I've done the 'non rods' version in Shapeways 25-tonner shells when those were available.
Non 12v motor, not enough torque, poor wheels, poor pickup, rocket fast. Fun but not really practical. Cheap though. I sure tried a lot of them.
The larger motor, spur to transverse worm to both axles design is the winner. And the best craftsmanship on that design remains Showcase / Toma Model Works for the chassis. Those are just incredibly performance. Chris333 uses those in his dinky steam and the frame he did with their parts is in my Porter. Outstanding.
I have a similar design in my 'final' GE 25-tonner, it's really good but a Toma would be better. But I think he's hit the same nightmare with tariffs and shipping as everyone else has in the last year and a half. It's killed off a lot of cottage efforts like his since the DeMinimus rules went in.
