5 ms·

The Mechanical Battery

60 points by ph0rque 18y ago

JoelSutherland 18y ago
I wonder what it is like to steer a bus with a 3 ton spinning disc inside: http://en.wikipedia.org/wiki/Precession#Torque-induced http://en.wikipedia.org/wiki/Precession#Torque-induced
- eru 18y ago
  Just take two and spin them in opposite directions.
  - eru 18y ago
    While I think about it: You could even install the two disks spinning horizontally, and the bus would be even more stable against tilting.
    - pedalpete 18y ago
      I believe this is what they use in large cruise ships for stability.
    - ajross 18y ago
      If they're counterspinning with equal angular momentum, there won't be any gyroscopic effects at all. The precession torque from one wheel is exactly opposite to the other. The only gotcha is making sure that torques get applied equally to both wheels to keep them at the same speed, even if the enclosure itself is rotating. But I'm skeptical. Anything with moving parts has failure modes. Huge stationary flywheels as building or municipal storage devices make a lot more sense to me than putting one in a car.
    - DaniFong 18y ago
      This actually messes up the steering geometry. you need the steering system to be only barely in the region of stability, otherwise it takes too much effort and energy to turn. And during turns, four wheeled vehicles bank slightly, which is very important to maximize the normal force on the outside wheels to increase frictional contact with the road. In general, the dual-mass oppositely rotating flywheels work best: there's a miniature system like this in every car to even out engine vibrations.
      - ph0rque 18y ago
        Question for you Danielle: are the dual-mass oppositely rotating flywheels usually side-by-side, or wheel-in-wheel? Is there any advantage to one or the other?
        DaniFong 18y ago
        They're typically side by side. Generally in-wheel systems are expensive, because they're harder to manufacture and of course the flywheel system should be suspended, so you have to fit a suspension system in there as well. Space isn't at a premium in cars, and on motorscooters and motorcycles they just use a high rpm engine (10000 rpm in typical operation) to have smoother torque output.
ph0rque 18y ago
Just finished reading a 2000 Wired article about the state of the art of flywheels at that point: http://www.wired.com/wired/archive/8.05/flywheel_pr.html http://www.wired.com/wired/archive/8.05/flywheel_pr.html. This makes me wonder: with all the excitement about graphene, what rpms would a flywheel made from shells of graphene be able to achieve?
ivank 18y ago
Don't miss Radiatidon's comments, especially #7
- Flemlord 18y ago
  For convenience: Christopher S. Putnam said ”unique to flywheel designs is the gyroscopic effect, which causes spinning objects to resist changes to their orientation. As stated a flywheel resists change in its angular location. In playing with various test apparatuses during the 1970,s & 1980’s, we strove to design and build a “floating” cradle to contain the flywheel. This cradle would in theory keep the flywheel facing in the same direction no matter how the vehicle moved and/or turned. Theory does not always pan out in the real world. Christopher S. Putnam said ”all of which must be released very quickly if the flywheel breaks apart or falls off its axle.” We did sufferer various breakdowns, as the flywheel’s mounts would shatter under the extreme forces that such a device operates under. Also we had a casualty when one test apparatus had a minor flaw in structure of that flywheel. We had powered-up the flywheel and was preparing to test yet another combination of bearings, magnets, and high tensile frame structure. It was giving off a most pleasant thrum and there was hardly any deviation in the floating axis. Suddenly there was a weird sounding pop, and the warning systems came on-line. This shut down the power to the flywheel and engaged the slow-brake to power down the spin. Unfortunately this was too little and too late. The floating axis shifted and sent harmonic vibrations throughout the support structure. With an ear-piercing squeal the highly spinning metal gave off its death cry. The device literally came apart sending shrapnel in a vector perpendicular to the common axis of the flywheel. The safety shield that incased the device did not live up to its design as the debris tore through it like so much tissue paper. Unfortunately there was a fellow standing in front of it when this happened. Like a scene out of some sick horror flick, he was instantly split from crotch to forehead. Considering the amount of damage, it was amazing that we suffered only the one death. The project was canceled shortly after that. …as interesting as this article is, I wish that I had not read the damn thing. It brought back bad memories. Memories that are just as vivid as if it just happened. I was standing next to him, and as he fell I tried to catch him…
mixmax 18y ago
Flywheels are actually used in some state of the arts yachts to keep the yacht level no matter how the weather is. It is mounted midship in the hull below the waterline and keeps the yacht from rolling. Ferretti uses this system. Since storing electricity is a problem at sea, and most yachts carry a truckload of batteries maybe there is a business opportunity for some flywheel-hacker...
