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Author Topic: Double Pendulum Power  (Read 78702 times)

vince

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Re: Double Pendulum Power
« Reply #45 on: October 24, 2013, 09:25:05 PM »
@ nybtorque

I find it extremely strange that you have shown no curiosity or interest in my one arm build of your device. You have made no comment at all,not even to dispute it. I know that if I had a design for something and not the ability to build it I would be very interested in someone elses build of the device and their observations.
I'm not sure if you feel I have not captured the intent of your design or maybe you feel that a bad build will tarnish your predicted results.
Let me assure you that I understand your design and have implemented it into my build. Basically you are driving an outer pendulum( rotating offset weighted wheel) with gears or belts in my case via an inner pendulum which is free to rotate (occilate) around the primary driving axle. You are then harnessing the inner pendulum occilations for power.
When I first read your paper I felt you had a clever idea and was determined to prove it out for myself. I was going to build a 2 arm version as in your balanced design but I only had two matching gears and did not want to spend money on an unproven idea. I decided that the one arm version although unbalanced should net results in occilations to prove the concept.

My machine is driven by a 1/2 hp dc 5000 rpm motor with variable speed. There is a 1 to 4 reduction in speed from motor to rotating pendulum. If you hold onto the driven pulley that drives the rotating pendulum (that is after a reduction of 1 to 4) you can stop the motor with ease even at full power. It is not a strong motor at all. I did not post observations until now because I was testing different speeds and offset pendulum weights.
What I found was that indeed as you predicted there is a critical minimum weight that will begin occilations on the inner pendulum arm depending on it's design.
In my case the occilations began with 1/2 lb. at 2 1/4" radius. Speed was not as important in my observations as it started to ocillate immediately even at low speed. Speed however did make a huge difference in output power of the occilations. The amplitude of the occilations was hard to measure but it was somewhere between 1/4 and 3/4 of an inch at about 6 inches from pivot of the inner pendulum.
This is where a two arm balanced machine would shine . The one arm version would shake itself apart if not held down firmly.
Holding onto the ocillating pendulum it was impossible to hold it from occilating even with my full body weight leaning into it.
It is extremely powerful in it's ocilations.
The real challenge that I see is harnessing that small movement to a generator
To all you math experts out there I cannot verify my observations with math so I leave that to you to debate. What I do know' is that if you build this thing you WILL be impressed. 
Going to be looking for some gears or will make some to build a balanced two arm version. Hopefully some one will come up with a generator that can harness this power.
Hats off to you ncbtorque!

Vince


telecom

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Re: Double Pendulum Power
« Reply #46 on: October 24, 2013, 09:31:05 PM »
Hi Vince,
I'm very interested in your implementation.
Can you please post more pictures.
Thank you.

LibreEnergia

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Re: Double Pendulum Power
« Reply #47 on: October 24, 2013, 10:38:34 PM »

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... :)

So tell me, what would happen were you to integrate those derivatives over time.. You'd be back to energy and velocity, and unless your analysis was flawed you would have a conservative result.

If a double pendulum contain pivots with friction (or generators) then you need to include a damping term into your simulation equations just like you would if it was damped simple harmonic motion. I'm not seeing that in your simulation.

The damping term would be a counter torque proportional to angular velocity at the pivot.


telecom

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Re: Double Pendulum Power
« Reply #48 on: October 25, 2013, 01:28:01 AM »
These people are using a very similar concept, except they make the output to rotate,
rather than oscillate.

http://www.universalengines.com.au/how-ue-works

The double pendulum always stops because they don't use a part of the output to
maintain the input speed. This can be achieved by  rectifying AC from the generator and sending part into the input motor, another part to lightbulbs.

nybtorque

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Re: Double Pendulum Power
« Reply #49 on: October 25, 2013, 06:23:53 AM »
So tell me, what would happen were you to integrate those derivatives over time.. You'd be back to energy and velocity, and unless your analysis was flawed you would have a conservative result.

If a double pendulum contain pivots with friction (or generators) then you need to include a damping term into your simulation equations just like you would if it was damped simple harmonic motion. I'm not seeing that in your simulation.

The damping term would be a counter torque proportional to angular velocity at the pivot.


You're absolutely right. But there's one big difference between integrating acceleration and power... acceleration is vectorbased and it changes direction as the pendulum is oscillating, so the velocity (and kinetic energy) never get very high... But, power is scalar and when you integrate you get energy regardless of direction. This is one key feature of the report. Probably not emphasized enough.




nybtorque

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Re: Double Pendulum Power
« Reply #50 on: October 25, 2013, 08:20:45 AM »
@ nybtorque

I find it extremely strange that you have shown no curiosity or interest in my one arm build of your device. You have made no comment at all,not even to dispute it. I know that if I had a design for something and not the ability to build it I would be very interested in someone elses build of the device and their observations.
...


