Spindles, Cams and Gears

In essence, music and automata movement are both fundamentally driven by a circular motion around a spindle. The spindle is usually an extension of a turning shaft from the musical movement.

One basic item for creating movement is the cam, which defines a locus around a fixed position on the turning spindle. Aside from an eccentric circular cam, the edge of the cam has to veer from a true circle to be of any value in creating  automata movement. Simply put, an irregular cam edge is closely followed by a rider which is linked directly to automata movement. However, as the rider exerts some back pressure on the cam, over time this would cause an improperly attached cam to detach and "roll" around the spindle. When that happens, no automata movement would be created.

In my earlier pieces, I had glued the cams onto a very thin wire or tubing. I had used thin material such as cardboard, rigid plastic or plywood for cams, and thin wire or tubing for spindles in order to minimise the space in my mechanisms. However, some of these cams have separated from their spindles and the mechanisms have failed now because the glue had dried out over time. I note that the thin wire tended to flex, exacerbating the problem over time.

I think that I will now try to use square tubing for the spindles for the following reasons:-

- hollow tubing is preferred over solid wire as it is lighter and easier to cut.
- the cams will not "roll" around a square spindle shaft.
- the square tubing provides the rigidity for my purpose.

The larger the square tubing, the smaller the chance for the cam to roll around the spindle.

I will also try to use rigid plastic, sheet metal or thin wood instead of cardboard for making the cams. This is simply because over time, the cardboard is less durable and will develop "spotting" or "foxing' due to acidity and humidity in the air.

However, I note that many of the plastic wheels that I have are pre-moulded with a circular centre hole. For now, the best solution is to find the best sized round spindle for each of these wheels and glue them. For the larger wheels, I may add additional spindle supports on either sides of the wheels for further stability.