RE: VC vs AWD

[QSHIPQ@aol.com]

Dave writes:
>>whoa scott!  pull up!  think about what you have just said...

OK, but I get to smile in my beer.  You've missed this concept for a couple 
years.

>scott: "Toyotas system for example, uses an open diff center differential
>that transmits power equally to both front and rear driveshafts (effectively
>an open center diff awd).  When slip occurs, the VC coupling effectively
>locks the center and rear drivshafts (think of it being "around" the center
>diff)"

>>simple question here scott.  how can the centre differential distribute
>>power equally both front and rear *through* the vc, when slip has 
notoccurred?

Cuz it's an open (or fixed split) diff "until" slip occurs, then it's a VC 
locked diff.  This requires that you understand how a "VC Differential Lock" 
(accepted common term for the concept) works.  Remember, a VC center 
differential is not the same.  I'm all for white paper, I assert you might be 
just missing one or two :) 

>you should know that a vc does not start to lock *until* slip has occurred.

*Absolutely*, *positively* correct

>therefore, in the normal mode (equal traction, no turns), there is *no*
>slip, *no* vc lock, and ipso facto *no* drive through the vc.  that equals
>2wd.  when slip occurs (cornering for instance), then you have 4wd.

Incorrect.  I am NOT speaking of a VC center differential, you are above.  
You are missing a huge concept here, Dave.  I'm smiling at the thought.  
Let's forget the torsen for now, it's roiling water under the bridge.  You 
*now* also misunderstand the difference between a center Viscous Coupling 
diff and a center Viscous Coupling Differential Lock.

>it's still "full-time awd" as far as the marketers are concerned, just not 
as we
>know it.  ditto the haldex.  you just bought the marketing spin without
>thinking :-)
>you need to understand how a vc works.  because the vc is a friction device,
>it cannot sustain long periods of lock (hump) without damage (heat).
f>wiw, there is a comprehensive discussion of these issues in the paper "a vc
>in the drive train of an awd vehicle" sae #860386.

Again, you refer to a center VC and the Haldex (both part time 4wd), I'm not, 
 the above sae is not the *appropriate* 'white paper' for this concept.  It's 
not commonly considered for a center VC to be awd, it's part time 4wd, as 
your "white paper" above so states.  Humping refers to the VC plates actually 
touching each other (increasing the VC locking effectiveness, again under 
"extreme conditions"), not at all the concept I'm speaking of.  Major hint:  
How can a VC front or rear diff be open (50% of Trg), then be locked with 
slip?  Or do you propose that a front and/or rear VC diff is always a single 
drive wheel until slip, not a open diff?  The concept and design is 
'basically' the same.

Your friends at Toyota are looking for some historical credit here, misubishi 
just improved it.  That mitsu evo sticker you saw was correct as printed.

Mercy, *and* you know torsens?  We need more 'white paper' indeed.  
:)

Scott Justusson