@ Vince


I'm sorry I haven't responded to your posts yet. I just want you to know that I'm very grateful and have extreme curiosity in your work. I will take the time and look at pictures and try to grok your machinery later today to se if I can give valuable input.


Regards NT

nybtorque

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Re: Double Pendulum Power
« Reply #51 on: October 25, 2013, 11:20:59 AM »
@ nybtorque

I find it extremely strange that you have shown no curiosity or interest in my one arm build of your device. You have made no comment at all,not even to dispute it. I know that if I had a design for something and not the ability to build it I would be very interested in someone elses build of the device and their observations.
I'm not sure if you feel I have not captured the intent of your design or maybe you feel that a bad build will tarnish your predicted results.
Let me assure you that I understand your design and have implemented it into my build. Basically you are driving an outer pendulum( rotating offset weighted wheel) with gears or belts in my case via an inner pendulum which is free to rotate (occilate) around the primary driving axle. You are then harnessing the inner pendulum occilations for power.
When I first read your paper I felt you had a clever idea and was determined to prove it out for myself. I was going to build a 2 arm version as in your balanced design but I only had two matching gears and did not want to spend money on an unproven idea. I decided that the one arm version although unbalanced should net results in occilations to prove the concept.

My machine is driven by a 1/2 hp dc 5000 rpm motor with variable speed. There is a 1 to 4 reduction in speed from motor to rotating pendulum. If you hold onto the driven pulley that drives the rotating pendulum (that is after a reduction of 1 to 4) you can stop the motor with ease even at full power. It is not a strong motor at all. I did not post observations until now because I was testing different speeds and offset pendulum weights.
What I found was that indeed as you predicted there is a critical minimum weight that will begin occilations on the inner pendulum arm depending on it's design.
In my case the occilations began with 1/2 lb. at 2 1/4" radius. Speed was not as important in my observations as it started to ocillate immediately even at low speed. Speed however did make a huge difference in output power of the occilations. The amplitude of the occilations was hard to measure but it was somewhere between 1/4 and 3/4 of an inch at about 6 inches from pivot of the inner pendulum.
This is where a two arm balanced machine would shine . The one arm version would shake itself apart if not held down firmly.
Holding onto the ocillating pendulum it was impossible to hold it from occilating even with my full body weight leaning into it.
It is extremely powerful in it's ocilations.
The real challenge that I see is harnessing that small movement to a generator
To all you math experts out there I cannot verify my observations with math so I leave that to you to debate. What I do know' is that if you build this thing you WILL be impressed. 
Going to be looking for some gears or will make some to build a balanced two arm version. Hopefully some one will come up with a generator that can harness this power.
Hats off to you ncbtorque!

Vince


@ Vince


First, great machine! You got the principles right and from what I can see right now it validates my model. I miss some information; for example the mass and dimensions of the inner pendulum. Also I would like to know if it is correct  that the outer pendulum was rotating at 1200rpm and the mass and radius was about 225g, 5.7cm respectively when you got the approx. 1.2 cm amplitude?


If I assume the inner pendulum mass of 2 kg and radius of 0.4m I will get an amplitude of approximately 0.7 cm (1/4"). Does this make sense? With this configuration vibrational output would peak at 137W and average about 66W. If you put 80kg of bodyweight on it you would damp out about 97% of the amplitude as an example (but certainly still feel the vibrations...).


Then, if you want to increase the output the rule of thumb is that a double pendulum mass gives four times the output (power of two) and double rotational speed eight times output (power of three). Also it would improve performance to reduce the mass of the inner pendulum as much as possible. Output will peak when it has about the same mass/load as the outer pendulum.


An interesting consequence, that I have not thought about before, is that the belts probably acts as springs damping the feedback momentum to the outer pendulum wheel. There could also be friction between belts and wheels? Do they get hot?
Maybe some of it travels all the way back to the motor? It would be interesting to analyze the voltage and current going there. Maybe  there are some interesting spikes? If cogwheels/chains were used there would certainly be.


When I think about it now, maybe this is the easiest way to validate the output. Eliminate losses in the transmission and measure the feedback power in the actual motor, then acting as a generator at the same time. (I'm not sure how difficult it is though)


Good luck with your work and keep going... 


Regards NT


vince

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Re: Double Pendulum Power
« Reply #52 on: October 25, 2013, 09:22:05 PM »
@ NT

I have disassembled the machine but took some measurements for you to peruse before doing so.

motor draw, diving central pulley but not the pendulum wheel--3.9 amps  120 volts
motor draw, driving pendulum with no resistance, 490 rpm at central shaft --- 4.5 amps  120 volts
motor draw, driving pendulum with strong resistance at occilating pendulum, 490 rpm at central shaft---4.5 amps 120 volts
motor draw , with and without resistance at occilating pendulum, 1480 rpm at central shaft---6. 5 amps  120 volts

Note: All measurements taken by clamp on meter on one ac wire feeding PWM
         RPM measured on central shaft by laser tachometer
         Because of extreme vibration measurements are not considered definitive

Vince

vince

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Re: Double Pendulum Power
« Reply #53 on: October 25, 2013, 09:59:41 PM »
@NT

As this is your design, I do have some questions.   To design and build a proper machine that can be harnessed for testing I would appreciate your comments on the following questions.

