Summer activities -- gardening, playing, etc. have delayed part 2 of my rocking toy post. We're canning tomato juice right now, which involves some basic hanging around to do the hot water bath -- so I have some "spare" time to do part 2.
In part 1 I explained the basic principle of a pendulum or other simple mechanical oscillators. My first photo shows the can opener that first got my attention:
It's a simple old-fashioned "church key" with a punch on one end and a crown cap remover on the other. In the context of a rocking toy, the opener rocks on the point of the punch and the arc of the cap remover.
The above photo shows the church key with some added weights -- a stack of small neodymium magnets. The idea was to raise the overall center of gravity so it was closer to the center of rotation. This in turn would reduce the oscillation frequency, which it did -- the new oscillation frequency was about 1 hertz.
And now, my version of the rocking toy. The main piece is about the same length. I drilled and tapped a hole on the left for the pivot, which is a bolt whose end was formed into a taper using my lathe. The right side has an arc machined into it, using my milling machine and rotary table. I smoothed the arc with some 220 grit wet/dry sandpaper. I also needed to bend the right-hand end down, to replicate the church key. To make sure the bend was exactly perpendicular to the long axis of the bar, I cut a slot (again, with my mill) from the top to bottom of the bar. It is about halfway through the bar. Then I put it in a vise and bent it until it was about the same angle as the church key.
The end result is a mechanical oscillator that, again, has a surprisingly low frequency -- although for some reason as yet undetermined, my version oscillates at a slightly higher frequency. Anyway, it is a fun "twiddler" to play around with.
If I was going to make another one, I would use cold-rolled steel instead -- it has a much nicer finish. And refine the corners on the left side so it has a more refined appearance. But those are just aesthetics.
