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Author Topic: Double Pendulum Power  (Read 78717 times)

TechStuf

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Re: Double Pendulum Power
« Reply #30 on: October 23, 2013, 09:26:36 PM »
Quote
The physics simulation "Phun" or "Algodoo" even comes with a couple of Chaotic Pendulums as example scenes. If you think that the chaotic pendulum cannot be modeled mathematically... how does Phun do it, by smoke and mirrors?

Umm...actually......yes.  (It's ok.  The little things are easy to miss.)

Smoke and mirrors are a part of the process.  I assumed you knew?

But then, you know what they say about assumption....

Or maybe not.



TS


P.S.  Math is rather like the Heavens.  Only the fool thinks he knows any one part of it completely.  But one of many cases in point:

http://en.wikipedia.org/wiki/G%C3%B6del's_incompleteness_theorems

Kator01

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Re: Double Pendulum Power
« Reply #31 on: October 23, 2013, 10:01:39 PM »
@nybtorque

it works. see this french guy nicbordeaux. His channel:

http://www.youtube.com/user/nicbordeaux?blend=21&ob=5

Real motion-speed : three full turns !

http://www.youtube.com/watch?v=3EIikIEHqwU

Slow-motion-speed:

http://www.youtube.com/watch?v=5IO-Ui6tmko

I had a few mail-exchanges in the last year. This time he does not react for some reason..I do not know

Regards

Kator01

LibreEnergia

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Re: Double Pendulum Power - AC power from Mech. Oscillator
« Reply #32 on: October 23, 2013, 11:47:55 PM »

What you and most other seems to miss is that the pendulums actually performs real work constantly; accelerating/decelerating mass; i.e. E(work)= m * a  * s. This is the work/power I calculate in the report, and propose might be partially productive (by replacing the mass by a resistive load or pumping water). And this does not violate the energy equilibrium.


I disagree. The system is given a certain amount of energy to start. After that this energy oscillates between kinetic and potential. With no friction it would continue forever. As such it acts as an energy STORE, but it is not GENERATING an excess of energy. If you bleed of the stored energy either by friction or using a generator, it will stop. The total amount of energy dissipated or generated will exactly equal the amount to energy given to it at the start.

Your proposal violates conservation of energy principles. Sorry, it just doesn't happen.

Your math is guilty of the same double counting error that Wayne Travis makes with his non working device, except your analysis is rather more complex.


 

TechStuf

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Re: Double Pendulum Power
« Reply #33 on: October 24, 2013, 12:00:20 AM »
Good find Kator.  There are numerous videos which point out the hilarity of hiding one's head in numbers.

The possibilities of resetting the device in that humble video demonstration alone, are numerous.

That is the funny thing about chaos.  It doesn't take much to cause many men's emotions to push their heads back under the comfy blanket of numbers. 

Another funny thing about chaos.  There are hidden within, many, many forms of order.  Order which man is neither capable nor worthy enough to experience, for long.

Chaos that's consistently repeatable, is no longer chaos.

And our "chaos" is, to those who've gone before (way before), is among the simpler forms of Order.

Of course, once all is said and done, there is lower order and then there's Higher Order.


TS

vince

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Re: Double Pendulum Power
« Reply #34 on: October 24, 2013, 12:17:57 AM »
Single arm version of nybtorque's double pendulum continuos drive machine.
Anybody curious? I was.


Vince

LibreEnergia

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Re: Double Pendulum Power
« Reply #35 on: October 24, 2013, 12:42:42 AM »
Good find Kator.  There are numerous videos which point out the hilarity of hiding one's head in numbers.

The possibilities of resetting the device in that humble video demonstration alone, are numerous.

That is the funny thing about chaos.  It doesn't take much to cause many men's emotions to push their heads back under the comfy blanket of numbers. 

Another funny thing about chaos.  There are hidden within, many, many forms of order.  Order which man is neither capable nor worthy enough to experience, for long.

Chaos that's consistently repeatable, is no longer chaos.

And our "chaos" is, to those who've gone before (way before), is among the simpler forms of Order.

Of course, once all is said and done, there is lower order and then there's Higher Order.


TS


Egregious bullshit. Even in chaotic systems , energy is conserved and this one is no different.