Do the offset weights have to turn in opposite directions ( CW and CCW) I realize that they must me positioned correctly to each other to balance the centrifugal forces but can the same thing be done with them spinning in the same direction.  This would open the design up to sprockets and chains and be less dependent on gear size and weight.

Is there an optimum radius for the offset weight?

Is there an optimum radius for the inner pendulum?

Does the weight of the pendulum matter as much in a balanced system where one side offsets the other?

Do you have any thoughts on a possible generator for the system? You mention a dc motor but if it is a brushed motor it would only utilize a few bars of the commutator and their respective coils. A PM motor would be better but can it generate any real power with such little movement even though the frequency would be high. Im not sure how a conventional ac generator would react?

Thanks
Vince



telecom

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Re: Double Pendulum Power
« Reply #54 on: October 25, 2013, 10:09:43 PM »
Hi Vince,
you have mentioned that you have a DC motor. I believe that in a DC motor you change speed by varying voltage, however your readings always show 120V.
How do you increase the speed of the motor in this case?

vince

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Re: Double Pendulum Power
« Reply #55 on: October 25, 2013, 10:40:34 PM »
Hi Telecom


You will see in my notes that voltage and amperage were measured at the ac input line to PWM ( pulse width modulator).  The voltage will remains the same at this point.  After it goes thru the PWM,  power is pulsed to the motor to vary the speed, Hence PWM. Read up on PWM and you will understand better.


Vince

gyulasun

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Re: Double Pendulum Power
« Reply #56 on: October 25, 2013, 11:08:29 PM »
...
Do you have any thoughts on a possible generator for the system? You mention a dc motor but if it is a brushed motor it would only utilize a few bars of the commutator and their respective coils. A PM motor would be better but can it generate any real power with such little movement even though the frequency would be high. Im not sure how a conventional ac generator would react?


Hi Vince,

I think that converting the oscillating movements into a rotary motion would solve the generator question?  Crankshafts like used in old steam machines?  and the wheel rotated by the crankshaft(s) would serve as a flywheel too and could surely drive a normal generator or alternator.

Thanks for all the measurements efforts!

Gyula

vince

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Re: Double Pendulum Power
« Reply #57 on: October 25, 2013, 11:33:02 PM »
Hi Gyula
That was my first thought but several problems arise .  First the stroke is to short to make any usable rotary motion . Levers a could be used to increase stroke but that adds complexity and drag. The other problem is the stroke gets shorter with loading which would never work with a crankshaft.
What do you think of a magnet or an electro magnet positioned over a core with a coil . It could be made to reciprocate with the pendulum and induce a current in the coil. I don't know how much movement would be required to have induction occur though.


Vince

gyulasun

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Re: Double Pendulum Power
« Reply #58 on: October 26, 2013, 12:23:08 AM »
Hi Gyula
That was my first thought but several problems arise .  First the stroke is to short to make any usable rotary motion . Levers a could be used to increase stroke but that adds complexity and drag. The other problem is the stroke gets shorter with loading which would never work with a crankshaft.
What do you think of a magnet or an electro magnet positioned over a core with a coil . It could be made to reciprocate with the pendulum and induce a current in the coil. I don't know how much movement would be required to have induction occur though.


Vince

Yes if the strokes are too short then no cranshaft-like convertion is practical. 

Veljko Milkovic has shown some conception on the coil - magnet induction, to utilize his two stage mechanical oscillator, the magnets could be moved by the strokes, see here:
http://www.youtube.com/watch?v=h4Do_dTI_Ow       from this link:  http://www.pendulum-lever.com/applications.html 

Even a small 1cm long displacement (stroke) can induce useful power, it mainly depends on the strength of the magnets.

Gyula

telecom

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Re: Double Pendulum Power
« Reply #59 on: October 26, 2013, 12:32:18 AM »
Hi Telecom


You will see in my notes that voltage and amperage were measured at the ac input line to PWM ( pulse width modulator).  The voltage will remains the same at this point.  After it goes thru the PWM,  power is pulsed to the motor to vary the speed, Hence PWM. Read up on PWM and you will understand better.


Vince
Hi Vince,
the reason I asked the question is because the power consumption is too high based on your data, in particular for driving the pulley alone.
Either it wasn't measured correctly or some bearings are jammed.
I suggest to take a fish scale and measure the actual turning torque .