I'm interested in the explanation behind why this won't work, though I'm sure it won't.
A Foucault pendulum is really just a big big pendulum, big enough to swing slowly back and forth for a long time. Such a pendulum is suspended from a high ceiling and set in motion. As it swings, the earth rotates beneath it, but the plane in which the pendulum swings stays fixed. Therefore, the plane of oscillation appears to turn slowly during the day. If you start it swinging east-west, it will eventually appear to be swinging north-south, because the earth has turned 90 degrees underneath it.
The Foucault pendulum is easiest to imagine if it's at the North or South pole, but in fact will work anywhere.
Now. We're going to build a Foucault pendulum. Normally, the pendulum is just suspended on a wire from the ceiling. In this case, though, we will put the weight on a rigid arm. A pin passes through the top of the arm, so it can swing to and fro.
However, with this arrangement, the pendulum cannot "rotate" (or, to be precise, it cannot maintain its plane of oscillation as the Earth turns, because its mounting can't turn that way).
So, we fix the pin on a metal plate, and fix this plate on the ceiling so that the plate can turn (with its axis vertical).
So far, so good. The pendulum can swing to and fro on its pin, the plate carrying the pin can turn in the horizontal plane, and so everything will work. Over the course of the day, the plane of oscillation of the pendulum will rotate 360° relative to the building. If we make a mark on the plate on the ceiling, we will of course see that it too rotates 360° during the day.
OK so far?
Now, we're going to do something odd. We're going to glue some magnets to the edge of the plate on the ceiling, and fit some coils of wire to the ceiling itself.
Now, as the pendulum swings and the plate rotates once per 24 hours (it's actually the ceiling and everything else which is rotating, of course), the magnets will turn slowly underneath the coils and - carpe emptor! - electricity will be generated in tiny amounts.
What we've done, in effect, is to create a cumbersome dynamo in which the plate is the stator (held in one place by the swinging pendulum, whose plane of oscillation stays still), and the rotor is the earth itself (including the coils which we glued to the ceiling).
We're NOT OVER UNITY (we're not over unity or - to put it another way - we're NOT over unity), because the electrical energy we extract actually damps the earth's rotation a little. We're using the rotational energy of the earth as a giant flywheel, and extracting a teensy part of its energy.
We could do the same thing if we just put magnets on the surface of the earth, and nailed lots of coils to the moon, using the earth as the rotor and the moon as the stator.
Now, I know everyone will tell me that this *won't* work, but I want to know *how* it won't work. I presume that, whatever energy we get out of the coils is going to be sapped from the oscillation of the pendulum, instead of from the rotation of the Earth, but I don't see how.-- MaxwellBuchanan, Jul 24 2010 A similar idea http://verens.com/2...he-coriolis-effect/ [ldischler, Jul 24 2010] Corryvreckan http://en.wikipedia.org/wiki/CorryvreckanImpressive. [8th of 7, Jul 24 2010] Foucault's Flywheel Foucault_27s_20Flywheel [xaviergisz, Jul 24 2010] The pendulum and gyroscope ideas, with !!!!!!!!!! http://mb-soft.com/public2/earthrot.htmlTo quote: "Of course, I could be wrong! Until I get some math problems solved, I will not know! I am pretty confident on this, and I can nearly taste it! Interestingly, if I am right, the device would NOT work at the Equator! Fortunately, human beings seem to like to live at around 40° Latitude, where it figures to work very well!" [ldischler, Jul 25 2010] (?) On the Dynamics of the Dynabee http://www.hep.prin...k_jam_62_321_00.pdf [ldischler, Jul 25 2010] US 8299636 https://www.google.com/patents/US8299636Magnetized foucault pendulum electrical energy source [xaviergisz, Sep 13 2013] So you're going to get energy from the rotation of the earth? Decades ago I bought one of those spinning tops with the hidden magnets when they first came out, and convinced my roommate that it got its energy from the rotation of the earth, but couldn't be commercialized because of the random nature of the top as it spun along the parabolic surface. He spent an entire month trying to invent some method of harnessing that energy. Of course, angular momentum is conserved, so if you slow down the earth, you have to speed up something else, and you're not doing that here.-- ldischler, Jul 24 2010 Ah, I knew angular momentum would rear its ugly vector sooner or later. But I'm still curious to know the mechanism - ie, do we have to put extra energy to keep the Foucault pendulum moving if we couple it to a dynamo like this? And, if so, how do the various torques act to slow the pendulum in such a way that we have to put the extra energy in?-- MaxwellBuchanan, Jul 24 2010 //We all lack the attention span to have got as far as that question.//
I know. I worry sometimes that I have viral vernonitis.-- MaxwellBuchanan, Jul 24 2010 I think the energy is taken from the rotation of the earth.-- Voice, Jul 24 2010 I wish it were, and I can't see why it's not, but I'm sure it isn't.
