8 ms·
Magnetic Bearings Might Keep Motor Spinning for Millennia
- blueadept111 8y agoThis motor needs to put into a vacuum chamber pronto!
- sevensor 8y agoFunny you should mention that. Hi-vac turbo-molecular pumps often use maglev bearings. This is the pump that takes a chamber from low vacuum (like 1 torr) to high vacuum (like 1e-6 torr). It's a turbine that resembles a small jet engine.
- spenczar5 8y agoIt's a cool project, but (as many other commenters noticed) most of the battery's energy is being dissipated through the resistors, so it's not going to last for millennia as built. Still very cool, though.
- szczys 8y agoActually, I think it could last for millennia as built. Just not the full 89,000,000 years as mentioned. Even if you ditch the theory, there's a good chance this will keep running as built for several decades and that's pretty crazy. Makes me want to build one and let it run.
- dekhn 8y agovoyager is a 40 year old spacecraft which still runs. A terrestrial magnetic bearing running for decades is not crazy.
- hn_throwaway_99 8y agoVoyager is also powered by big balls of plutonium.
- dekhn 8y agothat wasn't my point. My point was that mechanical things can move for long periods of time, there's nothing crazy about that. https://en.wikipedia.org/wiki/Oxford_Electric_Bell https://en.wikipedia.org/wiki/Oxford_Electric_Bell https://en.wikipedia.org/wiki/Beverly_Clock https://en.wikipedia.org/wiki/Beverly_Clock https://en.wikipedia.org/wiki/Atmos_clock https://en.wikipedia.org/wiki/Atmos_clock
- MrEldritch 8y agoThe mechanical aspect of this has nothing whatsoever to do with why it wouldn't last for millennia - it's the fact that it's coupled to a resistive load that will dissipate power from the battery much faster than the motor itself uses, and act to brake it over time as the battery voltage drops.
- alanbernstein 8y agoAre there mechanical components on Voyager?
- amelius 8y agoAnd what is their duty cycle?
- dekhn 8y agoJPL knows. BUt more importantly, when the original thrusters broke after 37 years, they were able to switch the backups and it worked fine. To me, remotely fixing a space probe beats a spinning magnetic bearing on earth for amazing engineering any day.
- dekhn 8y agohttps://www.newscientist.com/article/2155460-nasa-fires-voyager-1s-engines-for-the-first-time-in-37-years/ https://www.newscientist.com/article/2155460-nasa-fires-voya... Also (from https://voyager.jpl.nasa.gov/mission/did-you-know/ https://voyager.jpl.nasa.gov/mission/did-you-know/): The electronics and heaters aboard each nearly one-ton Voyager spacecraft can operate on only 400 watts of power, or roughly one-fourth that used by an average residential home in the western United States. A set of small thrusters provides Voyager with the capability for attitude control and trajectory correction. Each of these tiny assemblies has a thrust of only three ounces. In the absence of friction, on a level road, it would take nearly six hours to accelerate a large car up to a speed of 48 km/h (30 mph) using one of the thrusters. The Voyager scan platform can be moved about two axes of rotation. A thumb-sized motor in the gear train drive assembly (which turns 9000 revolutions for each single revolution of the scan platform) will have rotated five million revolutions from launch through the Neptune encounter. This is equivalent to the number of automobile crankshaft revolutions during a trip of 2725 km (1700 mi), about the distance from Boston,MA to Dallas,TX. The Voyager gyroscopes can detect spacecraft angular motion as little as one ten-thousandth of a degree.
- rootusrootus 8y agoThey are only claiming 89,000 years, not 89 million. But yeah, probably a few decades is plausible, the battery isn't going to last thousands of years.
- caf 8y agoI do wonder how long you could engineer a capacitor to last, though - given you have little constraint on its physical size.
- scottlocklin 8y agoThe magnet is the weak link. I'm pretty sure the battery will last longer.
- m463 8y agoyou could fix that with a small solar cell - I imagine the cell on a solar caclulator that works indoors would be sufficient.
- deleted 8y ago[deleted]
- tener 8y agoAfter pumping out the air and adding a small solar panel I guess it could spin basically forever?
- MrEldritch 8y agoSolar panels wear out pretty quickly, actually - within decades. UV light's nasty stuff.