- ph0rque 18y ago
  I just found my stabilization system + battery storage for my super secret artificial island plan :~)
  - mixmax 18y ago
    http://thebuilderblog.wordpress.com/2008/03/25/az-island/ http://thebuilderblog.wordpress.com/2008/03/25/az-island/
    - ph0rque 18y ago
      Actually, I was thinking more along the lines of: http://ecoble.com/2007/11/18/250000-bottles-amazing-recycled-mexican-island-paradise/ http://ecoble.com/2007/11/18/250000-bottles-amazing-recycled...
- DougBTX 18y ago
  > most yachts carry a truckload of batteries All we need is a second flywheel battery to power the first one...
maxklein 18y ago
When you have an accident, what happens to the giant spinning wheel in your car? Does it roll out and down the road?
- eru 18y ago
  It's more likely to break apart violently.
mdasen 18y ago
A flywheel-based battery, on the other hand, can reach energy densities 3-4 times higher, at around 100-130 watt-hours per kilogram. The problem is that the author compares fly-wheels to lead-acid batteries. Lithium-ion batteries can easily achieve 150-200Wh/kg beating flywheels. Plus, there are huge advances being made in chemical batteries such as those made by A123 Systems.
- DabAsteroid 18y ago
  (Energy per weight is not energy density. It is specific energy. Energy density is energy per volume.) A123 batteries are not notably high in specific-energy capacity. They are notably low in internal resistance. Big difference.
- DabAsteroid 18y ago
  Lithium-ion batteries can easily achieve 150-200Wh/kg Li-Ion in vehicles usually involves redundancy so as to minimize the discharge-damage to the cells. The Tesla Roadster batteries weigh about 400 kg and are rated to hold about 50kWh = 125 Wh/kg. http://www.teslamotorsclub.com/technical-discussion/354-tesla-roadster-batteries.html http://www.teslamotorsclub.com/technical-discussion/354-tesl...
TrevorJ 18y ago
Very interesting, although I take some issue with the thought that gasoline is more dangerous than a fly wheel. Different dangers perhaps. In spite of what the movies say, the energy in a gas tank can't be expended instantly in the explosive way a disc can come apart.
- eru 18y ago
  I had a CD come apart in a very cheap drive once. I remember calculating that the outer regions of a CD spin at almost the speed of sound in a modern CD drive. (But do not take my word for it - until I do the calculation again, it's been some time.)
huherto 18y ago
"to flywheel designs is the gyroscopic effect, which causes spinning objects to resist changes to their orientation." Is this why you do not fall from a bike when it is moving forward?
- shimon 18y ago
  Yes.
  - DaniFong 18y ago
    Actually, the gyroscopic action contributes but it isn't dominant. The dominant effect is the steering geometry, notably the caster angle -- the amount the wheel is ahead of the forks. This article is worth reading; it's an investigation into bicycle stability. http://ist-socrates.berkeley.edu/~fajans/Teaching/MoreBikeFiles/JonesBikeBW.pdf http://ist-socrates.berkeley.edu/~fajans/Teaching/MoreBikeFi...
    - eru 18y ago
      Classic article. In order to find out what makes a bicycle stay upright, the author tries to build an unridable bicycle. And that's harder than it sounds. Quote: "It seems a lot of tortuous effort to produce in the end a machine of absolutely no utility whatsoever, but that sets me firmly in the mainstream of modern technology."
rsheridan6 18y ago
This seems like an ideal way to store energy from home solar or wind power. The safety problems would not be an issue at home, where you could either bury it or put a really heavy shield around it. Maybe this is irrelevant since you can get paid for giving electricity to the grid - unless, of course, you're not on the grid.
- DaniFong 18y ago
  It's not quite ideal, since flywheels will still spin down, and the duty factor on wind and solar ranges near 11%. Compressed air is actual a decent contender in this area.
timtrueman 18y ago
I'm surprised nobody's mentioned Formula 1 yet. Next season will see the introduction of the Kinetic Energy Recovery System (KERS). Basically it's 40kg flywheel capable of storing 60kW of energy recovered from braking that will allow for 6.5 seconds of additional acceleration. This is an attempt to make overtaking a more frequent and exciting proposition. Regulations allow for electrical or mechanical implementations. BMW chose electrical and has already seen how dangerous it can be: http://www.youtube.com/watch?v=fzaQ-t1ojPU http://www.youtube.com/watch?v=fzaQ-t1ojPU http://www.formula1.com/news/headlines/2008/7/8086.html http://www.formula1.com/news/headlines/2008/7/8086.html
twopoint718 18y ago
This reminds me of a little sidebar in "Fundamentals of Physics" (Halliday et al. 6th ed.) that talks about how dangerous a rapidly spinning object can be. They listed a case study from Test Devices Inc. where a solid steel disk exploded from a test rig while spinning at 14 krpm. There were lead bricks thrown into the hallway, a door was now in the parking lot, etc. Amazing. (This was a solved exercise, ans: about 20 MJ)

