h a l f b a k e r yA hive of inactivity
add, search, annotate, link, view, overview, recent, by name, random
news, help, about, links, report a problem
browse anonymously,
or get an account
and write.
register,
|
|
|
Please log in.
Before you can vote, you need to register.
Please log in or create an account.
|
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.
A similar idea
http://verens.com/2...he-coriolis-effect/
[ldischler, Jul 24 2010]
Corryvreckan
http://en.wikipedia.org/wiki/Corryvreckan
Impressive. [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.html
To 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/US8299636
Magnetized foucault pendulum electrical energy source [xaviergisz, Sep 13 2013]
[link]
|
| |
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. |
|
| |
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? |
|
| |
//We all lack the attention span to have got as far as that
question.// |
|
| |
I know. I worry sometimes that I have viral vernonitis. |
|
| |
I think the energy is taken from the rotation of the
earth. |
|
| |
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. |
|
| |
//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. |
|
| |
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. |
|
| |
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. |
|
| |
// 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> |
|
| |
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. |
|
| |
/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. |
|
| |
//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. |
|
| |
//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.) |
|
| |
//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? |
|
| |
//I don't disagree that the Buchanan-Foucault Generator will produce energy// |
|
| |
Nope. The generated energy must be negative. |
|
| |
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. |
|
| |
//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. |
|
| |
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. |
|
| |
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. |
|
| |
It's anti gyroscillation with your name on it, but it'll work. |
|
| |
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. |
|
| |
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,) |
|
| |
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." |
|
| |
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? |
|
| |
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. |
|
| |
I think I'll post a new idea relating to the Powerball model... |
|
| |
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. |
|
| |
I'm with Mr. Brain on this one. |
|
| |
//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) |
|
| |
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. |
|
| |
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. |
|
| |
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.... |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
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. |
|
| |
//I'll let you know when I start getting interested in
moths.// |
|
| |
Apparently they use WiFi. |
|
| |
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. |
|
| |
//Geothermal energy is an inertia sapping form of human energy production.// |
|
| |
//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. |
|
| |
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. |
|
| |
Please don't slow down the Earth's rotation with your machine.
Its getting hot enough this summer. |
|
| |
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. |
|
| |
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. |
|
| |