e7panded too much, the spring attempts to compress that it will return to its original position; but in compressing it again overrides. In doing this the wheel may be raised clear of the road and the frame conse8uently drops. The result is an oscillating motion of the spring that causes the wheel to rebound or bounce up and down several times, after a bump is encountered. If, in the mean time, another bump is encountered, a second series of rebounding will be started. On a bumpy road, and particularly in rounding a curve, the oscillations might be so serious as to cause the driver to lose control of the vehicle.
A shock absorber is basically a hydraulic damping mechanism for controlling spring vibrations. It controls spring movements in both directions< when the spring is compressed and when it is e7tended, the amount of resistance needed in each direction is
determined by the type of vehicle, the type of suspension, the location of the shock absorber in the suspension system and the position in which it is mounted. &hock absorbers are a critical product that determines an automobile=s character not only by improving ride 8uality but also by functioning to control the attitude and stability of the automobile body.
PRINCIPLE OF OPERATION
The damping mechanism of a shock shoc k absorber is viscous damping. 3iscosity is is the property of a fluid by virtue of which it offers offers resistance to the motion of one layer over the ad>acent on. The main components co mponents of a viscous damper are cylinder, c ylinder, piston and viscous fluid. There is a clearance between the cylinder walls and the piston. 5ore the clearance more will be the velocity of the piston p iston in the viscous fluid and it will offer less value of viscous damping coefficient. The basic system is shown below. The damping force is opposite to the direction of velocity.
I?"-$ARN"$, II?0I&TON, III?3I&"O!& %-!I
The damping resistance depends on the pressure difference on the both sides of the piston in the viscous medium. The figure shown below shows the e7ample of free vibrations with viscous damping.
The e8uation of motion for the system can be written as m7 @ c7 @k7 1
Energy dissipation in is!o"s da#ping $
%or a vibratory body some amount of energy is dissipated because of damping. This energy dissipation can be per cycle. Rate of change of work 2 is called energy. %or a viscously damped system the force % is e7pressed as % c7 cd7Bdt, where 7 d7Bdt 2ork 2ork done 2 %7 Ccd7BdtD 7 The rate of change of work per cycle i.e. $nergy dissipated
-et us assume the simple harmonic motion of the t ype 7 AsinEt Cd7BdtD F EFAFcosFEt This shows that the energy dissipation per cycle is proportional to the s8uare of the amplitude of motion. The total energy of a vibrating system can be b e either ma7imum of its potential or kinetic energy. The ma7imum kinetic energy of the system can be written as $ C($D ma7 #B*m7Fma7
#B*mEFAF
SHOCK ABSORBER ACTION
&hock absorbers develop control or resistance b y forcing fluid through restricted passages. A cross?sectional view of a typical shock absorber is shown below. Its main components and working is also given below.
The inside parts of a shock absorber
The upper mounting is attached to a piston rod. The piston rod is attached to a piston and rebound valve assembly. A rebound chamber is located above the piston and a compression chamber below the piston. These chambers are full of hydraulic fluid. A compression intake valve is positioned in the bottom o f the cylinder and connected hydraulically to a reserve chamber also full of h ydraulic fluid. The lower mounting is attached to the cylinder tube in which the piston operates.
uring compression, the movement of the shock absorber causes the piston to move downward with respect to the cylinder tube, transferring fluid from the compression chamber to the rebound chamber. This This is accomplished by fluid moving through the outer piston hole and unseating the piston intake valve. uring rebound, the pressure in the compression co mpression chamber falls below that of the reserve chamber. As As a result, the compression valve will unseat and allow fluid to flow from the reserve chamber into the compression chamber. chambe r. At the same time, fluid in the rebound chamber will be transferred into the compression chamber through the inner piston holes and the rebound valve.
&pring &chematic iagram of the Interior of a &hock Absorber
FOR%S OF SUSPENSIONS AND T&PES OF SHOCK ABSORBERS
3arious 3arious types of shock absorbers are available in the market. Out of that the widely used types and their characteristics are given b elow. Type
0roduct
"haracteristics
The outer part of the double do uble tube is used as a gas ga s chamber, which is filled with low? pressure nitrogen gas. This type can provide stable damping force. ouble?tube Do"'(e)*is+'one ,%"(ti(in-
&eparation between oil and nitrogen gas by a free piston provides stable damping force, as well as high performance.
