> >         3.  Maximum traction isn't developed with no wheelspin,
> >         anyway; the most acceleration is developed when the tires
> >         are slightly slipping
> >
> >     -Andy
> >
>         Correct, it is around 6 to 10% slippage
>
>         Dennis
>

Just wondering - is this a known formula / observed rule in drag
racing or can it be applied more generally? A little off topic now but
I have often pondered this and tried to figure out my own
explanations, thinking how a micro based traction control system
might tackle the problem of fast starts for ant kind of race car.

Though a slightly different situation, my experience is with two
stroke 250cc moto-x bikes that develop 45-50hp. The formula for a
fast start on soft dirt / grass surface is a high gear, say 3rd or 4th,
and full throttle. As land speed increases the revs drop back
slightly to that magical max engine torque / max traction magic
value and for a while acceleration greatly exceeds that possible
with zero slippage. (My brother and I have verified this by extensive
side by side standing start tests on a grass air strip!) My guess is
best acceleration occurs somewhere around 20%-50% slippage
shortly after the start for as long the engine torque can keep up this
condition.

Similar technique works when stuck in mud at the bottom of a
slippery gully. Put the bike in first gear and it wont budge no matter
what the revs, do the 3rd/4th gear full noise trick and it's amazing
how traction develops.

Probably quite different to the drag car situation but I'm still
interested in the laws at work here. Oh yeah, to get back on topic
you could super glue DIP packaged PIC16F84's, with legs pointing
up, to the drag track for more traction. You'll need around 35000 of
them for two rows 0.25 mile long, but the good part is you don't
need to program them.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile: 025 334 069
eMail:  brent.brown@clear.net.nz