[s-cars] Off topic - New Volvo S60 ? - Drat and double DRAT!

[Robert Myers]

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Thus respondeth the newly acclaimed Haldex Boy.  :-D

Bob

At 07:03 PM 1/5/2011, qshipq at aol.com wrote:
>*This message was transferred with a trial version of CommuniGate(r) Pro*
>
>
>  They aka'd me 'Torsen Boy' for a reason, I'm pretty nerdy about 
> how differentials and locking axle 4wd systems work, it's my thing 
> I guess, has been for many years.  I get really picky when 
> incorrect terms are used for a relatively simple concept.  It's 
> just plain incorrect to state that power is 50f/50r on ANY center 
> differential or locked axles with a single, sole and only 
> exception:  An open differential will ALWAYS distribute power 50/50 
> to two axles, regardless of variables, period.    Which means 
> specifically, no other differential or locked axles can, other than 
> in theory.  If all the variables are just right, a locked Haldex 
> can pass thru a 50f/50r power split state in theory.  Any other 
> moment in time or input variable, it's not.
>
>By theory it can I mean you go back to how a Haldex works, 
>specifically what's making it 'lock up'?  It's a combination of 
>variables that makes the 50/50 nary impossible in that locked up 
>state.  What you state in your 50f/50r is the commonly accepted way 
>to define an open differential, it's not really a property or 
>description of a Haldex.
>
>Technically, your description of a gen 1 quattro is not correct 
>either.  To the Haldex locked in a straight line (simple 
>example):  If torque follows weight transfer in a locked f/r axle 
>quattro in a straight line on a hi cf track, how exactly can you 
>ever be 'roughly equal to all wheels with infinite traction"?  There 
>is no such thing Cody, torque will only be equal if you are coasting 
>where Trg (torque ring gear) = 0.  As soon as you speed up or slow 
>down, torque follows weight transfer again.  Add Hap 670hp foot to 
>the floor or jam a set of Big Reds, torque to the axles is not 
>roughly equal, not even close.
>
>Cheers
>
>S 'torsen boy' J
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>-----Original Message-----
>From: John Cody Forbes <cody at 5000tq.com>
>To: qshipq at aol.com <qshipq at aol.com>
>Cc: t44tqtro at gmail.com <t44tqtro at gmail.com>; mtgadbois at aol.com 
><mtgadbois at aol.com>; pkrasusky at ups.com <pkrasusky at ups.com>; 
>s-car-list at audifans.com <s-car-list at audifans.com>
>Sent: Wed, Jan 5, 2011 1:07 pm
>Subject: Re: [s-cars] Off topic - New Volvo S60 ? - Drat and double DRAT!
>
>
>Talking about power/torque splits is always going to be confusing 
>because it depends on so many factors. In theory a gen1 quattro with 
>all the locks on CAN put 100% power to any single rear wheel, the 
>rears as a pair, the fronts as a pair, or 3 wheels as long as two of 
>them are in the rear. I fully understand what you are saying and 
>agree, but I chose to go with the commonly accepted way of conveying 
>the point. With infinite tire traction the power is going to be 
>roughly equally distributed between all of the wheels when the 
>Haldex is engaged. When disengaged the Haldex is basically as if you 
>removed the prop shaft. Except for oil friction there is zero force 
>being transmitted from the transmission to the rear diff. Thus is 
>why it is completely safe to tow a Haldex car with the rear axle on 
>the ground and the front lifted. According to VW you can even dyno a 
>Haldex car as if it was front wheel drive.
>
>
>My initial statement may have left out that when I said "clutch is 
>engaged" I meant the Haldex clutch pack, yes. The point stands that 
>when the Haldex clutches are fully engaged with no slip (slipping 
>the Haldex is a possibility, but pretty remote except for extreme 
>circumstances) the rear diff is tied solidly to the transmission 
>output shaft, and most lay persons will see that as being tied to the engine.
>
>-Cody (mobile)
>
>On Jan 5, 2011, at 12:12 PM, qshipq at aol.com wrote:
>
>
>
>
>  Cody
>"50/50 power split"  is the most common mis-statement about locked 
>axles, not oversimplified, just not correct on any level or 
>description of locked axles.  Not sure your question if you reread 
>your statement below.  The rear prop shaft is ALWAYS connected to 
>the transmission and is always spinning at the input of the Haldex 
>in the rear diff.  When the coupler is engaged there absolutely can 
>be slippage, my point to your simple exact statement "when the 
>clutch is engaged the rear wheels are completely locked to the 
>engine".  That's just not correct as written.  I suspect what you 
>meant to write was "When the Haldex is fully locked, the rear 
>differential is completely locked to the prop shaft 
>(transmission/input axle)".  To exactly what you wrote on the other 
>hand, when the clutch is engaged the rear wheels are not 'locked' to 
>anything. Specifically the rear axles can slip in relation to the 
>input shaft speed up to fully locked = any state less than a fully 
>locked up Haldex coupler.
>
>HTH
>
>SJ
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