RE: Torsen Tech

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

guys this is pissing me off.  i get 10 messages in my inbox this morning all
to do with the bloody torsen, and all of them saying basically the same
thing and propagating the same error.

and all of them copied to the mother list.

so what is the purpose of the torsen sub list?

apparently scott, dave (and others too probably) do not believe the audi
torsen paper when it states that the torsen locks axles speeds prior to the
bias ratio.  ok, so lets look at what the paper actually says...

audi says that "0.2% of forced slip occurs between the axles" with a torsen
in the prescribed turn.  your claim is that this means that the torsen is
allowing axle speed differences.  i say clearly it is not.  audi make that
very clear in the preceding paragraph when they say...

"for the acceleration manoeuvre with the torsen centre differential, it is
presupposed that the torque split limits are *not* exceeded, so that it is
*not* called on to compensate for *different* wheel speeds".

that makes it pretty clear, but to make sure the point is not missed (yeah
right) it is made even clearer in the next paragraph...

"on a high grip surface, the torque split limit is reached at a radius of
about 15 metres.  with tighter radii the differential *starts* to
accommodate different speeds of rotation at the two axles".

so, apparently now when engineers tell us that the axle speeds with a torsen
prior to the bias ratio are locked and they do this through measurements in
a controlled experiment, you just don't believe them because you know
better???

to make this even clearer, may i direct you to the imeche zexel torsen paper
which i posted last year.  page 5 presents the basic conditions of operation
of the torsen differential.  they are:

t(rg) = t(e) + t(i)  rg = ring gear (input torque), e= external axle,
i=internal axle (output shafts whatever).

and *one* of the following:

1) when delta(w)<>0 then t(max)/t(min) = torque bias ratio or
2) when delta(w)=0  then t(max)/t(min) < torque bias ratio.

where delta(w) is the relative wheel speed differences (i.e. axle speed
differences).

so the torsen **by definition** allows *no* output shaft speed differences
when it is *not* at the bias ratio (equation 2).  read the equations
again....

if you still don't accept this, check out the graphs in figure 6 on page 6.
there is a very large box with the letter "z" and a bloody big arrow
pointing to the part of the graph where there is no output shaft speed
difference in the torsen.  and the text says "we can display a remarkable
'z' point on the torque and speed difference curves.  it represents
operating conditions that are ****identical**** for ****any**** kind of
differential where for a defined lateral acceleration, delta(w)=0 and t(e) =
t(i).

read that again...

once again, the (audi) torsen locks the output shafts (no speed differences)
until it reaches the bias ratio, and then it allows output shaft speeds to
differentiate, while holding torque at the bias ratio levels.

hence, before the bias ratio, the torsen is producing the same torque
proportioning effects as the locker because both are allowing no output
shaft speed differentiation.  the only input to both devices at this point
is traction (both longitudinal and lateral grip and slip).

if you continue not to accept this point, i can see no point in furthering
this discussion.

and can we take this off the mother list (ego's permitting of course), and
then can we move on...

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

-----Original Message-----
From: owner-torsen@audifans.com [mailto:owner-torsen@audifans.com]On
Behalf Of QSHIPQ@aol.com
Sent: Thursday, 4 November 1999 02:28
To: torsen@audifans.com
Subject: Re: Torsen 201


In a message dated 11/3/99 2:24:51 AM Central Standard Time,
Dave.Eaton@clear.net.nz writes:

> yes there is confusion here.  the audi sae paper makes it clear that there
>  is *no* axle speed difference before the bias ratio, while freeman's
paper
>  (and his torsen model) implies that there is a small amount before full
>  biasing occurs.

The audi paper says the same thing.  Forced slip between axles at 62/38,
means there *is* axle speed differences before the BR

-----Original Message-----
From: owner-torsen@audifans.com [mailto:owner-torsen@audifans.com]On
Behalf Of QSHIPQ@aol.com
Sent: Thursday, 4 November 1999 09:00
To: torsen@audifans.com
Cc: quattro@audifans.com
Subject: RE: Torsen Tech


Dave L writes:
>...
>What does all this data mean? I can make the following
>conclusions:
>1) the torsen in the 80 quattro has different operating characteristics
>than the torsen in a humvee.
>2) the torsen does indeed allow wheel speed differences when
>operating within it's bias ratio. And the wheel speed differences
>follow the data points I presented above. It does not *lock* the
>output shafts together where they must rotate at the same speed.
>
>3) ??? Anyone else?
>-
>Dave Lawson

3)  Axle speed differences at a given torque bias ratio due to relative slip
angles (turning radius) don't affect the chassis dynamics of U or O while
turning.


Scott Justusson