60 points by ph0rque 18y ago

I wonder what it is like to steer a bus with a 3 ton spinning disc inside: http://en.wikipedia.org/wiki/Precession#Torque-induced http://en.wikipedia.org/wiki/Precession#Torque-induced

eru 18y ago
Just take two and spin them in opposite directions.
- eru 18y ago
  While I think about it: You could even install the two disks spinning horizontally, and the bus would be even more stable against tilting.
  - pedalpete 18y ago
    I believe this is what they use in large cruise ships for stability.
  - ajross 18y ago
    If they're counterspinning with equal angular momentum, there won't be any gyroscopic effects at all. The precession torque from one wheel is exactly opposite to the other. The only gotcha is making sure that torques get applied equally to both wheels to keep them at the same speed, even if the enclosure itself is rotating. But I'm skeptical. Anything with moving parts has failure modes. Huge stationary flywheels as building or municipal storage devices make a lot more sense to me than putting one in a car.
  - DaniFong 18y ago
    This actually messes up the steering geometry. you need the steering system to be only barely in the region of stability, otherwise it takes too much effort and energy to turn. And during turns, four wheeled vehicles bank slightly, which is very important to maximize the normal force on the outside wheels to increase frictional contact with the road. In general, the dual-mass oppositely rotating flywheels work best: there's a miniature system like this in every car to even out engine vibrations.
    - ph0rque 18y ago
      Question for you Danielle: are the dual-mass oppositely rotating flywheels usually side-by-side, or wheel-in-wheel? Is there any advantage to one or the other?
      - DaniFong 18y ago
        They're typically side by side. Generally in-wheel systems are expensive, because they're harder to manufacture and of course the flywheel system should be suspended, so you have to fit a suspension system in there as well. Space isn't at a premium in cars, and on motorscooters and motorcycles they just use a high rpm engine (10000 rpm in typical operation) to have smoother torque output.

ph0rque 18y ago

Just finished reading a 2000 Wired article about the state of the art of flywheels at that point: http://www.wired.com/wired/archive/8.05/flywheel_pr.html http://www.wired.com/wired/archive/8.05/flywheel_pr.html. This makes me wonder: with all the excitement about graphene, what rpms would a flywheel made from shells of graphene be able to achieve?

ivank 18y ago

Don't miss Radiatidon's comments, especially #7

Flemlord 18y ago
For convenience: Christopher S. Putnam said ”unique to flywheel designs is the gyroscopic effect, which causes spinning objects to resist changes to their orientation. As stated a flywheel resists change in its angular location. In playing with various test apparatuses during the 1970,s & 1980’s, we strove to design and build a “floating” cradle to contain the flywheel. This cradle would in theory keep the flywheel facing in the same direction no matter how the vehicle moved and/or turned. Theory does not always pan out in the real world. Christopher S. Putnam said ”all of which must be released very quickly if the flywheel breaks apart or falls off its axle.” We did sufferer various breakdowns, as the flywheel’s mounts would shatter under the extreme forces that such a device operates under. Also we had a casualty when one test apparatus had a minor flaw in structure of that flywheel. We had powered-up the flywheel and was preparing to test yet another combination of bearings, magnets, and high tensile frame structure. It was giving off a most pleasant thrum and there was hardly any deviation in the floating axis. Suddenly there was a weird sounding pop, and the warning systems came on-line. This shut down the power to the flywheel and engaged the slow-brake to power down the spin. Unfortunately this was too little and too late. The floating axis shifted and sent harmonic vibrations throughout the support structure. With an ear-piercing squeal the highly spinning metal gave off its death cry. The device literally came apart sending shrapnel in a vector perpendicular to the common axis of the flywheel. The safety shield that incased the device did not live up to its design as the debris tore through it like so much tissue paper. Unfortunately there was a fellow standing in front of it when this happened. Like a scene out of some sick horror flick, he was instantly split from crotch to forehead. Considering the amount of damage, it was amazing that we suffered only the one death. The project was canceled shortly after that. …as interesting as this article is, I wish that I had not read the damn thing. It brought back bad memories. Memories that are just as vivid as if it just happened. I was standing next to him, and as he fell I tried to catch him…

mixmax 18y ago

Flywheels are actually used in some state of the arts yachts to keep the yacht level no matter how the weather is. It is mounted midship in the hull below the waterline and keeps the yacht from rolling. Ferretti uses this system. Since storing electricity is a problem at sea, and most yachts carry a truckload of batteries maybe there is a business opportunity for some flywheel-hacker...

