I've put together a nearly finished version of the worm gear model.

There are 24 teeth on the main gear so it takes twenty four turns of the handle for one complete revolution of the main gear.

I have a few small changes to make to the layout then I'll be putting it together as a downloadable.

After that I'm planning to make an automata with the worm gear at its core. A snail is the model that springs to mind but I'm wondering if that is too obvious…