Alltrac and 4WD

[Blaine Hufnagle]

I thought I'd add my $.02 worth to this discussion.

Here is an attempt at giving an explanation to the workings of a Viscous
coupling, which is at the heart of most, if not all, AllTrac systems.
A viscous coupling contains a box of some sort, usually a cylinder, that
houses the main components. Into each end go the driveshafts, and each shaft
has on the end of it a series of interleaved, slotted plates. Surrounding
these plates is a silicon based fluid, from which the viscous coupling derives
its name. This fluid is very heat sensitive, and heating causes it to solidify
into something about the consistency of frozen roof tar.
When the driveshafts into each end spin at the same rate, there is no speed
difference between the plates on each end, and therefore the fluid doesn't shea
(oops.. shear). (I forgot to mention that the normal fluid consistency is about that of warm roof tar... the high viscosity of the fluid is what enables it to effectively transfer drive power to the driveshafts.) When the two shafts turn
at a slightly different speed, such as when in a normal turn, there is minimal
shearing, and the fluid warms only slightly. This warming contributes little
to the hardening of the fluid, so the shafts are still able to turn at that
slightly different rate. However, when the shafts turn at greately different
rates, such as when you lose traction at one axle,(or wheel, in the case of
viscous coupling limited slip differentials, which do exist in production)
the fluid is sheared at a very high rate. this shearing produces a large amount of heat, and the fluid, being heat hardening, solidifies to the consistency of
frozen roof tar, or something of equal hardness. (concrete comes to mind...;) )Since the fluid is frozen stiff, the drive plates are no longer able to spin at
different rates, and therefore traction is applied. The fluid cools down at
a fairly slow rate, so traction is available for a short time. If there is still a traction loss, (ergo, you are mud bogging.. something not recommended in to do in a Honda... ;) ) the fluid will be kept shearing, and therefore hot, and
therfore hard, transferring power until it isn't needed any more. If you get
back to hard ground, and the shafts are once again spinning at an equal rate,
the fluid cools off and becomes semi-soft once again, ready to direct traction
again instantly if the need arises.

Hope this helps. :)

Ironman
a.k.a. Blaine Hufnagle

[split krill soup]

In rec.autos, n253by@tamunix (Blaine Hufnagle) writes:
|
| A viscous coupling contains a box of some sort, usually a cylinder, that
| houses the main components. Into each end go the driveshafts, and each
| shaft has on the end of it a series of interleaved, slotted plates.
| Surrounding these plates is a silicon based fluid, from which the viscous
| coupling derives its name. This fluid is very heat sensitive, and heating
| causes it to solidify into something about the consistency of frozen roof
| tar.

I seen it, as they say. A children's toy is being marketed under the
name "GUK" which seems to be precisely this stuff. It's kind of pink
(although I'm not sure if that's its natural color) and almost watery
when left alone. A salesperson was demonstrating the stuff, scooping
up handfuls of it, then pressing it together and rubbing it. Various
undistinguished shapes would appear and then melt again. It reminded [remound]
me of a computer art published in SIGgraph a while ago: an image with
a vase made of water rising out of an ocean. The vase had ripples on
it just like the ocean. The mandrel really didn't have anything much
to say about it, but he's pretty quiet most of the time anyway. Might
be neat to watch primates play with the pink stuff, but they'd mostly
get bored and try to eat the stuff. I wonder what it tastes like. A
bigger problem is what would happen in the warm stomach of a children
who ingested this stuff. The chemical properties might be harmless,
but something the consistency of frozen roof tar might present an odd
challenge to a children's digestive tract. If the substance could be
made into a coating of some sort it could be applied to the skin with
a brush. When the person attempts to run, he would be immobilized. A
penal institution might be interested in this. I'm not sure why they
call them penal institutions. Sounds kind of sexist to me. I really
have no joke here, I just like saying "penal." Freud never postulated
a penal retentive personality type. But you knew that already didn't
you. The pink GUK stuff might make a neat condom too. Rub some onto
your penal and it will solidify into frozen roof tar and this'll keep
the evil impregnating nasties out. Also, it will hold its shape, so
that intercourse can continue indefinitely as long as there is enough
friction and heat. A vicious coupling, as they say.

[Bear]

[stuff about GUK deleted]

For anybody who's interested. All GUK is is a mixture of
water, cornstarch and a coloring (food coloring works). It has exactly
the same look, feel, and behaviour. What this has to do with autos
is beyond me though...

Behram

[Blair P. Houghton]

In article <2752409...@orion.oac.uci.edu> bpa...@orion.oac.uci.edu (Bear) writes:
>For anybody who's interested. All GUK is is a mixture of
>water, cornstarch and a coloring (food coloring works). It has exactly
>the same look, feel, and behaviour. What this has to do with autos
>is beyond me though...

The man who invented the positive shear coefficient
is a greater man than even Otto Titzling.

--Blair
"Verner Fon Brlrown voot be prgrout
to know dat zilly puddy vaz
part uff de zpaze rgraze."