mayf what kind of force are we talking about?
What force, in pounds, would it take to move a mass of 300 pounds
.5 inch on 10 ms? Accelerate for .25" decelerate for .25".
Using current in a coil suspended between ceramic magnets, my hard drive
does it in 8 ms max. Of course the mass is only a few grams.
This is an example of very fast accurate positioning technology currently
available.
Of course you've already pointed out the scaling problem. I've seen
some impressive hydraulics at work, 200 lb. moved 10" in 80-90 ms
using 6,600 psi. (very dangerous stuff)
This thread is fun!
Bryan
DrMayf wrote:
>
> 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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