Working Model of Perpetual Motion

AgingYoung said:
Some of the energy a weight generates as it falls is going to be consumed to overcome the inertia of the structure holding it along with other weights in addition to frictions. Do you consider that work (overcoming inertia and friction) to be part of the equation?
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Congratulations. You've just stumbled upon one reason why perpetual motion is impossible. Parasitic losses due to things like friction.
 
AgingYoung said:
I should have said, 'all possible losses yet still manages to turn.'

Gene

edit: it occurred to me after I posted this ....any heat loss would be caused by friction. If the wheel would turn and overcome friction it would naturally be making up for any loss due to heat. Similarly if it had to make a little noise or a lot of noise to turn yet still turned it would none the less be turning. Any wheel that could turn would obviously be overcoming any obstacle it would need to overcome.

edit II: the 2nd law of Thermodynamics is a separate concept
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First off, you can't claim frictionless. If you have any atomic interactions, you'll have a friction.

Further I've already metioned that no material is without some viscoelastic property. It all depends on the time scale. Metals and ceramics will creep under a force under enough time (perhaps billions of years), but it's still there.

What about all surrounding matter and it's gravitational forces? Don't these forces also act to slow down the motion as well.

Like I said we may get close, but never 100%.
 
Big Al said:
One aspect of PMM that people often seem to overlook is the concept of work. A permanently spinning wheel is not a machine until it actually does some useful work (e.g., moves a load, heats some water etc.).

And it's not a perpetual motion machine until it can do that over and over again.
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Are you sure about this? Who says this? I have never heard this. Steer me to whoever made this rule.

I was always under the belief that any machine that did not have a power source...no fuel, electricity, etc.,... even which includes existing and non-depleteable and always constant sun, water and wind sources...would qualify as perpetual motion so long as it could remain in motion. Hence, perpetual 'motion'. Not a perpetual 'work' machine.

We all know, I think, that if one were to come up with a perpetual motion machine, even if it has has no residual energy to do any useable 'work'....that would be the easiest to make. But...let's see you even come up with one that does not use any of the things I list, that can still remain in motion, uselessly.
 
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drkitten said:
Congratulations. You've just stumbled upon one reason why perpetual motion is impossible. Parasitic losses due to things like friction.
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That said....I wonder who has come up with the longest running machine that will simply start with perhaps just a bump, and keep running for hours...days?...weeks?...months?...years? I do realize to quatitatively assign some rule regarding starting the machine may prove difficult, since any machine utilizing the flywheel method and employing some gigantic initial spin, could skewer the results comparing one machine against another. Unless...one were to come up with some other measure of gauging a machines loss of momentum by timing the loss of it's speed per each revolution.

It would be interesting to find out what kind of machine holds the world's record.
 
Iamme said:
Are you sure about this? Who says this? I have never heard this. Steer me to whoever made this rule.

I was always under the belief that any machine that did not have a power source...no fuel, electricity, etc.,... even which includes existing and non-depleteable and always constant sun, water and wind sources...would qualify as perpetual motion so long as it could remain in motion. Hence, perpetual 'motion'. Not a perpetual 'work' machine.

We all know, I think, that if one were to come up with a perpetual motion machine, even if it has has no residual energy to do any useable 'work'....that would be the easiest to make. But...let's see you even come up with one that does not use any of the things I list, that can still remain in motion, uselessly.
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A planet moves perpetually without a power source. However, if you tried to get any work out of it, it would lose energy and spiral in towards its sun.

Work is an important factor in defining a machine. The simplest defined machine is a lever. However, can it be considered a lever if it isn't being used to lift weights (i.e., doing work)?
 
Big Al said:
A planet moves perpetually without a power source. However, if you tried to get any work out of it, it would lose energy and spiral in towards its sun.
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Er, no. There are still frictional losses in planetary orbits.
 
There are frictional losses in any orbit... hit enough dust and you're slowing down. Space is full of it. The counter to that is you're also speeding up a lot of space dirt by deflection. All orbits eventually decay.
 
OK, granted. :blush:

Nothing is perpetual. Given enough time, even protons decay into neutrons and positrons. I'll just hide behind the caveat that "certain factors have been neglected as negligible".

That's also the slip of many a PM-bleever.
 
A wheel-based perpetual motion machine is very easy to test. Since it can produce more power than needed to drive it, a small push will make the wheel spin slowly at first, then faster and faster until it flies apart from centripetal forces! A well-designed perpetual motion machine will fly apart very quickly, which is why you should never operate one without a load.
 
bjb,

Two intrinsic loads for a pmm would be air resistance and frictions. Even if you reduced those to very slight levels centrifugal force would have a governing effect. As cf increased it would limit the range of the mass causing the rotational force.

I know someone working on a wheel that is driven by cf. If a pmm is possible I don't think it will be found there. If it is then it would have a tendency to fly apart as you mentioned. imo a cf driven pmm couldn't be merely a mechanical device. It would require an electro-mechanical control system that would need to factor itself into the dynamics it was attempting to control. If it were possible it's the sort of project you would expect nasa or boeing to develop. I don't think it is.

Gene
 
AgingYoung said:
Some of the energy a weight generates as it falls is going to be consumed to overcome the inertia of the structure holding it along with other weights in addition to frictions. Do you consider that work (overcoming inertia and friction) to be part of the equation?
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I'm not sure what you mean by "energy [...] is going to be consumed to overcome the inertia of the structure holding it." Can you clarify?
 
Energy of a falling weight is kinetic energy.

I have to add that a pure inertia does not dissipate energy, it only stores it in form of kinetic energy as the inertia is accelerated. Friction, of course, is the enemy of perpetual motion machines, partly because frictional losses (heat) are part of the work that any machine must do. Unfortunately, not all of the work performed by a machine is available at the output shaft.
 
69dodge,

That energy is, as bjb said, kinetic. A wheel at rest is going to want to remain at rest. If you want to rotate it you will need to exert some force. The potential energy of some mass could be that force. As that potential is realized in motion or kinetic energy it will overcome the inertia of the wheel.

In addition to that inertia the potential is going to have to do the work of overcoming frictions. My point is that a wheel that simply turns is doing work and could be considered a machine.

Gene
 
GzuzKryzt said:
The increase of stupidity seems perpetual. Uga buga.
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The Second Law of Wormodynamics: "In a closed-minded system, dumbtropy tends to a maximum."

If we could find a way to harness the power of stupidity, it would make controlled thermonuclear fusion look like small potatoes.
 
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