Thanks for all the info on the tank drive! I was aware of that style (central motor with universal joints) but never heard that term.
It would seem to me, that with the way it's implemented in the 3rd Rail models, the drive shaft would need to be able to lengthen when going around turns since the pivot point is further forward. Do they use a slip yoke of some sort?
The Athearn HO models I had in my youth used a similar design, but the driveshafts went to a worm gear with a universal joint above the pivot point.
