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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 01/31/2011 :  02:56:38  Show Profile Send H. Humbert a Private Message  Reply with Quote
I think I have joined the ranks of the truly crazy, because tonight I have come up with an idea for a perpetual motion machine. Well, not perpetual in that it could run forever, since friction would eventually break things down, but perpetual in the sense that it generates more energy than it needs to run.

Ok, here's the set up: imagine a big cube that weighs something like 2 tons. If that cube were set down onto some kind of hydraulic cylinder that would then turn a turbine(s) and generate electricity, how much power do you think could be generated? Probably a descent amount, but never enough to raise the 2 ton cube up again, right? Some energy must be lost in the transfer.

But now I know that elaborate pulley and counterweight systems can be devised so that such weights can be lifted with minimal effort from as little as a single person. I think I've seen car lifts that can be moved up and down by yanking on a pair of chains.

So if the cube was strapped into such an apparatus, then all we would need to devise is some sort of toggle mechanism that could either engage or disengage the pulley system, changing the cube's relative weight. Unsupported on the way down, allowing the cube to press down with its full weight and deliver maximum energy; and supported on the way up, so that the entire cube could be lifted using no more energy than that which is required to spin a small motor, leaving plenty of extra power to spare.

So could you get more energy out of this set up than it would take to run? Did I just invent an infinite energy machine? I'm willing to give SFN 10% of all proceeds should my plan succeed.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie

Edited by - H. Humbert on 01/31/2011 02:59:44

Dr. Mabuse
Septic Fiend

Sweden
9672 Posts

Posted - 01/31/2011 :  03:30:42   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
What have you've been smoking, and can I have some to?


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filthy
SFN Die Hard

USA
14408 Posts

Posted - 01/31/2011 :  05:39:48   [Permalink]  Show Profile Send filthy a Private Message  Reply with Quote
It is said that all things are possible, and I don't believe that for a minute.

How&ever, a weight system can indeed provide energy, if not perpetual motion, as has been shown many times.
one of the best examples is this:



I once thought up a plan for a trebuchet that used pnumatics rather than the massive weights. By my calculations, it would fling the reeking corpse of a smallpox victim over any castle wall at all.

Sorry Doc, but everybody in Granville County is smoking twigs and seeds. I'd share, but it's dry, bro....




"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)

"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres


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Dave W.
Info Junkie

USA
26001 Posts

Posted - 01/31/2011 :  05:52:09   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by H. Humbert

But now I know that elaborate pulley and counterweight systems can be devised so that such weights can be lifted with minimal effort from as little as a single person. I think I've seen car lifts that can be moved up and down by yanking on a pair of chains.
While they rely on gear or pulley ratios to reduce the force required to do the work, the total work done is the same. I'm horrible with units of work and force, but basically if it would require force X to lift a big weight 1 meter by a single rope, a block-and-tackle set with a 100-to-1 ratio allows a person to exert a force of only X/100, but they need to pull 100 meters of rope to lift the weight a single meter. Since the total work is force times distance, the work done would be identical.

Engine lifts make you pull a lot of chain to move the engine just a few inches. The total work done is the same as if you could just grab the engine block and heave.

There ain't no free lunch.

- Dave W. (Private Msg, EMail)
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BigPapaSmurf
SFN Die Hard

3192 Posts

Posted - 01/31/2011 :  06:58:15   [Permalink]  Show Profile Send BigPapaSmurf a Private Message  Reply with Quote
Yep, that little motor would just have to work longer to do the same job.

"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History

"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini
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BigPapaSmurf
SFN Die Hard

3192 Posts

Posted - 01/31/2011 :  06:59:18   [Permalink]  Show Profile Send BigPapaSmurf a Private Message  Reply with Quote
Just use a windmill or waterwheel to recrank it, or slaves if you have some.

"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History

"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 01/31/2011 :  11:42:04   [Permalink]  Show Profile Send H. Humbert a Private Message  Reply with Quote
Originally posted by Dave W.
Engine lifts make you pull a lot of chain to move the engine just a few inches. The total work done is the same as if you could just grab the engine block and heave.

There ain't no free lunch.
Yeah, I sort of figured out my own error as I was typing this up, I was thinking about the car lift and remembered having to pull and pull and pull on the chain just to get the car lift to rise a few inches, as you said, so it occurred to me that it might be the same amount of work just distributed differently. Ah, well. I guess it's not an infinite energy device. Thanks for the explanation!


