Storing Cookies (See : http://ec.europa.eu/ipg/basics/legal/cookies/index_en.htm ) help us to bring you our services at overunity.com . If you use this website and our services you declare yourself okay with using cookies .More Infos here:
https://overunity.com/5553/privacy-policy/
If you do not agree with storing cookies, please LEAVE this website now. From the 25th of May 2018, every existing user has to accept the GDPR agreement at first login. If a user is unwilling to accept the GDPR, he should email us and request to erase his account. Many thanks for your understanding

User Menu

Custom Search
« previous next »
Pages: [1]   Go Down

Author Topic: Where do the input energy go, and can it be reversed?  (Read 7979 times)

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Where do the input energy go, and can it be reversed?
« on: January 06, 2013, 12:16:26 AM »
Hi,


I have been thinking of an experiment with gyros orbiting a center. Look at the picture. There is two gyros atached to each rod. The green rim is toothed so the gear on the gyro will let the gyros start spinning as they orbit.


As you all know a gyro resist disalignment. However, this system will force the gyro to disalign all the time as soon as the gyros start orbiting. That means we have to apply energy into the system even if the gyros orbits at constant rate. KE that was built up under acceleration is now constant, but besides friction, there is added energy to maintain the systems velocity. This is energy we appearently cannot get back - even if the system was frictionless.


Could you please explain to me where the energy goes?
Can the system be reversed by using something like a reversed gyro, and get more energy out than we put in?


Vidar
Logged

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Re: Where do the input energy go, and can it be reversed?
« Reply #1 on: January 06, 2013, 10:04:32 PM »
Anyone?
Logged

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Re: Where do the input energy go, and can it be reversed?
« Reply #2 on: January 19, 2013, 09:26:01 PM »
No one with the brains here who can explain where the input energy goes? Is it too complicated?



Vidar
Logged

TinselKoala

  • Hero Member
  • *****
  • Posts: 13958
Re: Where do the input energy go, and can it be reversed?
« Reply #3 on: January 19, 2013, 10:13:06 PM »
Forced precession of gyroscopes can be pretty complicated to understand, especially if the initial assumptions made are incorrect.

Energy is conserved, momentum is conserved, linear momentum and angular momentum are conserved separately. The forced precession of gyroscopes will drive you crazy. Where does the input energy go? It goes to the same place it always does: It winds up being dissipated as heat, into the environment. Can it be reversed? It can be swapped back and forth between potential and kinetic forms, losing a bit to heat with each swapping.

Or, if you are clever, you can use forced precession to spin up the gyro rotor and use the spin to generate electricity to power some lights.

http://www.rei.com/product/699801/dynaflex-lighted-gyro-power-ball

Taking one of these apart reveals a mechanism that is very similar to what's drawn in the post above. There is an equatorial groove that the axle of the ball fits into. The axle can move all around the outer sphere within this groove. By rocking the thing with the right "twisty" motion with the wrist after giving the rotor a slight initial spin, you force-precess the rotor, but it's restrained by the groove and its axle can only move around in this groove , and so the rotor spins up to quite high speeds.


Logged

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Re: Where do the input energy go, and can it be reversed?
« Reply #4 on: January 19, 2013, 10:31:20 PM »
Say we prevent precession by frictionless guides - see illustration. We apply a vertical torque to the gyro just to challenge the rigidity of the gyro as it spins. The applied torque will make the gyro move in the same direction - admittedly, the gyro will resist this motion, but that is the whole point with this experiment.


If we only discuss torque and distance around a circumference, there is work done to the gyro - appearently. This work is done to challenge rigidity, not solely friction. Friction is a part of a real system, but is not the whole reason why input work is neccessary - or what?


You might reply that the spin of the gyro will lose KE as we do work to challenge rigidity. It probably will. But what if the applied work also is sustaining the speed of the gyro?


Then we appearently apply work that is doing nothing since KE in the system is constant.


I have tried to searched the internet for answers to such experiments, but cannot find one single example that is exactly what I'm asking for...


Vidar
Logged

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Re: Where do the input energy go, and can it be reversed?
« Reply #5 on: January 20, 2013, 08:48:16 AM »
I got an answer at www.physicsforums.com. The guides will apply torque as well. But I wonder if this torque can be considered as torque the guides does not move.

Edit: If we take away the guides and add a second gyro which spinns the opposite direction. Will that system be rigid in any way? I know that precession is not longer present due to the counter rotationg gyros.


Vidar
Logged

Low-Q

  • Hero Member
  • *****
  • Posts: 2847
Re: Where do the input energy go, and can it be reversed?
« Reply #6 on: January 20, 2013, 09:55:52 AM »

Found some information about counter rotating gyros that was used to stabilize the Gyro Cycle:
The Gyro Hawk was a gyro-stabilized vehicle which used a two-gyro counter-rotating system." So, I got an answer to this question. Counter rotating gyros provides rigidity regardless of which perpendicular direction the torque is applied. No precession, just rigid (to a certain extent).


So, if I analyze such a system, the counter-rotating gyros will resist any change in alignment. That also means that the second counter rotating gyro in the experiment with or without the guides will slowly move downwards. The question is how slow compared to the angular momentum of the gyros, and the applied torque.


Work has to be done in order to turn the gyro perpendicular to its spin. Where do this input work go if all bearings are frictionless magnetic bearings?


Vidar
Logged
Pages: [1]   Go Up
« previous next »