Hi Bob, and Listers,
You said:
>Dan's torque arm, on the other hand, transfers weight to the front
during
>braking which increases dive. If you want to see what I mean, try
dumping
>the clutch in reverse! I would like to see a comparison of stopping
>distance with and without the torque arm. Of course, with the Tiger's
drum
IMHO, I disagree with your analysis. Since the forward end of the torque
arm is a fore/aft pivot (even if it's a sliding, cylindrical bushing),
it can't torque the body. If I consider the body to be a rigid thing (in
the fore/aft plane, anyway), I can look at it in the following way: The
brakes apply a torque to the rear axle, which is the same no matter how
the rear axle is suspended. An equal and opposite torque is generated in
the body, because there is no actual body or rear axle rotation
generated as a result of applying the brakes (hopefully, anyway), other
than a few degrees of dive. This reaction, again, is the same for any
system of rear axle location.
So why all the fuss about torque arms, traction masters, etc.?
One big reason is that as far as axle torque is concerned, the rear leaf
springs are basically undamped, so if we apply a large torque input
(braking or acceleration) we can wind up the springs, into an S shape,
and if we then exceed the traction limit, the spring snaps back and can
be made to oscillate until you let off the offending pedal, causing the
dreaded 'axle tramp' we all know and love. This effect is worse if the
car has been lowered by using spacer blocks between the axle and the
spring.
The torque arm is mounted rigidly to the axle (in the intended
direction, anyway). When a braking torque is applied to the rear axle,
it applies a downward load to the forward end of the arm. If I consider
that end of the arm mounted to the body with a pivot, then the rear
axle, on the other end of the arm, will move upward towards the body,
until the spring resistance is equal to the vertical load generated by
the braking torque. In effect, braking torque compresses the rear
suspension. So I say that the torque arm acts as an anti-dive device
under braking. Under acceleration, the torque arm has the effect of
extending the rear suspension, helping to plant the rear end, and
increasing the available traction.
Comments?
Theo
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