TechStuf

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Re: Double Pendulum Power
« Reply #36 on: October 24, 2013, 01:16:47 AM »
Quote
Egregious bullshit


Since you speak admittedly as a connoisseur, are you using the word egregious in the primary or secondary definition?  Just curious.  Definitions, like all other areas of reality, have a way of going round and round perpetually.


As for bullshit ..... there's "LibreEnergia" to be found in there too.
 

 ???



TS

LibreEnergia

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Re: Double Pendulum Power
« Reply #37 on: October 24, 2013, 01:38:15 AM »

Since you speak admittedly as a connoisseur, are you using the word egregious in the primary or secondary definition?  Just curious.  Definitions, like all other areas of reality, have a way of going round and round perpetually.


As for bullshit ..... there's "LibreEnergia" to be found in there too.
 
 ???

TS

In this case it would not matter if it was the modern or archaic usage. The operative word is still 'bullshit'.

norman6538

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Re: Double Pendulum Power
« Reply #38 on: October 24, 2013, 01:47:47 AM »
Measuring this device could be done with a small weight on a string with a ratchet and then compare the distance lifted (work done) with the work used to  and start the double pendulum.

I did this with a wheel version of the Milkovic device and did not find anything extra.

But the big problem is when you take work out of the balance or pattern you disturb that balance and tend to shorten the cycle.

Norman

TechStuf

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Re: Double Pendulum Power
« Reply #39 on: October 24, 2013, 01:52:24 AM »
Quote
In this case it would not matter if it was the modern or archaic usage. The operative word is still 'bullshit'

We get it.  LibreEnergia sure knows his cases of bullshit.


You've already declared yourself an expert on the stuff...


Why rub it in?

gyulasun

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Re: Double Pendulum Power
« Reply #40 on: October 24, 2013, 10:25:02 AM »
Single arm version of nybtorque's double pendulum continuos drive machine.
Anybody curious? I was.


Vince

Hi Vince,

Thank you for showing the single arm version.  I am curious...  so if you could share your findings or impressions, that would be very helpful.

Greetings,  Gyula

nybtorque

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Re: Double Pendulum Power
« Reply #41 on: October 24, 2013, 10:31:51 AM »
Your "model" can be falsified simply by observing that the "double pendulum", more commonly known as a Chaotic Pendulum, always comes to a stop.

Consider this: If you had really sticky bearings the thing would swing a few times and slow down and stop. Right? SO decrease the friction a little bit. Now it takes a bit longer to run down and stop. Reduce friction even more, even put it in a vacuum. It takes a bit longer... but it still stops.

Why? Because the friction eventually dissipates _all_ the energy you put in with your initial starting impulse... and nothing comes in from anywhere to replace it.

If there were _any_ excess energy in the system, by reducing friction to some arbitrarily small value... a value that is less than the magical "incoming" or created power... it would not stop swinging.  But it always does. Therefore... there is no extra energy, no excess power coming in.

ANY load you put on the system will make it come to a stop faster.


The physics simulation "Phun" or "Algodoo" even comes with a couple of Chaotic Pendulums as example scenes. If you think that the chaotic pendulum cannot be modeled mathematically... how does Phun do it, by smoke and mirrors?


I think you've misunderstood. Modeling the double pendulum mathematically is EXACTLY what I've done by solving Euler Lagrange numerically using Runge Kutta. I doesn't get much better than that... Preservation of energy sort of comes with the deal. And yes, if you take kinetic/potential energy out of the system it will stop eventually, as in the case of friction.


However. Consider this: You have a double pendulum swinging freely, preserving energy. Then you start increasing friction but ONLY for the inner pendulum. What will happen? Well, the inner pendulum will slow down (act heavier). And by acting heavier it will accelerate less  and therefore exchange less kinetic energy with the outer pendulum during each oscillation. I the end friction will be 1 and the inner pendulum will stop, but the outer pendulum will keep rotating/swinging, preserving it's energy. And keep acting on it's fixture (fixed or a mass free to move) with centrifugal force without any more energy added. Like a single pendulum...


