RE: Torsen stuff

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

the torque bias ratio definition is "tbr = t(max)/t(min)" where t(max) is
the *maximum* torque able to be supported across the diff, and t(min) is the
*minimum* able to be supported.  sorry scott, but its a constant for a
particular limited slip diff design (e.g. torsen).  it is not a variable.
never a variable.  tbr for an open diff is 1.  by definition (a point you
now accept).  for a torsen, it depends upon the design.  usually for audi
applications 3:1, sometimes 4:1.

scott also states that "The torsen uses *two* inputs to proportion torque.
Relative slip angles and/or traction.  The locker doesn't use *any* inputs
to proportion torque, cuz it has no bias ratio.  A locker *can* support 100%
torque at either axle.  That's only a traction argument.  Explain how that
can be a slip angle argument? "

happy to help scott.  your misunderstandings of this fundamental point are
encapsulated neatly in this paragraph of yours.

the locker uses *exactly* the *same* set of inputs to apportion torque as
the torsen.  neither can tell the difference between traction and relative
slip angles.  why?  because with either differential, torque is apportioned
according to *tractive force* (torque reaction call it what you will), which
is just another way of saying relative slip.  with the scenario being a
torsen or locker quattro cornering hard, the f/r driveshafts are locked,
therefore there is more slip at the front than the rear which means more
tractive force at the rear which is where more torque gets sent.
progressively.  exactly the same scenario for the locker and the torsen.  by
design.  neither can do anything else.  they're both dumb.

btw, in both scenarios you can mess with the torque distribution by messing
with the front slip angles (by steering input, whatever).  once again, the
only difference between the torsen is on corner entry where the torsen
maintains a 50% torque distribution f/r, and the locker can't, and the fact
that with the torsen, torque distribution is eventually limited by the
torque bias ratio.  which the locker cant.

your misunderstanding (and others i might add) on this point is at such a
fundamental level that it negates your handling argument completely.
however, i do now understand why you make the claims you do, based on these
mis-understandings.

hth,
dave
'95 rs2
'90 ur-q
'89 mb 2.3-16

-----Original Message-----
Date: Tue, 19 Oct 1999 09:55:25 EDT
From: QSHIPQ@aol.com
Subject: RE:  Torsen stuff

Dave E writes:
>scott, a fundamental understanding of the torsen is required before you can
>understand how it works in a vehicle.  it's finally starting to become
clear
>where your misunderstandings are:

Ok, so when I walk thru this, you answer my overdue 885140 quiz?

>1) bias ratio.  you completely misunderstand this. the bias ratio is not a
>variable, it's a given for a particular differential design (set of gears).
>it is the maximum ratio of torque bias the diff will support between
shafts.
>hence your statement "bias ratio [sic] rear varies with every turn" is
plain
>wrong (and nonsensical).  bias ratio is a *constant*, not a variable as you
>state.  in a torsen, bias ratio is determined by the respective worm gear
">interfaces" which also govern the degree and rapidity of locking
behaviour.
>much like the setup of a vc where different silicones change the speed of
>locking.  anyway, i digress...

Please, one concept at a time.  Problem:  can we take a turn *at* a Bias
Ratio other than 75r/25f without *any* traction intervention.  You say BR is
a constant, technically correct for a traction input.  However, it's not a
constant with a slip angle input.

 >each
>differential uses the *same* inputs.  in other words, the *only* thing
which
>causes the torsen (and the locker) to proportion torque is the
*differences*
>between front and rear slip.  ok?

Whoa up Dave.  The torsen uses *two* inputs to proportion torque.  Relative
slip angles and/or traction.  The locker doesn't use *any* inputs to
proportion torque, cuz it has no bias ratio.  A locker *can* support 100%
torque at either axle.  That's only a traction argument.  Explain how that
can be a slip angle argument?

Scott Justusson