RE: differential sources

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

peter, there are a range of white papers available.  mainly from the sae,
but also from manufacturers themselves.

i chose to go down this track simply to attempt to understand the aspects of
these sorts of devices which were clearly little known (or contentious), ad
attempt to allow some science to enter the debate.  my theory is simply
that, provided manufacturers proprietary influences allow it, a search of
suitable sources would seek to illuminate what has been in the dark, and
attempt to add light to what was, errrr, dim.

primarily my investigation concentrated on the torsen.  i was concerned by
the early claims that the chocholek paper was the "bible" on the torsen, and
the lack of effective description in this paper on the use of a torsen in a
centre diff application meant that it was not intended for this, and that
ipso facto, the chocholek paper was it.  it clearly isn't.

i have found a number of very useful papers, which show clearly that the
torsen was intended as a centre differential.  there is a 1988 sae paper
form audi which described the manner in which a torsen acts in a turn (i'll
post more about this later), and a zexel paper which details centre diff
behaviour (albeit with the major emphasis on tcs systems).

as for posting papers, i can't really with those from the sae without a very
public breach of copyright.  with those from manufacturers i figure that
this issue does not exist, and so have made available to others the
torsen&tcs paper and the haldex paper.  the sae will happily send papers in
exchange for some money.  it's a very good service and works well...

from the sae (electronic copies available):
990740 "a modular hmmmv dynamic powertrain system model" - this contains a
complete torsen model for the humvee.
990743 "the influence of various 4wd driveline configurations on handling
and traction on low friction surfaces".
"traction and handling safety synergy of combined torsen diff and electronic
traction control" autotch '95 (i have scanned this one).

from the sae (electronic copies not avaiable):
885140 "the influence of a torsen centre differential on the handling of 4wd
vehicles"
950303 "a study on the effects of active yaw moment control"
952644 "a survey of awd traction control and systems strategies"
930670 "intelligent 4wd"
920611 "viscous couplings in 4WD vehicles"
861371 "mercedes 4matic"
940831 "analysis of traction control systems augmented by lsd's"
960718 "visco-lok: a speed-sensing lsd with high-torque progressive
engagement"
861369 "permanent and part-time 4wd and typical tractive force distribution"
940831 "analysis of traction control systems augmented by lsd's"
860386 "a viscous coupling in the drive train of an awd vehicle"
880698 "porsche dynamic slip control clutch"

other papers which are interesting from the asme (again photcopies only)
are:
"longitudional dynamics and performance assessment of awd vehicles", chen
"comparison of the dynamics of conventional and worm-gear differentials",
freeman
"4wd powertrain models for real-time simulation", freeman

happy reading.
dave
'95 rs2
'90 ur-q
'88 mb 2.3-16

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

Date: Mon, 4 Oct 1999 11:54:11 -0400
From: "Peter Berrevoets" <peterb@mysysltd.com>
Subject: RE: Diffs, sometimes opinion

As one intrigued, amused and entertained by this particular debate, I am
also interested in these "White Papers" and would certainly appreciate
receiving a copy if they could be made available. The URL would also be
fine.

Don't suppose Scott that you have videos of the spin behaviour - it should
be a very pronounced and easily visible progress if one knows what to look
for.  That would make for some very interesting viewing indeed.

I love engineering theory because when applied to the real world it is
almost always replicable.

Peter
1990 200TQ