Jim,
Interesting discussion!
We may be quibbling over terminology here, but it is gears that steer the Sherman. The slowing down that happens to one side of the ingenious Cletrac diff by pulling back a tiller is caused by stopping (or as you suggest, slowing) the large steering/brake drum. This reduces the drive gear ratio to that track. The differential then does its thing and speeds up the other track.
On the subject of just slowing down the steering/brake drum, I get the impression the jury is against this type of operation, which makes sense to me. Braking of the drum should be firm and positive to minimize slippage and heat. This means the radius of a turn is dictated by the number of "short, smooth pulls" that are performed during a turn. Obviously, the tightest turn is when the brake is held firmly on throughout the turn.
It's not clear to me in your last post whether you are advocating light, slipping application of the brake for a large turn radius, or not?
By the way, when I first drove a Sherman, I thought there was something wrong with the steering. I since found out that a controlled diff gives a fixed turn radius regardless of speed, and the Sherman's turn radius (or was it circumference?) is around 70'! No wonder she's a pain to manoeuvre in tight spaces.
Malcolm
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