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
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Dr. Mabuse
Septic Fiend

Sweden
9672 Posts

Posted - 01/31/2011 :  11:44:45   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
Here's a thought experiment simiar to the one you propose:

1) Lift a crate with 8 sixpacks of chilled beer from the floor up to the kitchen table. Then rest.

2) Then turn to the other crate, pick up the other 8 sixpacks to the kitchen table one by one, and finish off with the crate as well.

Question: are you less exhausted after the second task? (even if you know you can start drinking the beer?)

In both cases, the same amount of work has been done.
Almost anyway. The #2 task actually takes more energy, let's see if you can figure out where the rub lies.


Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

Support American Troops in Iraq:
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 01/31/2011 :  12:07:24   [Permalink]  Show Profile Send H. Humbert a Private Message  Reply with Quote
Originally posted by BigPapaSmurf

Just use a windmill or waterwheel to recrank it, or slaves if you have some.
Exactly! Lately I've been thinking a lot about using weights or pendulums to generate electricity, something that can be reset with minimal human effort. I had the idea for a gravity lamp but someone went ahead and invented it without me. You get 4 hours of light by simply lifting a weighted carriage. That's extremely cool, in my opinion. I can foresee a future where many home appliances are powered locally in this way. Reset a weight and use the sewing machine or whatever. Or go out in the back yard raise the 2-ton cube again to power the house for the day. Many old grandfather clocks were powered by just such a system of weights and counterweights.



What about pendulums? They can provide steady power to clocks for a descent amount of time. Could they similarly light a very efficient lamp? Why isn't anybody working on this? I'm only an English major, folks!


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
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filthy
SFN Die Hard

USA
14408 Posts

Posted - 01/31/2011 :  12:47:24   [Permalink]  Show Profile Send filthy a Private Message  Reply with Quote
A pendelum is more of a control than an application -- a throttle of sorts. How fast or slow the clock runs is controlled by the position of the weight at the end of it.

It's called a "chain fall" and is a valuable tool in any mechanic's or millright's shop. Like Dumbledore's phonix, it can lift tremendous loads and, more importantly, can slowly, almost daintly, put those loads down in the exact position required by the job wihout crushing too many fingers. They are best known for doing engine replacements but have other uses around 'most any shop.




"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)

"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres


"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude

Brother Boot Knife of Warm Humanitarianism,

and Crypto-Communist!

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BigPapaSmurf
SFN Die Hard

3192 Posts

Posted - 01/31/2011 :  13:03:38   [Permalink]  Show Profile Send BigPapaSmurf a Private Message  Reply with Quote
Yeah it's the clock springs and not the pendulum you need.

"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History

"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini
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Dave W.
Info Junkie

USA
26001 Posts

Posted - 01/31/2011 :  13:05:18   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by H. Humbert

I had the idea for a gravity lamp but someone went ahead and invented it without me. You get 4 hours of light by simply lifting a weighted carriage. That's extremely cool, in my opinion.
It would be, if it worked. Look at the "Inventor concedes error" section at the bottom of the page: to get as much light as claimed, there would have to be either 4,000 kg of weights, or the 50 pounds of weights would need to fall 259 meters.

Note that it was 50 pounds to begin with! To reset the lamp, you'd take the weights off, turn the lamp over (hourglass-like), and then put the weights back on at what would then be the top. If there were ten five-pound weights, it'd mean a serious workout for an octogenarian, a child, or someone with back problems.
I can foresee a future where many home appliances are powered locally in this way. Reset a weight and use the sewing machine or whatever. Or go out in the back yard raise the 2-ton cube again to power the house for the day.
To get one watt of power for an hour, you need about 367 kilogram-meters of weights. In other words, a mass of 367 kg falling one meter over the course of one hour will generate 1 watt given 100% efficiency of power conversion. Or, 36.7 kg falling 10 meters over that same hour. Or 3.67 kilos falling 100 meters. If you need more wattage or more time, simply multiply. 1 watt for three hours requires 367*3 = 1101 kilogram-meters (kgm). 100 watts for half an hour requires 367*100*0.5 = 18,350 kgm.

These are not small figures. To run a microwave for three minutes would require a 200-kg mass falling over 100 meters.

This is why hydroelectric dams tend to be very tall. Water is heavy, and getting a lot of it to fall a long distance allows one to generate lots of power.
Many old grandfather clocks were powered by just such a system of weights and counterweights.
Clocks are an extremely low-power device. Milliwatts, tops.
What about pendulums? They can provide steady power to clocks for a descent amount of time.
Actually, they don't. The weights provide the power. The pendulum just tilts the escapement back and forth, which keeps the time steady. If the pendulum provided the power, it'd have to be huge (per the calculations above) to keep going for more than one tick.

