Naturally, as soon as I finished writing this explanation I found this
site on Google:
http://www.rmahc.com/differentials.html
-----Original Message-----
From: Bill Babcock
Sent: Thursday, February 07, 2002 11:16 AM
To: 'Barr, Scott'
Cc: 'fot@autox.team.net'
Subject: RE: Rear Wheel lift
It's fairly simple. Quaife diffs use the rather strange characteristic of
a worm gear that while it's easy for a drive gear to turn the worm, it's
very hard for the worm to turn the drive gear. So when a wheel loses
traction with a quaife the amount of torque sent uselessly to the freely
spinning gear is limited by the friction of the drive forces working
essentially backwards through the worm gear (the gear continues to rotate
in the forward direction, but some of the force is applied to the drive
gear by the differential motion of the two output shafts which are coupled
to the worm gear sets). Not all the force is applied to the wheel that
still has traction, but some of it is wasted in spin.
A clutch-type diff works kind of like a Detroit locker, only more gently.
The differential speed of the gearsets, or more accurately, the
differential torque applied to the two output shafts, actuates the clutch,
usually by a pin sliding up a ramp against spring pressure, to lock the
diff. The action is more positive since it directly locks the
differential, making it in effect a solid axle, rather than biasing the
torque so that some of it is still applied to the driving wheel. You can
see the difference easily in driving the car. With a Quaife, turning into
a turn tightly enough to unweight the inside wheel causes the motor to rev
a little as the wheel spins, but the car still drives into the corner.
With a clutch diff the increase in revs is imperceptible, and the drive
into the corner is stronger since no torque is wasted on spinning the
wheel.
A locker does the same thing, but it uses a ratchet to completely lock the
diff, suddenly (BANG!). The differential torque turns against the ratchet
and the diff locks.
You can tell exactly how a locker works by looking at it. Likewise a
clutch-type diff. When you look at a quaife you think "what the hell does
this do?", but they are very nice for their intended use.
-----Original Message-----
From: Barr, Scott [mailto:sbarr@mccarty-law.com]
Sent: Thursday, February 07, 2002 10:24 AM
To: Bill Babcock
Subject: RE: Rear Wheel lift
<<Quaife's are torque-biasing diffs, ATX's are true limited slips>>
I still haven't taken apart enough diffs to know the difference, even
theoretically. Would you mind explaining the difference?
Scott Barr
sbarr@mccarty-law.com <mailto:sbarr@mccarty-law.com>
(920) 766-4693
(920) 766-4756 (fax)
-----Original Message-----
From: Bill Babcock [mailto:BillB@bnj.com]
Sent: Wednesday, February 06, 2002 7:13 PM
To: 'Joe Curry'
Cc: 'fot@autox.team.net'
Subject: RE: Rear Wheel lift
Replace your Quaife with an ATX and you won't care so much if you lift a
wheel. Quaife's are torque-biasing diffs, ATX's are true limited slips.
I think the main reason LBCs lift wheels is that the roll center of the
front is different than the roll center of the back. Real suspension gurus
might be shaking their heads at such twaddle, but I think it's true.
Usually that means bringing the front roll center up, though with your
rotoflex rear suspension you might be able to bring the rear lower. I
don't know much about them. Theoretically a heavier rear sway bar will
force the outside wheel down, but in practice, that much force will
increase the rear end steer, make the car too tight and will probably
screw up the turn in. Not what you have in mind for autoX.
You could also get a passenger to hang their ass out like a sidehack.
-----Original Message-----
From: Joe Curry [mailto:spitlist@gte.net]
Sent: Wednesday, February 06, 2002 2:25 PM
To: Friends of Triumph
Subject: Rear Wheel lift
Hey Guys and Gals,
I have been having a ball figuring out the limits of Tiny Tim (the
Autocross Spit) now that I have the S2000 engine performing as it is
supposed to.
My most immediate problem is that on a hard corner, I am lifting one of
the rear wheels.
Bear in mind that I have a Rotoflex rear suspension and a Quaife LSD.
What recommendations do you have about how to keep all four tires firmly
planted on the pavement?
I eagerly anticipate all the learned replies!
Regards,
Joe (C)
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