A cam with 2 lobes operates on the roller on the micro-switch and excites the coil when the piston is in the centre of it’s travel.
The cylinder and piston are both machined from ebony with small permanent magnets at the centre of the piston. The ebony piston runs very freely against the ebony cylinder. The engine only runs for small bursts and so there is no need to lubricate this interface, but I imagine a small amount of silicon polish would work very well.
A 9V battery is hidden in the wooden base and the engine is switched on by pressing the button that you can see in the side of the case. The flywheel is flicked and the motor runs.
The flywheel is turned from pewter, I cast a cylinder of metal in a block of wood with a hole formed using a hole saw. The hot pewter does burn the wood, but once it has burnt the outer surface it doesn’t go any further. Let the metal solidify and then remove it from the wood with a hammer.
This is a simple model that can be made in a couple of afternoons and is a pleasing executive toy.
Don’t expect significant power, the motor runs smoothly, but can easily be stopped with some drag on the flywheel.
More of my engines are in my gallery page.