PRR RS-1 - Electrical Short
After taking the engine to local shows and having it run for 6-8 hours per day at several shows, all of sudden one day the engine caused my layout's DCC system to report a short (4 beeps upon power-on). I quickly narrowed-down that it was this RS-1 engine.

My assumption was that some wire must have been rubbing up against the flywheel, the insulation wore off, and it is now causing a short. But that was not the case once I had opened the engine. I eventually figured out that it was the rear truck. I completely removed the truck from the engine and put the engine aside. Sure enough, when I held my continuity tester against the two screws to which the power pickup wires are connected with the sidewalls of the truck, it reported a short. Further investigation led me to the fact that the bottom plate of the truck was the cause of the problem. Both the truck's sidewalls and the bottom plate are metal, but they are all coated. I could not see where the coating had worn off, but apparently it did. The front truck does not (yet) suffer from that same problem.

The electrical short was triggered as soon as I tightened the bottom plate to the truck. My first (and quick) solution was to put a thin coating of liquid electrical tape on the bottom of the vertical side walls. After sufficient curing time, I installed the bottom plate. Voila, problem solved. Well, for about 30 minutes of operation. Several days later all of a sudden my system shut down again with a short. I removed the RS-1, and the warning went away. Back to the drawing board, so say...

I removed all the electrical tape, and decided to implement a more permanent solution. The solution is to electrically isolate the bottom plate from the vertical side walls of the truck. I loosened the screws that hold the truck's sideframe assembly to truck. I then removed the two small screws that hold the bottom plate in place.
Electrical Short
I cut pieces of 0.010" styrene to the dimensions of the bottom plate. The gears that are mounted to the axles of the wheels in the truck protrude below the vertical sidewalls of the truck, so a small clearing needs to be made in the styrene. I made two sections of styrene, one for each truck.
Electrical Short
Next, I pre-drilled two holes for the bottom plate's mounting screws in the styrene, using the bottom plate as the guide.
Electrical Short
I then placed the styrene on the truck, put the bottom plate on top of that, installed the two screws, and tightened up the sideframe assembly. It goes together well and it provides the electrical isolation needed for the bottom plate.

Update: I only did this to the rear truck. However, almost two years later, all of a sudden my engine stopped running again. I checked, and sure enough there was another short. As soon as did this same treatment to the front truck, the short went away. I guess the bottom line is, if you build one of these Railmaster Hobbies engines (RS-1, S-1, etc.), you might want to go ahead and do this to both trucks to begin with, to save yourself the trouble of "debugging" this later on.
Electrical Short