I was trying to think of a way to tap the vast stored rotational energy of the earth, but for this you need something which is not rotating, relative to the earth. The plane of the Foucault pendulum seemed like one option. Another would be a big mother gyroscope, with its axis horizontal.
But look at what happened to poor old Professor Laithwaite. Invented the linear induction motor, then started playing with gyroscopes and went bonkers.-- MaxwellBuchanan, Jul 24 2010 //you need something which is not rotating, relative to the earth. //
Or something that is, like the moon. When you tap the tides, you slow the rotation of the earth and kick the moon into a higher orbit.-- ldischler, Jul 24 2010 Question: the earth turns, the pendulum stays still. The generation of power (which as far as I can see has to happen) will slow the earths rotation by a tiny amount. Or speed up the pendulum, depending on how you look at it (special relativity). How can slowing something (taking off energy) equate to speeding something up (adding energy)?
Confused of Tunbridge Wells.-- wagster, Jul 24 2010 I don't think that's the problem. Or at least your problem is an explicable one.
Consider a flywheel energy-storage device (such things exist, verily). The flywheel starts off spinning fast (which is where we come in), and is then engaged with a dynamo, which generates electricity, and the flywheel is slowed, eventually to a standstill. This is the same idea, just using the Foucault pendulum to hold the dynamo stators still while the Earth turns the rotor.
And you're not of Tunbridge Wells.-- MaxwellBuchanan, Jul 24 2010 // started playing with gyroscopes and went bonkers //
No, he didn't. He was getting too close to the Big Secret, so he had to be quietly sequestered and replaced by a replicant programmed to convince the world at large that he was bonkers.
Please be reassured that he was treated extremely well, and greatly enjoyed the remainder of his life (which was long and healthy), seeing and doing things he had never imagined in his wildest dreams, as well as getting to work on the Big Secret.
As to the idea, the best way of harnessing planetary rotational energy, on your planet anyway, is in fact tidal power, although you do need to be a tad more ambitious than you have been so far.
<Throws meaningful glance at Corryvreckan>
<link>-- 8th of 7, Jul 24 2010 Tidal power is all very well and good, but to work well, it needs to be done near the sea, if not actually in it.-- MaxwellBuchanan, Jul 24 2010 /the electrical energy we extract actually damps the earth's rotation a little//
Won't this also apply a slight torque on the pendulum, causing it's plane to rotate in the same direction as the earth? Unless you're using Saturn for the pendulum's bob, the pendulum's angular velocity is going to change much faster than the Earth's, what with the conservation of angular momentum and all. So from a fixed reference frame, the pendulum will start rotating, while the Earth's rotation will slow down by a tiny bit. Any power generated will be limited by the pendulum's change in angular momentum.-- SirBobofBobton, Jul 24 2010 //pendulum will start rotating, while the Earth's rotation will slow down by a tiny bit.//
Yes, that's quite true. But the same can be said of a flywheel energy storage system: the flywheel drives the rotor of a dynamo, which generates electrical power. But the fields (plus friction) naturally try to drag the casing of the dynamo around, and this in turn tries to drag the earth around.
So yes, there will be a torque trying to turn the plane of rotation of the pendulum, and it will succeed to some extent, but not completely.
Basically, we have a planet trying to turn, and a pendulum whose mounting-point is trying to stay still. Between the two of them, we generate energy.-- MaxwellBuchanan, Jul 24 2010 //o yes, there will be a torque trying to turn the plane of rotation of the pendulum, and it will succeed to some extent, but not completely//
Why won't it succeed completely? In the flywheel case, the dynamo is going to apply equal and opposite torques on both the Earth and the flywheel, causing the flywheel to slow down and the Earth to speed up (slightly). Eventually, the Earth and the flywheel are are going to be rotating at the same rate, at which point we say the flywheel has stopped.
