Robert,Why not power ALL wheels?
Seems that if some load is on unpowered wheels, that allows more slip because less weight on powered wheels.
It really has nothing to do with load. The e units were primarily designed for speed and maintaining passenger scheduals I believe the center axle had somthing to do with keeping the truck from "hunting" or trying to climb out of the rail at high speed.The e units were not freight units & were not geared for low speed high tonnage drags.That kind of abuse would burn up their traction motors. By the way has anyone tried to google earth the spot where that tbolt & building stood?