Regards NT

nybtorque

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Re: Double Pendulum Power - AC power from Mech. Oscillator
« Reply #42 on: October 24, 2013, 10:55:10 AM »
I disagree. The system is given a certain amount of energy to start. After that this energy oscillates between kinetic and potential. With no friction it would continue forever. As such it acts as an energy STORE, but it is not GENERATING an excess of energy. If you bleed of the stored energy either by friction or using a generator, it will stop. The total amount of energy dissipated or generated will exactly equal the amount to energy given to it at the start.

Your proposal violates conservation of energy principles. Sorry, it just doesn't happen.

Your math is guilty of the same double counting error that Wayne Travis makes with his non working device, except your analysis is rather more complex.


As I said, using Euler Lagrange guarantees that the math is in accordance with the conservation of energy principles. It IS the principles. Do you disagree with the fact that the pendulum masses constantly accelerates (decelerate) as they exchange pot/kin energy, and that Energy=mass*acceleration*distance?


What I have done is to analyze the work performed by the inner pendulum mass using Euler Lagrange and the above basic equation. A flywheel with a constant speed of rotation STORES energy. This is something different. Here we have constantly accelerating masses; a whole different animal and it performs work constantly without energy added. The trick is how to make it useful, and add energy to overcome friction, etc.


LibreEnergia

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Re: Double Pendulum Power
« Reply #43 on: October 24, 2013, 12:42:40 PM »

Preservation of energy sort of comes with the deal. And yes, if you take kinetic/potential energy out of the system it will stop eventually, as in the case of friction.


There is no difference energy-wise between a pivot that has friction and a pivot joint containing a generator where the energy generated drives an external load. Both will dissipate energy from the system. Both will cause it to stop.

The pendulum does not simply 'act heavier'.  Any kinetic energy it has will be reduced as it either drives an external load or is dissipated as heat. It CANNOT do both, as in drive an external load and maintain kinetic energy.  The reduced kinetic energy is then translated into less potential energy, and the system eventually stops.


nybtorque

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Re: Double Pendulum Power
« Reply #44 on: October 24, 2013, 04:32:25 PM »
There is no difference energy-wise between a pivot that has friction and a pivot joint containing a generator where the energy generated drives an external load. Both will dissipate energy from the system. Both will cause it to stop.

The pendulum does not simply 'act heavier'.  Any kinetic energy it has will be reduced as it either drives an external load or is dissipated as heat. It CANNOT do both, as in drive an external load and maintain kinetic energy.  The reduced kinetic energy is then translated into less potential energy, and the system eventually stops.


Sorry, I've been a bit unclear. My mistake! I agree that friction in the inner pendulum joint drains the inner pendulum of kinetic energy. What I meant is  that it "acts heavier" from the perspective of the outer pendulum.


Do you agree that friction at the inner pendulum joint doesn't drain kinetic energy from the outer pendulum?  Do you agree that if you stop the inner pendulum (go from friction 0 to 1 in an instant) the outer pendulum will keep moving with the kinetic energy it had at that moment (but the inner pendulum kinetic energy will turn into friction/heat)?


But, now, the most important part. How much energy did you actually need to stop the outer pendulum short and drain it from its kinetic energy (mv^2/2). Well, if it was rotating with a constant speed, that would be it.


But it's not... It's accelerating (oscillating) with considerable torque. If we take an example: I'm looking at a spreadsheet with a simulation of a 50Hz system with dt=1/1000s. At one particular moment a 1kg pendulum on a 20cm lever has v(t)=25rad/s and a(t)=3000 rad/s^2.  So if you stop it short in an instant, you're right, you only need to drain it of kinetic energy; 12.5 J. BUT you will experience a static torque of 120Nm trying to hold it (thats really hard, but not work per se... :) .


So, lets imagine instead that you want to reduce both velocity and acceleration by 50% on a continuos basis. Since the mass is still moving you need to take acceleration into account to do that. Of course you can reduce velocity instantly by using 9.38 J of energy (3/4 of the kinetic energy). It will now move at 12.5rad/s instead but still performs work of P(t)=1500W at that velocity and acceleration. To reduce the acceleration from 3000 rad/s^2 to 1500 rad/s^2 you consequently need to apply 750 W at that particular time.


And no, this does not violate the conservation of energy principles. Because we're dealing with the derivatives of energy and speed, i.e. power and acceleration. Much more interesting if you ask me... :)