GeroDisc differential (long)

[Todd Young <tyoung@wamnet.com>]

I posted a comment last week about the 1999 Jeep Grand Cherokee
"Quadra-Trac" and how it uses a newer technology in limited slip
differentials called GeroDisc. Basically it is a set of clutches with a
gerotor pump that senses slip on an axle and then increases pressure in
the clutches to improve torque distribution. I promised a writeup on
GeroDisc to a few people so here it is, the following is an excerpt from
some literature they sent me a year or so ago:
----------------------------
WHAT IS GERODISC?
GERODISC is a hydro-mechanical limited slip and coupling device
incorporating a hydraulic pump section, a piston, and a clutch pack. It
has been designed as a "clean sheet" approach not tied to a prior
technology nor to a dedicated manufacturing process.

HOW DOES IT WORK?
ASHA's GERODISC limited slip differential/coupling is sensitive to, and
controls the delta rpm between the right and left wheels of a drive axle
and/or the front and rear axles of an All Wheel Drive or 4 wheel drive
vehicle.
In straight line motion, the drive wheels turn at the same speed with no
resultant GERODISC pump action. When a low delta speed occurs between
the drive wheels, such as negotiating a curve or parking maneuver, the
pump develops some nominal pressure and oil volume which is discharged
through an orifice created for this purpose.
When a predetermined higher delta rpm is encountered, such as occures
with a loss of traction at one wheel, the pump then operates at a rate
higher than the orifice is tuned to discharge. A simultaneous hydraulic
pressure is developed, which is subsequently applied to a piston and
associated clutch assembly, resulting in a very precisely controlled
transfer of torque. The torque transfer engagement occurs within 1/7 of
a revolution when the predetermined delta rpm is reached.
GERODISC does not lock up. As soon as GERODISC causes the delta rpm
between the two wheels to become more synchronous, pump pressure is
commensurately reduced to a point where the friction elements assume a
passive mode. Instead of jerking, or a harsh transitional engagement,
wheel spin is slowed and eliminated with a very powerful, fluid action.
GERODISC's hydraulic damping reduces the tendency to hunt between engage
and disengage modes.
----------------------------
This looks to me to be a very promising technology, I would love to put
one in the tranaxle of my front wheel drive 90S, not quite a Quattro,
but it would be nice in the snow we get here in Minnesota.

For more information:
ASHA CORPORATION
600 WARD DRIVE, SUITE C
SANTA BARBARA, CA 93111
805-683-2331

Sales & Marketing, USA:
ASHA SALES & MARKETING
Ken Black, VP Sales & Marketing
12218 Woodlands Court
Plymouth, MI
313-455-2331

I've got some e-mail addresses too, if you want them, respond to me
direct.
There is also a Europe address for you guys across the pond.
(Sorry for any typos.)

--
Todd Young              WAM!NET Inc.
tyoung@wamnet.com       6100 West 110th Street
612-886-5051            Bloomington, MN 55438-2664
800-585-1133 ext.5051   http://www.wamnet.com/