I don't disagree that the Buchanan-Foucault Generator will produce energy; it's a question of how much. A 1000kg mass rotating 10m from its axis at 1rpd has about 7J of rotational energy, which is what we'd be extracting. I have no idea what the effect of a pendulum's swing would have on it's rotational energy, but my guess is that 7J figure would still be the upper bound.
(As an aside, with a 100m length, it would take a little under 5kJ to get the bob 10m from the centerline.)-- SirBobofBobton, Jul 24 2010 //Why won't it succeed completely?// Well, in fact, eventually it must, I suppose. But the point is that work has to be done to do so. Fundamentally, it's no different from any other dynamo - the stator is trying to slow the rotor down, and the rotor is trying to speed the stator up.
//energy; it's a question of how much.// Indeed it is. First, let me reiterate that this is not an over-unity device; any apparent net energy output will be taken from the Earth's rotational energy. Now, it certainly takes energy to start the pendulum, but we can ignore that and assume we're going to run the system for an infinite time by keeping the pendulum swinging.
We can assume that it takes zero energy to keep a **normal** Foucault pendulum swinging (ie, we can run it in a vacuum; we can have bearings with arbitrarily low friction).
So the real question is this: does the pendulum lose energy as a result of our turning its mounting bracket into a 1rpd dynamo? And if it does, does it lose energy faster than it generates it?
Again, please note, regardless of the answers above, this is not an overunity device. At best its a method for extracting rotational energy from the planet, and I bet its not even that. But why not?-- MaxwellBuchanan, Jul 24 2010 //I don't disagree that the Buchanan-Foucault Generator will produce energy//
Nope. The generated energy must be negative.-- ldischler, Jul 25 2010 This is not a perpetual-motion machine. It is a means of harvesting the Earth's rotational energy.
Whether it is theoretically possible to take energy from the Earth's rotation (to slow the Earth) while standing on it is one problem. (Tidal power is Moon powered, I think, and another matter, even if the Moon does wind up slowing the Earth because of it.)
If robbing the Earth's rotation while standing on it is theoretically possible, practicality rears its ugly head.
The pendulum is not a good way to make such a device, that much I can say.
The goal, as best I can describe it from my work on this some years ago, is to move something toward and away from the Earth's axis, capturing the difference in velocity between the two locations.-- baconbrain, Jul 25 2010 //This is not a perpetual-motion machine. It is a means of harvesting the Earth's rotational energy.//
Doesn't matter, it still violates a basic law of physics. Perpetual motion machines violate the second law of thermodynamics, while this idea violates the conservation of angular momentum. Like the second law, this law has never been shown to be violated by any process.-- ldischler, Jul 25 2010 That's where I got lost, and why I don't know if this is possible.
If we assume that something, somewhere must be rotating with just as much rotational energy as when we started, it is impossible. But cannot the rotational energy be converted to, say, heat? That's where I started barking.-- baconbrain, Jul 25 2010 yes, but is it an "over unity" device ?
Saner minds may prevail, but I'm gonna guess that the amount of energy it took to raise the pendulum for the original swing is the amount of energy you'll get out of it.
What you'd be doing by putting a damper on it is siphoning off plain old precessional energy: each swing would get lower and slower.-- FlyingToaster, Jul 25 2010 It'll work.
It's anti gyroscillation with your name on it, but it'll work.
(+)-- 2 fries shy of a happy meal, Jul 25 2010 Reduction to absurdism: a heavy shaft has a gyroscope attached to the end. The gyroscope is mounted on a pivot so that when the shaft rotates the gyroscope doesn't. Normally the shaft (earth) is spinning on its axis, and the gyroscope (pendulum) is spinning on a perpendicular axis and that axis remains stationery.
Now link those two together with a coil and magnet to generate power from the relative speeds of rotation. The shaft will slow down, but I think it will also try to precess. So in conclusion, not only will the earth slow down, angular momentum is conserved due to change of Earth's precession.
