Rebuilding the Drive train
This model was originally built with an open frame motor and a poor quality brass gearbox. Here are a couple of photos of the original drive train configuration:
Since the gearbox was noisy, I decided that it had to go along with the open frame motor. This presented a bit more of a challenge than the usual gearbox swap due to the way the original gearbox fit over the wheel bearings. Here is a photo from the bottom showing the main wheel bearings extending right up to the sides of the worm gear.
In order to fit a new gear box, the bearings on the main drivers would have to be shortened. I suppose that I could have just ground a bit off the inside edges, but since I have the tools I decided to turn a new pair of bronze bearings to replace the original ones. Here’s a picture showing the old and new bearings:
With the new bearings in hand it was a simple matter to pull the worm gear and replace it with the one from a NWSL 36:1 idler gearbox. At the same time I quartered all the driver sets to fix the loping problem.
I replaced the motor with a new 16 x 30 mm can motor from North West Short Lines. Using a 5/8” (15.9mm) ball end mill I made a motor cradle out of a piece of 3/8” x 1/2” brass bar stock. A hole was drilled and tapped in the bottom of the motor cradle so that it could be fastened to the frame using the original motor mounting hole. The motor was attached to the cradle using silicon rubber. On the lathe I turned a flywheel as big as would practically fit in the space allowed. I had to make a custom one as I didn’t have room for a standard 16mm flywheel from NWSL.
I made a torque arm to connect the motor to the gearbox from a piece of 16 mil brass stock. The gearbox end was fastened with a pair of 1.4 mm screws, and the motor end used a custom turned shouldered screw. Universals from NWSL were used to connect the motor to the gearbox.
Here are a couple of photos of the new motor and gearbox installed:
Last updated - April 19, 2004