- FreeFull 8y agoHow quickly would a protective coating on the glass wear out? Or the green/brown colouring that gets added to beer bottle glass.
- Pharmakon 8y agoHow much would such a coating reduce the efficiency of the panel though? I’m seriously asking btw, I don’t know the answer or very much about PV panels.
- 14 8y agoThat seems to be the fantastic part of this motor. Even if you traded off almost all efficiency in order for protectiveness of the material instead, this machine runs on such a low power you could make those trade offs. What you could use this motor for I am unsure.
- Pharmakon 8y agoToo cool. Hey, could these bearings be used in something like a water wheel or windmill? I realize the technology isn’t there yet, but if it could then really you’d could have lowered maintenance costs, slightly increased efficiency, and probably a lot less noise.
- MrEldritch 8y ago
- baybal2 8y agoNo, diamagnetics will be receiving rotational momentum from the spinning magnet, microscopic, but still non-zero.
- MertsA 8y agoIt's a shame when comments like these are downvoted. You're spot on, magnetic bearings certainly have a very small drag, but it's not zero. Going over that reed switch will also produce a tiny amount of drag, it's miniscule by any measure, but it's still additional drag. Even just the fact that it's a spinning magnet passing by that conductive copper is going to induce a tiny drag force. What would be cool is a version of this but instead of permanent magnets in the rotor make it an induction motor or an electrostatic motor.
- MrEldritch 8y agoHe's being downvoted because that's completely irrelevant - the thing isn't relying on just coasting for millennia. That figure's based on the actual, measured power draw of the motor, which includes the bearing friction and other drag, and dividing by the energy stored in the battery.
- teekert 8y agoWhat about those devices that harvest radio (wifi a.o.?) waves? What do they generate?
- eckza 8y ago> but it seems clear that his motor will likely outlive any chemical battery used to power it ... I don't think that whoever typed this sentence up, thought very hard about it.
- gpm 8y agoConsidering he's currently powering it with a chemical battery rated for 40 years, I think that's a pretty unnecessary jab.
- JoeAltmaier 8y agoWhen talking times like that, lots of 2nd-, 3rd- and 4th-order effects become important. Like flexing of the mechanism due to Coriolis forces, or coupling between the magnet and the earth's magnetic field. Heat losses that will stop the motor in years, not millennia.
- sathackr 8y agohe's measuring the actual current draw of the running system with a meter. Are you saying that Coriolis forces and the earth's magnetic field will have a greater effect on the system in a few years as opposed to now?
- JoeAltmaier 8y agoThe idea was, it could run forever in an evacuated chamber? Else the idea is meaningless; the battery would decay to dust.
- JumpCrisscross 8y ago> it could run forever in an evacuated chamber? Space?
- mrtnmcc 8y agoHe didn't say whether the rate of rotation was measured over time. It's possible the rate was decaying and the 150nA supplied was not a net positive.
- deleted 8y ago[deleted]
- hwillis 8y agoCool, so you didn't read the article.
- pgt 8y agoAs per HN guidelines, assume the poster read the article and respond to the strongest interpretation of their point: https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- acomjean 8y agomight be useful for those "flywheel" based energy storage devices. https://en.wikipedia.org/wiki/Flywheel_energy_storage https://en.wikipedia.org/wiki/Flywheel_energy_storage (My favorite part of the article where it talks about trying to use in vehicles...)
- ip26 8y agoArguing about how many millions of years it will run for seems to be missing the forest for the trees. IMO the real message here is, holy crap magnetic bearings are amazing, now how do we get them into everything else?
- stefan_ 8y agoWhy, bearing losses do not matter.
- ip26 8y agoI won't say you're wrong, the losses are small. But I guess they remind me of other technologies in the past that were by themselves incremental improvements, but as cost came down and they were put together with other incremental improvements, our capabilities advanced significantly & in ways we may not have expected. For one, I think bearings wearing out is the main failure mode of most electric motors.
