Neil Williams wrote:
On 2014-10-27 09:44:36 +0000, Neil Williams said:

On 2014-10-27 09:22:46 +0000, Roland Perry said:
That sounds fine if you aren't attempting to put any power on the road
through the 'spinning' wheel. I'm looking at the case where you
want about half the power that would otherwise be sent through
the rubber to remain.
Then you apply partial braking, the effect of which is to send it to
the other wheel (with a small loss via friction).

Imagine, say, you have a mains-pressure water tap with a Y piece added to
it. The Y piece is large enough to take the maximum flow from the tap on
either side (the cross-section of each side of the Y piece being the same
as or greater than that of the pipe feeding the tap). You place your
hand over one side of the Y piece completely - all the water goes out the
other way (this is the effect of braking one wheel fully with a
non-locked diff). You release the hand a bit and some water can flow out
of the "blocked" side - this is the effect of partially braking the
wheel. You will note that in neither case is significant force applied to your hand.

You partially block both sides - such that the "engine" is having to do
some work. In that case, there is force applied to both sides (on one
side the road, on the other side the balancing effect of the brakes),
though. This is what it would be like when the system applied partial
braking. I guess what you have is that the brake on the "spinning" side
is having to apply the same force as the wheel is applying to the road on
the other side, which as it can stop the vehicle it's probably more than capable of.

So I suppose a bit of both. But the fact is (a) it works and (b) it's
simpler and cheaper than locking or limited slip diffs.

I think it's more than than that: it's certainly simpler, cheaper and
lighter than a locking or limited slip diff, but I think it's better too,
as some limited amount of torque can be delivered through the low friction
wheel by carefully modulating or pulsing the braking force on it.

It also works when both wheels have very little friction: with a locking
diff, they'd probably both spin, but with ASC some small amount of traction
may be deliverable through one or both wheels.