Nickthesteam,
Yes a lot of the older engine makers done this and created many designs that were never recorded.
My hope is that it was based on some engine plan that was in model engineering magazines of the past.
What was puzzling me was a hole that goes through both sides of the frame and what it was for, it appears to have had a shaft of some sort running through it but what its purpose was I do not know, i will take a picture to make it clearer.
I will probably draw up some plans of the parts and their dimensions once i get the engine running.

Jacko,
Yes it looks like the mechanics is on the same principal.

looks like a modern version of this

https://npmccabe.tripod.com/olddesign.htm

Hi, I would say that is a one off engine for which there was probably no drawings as such, maybe a few sketches on the back of a Woodbine packet but otherwise a design from the mind of the builder...