As far as I know, Weaver made every one of their locomotives available in 2-rail and 3-rail versions.
3-rail locomotives had wheels with wide treads and large flanges, large 3-rail couplers and roller pickups for the center rail. They had electronic reversing units (later TMCC and sound) and were made to run on AC current. The wheels were not insulated from the axles and if these locomotives were placed on a 2-rail layout, they would create a dead short.
2-rail locomotives had wheels with narrow treads and small flanges, Weaver scale couplers (plastic Kadee knockoffs) and metal wipers against the wheels to pick up power from the rails. They ran on DC current, not sure if they did any with DCC decoders or sound. The wheels are insulated from the axles.
You cannot run your 3-rail Weaver Diesel on a 2-rail layout.
