[torsen] Re: Haldex Riddle

Keith Maddock Keith.Maddock at trw.com
Wed Nov 20 08:21:30 EST 2002

I'm missing the riddle here.

The difference between VC and a pump-style LSC is simple.  A VC can't lock.

The VC has a maximum clamping force of how much torque the fluid can transfer before it just starts getting hot and overheats.  A VC, to my knowledge, can never lock. Up to a certain point, proportional speed difference between the two sides will increase the coupling force.  Additional speed difference past that point will just continue to slip the coupling and generate heat.  BBQ anyone?

A pump-style LSC wil continue increasing hydraulic pressure as long as there is a speed difference.  The more hydraulic pressure there is, the higher the coupling clutch force.  Eventually it will lock the clutch and/or activate the pressure releif-function.  If you have a weak capacity clutch, the pump-style LSC will get stuck just the same as the VC. (A problem with the LSC in the Ass-tek, I have heard)

The hydraulic pressure is a function of the ABS(AlphaFront-AlphaRear)... 

Its the exact same concept when the pump-style LSC is used in a differential. It doesn't matter if the Left side velocity is higher or the Right side velocity is higher.

Take a look at 
As long as one part is spinning faster than the other (green or blue), the pump will start pumping.

What have I said that would indicate that I am missing this concept?


Keith Maddock, TRW Automotive,  Koblenz, Germany
Slip Control Systems, Systems Design, Traction Control
+49 (0)261/ 895 2474     -    -    keith.maddock at trw.com

>>> <QSHIPQ at aol.com> 13:44:05 20.11.2002 >>>
How does one fool a speed VC into digging a hole?

Try driving it in sand.

Curiously, Haldex claims in this scenario they can *increase* and hold 
clamping force (volvo uses this claim in their XC comparos).  Now Haldex also 
claims "Haldex is activated whether the input shaft is rotating faster or 
slower than the ouput shaft".  

You guys are missing something.


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