Join Date: Aug 2008
Location: Cassidy, British Columbia, Canada
Model: '84 1200 Int.
The whole idea behind a damper, (usually wrongly called a shock absorber) is to slow down the movement of the suspension. Metal springs, whether coil, leaf or torsion bars have a tendency to absorb energy (from a bump) and return¬*it with almost as much energy. Without some form of damping the spring would rebound past the original rest point and return again and again until friction in the system absorbed the energy imparted by the original bump. A sprung vehicle with no dampers can be forced down and released quickly and it will continue to bounce up and down till it comes to rest. When the wheel strikes a bump¬*it will bounce off the bump into the air till the energy in the spring forces it back down again where it will bounce back up again. Having the tire off the ground, bouncing isn't going to help us at all so we have dampers installed. Inside the damper is a¬*cylinder full of oil¬*and a piston connected to a rod. There are a series of small passageways through the piston that will allow it to move up and down but the oil from one side must flow through the passageways to get to the other side. Oil will not compress so for the piston to move it must¬*displace the oil. This is easy to do if it is done slowly, but to do it quickly takes more effort the faster it is done.
So, when the wheel hits that bump, the spring absorbs the energy, but when it rebounds back to it's normal state the damper tries to slow it down, and prevent it from bouncing around like a pogo stick. The compression damping (First impact) is often designed to be less than the rebound damping to give a smoother ride.
Air, in a compressed state has energy, and bounce (a basket ball)¬* but it does not develop a resonance the same way as a metal spring so will bounce much less each time it bounces. Compare the way a basketball bounces with the way a ruler held over the edge of a desk and flicked vibrates. Not a perfect analogy since a basketball bounces more from the stretch in the rubber and a ruler is of course hardwood, (at least when I went to school) but the idea is there. If you have ever dropped a valve spring on end onto a hard floor you know exactly what I mean, This is the reason over the road trucks are beginning to opt for air ride suspension.¬*
There are two kinds of fools: one says,"This is old, therefore it is good"; the other says,"This is new, therefore it is better."Ě William Ralf Inge
\'02 GASGAS Trials
\'56 Norton Dominator 600