[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Just say ahhh.... No thanks

>scott, you still don't get the basics of differential operation.  and until
>you do, you can't form a baseline understanding for anything else.  and
>simply repeating your points just compounds your ignorance by emphasising
>your reluctance to admit a mistake, and to move on - to learn in other
>words.  other people don't seem to have any difficulty with these concepts,
>and because its only you who seem to be struggling, i'll keep it brief...

Now you are not being civil anymore, as I suspected earlier, time to drop 
Dave.  The confusion created has to do with Trg, primary axles, and secondary 
axles, traction and torque.  Mostly created by you, with all due respect.  
You are interchanging some terminology that indicates all of the above are 
equal.  They are not.

>on open differentials: "In the first place, we need to remind ourselves
>that, baring limited slip devices, a conventional differential is merely an
>ingenious mechanical device for allowing relative movement between its two
>outputs (the driveshafts to the wheels) while ensuring a 50:50 split of its
>input torque between them."

>on the locking differentials: "In locking a differential, you destroy it's
>ability to split torque evenly.  If the front end of the car will not accept
>the torque because of the spinning wheel, then all the torque will be feed
>back to the back end (or, of course, the other way round)."
>with regards to the torsen, you don't understand it either.  the torsen
>doesn't and can't transfer 100% of torque in the "wheel-in-the-air" scenario
>we're discussing, as you assert.
>put simply, the torsen uses internal friction to provide a "torque bias
>ratio" greater than 1:1.  the internal friction (do i hear the quote "gear
>jamming device?") *only* occurs when there is slip, and prevents the *total*
>transfer of torque one way or the other.

You miss the point of your own argument.  If 1 wheel is in the air 100% of 
torque is at the rear wheels.  Total Trg decreases due to the BR, doesn't 
change the issue.  You are getting confused in not being consistent in your 
own terminology.

Look at it this way, after a wheel lifts, in a LSD 100% of Trg is at the 
traction wheel, whatever the BR.  The Trg is 100% with a locker, it's 
somewhat less with a torsen, it's almost 0 with an open.  Before the wheel 
lifts, we have a torsen that shifts torque up to BR, we have a locker that 
shifts no torque, in fact Trg is decreasing immediately due to the linked 
mechanical braking of the wheel accelerating due to slip angle.  An open 
shifts torque linearly to Engine Trg, because, to quote Chocholek:

"The drive axles associated with an open differential are interconnected by a 
bevel "gear set designed to divide equal torque between drive axles. This 
arrangement will "not support any substantial torque difference between the 
drive axles and, as a "consequence, offers very little resistance to 
differentiation. Virtually any attempt to "deliver an increased amount of 
torque to one of the drive axles will result in rotation "of the gear set as 
evidenced by differential rotation between drive axles. For "example, if one 
of the drive wheels should lose traction, any attempt to deliver "additional 
torque to the other drive wheel having better traction will result in 
"undesirable 'spin up' of the wheel having poorer traction"

So in summary, an open reduces Trg linearly to torque shift, a torsen shifts 
up to the BR before reduction of Trg, and a locker shifts no torque until 
lifted, in fact it reduces Trg with ANY attempt at differentiation. Once 
lifted (or no traction) 100% of Trg is at the opposing driveshaft.  ALL other 
times it is split 50/50 by definition.  It will brake and drag wheels around 
a corner to assure this.  A locker can't support ANY differentiation.  
Neither can an open.  Two different outcomes.

>the amount transferred (the bias ratio) is determined by the choice of gear
>cuts and friction washers.  the reason for the design is because (as you
>yourself asserted during the spider debate debacle), such an all-or-nothing
>>scenario is not always a good thing.  quite simply, this is one of the
>primary reasons for the development of these sorts of "limited slip"devices.
>i am more than happy to provide more sources. perhaps, to save wob just
>email me privately.

I appreciate ALL you help in this Davey.  I'll take a pass on your offer, I 
not the one unclear as to traction, torque, Trg, and differentiation.

I suppose we could just drop it.  I'm seeing very educated guys trying to 
explain torque, not doing such a great job.

Scott Justusson