&ingle?tube
/H& 0AS %I--$ SHOCK ABSORBERS1
The rapid movement of the fluid between the chambers during the rebound and compression strokes can cause foaming of the fluid. % oaming is the mi7ing of free air and the shock fluid. 2hen foaming occurs, the shock develops a lag because the piston is moving through an air pocket that offers up resistance. The foaming results in a decrease of the damping forces and a loss of spring control. uring the movement of the piston rod, the fluid id forced through the valuing of the piston. 2hen the piston rod is moving 8uickly, the shock absorbers oil cannot get through the
valuing fast enough, which causes pressure p ressure increases in front of the piston and pressure decreases behind the piston. The result is foaming and a loss of shock absorber control. The need for a gas filled shock absorber arises here.
0AS FILLED SHOCK ABSORBER
The gas filed shock absorbers is designed to reduce the foaming of the oil. It uses a piston and oil chamber similar to other shock absorbers. The difference is that instead of a double tube with a reserve chamber, a dividing piston separates the oil chamber from the gas chamber. The oil chamber contains a special hydraulic oil and the gas chamber contains nitrogen at *+ times atmospheric pressure. The schematic diagram showing the inside parts of a gas filled shock absorber is shown below.
The inside parts of a gas?filled shock absorber. 2hen the piston rod is moved into the shock absorber, oil is displaced as in double tube principle. This oil displacement causes the dividing piston to press in the gas chamber, thus reducing it in siGe. 2ith 2ith the return of the piston rod the gas pressure returns the dividing piston to its starting position. p osition. 2henever the oil column is held at a static pressure of appro7imately *+ times atmospheric pressure, the pressure decreases behind, the working piston can not be high enough for the gas to e7it from the oil column. "onse8uently, the gas filled shock absorber operates without foaming.
T&PES OF 0AS FILLED FI LLED SHOCK ABSORBERS
T*in2 t"'e *it+ (o* press"re gas.
Sing(e) t"'e *it+ +ig+ press"re gas.
LO/ PRESSURE T/IN) TUBE SHOCKS
Twin? Twin? tube gas technology design retains the classical twin?tube while adding at the top of the reserve tube nitrogen under relatively low pressure *.+? + bars instead o f *+? H1 bars used in high pressure shock absorbers. This pressure pressure is sufficient to to radically improve the efficiency of the shock absorbers.
HI0H PRESSURE SIN0LE) TUBE SHOCKS
as shock absorbers operate in the same principle of movement of the piston in an oil filled tube but they contain co ntain at one end a small 8uantity of nitrogen under high pressure C*+ barsD. The gas is prevented from mi7ing with the the oil by a floating piston. 2hen the piston rod passes into the bod y and displaces oil, the oil compresses the nitrogen even further. The volume of gas changes playing the role as an e8ualiGation
tube. The permanent pressure e7erted on the oil by the gas guarantees an instantaneous response and the 8uieter piston valve operation. At the same time this constant pressure eliminates cavitations and foaming which could momentarily degrade the effectiveness of the shock absorber.
/ORKIN0
T/IN2 TUBE SHOCK ABSORBERS $ T+e #ain !o#ponents are$
Outer tube, also called reservoir tube
Inner tube, also called cylinder
0iston connected to a piston rod
)ottom valve, also called foot valve v alve
!pper and lower attachment
Ho* does it *or-1 B"#p Stro-e$
2hen the piston rod is pushed in oil flows without resistance from below the piston through the orifices and the non?return valve to the enlarged volume above the piston. &imultaneously, a 8uantity of oil is displaced by b y the volume of the rod entering the cylinder. This volume of oil is forced to flow through the bottom valve into the reservoir tube Cfilled with air C# barD or nitrogen gas C4? barDD. The resistance,encountered resistance,encountered by the oil passing through the footvalve, generates the bump damping.
