[torsen] Re: EDL vs ELD explained.... Re: [s-cars] Exception ally lame q...

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Bob:
Comments inserted:
In a message dated 9/10/02 12:50:58 PM Central Daylight Time,
rpastore at animalfeeds.com writes:


>Scott:
>Isn't this "speed difference" more of a theoretical than an actual? Wouldn't
>the reality
>measured in a fraction or maybe a few degrees of shaft rotation, in essence
>being the
>combined lash in the drivetrain and within the torsen itself?

I believe Dave Lawson actually came up with an actual number of degrees in a
given scenario.  That said, it's so small that a torsen on the same axle (F
or R for example) couldn't take a turn without allocating torque.  In a
center application, you can actually hear the grinding of the torsen as you
force it to accept differing driveshaft SPEEDS.  The above statement sounds
like you believe a torsen can't accept a speed differential between axles.
It can, but it must be AT the bias ratio first.  So, lets say you take your S
car (78-22-78 torque allocation).  As you apply the gas, turn the wheel to
full lock.  The torsen will allocate 78% of the torque to the rear wheels, 22
f, then it will "open" and allow speed differential.  It's not at all happy
about it (hear the grinding, feel the lurching), but it will.

>Also, not exactly on topic, but related, somewhere in my archive I have an
>email from Mr. Hans
>Kluge, famous quattro trans builder/ex-development engineer ??, where he
>seems  to  attribute
>the 01E gear problems to a hammering that occurs because of the
>rocking-like-cycle of thrust
>loading on on one face of a gear then the other as the torsen hunts through
>the lash as it does
>its job of allocating torque.  I think it went on to say that it was easy to
>design a gear for
>a thrust load in one direction or another, but very dificult to design for
>the loads in both
>directions that the Torsen causes.

Makes perfect sense to me.  The thrust washers are brass, not a high torque
material.  The thrust gears are widely spaced and ramping up and down them
causes great stress (heat and fatigue) on the torsen pieces parts.  Many of
the guys that race them, find that they break easily.  The offroad truck boys
won't touch torsens because they can't handle large torque loading (the
airborn thing gets em every time).  Some of the early testing with the rally
cars showed that the torsen didn't handle jumps really well.  The same
problem is happening with the race cars, lift a wheel in a turn, put it back
down.  Reducing the bias ratio can help, but also screws up the use of
ABS/EDL, the main reason audi picked it up to begin with.

Remember too, that the torque splits are to all applied torque, that's engine
braking torque as well as accleration torque.

All that said, it would appear that the haldex is much better suited for
massive torque allocations, IMS the limit was big block kinda high.

HTH

SJ