Since Earth already has a 20-odd thousand year precession, one could presume that the Buchanans already experimented profusely with pendulums in the ancient world.-- Ling, Jul 25 2010 Dear all, I am inclined to agree with those that say this won't work, and I am tempted to agree with the argument based on conservation of angular momentum.
However, what's interesting (as in the case of "over-unity" devices, which this is NOT) is not so much whether or not it fails, but the *mechanism* by which it fails - the actual transfer of torques or whatever. That's what I'm trying to understand.
By adding the generator, we are indeed trying to "twist" the plane of the swing, and it is indeed rather like trying to twist the axis of rotation of a gyroscope. So, for this device to fail (as I think it must), the twisting of the plane must somehow take energy (and momentum) from the swing of the pendulum. If this happens, we will have to add energy to keep the pendulum swinging, and the net energy yield will indeed be zero (or negative, allowing for friction and air resistance).
I'm happy with all this, but I cannot get my head around the process by which twisting the plane saps energy from the swing.
(Oddly, Ling is right - the Beau Chansonne family, my very distant ancestors, had a penchant for pit-and-pendulum devices,)-- MaxwellBuchanan, Jul 25 2010 You're right MB, and the argument against it working is also an argument that you can add or subtract energy from a spinning gyroscope by twisting its axis. Twist it aginst its tendency to precess and you subtract energy; twist it in the other direction and you add energy. See the wikipedia discussion under "Gyroscopic exercise tool."-- ldischler, Jul 25 2010 Yes, I presume that's how the "Powerballs" work. (Google if not familiar).
The thing about the Powerball is that, by twisting its axis of spin correctly, you make it spin faster, and this spin is adequate to not only overcome friction, but also to power the LEDs and the display. In other words, the twisting energy provided by wrist is converted to rotational energy in the Powerball, and thence into electricity.
If I were to build a giant wrist sticking out of the ground at the North Pole at the right angle, and then attached to it a giant metal hand holding an enormous Powerball, then I would expect the turning of the Earth to turn the giant wrist carrying the hand holding the giant Powerball, and thence to spin-up the Powerball and generate electricity, slowing the Earth's rotation at the same time (just as the normal Powerball tries to slow the twisting of my wrist).
So, the question boils down to this:
What is the mechanistic difference between me turning my wrist to drive a normal powerball that generates electricity; and the rotation of the Earth driving a large powerball that generates electricity?-- MaxwellBuchanan, Jul 25 2010 Reading it again maybe it's not the same thing for the powerball, since they claim that friction is a necessary ingredient. But if you read the paper, "Dynamics of the Dynabee," you will become hopelessly confused. See link.-- ldischler, Jul 25 2010 I think I'll post a new idea relating to the Powerball model...-- MaxwellBuchanan, Jul 25 2010 Powerearth.-- ldischler, Jul 25 2010 This is still making my brain hurt. I do not know if it is possible to tap energy off the Earth's rotation, but I have thought of a way the pendulum can lose power in this scenario. Maybe.
The pendulum as described will swing back and forth less than an untrammeled pendulum. This is because it is not allowed to move sideways freely at the end of each swing. That sideways motion can be visualized as a portion of swinging the entire pendulum around in a great big circle, which would represent a lot of energy. The portion of that circle that is accomplished at the outer part of each swing is a temporary holding-outward of the pendulum through centrifugal inertia, and counts as energy in the pendulum, just as if it had swung out another inch or so. I think.
So depriving the pendulum of that centrifugal force cuts energy from each swing.
Maybe.-- baconbrain, Jul 25 2010 I'm with Mr. Brain on this one.-- Voice, Jul 25 2010 //So depriving the pendulum of that centrifugal force cuts energy from each swing. //
I can believe that. But it still leaves me worrying about the Powerball (qv - maybe pick it up over there)-- MaxwellBuchanan, Jul 25 2010 Your analogy is wrong, though. The pendulum is like a flywheel with its axis *horizontal*, not vertical.
