Magnetic Bearings Might Keep Motor Spinning for Millennia
hackaday.com
hackaday.com
For one, I think bearings wearing out is the main failure mode of most electric motors.
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.
> Spinning ferromagnets (such as the Levitron) can—while spinning—magnetically levitate using only permanent ferromagnets
> Pseudo-levitation constrains the movement of the magnets usually using some form of a tether or wall. This works because the theorem shows only that there is some direction in which there will be an instability. Limiting movement in that direction allows levitation with fewer than the full 3 dimensions available for movement (note that the theorem is proven for 3 dimensions, not 1D or 2D).
They're fantastic, move a lot of air and high static pressure, but the only noise that comes off them is the moving air, they're virtually silent. They also have a huge lifespan compared to fluid dynamic bearings, rifle bearings and sleeve bearings because there's no friction leading to wear on bearings.
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?
Space?
Still very cool, though.
Also (from 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.
"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."
In what sense?
>lowered maintenance costs
Not really, actually - hydrodynamic bearings already work on the "zero wear due to zero surface contact" principle. The reason this is using magnetic bearings is just because it needs super-super low friction, under super-tiny loads, in order to work.
>Probably a lot less noise
Bearings aren't generally noisy. If they were, they wouldn't be very good bearings!
I'm not sure about UV filters that will be stable for 1000 years. Regular glass blocks most UV, but lets through about 25% of the frequencies close to blue.
For museum and artwork protection time frames acrylic is popular. It blocks almost all UV and is still stable after 25 years. I don't know how that extrapolates to 1000 years.
...the most surprising thing probably is that it was being powered off a small solar cell under this dark blue plastic box. Any more power than that and the motor would spin up, lose control and fly out of stability. , https://youtu.be/wNcgnooayDc?t=129
Green glass is green because of iron (II) oxide (FeO), which is usually a naturally occurring contaminant of the sand used for glassmaking. Amber glass is amber because of FeS2. Neither change color under normal weathering conditions.
The duration of a protective coating depends on the coating, and its thickness. If you layer a glass pane under a synthetic sapphire pane, that would probably be better than a protective coating. The sapphire would protect the glass, and the glass would block UV-A.
PV cells definitely do degrade, but in terms of spinning a nearly frictionless thing in a vacuum, if a 5W rated single cell degrades to 2.5W over 75 years of being exposed to direct sunlight inside a glass vacuum jar, it's still way more than the required energy to keep the thing spinning.
Here's an example of a 30 year warranty for a fully assembled module (60 or 72 cells encapsulated in glass and back film), at >80% after 30 years.
http://www.jasolar.com/uploadfile/2018/0518/2018051809372413...
I was also wondering about thermocouples.
If you just wanted a simple stable multi-millennia clock you could make a large water clock[2] with pitch[3].
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.
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.
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.
https://en.wikipedia.org/wiki/Flywheel_energy_storage
(My favorite part of the article where it talks about trying to use in vehicles...)
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%.