Pivot Point with Low Friction

Question

Inspired by this question, I am looking for a low-friction pivot for a clock pendulum. The design uses magnetic repulsion to keep the pendulum going. A magnet is attached to the bottom of the pendulum and a coil is fixed just below it. My pivot now is a nail and a hole in a piece of wood, almost anything will be better.

I don't need help with the electronics or magnetics, I need to reduce the friction so it will last much longer with batteries.

The pivot needs to constrain the motion to a single plane so I can continue to use magnetic repulsion. The voltage generated by the coil as the magnet on the pendulum passes by triggers the coil repulsion circuit.

I have a toy that uses a rolling pivot, but this requires two points of contact to keep it centered. I could possibly put the two points much closer together to meet my needs.

I have seen designs that use two threads, but I really want something that looks like a clock pendulum.

Note that the pendulum is just for show, it won't be used as the timebase. The pendulum will weigh an ounce or two, although I have seen cool clocks where most of the clock was on the pendulum, this would weigh more.

What other pivot types are available? Nothing too exotic, something I can buy cheaply or build myself.

[my pictures]

Answer 1

I did some research and found that the most accurate pendulum clock ever made used a knife edge on agate. We can probably assume that low friction is necessary for accuracy. I'm not sure that I have the skills and tools to build something like this. I am decent at woodworking, not so much with metal. It would also be rather delicate and easily upset.

Of course, ball-bearings are often used, but these are usually optimized for heavy loads, and they are often lubricated with oil. Then I thought of something designed for light loads, fidget spinner bearings! A bought a high-quality bearing and modified my pendulum design to use it.

Unfortunately, I didn't get as much improvement as I expected. It seems to have about 3X less friction than a nail on wood. Maybe they are optimized for high speeds.

I improved the electromagnetic portion of the design to get about another 3X improvement. I am now in the ballpark of my goal (run for one year on 2 AA batteries).