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.

Thanks for the replies, keep em coming.

To clarify a bit. I’m not thinking of going all out on authentic scale detail, like some of the machine shop sets I’ve seen. What I’m hoping to achieve is simply creating something that looks reasonably proportioned.

I tend to work from a clean sheet Of paper, sketch then modify as I build things.
An example is a project im finishing up, a “bank vault bank”. While on the one hand it’s a coin bank with a sorting machine, on the other hand it’s a reasonable 1/6 scale old timey small town bank vault with a combination lock and rack and pinion bolt system relatively faithful to originals, all wood.

That’s kinda the idea with my thinking.  I’m mentally designing a woodworking shop with a lathe, drill press, and potentially a jig saw.  Here’s the catch. I want them all to be usable.  They may not be faithful copies of anything, but need to be plausibly proportioned. None of that 1/12 scale with a 1/4 scale crank kind of thing that blows it. 
So I’m kinda thinking along the 1/6 scale line of relatively large shop machines. A seven foot tall drill press or seven foot long lathe scales to 14 inches, for example.  The question of course is can I design a line shaft and pulley system that gives adequate power to really do this?  Experimenting with loads will have to be done first. I may need to reduce machine sizes or not. Some fakery, such as disguised ball bearings may help.

I hear you. I’ve been watching videos and studying pics.
Some authentic installations as well as many demo set ups. The problem with demo set ups  as I see them, is very often the engine owner just wants to spin something for the entertainment of the public, and may apply an engine far larger than needed to a load, and other times it’s not obvious whether or not that’s the case. Hence much of my confusion.
Conversely, a video of a working box factory showed relatively small engines used to operate some fair sized machines. 

I did see Jin’s boat propeller experiment video and noticed what was then apparently  the prototype M91. It seems to have handled the load nicely, and I agree would be a lovely engine in an RC work boat from the era. If I wasn’t legally blind and banned from the road, and still had a boat to chase after it, I’d have a go at a river scow myself. Har.