Peco sells a motorizing kit but I went another route.
The parts are listed in the video description. I've really come to appreciate how silent the motor is - the noise in the video is the sound-equipped loco. It's as slow as I could get it in the video - any less on the PWM knob and it wouldn't move.
Construction:
[ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ]
To be honest I'm pretty sure the ball bearings aren't needed - could have just sanded down the model's fake wheels to get rid of the screeching.
The weights are to overcome the springs in the electrical contacts. You are supposed to permanently glue a collar on the shaft to hold the bridge down, but that means you can't ever remove it and I at least needed to paint the pit.
As for attaching the motor, the shaft is a fairly snug fit but IIRC the actual attachment involves gluing a styrene strip into the bridge's hole to make it D-shaped, and then gluing it with Aleen's for an even tighter fit. It turned out to be very tricky to get the shaft square and true with the bridge's shaft because the bottom of the pit is dished - hence the shims. It would be easier to simply hang the motor from the bridge shaft and devise a way to constrain the motor from spinning instead of spinning the bridge. Then the weights wouldn't be needed either.
