Inspired by all the piano playing cats on the internet I’m working on a cam powered keyboard playing cat model. Here’s the sketch. Turn the handle and the Keyboard Kitty pounds at the piano keyboard.

My plan is to have two weighted cam follower in the base, one for each arm. When the cam is in the down position it will pull the arms upwards. When the cam follower is lifted the weight of the arm drops the arms back down again. Because the arm is operated with a pull rather than a push I can use a simple strap to operate the arms rather than having to make a rigid push rod. Hopefully this will make the mechanism simple to construct.

Here I’ve put together a prototype arm with a linkage and axle.

In my prototype I’ve fitted each arm into a separate body half. This allows the two axles, one in each shoulder, to move independently.

A simple wide strip of card joins to the two side together.

Pulling each strap raises the approriate arm. Just like that!

Here’s my artist impression of how it might all fit together.