Double Pendulum Power

[Low-Q]

truesearch:

No, unfortunately not. I dont have the skills and resources to make a prototype myself. But an easy experiment to verify the effect is to put a bicycle upsidedown and safely fasten a heavy tool of sorts inside the wheel, which then becomes seriously unbalanced. Then pedal by hand, try to keep one point fixed and measure amplitude and weight at another point.

The interesting part is that you do not need to pedal any harder with the tool fastened inside the wheel than without. And you can certainly feel (and measure) the output difference. This is the power of vibrations. And it becomes greater with increased frequency of rotation by a power of three.

This is true only if the unbalanced bicycle wheel is 100% fixed, or can viberate without friction. As soon as you try to get energy out from the viberation, there will occour a phase shift less than 180 degrees between the position of the weight and the position of where the bicycle wheel finds itself during bouncing up and down or side to side. This <180 degree shift will counterforce rotation, so that more input on the pedals are neccessary - ofcourse as much more input as the energy output are.


A perfect pendulum exchange kinetic energy with potential energy with 180 degrees delay. Friction or any form of attempt to take out energy will reduce this shift to less than 180 degrees and the pendulum will finally stop - even a double one.


Vidar

[nybtorque]

Hi Vidar,

Thankyou for your response.

Maybe I'm missing something here. But I cant see how friction in the inner pendulum can make the outer pendulum stop if it is frictionless. Friction in the inner pendulum will make the inner pendulum amplitude smaller, as well as a large inner pendulum mass will, but none of these forces are transfered to the rotation of the outer pendulum. This is what I try to show using Euler Lagrange in the report. Please elaborate on the physics here if you got another idea.

To be honest, I'm not suggesting any magic, merely exploring the case where we supply energy by rotation of the outer pendulum and examining the work performed by the inner pendulum mass. The reason why I find this interesting is because to do this we have to consider the energy of the vibrations, ie. both static and dynamic forces in the fixture point origination from the centrifugal force of the outer pendulum. If we want to eliminate the dynamic vibrations we need to apply a equally large force as the centrifugal force to move the inner pendulum mass. That is why I'm talking about an open system because it is normally done by the fixture point and the mass of the surroundings. 

[Low-Q]

Hi Vidar,

Thankyou for your response.

Maybe I'm missing something here. But I cant see how friction in the inner pendulum can make the outer pendulum stop if it is frictionless. Friction in the inner pendulum will make the inner pendulum amplitude smaller, as well as a large inner pendulum mass will, but none of these forces are transfered to the rotation of the outer pendulum. This is what I try to show using Euler Lagrange in the report. Please elaborate on the physics here if you got another idea.

To be honest, I'm not suggesting any magic, merely exploring the case where we supply energy by rotation of the outer pendulum and examining the work performed by the inner pendulum mass. The reason why I find this interesting is because to do this we have to consider the energy of the vibrations, ie. both static and dynamic forces in the fixture point origination from the centrifugal force of the outer pendulum. If we want to eliminate the dynamic vibrations we need to apply a equally large force as the centrifugal force to move the inner pendulum mass. That is why I'm talking about an open system because it is normally done by the fixture point and the mass of the surroundings.

These two pendulums are in one way or another connected to eachother, directly or indirectly (If I understrand right). For every action there is a reaction, and if you change the reaction in one part of a system it will also change the reaction in another part of the same system. Because one part of the pendulum is depending on the behaviour of the other part. Any condition that you affect by friction or energy output, will affect the rest of the system as you are tapping it from energy.


Vidar

[nybtorque]

These two pendulums are in one way or another connected to eachother, directly or indirectly (If I understrand right). For every action there is a reaction, and if you change the reaction in one part of a system it will also change the reaction in another part of the same system. Because one part of the pendulum is depending on the behaviour of the other part. Any condition that you affect by friction or energy output, will affect the rest of the system as you are tapping it from energy.

　

Thankyou for your clarification.

Yes, the Euler Lagrange equation describes what happens. That is the basis of my argument. There is no way you can reduce kinetic energy in the outer pendulum with friction in the inner one, since it can only act on the outer through that arm, which is always in a 90 degree angle in relation to the movement of the pendulum mass.

However, as I state; the two pendulum per se is not a closed system. So to be able to set up the equations for action/reaction the Newtonian way for the inner pendulum we have to take into account the forces that act on the fixture, both as momentum and as push/pull through the inner pendulum arm. The other side of that equation in my example is the centrifugal force from the outer pendulum. This is what I try to show in my report. The forces on fixture have to be part of the system. These are the vibrational forces I want to examine, and which a propose can be used to generate power.

[Low-Q]

@ nybtorque:
Maybe you could build a small prototype and take a video of it while playing with it. Because I'm not sure if I follow you on this


This is the design you're describing, right? http://htmlimg4.scribdassets.com/7720h8reps2iacuk/images/1-d7d911a5c0.jpg



Vidar.