Mayf.
All good points. The course is drug and as flat as we can get it with out
causing any further damage to the surface. The pressure ridges are
everywhere and run different angles, at different distances through out the
salt flats. They come in all sizes, widths and elevations. When dragging the
course they are flattened and some times a depression if left. We do
everything we can to back fill and compact with a slurry of wet salt weeks
prior to the meets.
When Mickey Thompson ran the two streamliners( the twin & the 4engine) there
was a lot of concern regarding the vehicles and solid suspension. Mickey's
remarks to the SCTA safety personnel was at the speeds he plans on going the
rigid chassis will not allow the wheels to react fast to drop into a
depression. It would be across it, say at 400 mph that's 352 ft/sec down the
course.
Now, the Noble - Green jet car did have a very expensive and Hi-tech
hydraulic active suspension. This was covered in one of the trade
magazines,Design news or Machine Design. Somewhere in my files I have the
article. Another thing was the belly pan was full of holes to let the air
under the car go somewhere and was exhausted through ducting in the back of
the car.
I don't know if a lot of the hot rodders are willing to go to this extreme.
The costs and design efforts for the average
lakes (Bonneville) racer I don't think would be in their budgets.
I followed and read everything I could on the Noble car as well as
Breedloves. The daily tech articles put out by the Noble camp was just plane
fantastic. They documented and published everything it took to achieve heir
goals.I copied everything I could find during the building to the breaking
of the sound barrier.
Glen
----- Original Message -----
From: "DrMayf" <drmayf@teknett.com>
To: <land-speed@autox.team.net>
Sent: Sunday, December 02, 2001 12:50 PM
Subject: Active Suspension Questions
> 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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