RE:RE: Spider Bite

[QSHIPQ@aol.com]

Mike writes:
>Finally, I think we need to determine the severity of the spider bite. In
>Phil's case, it was an utter and absolute loss of control and end for end
>spin into the countryside.I honestly think he could do that again even in
>his now-properly aligned car if he simply took the exact same turn 20%
>faster than he does now. The impression I'm getting is that "spider bite"
>is a FAILURE MODE - we have simply pushed the limits of the device too far,
>and this is how it reacts.

Careful here, we could push the limit based on driver judgement of turn in 
only (that could just be the percieved cf vs actual).  The severity of the 
spider bite, depends on all of the variables listed in 885140 (actually I 
think Dave E listed them all out in a former post).  I can say I've been 
bitten mildly, and severely, and can't isolate for anyone *all* the variables 
involved.  My most severe was in a 90q in the snow with a very mild steering 
input, in a high radius turn, at high speed.  The term 'significance' of 
variables enters the mind.

>What is deceptive to us and scary to us is that the infamous Torsen seems
>to behave itself very well and DOES give us the Quattro Advantage, UNTIL we
>push it just too far, at which point it gets spectacularly confused and
>blows the whole show, all at once, suddenly, big time.Best Regards

Mike come to steamboat and understand the torsen quattro advantage in a low 
cf environment, it gives you a different perspective of "behaving itself".  
Cf plays a major role, I watched Dave L try to control his torsen wagon 
there, and it was a scarey sight (with or without his rear locker mod), in 
fact, in the middle of one of his 'bites' I slid thru the inside of the turn 
with my locker.  It was quite a show!

Your post is interesting Mike.  I argue, what we are talking about isn't 90% 
or more, it's 70% and more, IME.  Look at it this way, the inputs to the 
torsen become most significant at a really high cf, and a really low one.  On 
a high cf turn, you tend to push the car closer to the limit of adhesion, 
*and* small amounts of tire slip produces torque shift.  On a low cf turn, 
the car is more sensitive to any U and O chassis dynamics.  So is Trg.  
Again, I only share my experience, that one isn't *necessarily* at the limit, 
in fact, many of the variables would indicate, you don't have to be close.

The other post from CJ Miller, indicates that the torsen is looking for 
equilibrium.  *Maybe* but not necessarily, only in a tractive sense, slip 
angle would indicate a torsen exactly isn't looking for equilibrium (or as 
you turned, torque would shift forward based on turning radius).  If a torsen 
is fooled by slip angle, that is a non equilibrium state (O) until the 
traction variable exceeds the slip angle one in terms of axle slip.  Then you 
could claim it seeks equilibrium (U), but we know from lockers that 50f/50r 
is U, so all we need is the torsen to work *towards* equilibrium (also a 
nature of the device), but address that in terms of chassis dynamics.  THEN, 
if you haven't changed the steering angle (or even if you have, up to 
straight ahead -oxymoron while turning), the torsen is forced back to a non 
equilibrium state, do to turning radius = O.  This can happen several times 
in a turn. 

I'm happy to accept all thinking as to who's btdt and what they *think* the 
reason was.  My only *claim*, is that in terms of chassis dynamics while 
turning, the spider bite *can* happen.  Isolating of the variables is a 
daunting task, and hardly my interest, but IME I'm careful with a torsen in a 
low cf environment.  My only interest really is, what does the resulting 
torque bias do to the chassis dynamics while turning in terms of U or O?  Get 
cf low enough and/or trg high enough, the "not likely" becomes the reality of 
an absolute traction device in a turn.

HTH

Scott Justusson