ph0rque 18y ago
I just found my stabilization system + battery storage for my super secret artificial island plan :~)
- mixmax 18y ago
  http://thebuilderblog.wordpress.com/2008/03/25/az-island/ http://thebuilderblog.wordpress.com/2008/03/25/az-island/
  - ph0rque 18y ago
    Actually, I was thinking more along the lines of: http://ecoble.com/2007/11/18/250000-bottles-amazing-recycled-mexican-island-paradise/ http://ecoble.com/2007/11/18/250000-bottles-amazing-recycled...
DougBTX 18y ago
> most yachts carry a truckload of batteries All we need is a second flywheel battery to power the first one...

maxklein 18y ago

When you have an accident, what happens to the giant spinning wheel in your car? Does it roll out and down the road?

eru 18y ago
It's more likely to break apart violently.

mdasen 18y ago

A flywheel-based battery, on the other hand, can reach energy densities 3-4 times higher, at around 100-130 watt-hours per kilogram. The problem is that the author compares fly-wheels to lead-acid batteries. Lithium-ion batteries can easily achieve 150-200Wh/kg beating flywheels. Plus, there are huge advances being made in chemical batteries such as those made by A123 Systems.

DabAsteroid 18y ago
(Energy per weight is not energy density. It is specific energy. Energy density is energy per volume.) A123 batteries are not notably high in specific-energy capacity. They are notably low in internal resistance. Big difference.
DabAsteroid 18y ago
Lithium-ion batteries can easily achieve 150-200Wh/kg Li-Ion in vehicles usually involves redundancy so as to minimize the discharge-damage to the cells. The Tesla Roadster batteries weigh about 400 kg and are rated to hold about 50kWh = 125 Wh/kg. http://www.teslamotorsclub.com/technical-discussion/354-tesla-roadster-batteries.html http://www.teslamotorsclub.com/technical-discussion/354-tesl...

TrevorJ 18y ago

Very interesting, although I take some issue with the thought that gasoline is more dangerous than a fly wheel. Different dangers perhaps. In spite of what the movies say, the energy in a gas tank can't be expended instantly in the explosive way a disc can come apart.

eru 18y ago
I had a CD come apart in a very cheap drive once. I remember calculating that the outer regions of a CD spin at almost the speed of sound in a modern CD drive. (But do not take my word for it - until I do the calculation again, it's been some time.)

huherto 18y ago

"to flywheel designs is the gyroscopic effect, which causes spinning objects to resist changes to their orientation." Is this why you do not fall from a bike when it is moving forward?

shimon 18y ago
Yes.
- DaniFong 18y ago
  Actually, the gyroscopic action contributes but it isn't dominant. The dominant effect is the steering geometry, notably the caster angle -- the amount the wheel is ahead of the forks. This article is worth reading; it's an investigation into bicycle stability. http://ist-socrates.berkeley.edu/~fajans/Teaching/MoreBikeFiles/JonesBikeBW.pdf http://ist-socrates.berkeley.edu/~fajans/Teaching/MoreBikeFi...
  - eru 18y ago
    Classic article. In order to find out what makes a bicycle stay upright, the author tries to build an unridable bicycle. And that's harder than it sounds. Quote: "It seems a lot of tortuous effort to produce in the end a machine of absolutely no utility whatsoever, but that sets me firmly in the mainstream of modern technology."

rsheridan6 18y ago

This seems like an ideal way to store energy from home solar or wind power. The safety problems would not be an issue at home, where you could either bury it or put a really heavy shield around it. Maybe this is irrelevant since you can get paid for giving electricity to the grid - unless, of course, you're not on the grid.

DaniFong 18y ago
It's not quite ideal, since flywheels will still spin down, and the duty factor on wind and solar ranges near 11%. Compressed air is actual a decent contender in this area.

timtrueman 18y ago

I'm surprised nobody's mentioned Formula 1 yet. Next season will see the introduction of the Kinetic Energy Recovery System (KERS). Basically it's 40kg flywheel capable of storing 60kW of energy recovered from braking that will allow for 6.5 seconds of additional acceleration. This is an attempt to make overtaking a more frequent and exciting proposition. Regulations allow for electrical or mechanical implementations. BMW chose electrical and has already seen how dangerous it can be: http://www.youtube.com/watch?v=fzaQ-t1ojPU http://www.youtube.com/watch?v=fzaQ-t1ojPU http://www.formula1.com/news/headlines/2008/7/8086.html http://www.formula1.com/news/headlines/2008/7/8086.html

twopoint718 18y ago

This reminds me of a little sidebar in "Fundamentals of Physics" (Halliday et al. 6th ed.) that talks about how dangerous a rapidly spinning object can be. They listed a case study from Test Devices Inc. where a solid steel disk exploded from a test rig while spinning at 14 krpm. There were lead bricks thrown into the hallway, a door was now in the parking lot, etc. Amazing. (This was a solved exercise, ans: about 20 MJ)