Where do the input energy go, and can it be reversed?

[Low-Q]

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?


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[Low-Q]

Anyone?

[Low-Q]

No one with the brains here who can explain where the input energy goes? Is it too complicated?



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[TinselKoala]

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.

[Low-Q]

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...


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