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Active Suspension Questions

To: <land-speed@autox.team.net>
Subject: Active Suspension Questions
From: "DrMayf" <drmayf@teknett.com>
Date: Sun, 2 Dec 2001 12:50:41 -0800
Not to fan the flames, but this is an interesting thread. I have no feelings
one way or the other, but, the technicalities of active suspension intrigue
and interest me. I like fiddling around with numbers, but, I do not have the
necessary data to even start an analysis. At B'ville, there has been some
comment that pressure ridges cause the wheels to bump and loose traction.
Don't we drag the entire course to make it as smooth as possible? Can
someone quantify how long (far, feet) the tires are out of contact with the
salt? How big is the bump or depression (i.e. deep or high, inches) that the
(a) wheel has to follow? In thinking about this, and I am no expert like
some of you, I find that some suspension changes have to happen very
rapidly. Consider that a vehicle is going about 250 mph. This is about 367
ft per second. If the dip or bump that causes the tire to be out of contact
is 10 feet long then it is out of contact for only 27 milliseconds. Now that
is a long time to electronics, but a life time to get large structure
moving. So the wheel load sense detects that the tire is no longer in
contact and tells the brain to move the wheel back into contact. It applies
some sort of fluid to cause a pressure to move a cylinder or strut.But that
stuff has mass and it has inertia. So it takes a bit of time to get moving.
I am not sure how much time but some time. So as some time passes the car
has moved down the track some distance, hopefully not beyond the distance
that caused the wheel to be out of contact with the salt. Cause if it does,
it might be pushing the wheel down into contact when the ground is coming up
at the wheel: a large rebound force might ensue, might it not? Jeeze, would
this cause the front end of the car to leave position and become less
aerodynamic?  Any way this is interesting stuff. If anyone has any real data
or good objectiove observations about tire contact with the salt and the
speeds at which it may have occurred , please let me know off   line?

mayf, the red necked, ignorant desert rat in Pahrump.

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