Double Pendulum Power

[nybtorque]

@ 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]

@ 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]

@ 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]

@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]

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?