Oh no! Something on topic! flywheels

I worked in a flywheel lab when I retired a year and a half ago (NASA's Glenn Research Center). A few years ago we also built a demonstrator for science fairs, etc. In our specific case we were demonstrating attitude control of a satellite using its power storage flywheels, getting two bangs for our buck.

I designed a turntable about 2 feet across mounted on a large lazy Susan bearing. Across the diameter were two motor/flywheel units. We used normal 1/4 hp ac motors driven by 3 phase speed controllers that the public could manipulate using joysticks. The flywheels were 10" round stock, about 4" thick. The controllers used a bank of 3 PAR spotlights as the regenerative braking load, when the flywheels discharged, the light banks lit up.

You could spin both motors up together and they would store energy but the turntable would not rotate. Then brake one of them and as it spooled down, the turntable would spin in one direction. Brake the other motor, it would turn the other way, etc. The idea was to point the turntable to a specific direction and hold it.

A bit different then yours, but lots of fun to build and it got a very good response from the kids.

In reality the satellite would have three flywheels in a pyramid and be able to maneuver in all three axis.

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Makes total sense. Thank you for sharing that with us.

Wes S

Sounds like something similar to the Rosen Motors hybrid powertrain concept. Check

Tony

Can you figure out how to extract useful energy from a realy BIG flywheel like...Earth?

Extract energy from tides...

i

It's been tried on busses, as I've been told, but a flywheel on any terrestrial vehicle presents a couple unique issues, mostly safety. First off, the possibility that it will come apart, either by internal or external forces, presents a serious hazard, as all that energy, which is normally designed to come out over a matter of minutes, will come out in a matter of nanoseconds, and the strength of the containment mechanism is a serious weight issue. The other one is the gyroscopic principle mentioned in another note. Flywheels, as some will recall, have a nifty phenomena called precession. Push the end of the axis in one direction and it will actually move ninety degrees in the direction of rotation. Not good in a bus or car, as that's a serious handling issue that the driver can't deal. (for a practical use of precession, motorcyclists use it all the time by pushing on one handlebar to go the other way.) No orientation of the axis will alleviate this problem completely. The noted article failed to mention the safety issue, which I'm sure is the real reason it failed to catch on. The trunk is the last place I'd put a bomb of that kind of energy. Our flywheel's target speed is 60,000 rpm, where it will put out 440VAC

3phase, 20 amps, for one minute, which is a helluva lot of energy to cut loose at the wrong time (and trashed the containment system when tested, which is what was supposed to happen.) 360 pounds of carbon fiber doesn't chunk out upon failure, as most other cast iron flywheels will, so that's the other safety issue: fragmentation bomb.

the research and experiments I've read about over the last few decades contradict this concern - with the 200,000 RPM flywheels running in vacuum, two things happen that apparently make them much safer than you would suggest - first is that if the vacuum is breached they rapidly decelerate (and turn to dust due to heating), and secondly, to get the tensile strength, they are brittle and if broken shatter into dust sized pieces which while energetic, don't have a lot of momentum. Of course, your reading may be more current, I haven't read up on this subject in a few years

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Might be a bit on the large and scary size for you but a decent motorcycle rear wheel and tyre will run at 2000rpm safely (equivalent to about 155mph for an 18" wheel). The energy storage would be quite respectable, but guarding would be necessary. On a smaller note brake disk rotors might be the sort of size you are looking for.

Mark Rand RTFM

Tom sez: "> Can you figure out how to extract useful energy from a realy BIG flywheel

Jeeze, Tom ! Don't you realize it's being done already? Whaddaya think powers the great generators that bring us daylight every day?

Bob Swinney

Like an old 5.25" full-height hard drive, or older/bigger than that? I have at least one of those in storage.

Right! On busses some 40 year ago in Switzerland. Recharge at the stops. I can see the precession... the bus hits a bump and flip on one side.

MG

Do you really want to do that? First the day will get longer and hotter, the nights longer and colder. Then eventually rotation will stop, half the globe will evaporate and the other half freeze. MG

"Carl McIver" wrote: (clip) (for a practical use of precession, motorcyclists use it all the time by pushing on one handlebar to go the other way.) (clip) ^^^^^^^^^^^^^^^^^ That's not quite right. Motorcyclists (and bicyclists) steer out of a turn, because that initiates the lean that is needed. To turn left, you need to lean left. You do that by moving the tires to the right, which you do by steering to the right.

we used a bicycle wheel in physics class.

Con Edison, the electric company in NY surplussed one of it's 1000MW generators, known as Big Alice, and donated it to MIT for it's fusion lab. I saw it on the rail siding in Cambridge.

They were going to put an electric motor on the shaft and spin it up at night, when electric demand was low, and then crowbar the generator side across some experiment and drain the energy in some small amount of time. I never saw it in use or saw a write-up.

That would be "big Allis", as in Allis-Chalmers, an old-time maker of major industrial equipment. Did they get absorbed into ABB?

Jon

Sure. You throw a weight on a string WAY out into space, and collect energy from the earth's magnetic field. Or, the solar wind. The string has been the practical problem on this one. It has to be really strong and really light.

Jon

So? You make it out of those "Blood Diamonds" everyone's squawkin' about. Then everyone benefits. (and we finally have our space elevator we've always wanted).

LLoyd

Actually it is aleady up and running... Google : homopolar generator.... Google : Faraday Disk

Consider that the first motor was a flat disk spinning in a magnetic field. Micheal Farady. Then he discovered that the magnet could spin too, as long as the poles were axial to the rotation..

Now look at the earth, it has a magnetic field axial to it's rotation, and the ground is conductive. The charge builds up near the surface if the earth, the atmosphere acts as an insulator, and the Ionoshpere acts as an outer plate of the (global) capacitor.

You have lived your entire life in an electric field, a few hundred volts per foot. Consider the voltage potential to a cloud, maybe a million volts. As the clouds rise and fall, the capacitance with ground changes, and the charge remains the same. The voltage therefoer will vary with the altitude of the cloud. Once the voltage is sufficient, Lightning.

This constant voltage field we live in is why electric sytems are always grounded. They would work fine with neither side being grounded, but the static charge would build up.

String a wire a few hundred feet over your property, insulated from ground, and check it in a few days. It will have a good charge built up under the right conditions.

There will be no current available, and no real practical use for the built up static charge.

But you can trace it back to the earth spinning on it's axis, axial to a magnetic field, and being a mostly (bulk) conductor.

The fact that the upper ionosphere is a large conductor, and the upper plate of a capacitor, explains many of the really strange upper space observations of lightning, Sprites, multiple simultaneous strikes in multiple states observed from space, etc.

It is a really amazing world we live in!