Last month I posted a question about insolating open frame motors so they could be used with a DCC setup. I got a few very helpful responses but no solutions. I finally think I have isolated the engine. Here is my solution.
I purchased a box of 2-56 X 5/8 nylon screws. I cut a piece of very thin plastic from a track package and fitted it between the motor and frame. I then simply mounted the motor with the nylon screw and voila no connection. You may have to grind the frame down some so the gears mesh properly. Thanks to all who replied
You can always use some of that plastic for a shim towards the rear of the motor mount to lever the gears into mesh. This would be easier than grinding the frame.
Sounds like a very good idea. As far as the motor working with a decoder, as long as it doesn’t overrun the decoders current limit it should be all right.
Most open frame motors have one motor brush insulated with a small piece of plastic/bakolite or paper. Insulating the other brush usually insulates the motor. I have insulated ‘Pittman’ style motors this way for several engines and the motor is now DCC Ready. To check your work, use a multimeter set to ohms and check for a short from the engine frame to each of the motor brushes. If there is no short, you are good to go!
The open frame motors in my ancient fleet come in three flavors:
One brush insulated from the frame, the other mounted to the frame without insulation. The OP’s technique is one way to deal with this situation. I have also heard of motors ‘glued’ to the loco frame with silicon caulk.
Both brushes insulated from the frame, one connected to the frame by the uninsulated wishbone spring and the other isolated by insulation on the opposite end of the same spring. The uninsulated brush can be isolated by slipping an insulating tube on the uninsulated spring end.
Both brushes insulated from the frame, one with its connecting ‘ear’ soldered to the frame. All that’s needed to isolate this type is to break the solder joint and connect a wire to the ‘ear.’
I also have a couple of catenary locomotives where the brushes were totally isolated and connected by separate wires, leaving the carbody dead. I presume that this was done to allow the modeler to arrange for power through the catenary if so desired. It wasn’t done to facilitate DCC installation - DCC wasn’t even a plan when they were built (the reversing headlights use a selenium rectifier!)
Chuck (Modeling Central Japan in September, 1964 - with locos built in the 1960s)
Ah, selenium rectifiers! Remember the smell when they shorted out?
My original HO layout used a selenium rectifier connected to the American Flyer transformer that went with my S-gauge set. To get better low-speed control I cut the connection that made it a full-wave rectifier and installed a switch there. With the switch “off” I had half-wave DC, which gave really good low-speed control.