[Land-speed] Car Spins

[NT788 at comcast.net]

Any steering input reacting to caster will load or unload one rear wheel.
Caster causes spins. There I've said it!

Jack








----- Original Message -----
From: "Skip Higginbotham" <saltrat at pahrump.com>
To: "Kirkwood" <saltfever at comcast.net>, "land-speed"
<land-speed at autox.team.net>
Sent: Friday, June 12, 2009 8:10:32 AM GMT -08:00 US/Canada Pacific
Subject: Re: [Land-speed] Car Spins

Well, in the absence of other speculation and no volunteers of data
supporting the effects of exhaust thrust nor thrust numbers, I would
suggest that exhaust thrust can push the front of a car in the
direction opposite the thrust. If the exhaust exit is in front of the
front wheels, most of it comes out on one side of the car and running
front wheel weight on the car is on the low side. If thrust values
are in the area of 50 lbs with a moment arm of, say 50 inches, then
2500 inch pounds of rotating torque would seem a lot for a car
"skimming along" the surface of the salt. And if it is not "a lot"
then it is, at least, some.
Having said that, I asked for help some time ago to see if anyone had
acquired any exhaust thrust numbers. I seem to remember that sometime
in the past, someone had measured exhaust thrust (zoomies) while
dynoing but the state of decrepitude of my memory prevents me from
having actual data and I don't have the skills necessary to calculate
it. My thought is that if such a side thrust condition exists,
coupled with an adequate moment arm, then a spin in the direction
opposite thrust is not only possible but, I think, likely. Consistent
spin tendencies in one direction would seem to support this
especially if the spin direction is opposite "normal".
Is there data (not unsupported opinions) to dispell this thought? If
there is, I would appreciate the opportunity to know the data so I
can stop thinking about this......

Thank you,
Skip





At 04:18 AM 6/12/2009, Kirkwood wrote:
>How about thrust angle? Does any car have perfect perpendicularity? B Without
>a laser how can you get closer than 1/16". Or, structural distortion from
>stress changing the thrust angle.
>
>
>
>Date: Wed, 10 Jun 2009 15:19:06 -0700, From: drmayf <drmayf at mayfco.com>
>
>. . . Are there reasons, theory, guesses, why a particular car would spin
>one way and consistently spin
>
>that direction?
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