- beambot 8y agoGreat example, also from rotating systems, is the harmonic drive gearbox -- a very compact & high gear ratio device that (curiously) uses a deformable metal "cup" (flexspline) rather than a 100% rigid piece of metal like a traditional gear. Huge improvement that is now commonplace in robotics. https://en.m.wikipedia.org/wiki/Harmonic_drive https://en.m.wikipedia.org/wiki/Harmonic_drive
- InclinedPlane 8y agoThis is an opportunity to look at the problem from a different perspective. Currently, in all mechanical designs bearing losses are small, because if they were not the design would probably be unworkable or unfeasible. But consider, maybe there are new things that could come into existence which are not feasible today because of bearing losses. The internet, for example, didn't make it newly possible to send mail to people, but it made it so much easier that it changed what it meant to send mail.
- 8y ago
- stevespang 8y agomultimeters of this sort cannot accurately measure such low voltages and amps since they by design inject low amounts of their own battery power into the system and measure what comes back.
- PhantomGremlin 8y agomultimeters of this sort cannot accurately measure such low voltages and amps That's an interesting point. I've used similar multimeters for many years and was not aware of that limitation. But for this particular design it would be trivial to determine both the voltage and the current to within about 1% accuracy. V = I * R Most of the voltage drop is across the 24 megohm resistor string. Measure the voltage across that, and you get the current flow, since you know the resistance is nominally 24,000,000 ohms. Most voltmeters have an impedance in the 1000+ megohm range, so measuring across the resistors won't introduce much inaccuracy. The resistors themselves appear to be 5% tolerance. But by measuring the resistance of the string (open circuit) with the multimeter you should be able to determine their actual value to better than 1%.
- zizee 8y agoAre there super capacitors with expected lifetimes measured in centuries / millennia? Making a device that could keep running long enough for civilization to fall into the dark ages, and then grow again from scratch does something funny to my brain.
- hwillis 8y ago> Are there super capacitors with expected lifetimes measured in centuries / millennia? No, certainly not. Supercapacitors self-discharge significantly faster than batteries do. Capacitance is proportional to the surface area of the electrodes and inversely proportional to the distance between them. Resistance is the opposite, so roughly speaking higher capacitance means higher self-discharge. The current go-to for long lasting batteries is lithium thionyl chloried, used in remote areas, embedded electronics and things like portable defibrillators. Those are some of the most energy-dense batteries available (though not rechargeable) and can hold most of their charge for over a half century. The Oxford Electric Bell[1] was linked in the comments under the post, and it has been ringing since 1840. It's not known what kind of battery it has, but its some kind of dry pile. Dry piles generate voltage via corrosion of metal (eg zinc) and have extremely high resistances between plates since there is no liquid electrolyte. As long as they are kept relatively dry they have incredibly long lifespans, although their power output is miniscule- orders of magnitude smaller than even this motor. It might make more sense to tap into an extremely long-lived source of power, such as geothermal. Over millennia tectonic shift is only a problem across a fault. As long as you can set up a thermal gradient (eg by pushing a stainless steel wire deep into a hole), you can run a Peltier (Seebeck) generator. Some semiconductors have meaningfully limited lifespans and eventually fail under normal use, but many are effectively inert and last as near to forever as we can figure. I'm pretty sure most thermoelectric junctions are the latter, with exceptions for radiation. They have a standard MTBF of just under 23 years with frequent thermal cycling, which is the most damaging thing you can do. It wouldn't be hard to imagine it lasting millennia in a sufficiently stable environment. [1]: https://en.wikipedia.org/wiki/Oxford_Electric_Bell https://en.wikipedia.org/wiki/Oxford_Electric_Bell
- hossbeast 8y agoPage needs a Buy Now button
- carapace 8y agoReminds me of the Long Now project 10,000 Year Clock[1]. If you just wanted a simple stable multi-millennia clock you could make a large water clock[2] with pitch[3]. [1] http://longnow.org/clock/ http://longnow.org/clock/ [2] https://en.wikipedia.org/wiki/Water_Clock https://en.wikipedia.org/wiki/Water_Clock [3] https://en.wikipedia.org/wiki/Pitch_drop_experiment https://en.wikipedia.org/wiki/Pitch_drop_experiment
- hu3 8y agoAnother long-lasting cool experiment: https://en.m.wikipedia.org/wiki/Pitch_drop_experiment https://en.m.wikipedia.org/wiki/Pitch_drop_experiment "The pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. 'Pitch' is the name for any of a number of highly viscous liquids which appear solid; most commonly bitumen. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop."
- beambot 8y agoCool project -- sort of like an electromagnetic radiometer.