One category of models usable in American OO are HO scale models that were produced with over scale bodies. While Mantua had a pre-war line of OO gauge models and track (in addition to their HO line), much later Mantua/Tyco produced a 4-6-0 in plastic, a model of Sierra Railroad No. 3. As noted in the NEB&W Guide to Mantua Steam Locomotive Models,

Based on the Sierra’s No. 3, a loco used by Hollywood in many films. It was also featured in the TV show, Petticoat Junction. The loco was originally built by Rogers in 1891. In 1929, it was seen in Gary Cooper’s The Virginian, but then put into storage until after WWII. In the ’50’s, when mainline steam was gone, it was brought back out for the camera for High Noon, The Great Race, Lassie, Gunsmoke, Bonanza, The Wild Wild West, and Little House on the Prairie. Currently (2006), the prototype is in pieces and needs funding to be restored. Unfortunately, the model was made to OO scale (1/76) rather than true HO (1/87).

A couple variations of this model were produced mounted either on 2-6-0 or 4-6-0 mechanisms and I had an eye out for one for years to convert to OO. Finally I located one cheap at a train show with a damaged boiler. My first plan was to replace the boiler but I was able to locate a new boiler that I could apply a more modern cab to, in this case from a Scale-Craft 4-6-0 body. My idea was to make the model look more like Hoosac Tunnel & Wilmington No. 21, a similar 4-6-0 which I had seen a photo of in the February, 1964 issue of Railroad Model Craftsman. With a few more detail changes and Schorr tender trucks it came out well. An unmodified HO version is also shown in the photo for comparison. The bell on my new model is a temp, it will be replaced.

How does it run? It runs nicely. The drive is not an easy job to modify but it is fairly straightforward, the hardest part being that you have to widen out the drivers on the existing axles without altering the quartering of the crank pins, and then add spacers to the frame to keep things from moving around too much. The locomotive when I first got it running ran better than every other locomotive on the roster, in fact, which was a bit of a bummer and motivated me that things had to change!

I chose number 9 as there was a gap in the roster of the real Kansas City, Mexico, and Orient RY at that number. If they had a number 9 it would have been a similar locomotive.