> can u please send me something about the shock absorber in technical terms
&
> how it works?
> Ashish Rikhie
If you have ever used an old fashioned tire pump to inflate your bicycle
tire, you know how a shock absorber works. Take that tire pump and fill it
with oil, then take the outlet hose and connect it so that it pumps the oil
back into the top of the tube. Feel (or imagine) the resistance to motion
when you try to pump it - it will go down while you push on it, and stay
where you leave it when you quit pushing. A shock absorber is exactly the
same device, with a slight modification to the valving so that it operates
in either direction. By adjusting the flow restriction (either an orifice,
or in our example, the diameter of the hose) you can adjust the amount of
force needed to move the handle. The flow restriction orifice on a car may
be different in each direction - this is a design factor considered by the
suspension engineer.
As you can imagine, just like the air pump, they tend to get hot when used
vigorously - this makes the selection of oil important, and in some
sophisticated designs, the orifice changes with temperature also (firming up
the ride on rough surfaces for better control.)
Some luxury cars of the 30s (Packard, Pierce Arrow, Studebaker Land Cruiser)
had adjustable orifices, the first two were driver controlled - so you could
select the ride firmness for the conditions you expected to encounter. A
wonderful and very effective idea - too expensive though, I guess.
Enough? I could go on, if you wish.
Dick Benjamin
---------
It's my understanding that the term "shock absorber" is a misnomer. It
doesn't actually absorb the shock. That is the job of the suspension springs.
The "shock absorber" actually is a harmonic oscillation damper.
The springs absorb the "shock" of dropping, when nothing is underneath the
wheel (going over a pothole or a sudden dip in the road), or rising, when
the wheel has to suddenly rise over a bump or object in the road.
When the springs are set in motion, they oscillate back and forth. They
have a period of oscillation. They are harmonic in that respect.
Of course, after you have hit that bump and are past it, you don't want the
springs to continue oscillating harmonically. You want them to return to
relative inactivity. That's where the "shock absorber" comes in. It
dampens the oscillation, or, in other words, reduces the vibration of the
springs, quickly to a zero vibration. If they are faulty and not doing
their job, your car will be bouncing down the road as the springs continue
to vibrate. I have driven a car with no shocks and it was up and down like
a pogo stick.
One of the tests that many people do to test their shocks, is to push down
on the top, near the wheels or on the bumper. You can get the car bouncing
up and down with continued application of force. It's not hard to do,
especially if you are a big, heavy man.
When you stop doing it, the car should quickly stop bouncing up and
down. Do it in a sideways direction (just put your foot on the bumper and
push it sideways a couple of times with the right timing) and you'll notice
that it doesn't stop as fast as the up and down bounce. That is because
the shock absorbers are not coming into play directly, as they do during up
and down movement.
You don't want to totally eliminate the oscillation because you want the
wheel to resume its original position in relation to the rest of the
car. When you pass the bump, you do want the wheel to go back down to the
regular level of the road, with minimum movement of the body of the
car. You do want the oscillation eliminated soon, however, or it will be
transmitted to the body of the car.
Dick's posting above explains how the shock absorber does its job as a
harmonic oscillation damper. My follow-up is my understanding of how the
shock absorber function fits in with the suspension.
Alan Harper
64 Mercury 3/4 ton flatbed
69 Dodge D100 pickup
76 Chrysler New Yorker Brougham
78 Chrysler New Yorker Brougham, St. Regis
92 Ford T-Bird
alan__harper@xxxxxxxxx
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