My new model involves making pinwheel gears. I used to do this in Illustrator and used the tutorial on the Cabaret Mechanical Theatre website for this. However, I no longer have this software and instead went for the Open Source alternative of Inkscape. I had trouble working out how to make the pinwheels at first but now have a method. I thought I'd create a PDF and provide a download link for those who are interested in it:
One of the nice things about making automata is that the materials do not necessarily have to be expensive. I'd find it hard to justify spending hundreds of pounds on a piece of software to assist with the design process, so I use a free alternative.
Of course, another alternative would be to just use a protractor, ruler and a compass but I always find my accuracy slightly off with this method.
I hope this helps. If you have any queries, please comment/contact me.