Well, that question doesn't have an exact answer. Ross always said it was a 2/5 size model of a 16 HP Advance, which is a scale of 4.8" to the foot. However, if you take the full size dimensions of a 16 HP Advance and multiply them by 2/5 (or divide by 4.8) none of them match up anywhere close with the way it actually turned out as built. As far as the figures go, it comes closer to being a 1/2 size of a 12HP Advance. I really think he just made a boiler about the size he wanted and built everything in proportion around it. It is smaller than a 1/2 size and larger than a 1/3. He used to say it was impossible to build one exactly to scale because first of all you can't build a scale fire.What scale is this engine?
Bob Hauetter of Parkville, Missouri was the guy who helped him with it. He was also a garage and wrecker operator like Ross, but had a fairly complete machine shop as well. Bob had built a 1/3 size double cylinder Rumely and later went on to build two other half size Rumelys. The first and second one were later owned by Ralph Levings and the third was at one time owned by Clarence Turnbull and the boys.If I recall, it did start out life as a boiler barrel that he found and he and another individual fit everything to it. I can't recall the other guys name that helped him with it. He had the machine shop. That size was common then, then the slightly larger, but still smaller than the modern half sizes started to show up. Many of those had the Soliman boilers in this area
Here are a couple of photos from the late 1980's or early 90's of it pulling at Mount Pleasant.This list that thing has pulled is endless. If anything was in the way of the parade at Mt Pleasant, that engine pulled it out of the way.