Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Though I know that strictly speaking, a scale model is a replica of something that did or does exist, or at least that’s how we usually think of it, there is a more general concept of scale, but I’m having a hard time using it with regard to the current hit and miss engines out of China.

I’m awaiting an M91 vertical hit and miss engine, and I’m thinking of building some things it might power, once I get a better feel for what it can handle. 

But how to “scale” those things is a conundrum.  When I did RC airplanes and boats, even  a fantasy one-off that wasn’t a true scale anything could be scaled by its relative size. If one simply looked at the size of the cockpit, for example, you could see that a quarter scale or 1/6 scale pilot would fiit, or whatever.  We also had scale references because our engines were sold based on scale expectations, even though not scale models of full sized anything in most cases.

So my problem is, do I think of the M91 or similar as really small scale versions of big engines, or fairly large scale versions of small engines?
Anybody have any thoughts?

Howdy AJ ..... and WELCOME to the Forum!!!

I think you could easily go either way with that scale/size equation, as the M91 and its brethren are not too far off from being reasonable scale representations of engines that were made in a fairly wide range of sizes with very similar overall appearance, so it could easily represent a scale model of some size of engine in a range of 1/12th to 1/4 and beyond, in both directions perhaps.