In article ,
wrote:

On Wed, 22 Dec 2004 22:03:44 -0500, "Bob Chilcoat"
wrote:

The Torsen track steering system is not the same as the Torsen differential,
which you are describing. The Torsen track steering system originally used
two conventional differentials, both hooked to the same output halfshafts.
One differential is driven by the engine output and its output is connected
to the left and right halfshafts in the normal way. The second differential
is driven by a "steering" motor, and its halfshafts are also connected to
the first differential's halfshafts, but with one key difference. On one
side, say the left side, the halfshafts are connect together with a chain
drive, or with gears through an idler gear, so that the two halfshafts turn
in the same direction. On the opposite side, say the right side, the two
halfshafts are connected together through a pair of gears, so that the two
halfshafts on that side turn in the opposite direction. If the steering
motor is not turning, the system of differentials and driven halfshafts
guarantee that the halfshafts of the first (engine-driven) differential turn
at exactly the same speed. If these halfshafts drive the left and right
tracks of a vehicle, the vehicle will go straight ahead. If, however, the
steering motor turns, the differential action of the two differentials will
cause the tracks to turn at different speeds, causing the vehicle to turn.
The faster the steering motor turns, the greater the differential speed and
the tighter the turning radius. The direction of turn is determined by the
direction the turning motor turns. If the engine and steering motor are
both turning at the same speed (assuming 1:1 ratios of the connecting
chain/gears) the tracks will turn at the same speed in the opposite
direction, and the vehicle will spin around its center. This is a much more
precise method of steering a tank or other tracked vehicle (or skid-steered
vehicle) than the conventional individual clutches and brakes. The original
version also was potentially much stronger and cheaper, since it used
standard, high volume truck parts. I see from the website that rcook5
posted that the system has now been intergrated so that steering apparently
no longer requires a separate motor. Looks very interesting.

Ah. Thanks for the explanation

Illustrations: http://www.gizmology.net/tracked.htm
The torsen track steering patent is basically a double differential
steering system with the steering input to two separate gears joined by
a chain instead of a shaft. Probably to get around a patent.
The units I've seen inside of some Cats are double differential, but
use a more convoluted arrangement of gears so two large ring gears are
side-by-side. Makes it more compact than what you see in these
pictures. Also gives the steering motor really good leverage, so it can
be smaller too. Can't find a picture of that, though.
BTW, found an interesting page during my search:
http://tinyurl.com/6t85h I like the half track near the bottom!

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