The drawings for these driving wheels were based on standard AAR practice, as found in the 1930 Locomotive Cyclopedia, as well as the G1MRA 1 scale wheel standards. While these standards were developed for 1:32 scale models operating on gauge 1 track, they were somewhat oversized (for reliability of operation), and therefore worked out remarkably close to a finescale profile for 1:20.3 scale on gauge 1 track. And they should work pretty reliably, since there are hundreds or even thousands of locomotives already using the G1MRA wheel profile.
When the spokes were properly profiled, I took the wheel back to the whitemetal shop, and had a whole set of wheels cast from it. I intended to use these as centers, and had steel tires made for them. The whitemetal was not really hard enough to suit me, however, so I took one of the centers, with a steel tire mounted on it, to a custom jewelry caster. This shop does eleven different kinds of metals, from zinc alloys to silver and gold.
The final castings were made in white bronze, which is much easier to cast
and machine than iron or steel, but has the appearance of steel. In the photo
are the castings, fresh from the foundry with the sprue stubs still on them.
I took a chance and had the flanges cast on them, as opposed to the usual
practice of leaving a thick border of material which is later shaped to the
size and profile of the tread and flange. I think this will work out fine,
because I took my caliper to the foundry when I went to pick them up, and
they were, at most, only about .010" out of round. This, I think, will be
easy to true up in a couple of minutes on the lathe.
Updated on 11 March, 1999.