- Dave W. (Private Msg, EMail)
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 01/31/2011 :  13:56:48   [Permalink]  Show Profile Send H. Humbert a Private Message  Reply with Quote
Originally posted by Dave W.
To get one watt of power for an hour, you need about 367 kilogram-meters of weights. In other words, a mass of 367 kg falling one meter over the course of one hour will generate 1 watt given 100% efficiency of power conversion.
Eeesh. Yeah, those figures are not encouraging. We'd need way more energy efficient machines. Maybe machines with biological components like muscle in them.

Ok, I think it's easier to use a smaller weight falling a further distance. My idea was to have a tall rod, maybe 10 feet tall say, cut spirally like a screw. A carriage could be set at the top of the rod and let to fall to the floor, spinning the whole time. Now, if the spinning carriage was fitted with magnets it could act as a turbine dynamo*, generating power that entire way down. (Obviously the grooves would need to be fairly frictionless so the carriage would slide to the floor using nothing but its own weight.) Once at the bottom, the carriage can be unlocked from the screw, slid to the top, and started down on its journey once again.

Would such a setup be capable of even powering an extremely efficient LED light source for a short time? If not, then I guess the idea is just flat out unworkable. I'm pretty discouraged after learning that the other gravity lamp doesn't work as advertised.

And thanks to everyone who clarified the function of pendulums.



* I'm not very sure of my terminology here.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
Edited by - H. Humbert on 01/31/2011 15:13:42
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H. Humbert
SFN Die Hard

USA
4574 Posts

Posted - 01/31/2011 :  14:12:53   [Permalink]  Show Profile Send H. Humbert a Private Message  Reply with Quote
Thinking about those emergency radios that may be run on a hand crank led me to find this item: Dynamo Lantern with Radio and Cell Phone Chargers. The product description says "Just one minute of hand-cranking yields 15 minutes of high-powered light." Not the best conversion efficiency, especially if that's a minute of vigorous hand-cranking, but it's in the ballpark at least.


"A man is his own easiest dupe, for what he wishes to be true he generally believes to be true." --Demosthenes

"The first principle is that you must not fool yourself - and you are the easiest person to fool." --Richard P. Feynman

"Face facts with dignity." --found inside a fortune cookie
Edited by - H. Humbert on 01/31/2011 14:41:42
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Dave W.
Info Junkie

USA
26001 Posts

Posted - 01/31/2011 :  15:24:49   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by H. Humbert

Would such a setup be capable of even powering an extremely efficient LED light source for a short time?
It's all about the distance between the mass and the ground. The path the mass takes to get there is irrelevant to the total kinetic energy available to put to work. So the screw-shaped path only figures in to how to get the energy out (a spinning magnet around a fixed coil would be a neat, if inefficient, idea!), and is irrelevant to the calculation of how much energy you can get.

The correction to the gravity lamp mentions that the highest-efficiency LEDs output about 135 lumens per watt, which seems to be about twice the brightness of compact fluorescent lamps (on a per-watt basis). To get light equivalent to a standard 60-watt bulb, you'd need to pump almost 6 watts into LEDs, so you'd need about 2,175 kgm. On a ten-foot tall screw, you'd have to use a 725-kg weight, and then you'd get light for only an hour (if the weight took two hours to fall, you'd only get 3 watts per hour).

Check out the wonderful cranking sounds in this video. You can get 86 lumens (one-tenth a 60-watt bulb) for a half hour with that flashlight, so the one minute of cranking required is effectively generating 117 kgm, which is going to be tiring.
If not, then I guess the idea is just flat out unworkable.
Yeah, that's pretty much why people dropped the weights and cranks and stuff as soon as electricity was cheap and plentiful.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
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Dave W.
Info Junkie

USA
26001 Posts

Posted - 01/31/2011 :  15:33:46   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by H. Humbert

Thinking about those emergency radios that may be run on a hand crank led me to find this item: Dynamo Lantern with Radio and Cell Phone Chargers. The product description says "Just one minute of hand-cranking yields 15 minutes of high-powered light." Not the best conversion efficiency, especially if that's a minute of vigorous hand-cranking, but it's in the ballpark at least.
They say it's a 0.7-watt LED. 0.7 watts for 0.25 hours is equivalent to 64 kgm. That's the same amount of effort to lift an average-weight person from the ground up to waist height, spread out over a minute.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
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