List
oops
A correction to the feet/second at 400 mph should have been 586.667 ft/sec.
Glen
----- Original Message -----
From: "glen barrett" <speedtimer@charter.net>
To: "DrMayf" <drmayf@teknett.com>; <land-speed@autox.team.net>
Sent: Sunday, December 02, 2001 1:40 PM
Subject: Re: Active Suspension Questions
> 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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