I bought this brass GP 20 on Ebay and plan on installing some Athearn trucks from a GP 35 and newer style motor and install DCC. I believe this GP 20 is an early 60's production. The frame is complete except for the railing on one side. The body is missing the exhaust stack and sand covers on the nose and rear. I have a lathe and milling machine and should be able to duplicate the parts.
The first thing I did was fill in the holes for the old pivot points with some brass rod and silver soldered them on the frame and milled it flush. After carefully measuring I drilled 3/16 holes for the new pivot points. Using some brass stock I made 2 new pivot points and soldered them on the frame. I then milled out the openings for the Athearn trucks. A frame was made out of 3/16 X 1/16 brass for the motor mount. I also milled away the opening for the motor and brass flywheels.
I started the wiring of the Athearn trucks. The tall stand-off tab was cut off and 2 holes were drilled with a # 56 drill bit and tapped for 0-80 brass screw. I tapped the hole part way and installed the screw then carefully forced it into the untapped section to have a good solid contact. The red and black wires were soldered on. Then the upper part of the screw was cut off. With the trucks fully turned neither the wires or brass screw contact the frame.
One of the repairs I made was to the front light and number board. That section which consists of 3 pieces was soldered on crooked. Upon heating it up to move it slightly it fell apart. I re-assembled it with silver solder so it would stay together as I heated it up and used regular solder to attach it back on.
This is another repair I needed to make. The ends of the air tanks are drilled off center. I tried to repair them but it did not work out. So I cut the tank ends off the bracket and made some new ones. I used silver soldered to attach them to the brass bracket and I will use soft solder to mount the wires and to mount it to the frame.
The air tanks are repaired and mounted on the frame. I used a thick piece of basswood and epoxied it to the frame for the motor mount. The wood was drilled to match the mounting holes on the motor frame and #1 brass screws are used to mount the motor. By using the wood it insulates its from the frame and keeps any vibration noise from getting into the metal frame.