Re: Wheelspin

["Jeremy R. King" <jrking@ces.clemson.edu>]

I put the book references in just for fun.  You're probably one of the
very few on this list that know what these are.  I'm still convinced
that "slip" and "wheelspin" are very different.  "Slip" is the
deformation of the tire contact patch - for straight line acceleration,
it would be the bunching up of neighboring points along the patch.  When
an accelerating torque is applied, the points on the contact patch bunch
up creating an accelerating force on the tire (think of a slingshot -
the tire stretches just after the contact patch making a forward force
on the patch).  In ANY case, when the tire starts to spin traction goes
down.  I don't care how much EXPERIENCE you've had, these are proven
engineering concepts with real world application.  How many top fuel
dragsters do you see lightin' up the tires off the line to get better
traction?  No, they actually reduce pressure in the tires to make more
of the contact patch stay on the pavement longer (read NO WHEELSPIN) to
get max acceleration.  If in fact the tires do start to spin, traction
goes down and they have to lift.  Seems like they oughtta know from
their real world experience.  

No hard feelings, just hard facts.  I don't disagree that you get better
acceleration in a roadcar by spinning the tires a little off the line -
I'd be an idiot to argue with this fact.  But to say that traction is
increased with "wheelspin" is not right.  "Slip", I will agree,
increases traction.  "Slip" is not equal to "wheelspin".

Jeremy

STEADIRIC@aol.com wrote:
> 
> >If you have questions on any of this, refer to "Race Car Vehicle
> >Dynamics" by Milliken and Milliken or "How to Make Your Car Handle" by
> >Fred Puhn or anything by Carrol Smith.
> >
> >In all my reading, I've never noticed the term slip angle equated with
> >wheelspin.  All wheelspin does is allow your engine to reach it's torque
> >band more quickly.  Traction actually goes down.
> 
> Not to get into a pissing contest but you've got a ways to go
> here......... In all my real world experience (And I've got lot's) Cf
> goes up with slip..... To a point.  Be it wheel spin or tire slip (Same
> thing just two ways of saying it...) For most street tires they need a
> 10% Delta V to get max Cf. For more detail get the SAE paper written by
> Harvey and Ressler.
> 
> Eric Fletcher
> Suspension Engineer for:
> Rossi Race Team
> Team No Fear
> DS Racing (Trans-Am cars)
> Etc, etc  I have also done most of those teams test driving....

-- 
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Jeremy R. King  Clemson University, S Carolina, USA
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