I’ve been approached by a client to make a particular automata piece for them based on something they saw on the internet. A large diameter gear is a prominent part of the mechanism. The one they saw had a large gear and small pinion operating at right angles. They were made as pin gears with brass pins. I have made many of these before but they can be noisy and a little jerky in motion. It might not fit with the “zen” mood of the piece so I decided to try to make wooden toothed gearing and set out to try my hand at a prototype.
I went to woodgears.ca, a very useful site for automata gearing, and used the gear template generator program for direction. The teeth have to be cut on a bevel to work well. You need to make an adjustment for the thickness of the gear and adjust the height of the teeth as well. The bevels are cut at the pressure angle of the gears.
I made a slight variation to the cutting technique, using a spiral scroll blade to cut the bottoms of the tooth gaps perpendicular to the gear face. The teeth do not run on this surface but they are very visible on the finished gear.
I was very happy how the prototype turned out after a couple hours of setup, careful scroll saw cutting, and a little filing.
Here’s a photo of the prototype.
Automata is a creative blend of my life interests , engineering, art and woodworking.