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

Say Jack ... this does sound like you are going to have loads of fun with this project, and I wish you luck with it and hope to see progress and results as they accrue.

Meanwhile, I hope you didn't misunderstand what I was intending to project, in that the actual size of you M91 engine is such that it could easily represent an approximate 1/12th scale of a rather large hit n miss engine of the type, or conversely, it may also be appropriately sized to represent an approximate 1/4 scale version of a much smaller prototype engine. The real engines of this type were frequently made in a wide range of horsepower ratings, and thus relative sizes, that were often simply scaled replications of each other.

Some on line time reviewing various Hit n Miss source sites will give you a much better feel for this than my words are likely to provide. Search engines can be your friends!