Davids Perpetual Motion Machine

[jonovid]

the name David Jones got my attention.
this  Perpetual Motion Machine is another bit of dubious kit.
looks like a quartz movement, that can run for one to two years before needing a battery change.

The creation of the late British scientist and author David Jones.
Adam Savage video.
link 
https://royalsociety.org/blog/2018/09/perpetual-motion/

I believe our Dave can do better then this!
something for the lab, maybe. besides ultrasonic gas leak detector clock.

[Cyberdragon]

Not a quartz clock, there's no connection between the wheel and anything besides a couple bearings. The general consensus is it's electromagnetic, like one of those spinning top/whatever toys. The magnets are on the wheel rim and the coils are in the beams. The battery is either in the frame or one of those boxes and the rest is fluff/decorative.

[wilfred]

What's dodgy about this machine?

Anyway there is also this video where the present owner discusses it.


Also there is this article in the April 1989 issue of Electronics and Wireless World which has an article on the ball bearing motor.
https://worldradiohistory.com/UK/Wireless-World/80s/Wireless-World-1989-04.pdf

It is discussed that it is known to slow down over a two year period and require maintenance. Whether that is replacing/recharging the batteries or re-lubrication as the oil dries out and friction increases.

[james_s]

I'd bet that there's a magnet in the frame and each of those boxes has a circuit similar to that used for the animation on the battery powered Kit-Cat Klock. Those have a double coil with a single transistor and a magnet attached to the pendulum. It runs for a year or two on a pair of C batteries. A carefully balanced wheel in a box with good ball bearings takes n extremely small amount of energy to keep it going. Actually it could be even simpler than that, there's a gray box near the hub that could easily contain a circuit and batteries. The copper pipe and the block with the heatsink in the base is obviously decorative.

[mikeselectricstuff]

Also there is this article in the April 1989 issue of Electronics and Wireless World which has an article on the ball bearing motor.
https://worldradiohistory.com/UK/Wireless-World/80s/Wireless-World-1989-04.pdf

The ball-bearing motor is not related - it's a curiosity with little practical use, drawing insane amounts of current to make a purely thermal motor.

[james_s]

Yeah I made a ball bearing motor once, it does work surprisingly well for what it is, but it required quite a few amps across a very low voltage and the bearing didn't last long at all.

I'd bet money this is either a battery powered circuit that either pulses a coil as a magnet passes by, or a very low power DC motor like the sort used in solar powered displays. It's possible that the round openings on each end of that gray box are solar panels but even just some alkaline batteries could keep the wheel turning for a few years. You only need just enough energy to overcome the losses from bearing and air friction and with good bearings that isn't much. Wall clocks that will run for a year or more off a single AA battery have been around for decades.

[Helio_Centra]

I would wager that the 3 boxes have permanent magnets in them. That the 2 U shaped  structures the wheel passes through are actually coils. And there's a battery and a motor controller in the box with heat sinks on it. The rest is just gonna be distractions.

So just a low power motor. And a motor with low resistance, low speed, and no load besides the rotor spinning for 2 years is nothing special.

[james_s]

The box with heatsinks is obviously just for show, something that runs that long cannot possibly be dissipating enough power anywhere for a heatsink to be necessary. Those copper tubes look like water pipe, all that stuff is purely decorative to impress non-technical people that think there must be something really powerful in there. The obvious place to put a battery and mechanism is in the gray box near the middle, I'd wager whatever mechanism it employees is all in there and everything else is purely decorative.

[Andy Watson]

Interesting how slow and measured the rotation is - almost as if those three boxes contain a time-piece with a pendulum that oscillats about once every 6 seconds. I.e. a long running clock. Perhaps powered by some environmental change like temperature or pressure.

https://www.watchtime.com/featured/running-on-air-the-history-of-the-jaeger-lecoultre-atmos-clock/

[james_s]

I think the video said the speed was gradually decreasing over time. I don't think there is anything regulating the speed except for Newton's first law of motion. Obviously there is very little energy available to keep it turning, so there must also be very little friction to slow it down, so the end result is it's going to turn at a very constant speed. It could be a high efficiency DC motor of the sort used in solar knickknacks, or it could simply be a coil that fires once each time a magnet passes over like the cat clock mechanism I mentioned, but either way the amount of torque applied is going to be minuscule, only enough to combat the friction.