But perhaps better to move over the the "Buchanan- Foucault-Powerball Generator", which is an extension of this idea.-- MaxwellBuchanan, Jul 25 2010 I think I follow. But I also disagree. In effect, the pendulum is acting as a gyro (with its axis horizontal, as we agree). That axis (which doesn't want to turn in the horizontal plane) acts as the "stator" in the system, relative to the earth which is the "rotor". The relative movement between stator and rotor is what allows you to extract energy, just as in a regular dynamo.-- MaxwellBuchanan, Jul 25 2010 OK - so I don't see where we disagree (or maybe we don't). I'm saying the energy comes from the spinning of the earth (which is slowed down as a result, teensily), which happens relative to the axis of the pendulum (which we agree is really just a glorified gyro).
I hate to accuse anyone of agreeing with me....-- MaxwellBuchanan, Jul 25 2010 I'll have a go at this.
The magnetic interaction between the rotor and stator is going to add some torsional strain internally to the pendulum, trying to 'wind it up,' so to speak. This will add some friction to the system at the pendulum swing pivot as well as make the pendulum find a new compromise pivot axis.-- RayfordSteele, Jul 26 2010 I don't understand why this is controversial - does it matter whether the earth moves, or the pendulum? Isn't it the *system* that's important. Let's take the same logical components and reassemble a flywheel in space that pivots around an axle at the end of a rod (think bycycle forks) containing a dynamo. Does the flywheel rotate and the forks remain stationary, or is it the forks that rotate around the flywheel? Depending on what any given observer is doing at the time, they will see spinning flywheels and/or forks - and both to the same result.
But to answer the question of where does the energy go/come from - wont it come from *both* the earth and the pendulum? If f=ma and a force is exerted on the system (as power is generated) then it is exerted on the *system* of both the pendulum, and the earth. That force will accelarate both of those objects in a ratio subjkect to their singular/combined masses. The pendulum's and the earth's. So both are affected, only one is more visibly affected than the other.
Like jumping off a building - you are attracted to the earth, but the earth is also attracted to you. However the comparative masses are such that it's silly to perform the calculations showing how the earth's position/velocity is affected, because the results will be so small.-- zen_tom, Jul 26 2010 resisting Foucault energy results in a slowing of the pendulum itself and not to any significant degree the motion of the earth.There is no free energy here, move along.-- WcW, Jul 27 2010 when you turn a gyroscope away from the natural (referential) plane energy is removed from the motion of the mass. This can be demonstrated in several ways. In addition there are many forces that do act to "steal" energy from the rotation of the earth. Heating the core is only one example. Geothermal energy is an inertia sapping form of human energy production.-- WcW, Jul 27 2010 //I'll let you know when I start getting interested in moths.//
Apparently they use WiFi.-- MaxwellBuchanan, Jul 27 2010 How about looking at this from another angle?
What happens to the Earth when you start the pendulum in the first place? Finally, when the pendulum is at rest again, what could have happened? My thinking is that either the initial Energy is locked up as heat (e.g. air resistance) or used to return the Earth to the original condition.
Between the beginning and end, I don't think any additional energy would be transferred from Earth to pendulum, otherwise it would swing higher (of course it might if the swing co-incided with the turning of the Earth - how long would the pendulum be in that case?), but with many swings I don't think it would get anything: a bit like pushing a swing a thousand times a second regardless of its position.-- Ling, Jul 27 2010 //Geothermal energy is an inertia sapping form of human energy production.//
Nonsensical.-- ldischler, Jul 27 2010 //I don't think any additional energy would be transferred from Earth to pendulum// You may be right. However, the New Improved Powerball version of this idea (qv) is a slightly different situation.-- MaxwellBuchanan, Jul 27 2010 ok so the influence of geothermal energy on earths inertia is immeasurably small. the solidification of a planetary core does slow rotation. a weak point i confess.-- WcW, Jul 28 2010 Please don't slow down the Earth's rotation with your machine. Its getting hot enough this summer.-- el dueno, Jul 30 2010 Answering my question above, a most interesting fact to those who find it interesting is that a pendulum whose period is 1 day will be 1.8 million kms long - about 5 times further than the moon.-- Ling, Jul 30 2010 I'm pretty sure that all of the energy you extract will actually be taken from the inertia of the pendulum itself, as this is the energy source for the rotation.-- WcW, Sep 13 2013 random, halfbakery