Rebuilding the drive train

Since this model was originally made back in 1967 it contained an old open frame motor coupled to the gearbox with a piece of very stiff rubber tubing.  I decided that I would replace the original motor and gearbox with upgrades from North West Short Line.  I selected a NWSL 20 x 32 mm can motor and their larger sized 0.4 mod 28:1 gearbox.  Since this is a large locomotive the larger 0.4 mod gearbox fit in between the frame without any modifications.


I milled a motor cradle out of a piece of 3/8” x 1/2" brass bar stock using a 3/4" (19mm) ball end mill.  On the bottom of the motor cradle I drilled and tapped a 2.5mm hole that lined up with the hole in the frame used to mount the original motor.  Silicon rubber was used to secure the motor to the cradle.  This mounting arraignment allows the silicon rubber to provide damping for the motor’s vibration while still allowing the motor to be easily removed if needed.


I replaced the rubber tubing coupling with a set of NWSL universals.  I drilled and tapped a couple of 1.4 mm holes along the gearbox top to secure one end of a new torque arm.  The torque arm is made from 16 mil brass sheet stock, and is 200 mils wide.  The motor was positioned in the motor cradle so that the 2 mm mounting holes were facing up.  I attached the motor end of the torque arm to the front motor mounting hole using a shouldered screw.  This secured the torque arm, but still allowed the joint on the motor end to rotate so that the gearbox could freely shift to the right or left as the locomotive goes around curves.


Here are a couple of pictures of the rebuilt drive train:



All of the driver wheels were loose on the axles.  So in addition to replacing the axle gear I pulled all of the wheels off the axles, re-quartered all the driver sets, and secured each wheel with Loctite.   The original driver springs were too stiff so I replaced them with NWSL light springs.  While I had everything apart, I cleaned up the wheel tires, and then re-plated them using a brush style silver plating kit.


Here are the before and after pictures of the drivers:




For reference here is a list of parts used in the drive train:


*    NWSL 20324-9  20mm x 32mm motor

*    NWSL 241-6      0.4 mod 28:1 gearbox

*    NWSL 482-6      U-joints

*    NWSL 21142-5   1.4mm x 2mm x .3 screws

*    NWSL 1401-1     Light driver springs

*    3/8” x 1/2" brass bar stock  (motor cradle)

*    16 mil brass sheet stock (torque arm)

*    2 mm x 0.4 shouldered screw (custom turned)


Page 5 - Last updated April 19, 2004


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