RE: Torque and diffs and... Agggghh....

["Dave Eaton" <Dave.Eaton@clear.net.nz>]

scott, you still don't get the basics of differential operation.  and until
you do, you can't form a baseline understanding for anything else.  and
simply repeating your points just compounds your ignorance by emphasising
your reluctance to admit a mistake, and to move on - to learn in other
words.  other people don't seem to have any difficulty with these concepts,
and because its only you who seem to be struggling, i'll keep it brief...

on the elementary principles of differential operation, perhaps this
description from the chapter "awd dynamics" from jeff daniels book "car
suspensions at work" will help you (page 136).

on open differentials: "In the first place, we need to remind ourselves
that, baring limited slip devices, a conventional differential is merely an
ingenious mechanical device for allowing relative movement between its two
outputs (the driveshafts to the wheels) while ensuring a 50:50 split of its
input torque between them."

on the locking differentials: "In locking a differential, you destroy it's
ability to split torque evenly.  If the front end of the car will not accept
the torque because of the spinning wheel, then all the torque will be feed
back to the back end (or, of course, the other way round)."

with regards to the torsen, you don't understand it either.  the torsen
doesn't and can't transfer 100% of torque in the "wheel-in-the-air" scenario
we're discussing, as you assert.

put simply, the torsen uses internal friction to provide a "torque bias
ratio" greater than 1:1.  the internal friction (do i hear the quote "gear
jamming device?") *only* occurs when there is slip, and prevents the *total*
transfer of torque one way or the other.

the amount transferred (the bias ratio) is determined by the choice of gear
cuts and friction washers.  the reason for the design is because (as you
yourself asserted during the spider debate debacle), such an all-or-nothing
scenario is not always a good thing.  quite simply, this is one of the
primary reasons for the development of these sorts of "limited slip"
devices.

i am more than happy to provide more sources. perhaps, to save wob just
email me privately.

hth,
dave
'95 rs2
'90 ur-q
'61 mb fintail

-----Original Message-----

Date: Tue, 25 May 1999 08:37:37 EDT
From: QSHIPQ@aol.com
Subject: Torque and diffs and...  Agggghh....

dave writes
>nope scott, you just don't see it.  you're misunderstanding what torque is.
>i'll say this one more time and then give it up as a waste of time, and
>bandwidth...
Thanks.

Using this
same argument, torque from a torsen is capable of delivering 100% to the
rear
wheels too.  Not the definition of an LSD.  I think the confusion is in the
definition of Bias Ratio and primary vs secondary axles and traction v
torque.  With a locked diff, you aren't creating any additional torque,
until
that wheel lifts, in fact, you have one axle reducing engine Trg.  With a
locked diff on the ground 50% of the torque is on each axle, by definition.
Lift one *torque shift* is 50%.  Lift an open torque shift is 100%.  You are
missing some basics in your argument.

>open
>differentials reliably split 50% of the torque each way.  all the time.
No, if you take a turn in an open diff, where is the torque dave.  ALWAYS on
the faster drive wheel.  100% torque shift.  That's not true of a locker.
Take a turn, torque decreases as it shifts, in fact one wheel will apply
braking torque to make sure, right up to total wheel lift.  Remember, all
this *shift happens* before you lift a wheel.  Lift a wheel, all LSD act the
same in terms of avaible torque to the ground, all opens act the same too.
Again the basics are missing.