PBL K-37 Remotor/Regear

My first Sn3 locomotive was a first run PBL K-37 that I bought before I knew they weren't worth as much as subsequent runs. Oh well, it's only money right? I ended up with two of these locos and so I set out to regear them to match speeds with my other locos and to smooth out the bottom end. I purchased a PBL 37:1 gearbox with Canon motor thinking it was a direct replacement, wrong, so I proceeded to modify what I had to make it work. I converted my painted model first and then the unpainted one. This little article will describe how I did it.


Picture 1. K-37 - the future #491.


Picture 2. The first step was to remove the pilot and trailing trucks and then the driver retainer.

Picture 3. After loosening the rods from the geared driver I removed the gearbox cover and lifted out the driver set. The equalization springs were removed and put aside and I promptly sent the driver to PBL to have the new gear put on (Not quite that brave yet).


Picture 4. This is where things started happening. Obviously the motor mounts are enough different where they are not direct replacements for each other. After surveying the problem I decided I needed parts of both so I...


Picture 6.   ...opened up the gearbox and turned the worm gear around so that the shaft was coming out of the other end.  

Picture 7.  I then strategically cut both mounts off and mounted a rubber pad to the front of the gearbox with Walther's Goo (what an appropriate name). I forgot to take a picture of this so use your imagination. I'm not taking it back apart. This pad rests on the tab that has two thread holes in it for attaching the driver retainer. With the gear box installed this pad keeps the gearbox from rotating forward but it still floats.

Picture 8. I drilled and tapped a 2mm hole in the frame cross member and a clearance hole in the motor mount. I then used another piece of the rubber for a shock absorbing spacer. The old motor mount holes line up with the new motor. I mounted the motor mount to the frame using the new mounting hole I added and the old one under the motor.

Picture 10. Top view. I then just re-assembled the superstructure and trucks and project over.

Completed Model

Now off to the paint shop. UPDATE - VIEW THE PAINTED MODEL