Decided to have a go at making a simple electric (DC) engine using wood.
Most of the components in this are made from 12mm Ply except for the crank and spokes on the fly wheel (which I made from offcuts of mahogany).
I hand wound the coil (that sits inside the piston looking bit on the drawing) on a nylon former that I turned on my lathe. The connecting rod is made from an old 5mm diameter nail I just cut down to size. This arrangement acts like a solenoid and pulls the wheel round for part of each flywheel revolution.
The wire I used on the coil was a bit too thin (It gets warm). To make and break the coil connection I used an old scroll saw blade that sits bent out so it makes contact with the cam. The blade acts much like a microswitch (which I didn’t have). When the cam rotates, the scroll saw blade touches a little metal contact to complete the coil circuit.
The cam is an old bit of brass that I hand filed into a suitable shape. The four bearings (Two for the crank and two for the fly wheel shaft) were just odds-and-sods I had in my spares box.