Re'o"nd Stro-e$
2hen the piston rod is pulled out, the oil above the piston is pressuriGed and forced to flow through the piston. The resistance, encountered by the oil on passing through the piston, generates the rebound damping. &imultaneously, some oil flows back, without resistance, from the reservoir tube through the footvalve to the lower part of the cylinder to compensate for the volume of the piston rod emerging from the cylinder.
%ONO) TUBE SHOCK ABSORBERS $ T+e #ain !o#ponents are$
0ressure cylinder, also called housing
0iston rod connected to a piston rod
%loating piston, also called separating piston
0iston rod guide
!pper and lower attachment
Ho* does it *or-1 B"#p Stro-e$
!nlike the bi?tube damper, the mono?tube has no reservoir tube. &till, a possibility is needed to store the oil that is displaced by the rod when entering the cylinder. This is achieved by making the oil capacity of the cylinder adaptable. Therefore the cylinder is not completely filled with oil; the lower part contains CnitrogenD gas under *1?H1 bar. as and oil are separated by the floating piston. 2hen the piston rod is pushed in, the floating piston is also forced down the displacement of the piston rod, thus slightly slightly increasing pressure in both gas and oil section. Also, Also, the oil below the piston is forced to flow through the piston. The resistance encountered in this manner generates the bump damping.
Re'o"nd Stro-e$
2hen the piston rod is pulled out, the oil between piston and guide is forced to flow through the piston. The resistance encountered in this manner generates the rebound damping. At the same time, part of the piston rod will emerge from the cylinder and the free CfloatingD piston will move upwards.
AD3ANTA0ES OF NITRO SHOCKS Instantaneo"s response $
)ecause the high pressure eliminates aeration CfoamingD, action is always is
immediate.
The low mass of gas and the single tube further improves response time.
Better 4ade resistan!e $
&ince there is no outer o uter tube, cooling is much better which gives a drastic
reduction in fade. Thus more consistent handling and control.
Better d"ra'i(ity $
&ingle?tube construction also allows for a larger internal working area, reducing
stress and fatigue for better durability.
e "arbon=s monodisc valving system features a single moving part that
drastically reduces inertia and friction, to improve durability and performance.
)etter cooling of the mono tube design results in lower operating temperatures
and thus longer life.
No need 4or re)ad5"st#ent$
The viscosity of hydraulic fluid changes as temperature chang es. This may
because of climate, season CsummerBwinterD or heavy duty Cmotorway cruisingD. cruisingD. The high pressure gas compensates immediately and automatically for changes in viscosity. TIPS BEFORE %OUNTIN0
A stiff stiff suspension does not necessarily mean good handling. Often the contrary. If still a stiff suspension is needed it should come from the springs. The function of the shock
absorber is to dampen oscillations of the spring by co nverting energy to heat. o not use shock absorbers to obtain a stiff suspension. &hock absorbers and springs each have their own function. Respect those functions.
o not use new shocks to compensate for old and tired springs. The shocks will soon fail when the springs are bad. 2orn shocks do not only reduce safety and handling, they also increase the risk of having a broken spring as the spring is allowed to oscillate.
/+en to '"y s+o!-s1
&hock absorbers last a long time, but they tend to degrade slowly throughout their life. &o when is it time to replace themJ
In some cases, a seal will rupture. A shock covered in oil is a good indication that it has failed. The age?old test of bouncing on a fender is really only a rough guide as to whether the vehicle needs new shocks. !sually the slow degradation in shock absorberKs performance wonKt be noticed until it affects handling fairly dramatically. dramatically. epending on how rough the roads are, modern shocks can last 1?#11,111 miles, but remember that a shock with 61,111 miles on it wonKt perform as well as a new one.
/+i!+ ones are rig+t1
"hoosing which shocks to buy largely depends upon what kind of vehicle and the kind of driving. As with most automotive components, it is important the specific vehicle, since mismatched shocks can drastically affect handling and could even be dangerous. The best advice will probably come from a mechanic who is familiar with the vehicle.
CONCLUSION
In the current scenario of automobile industry the n eed for vehicles which provides smooth and comfort ride is growing. Nitro shock absorbers are d esigned to be ultimate in performance and comfort. 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.