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I watched this video on double gyroscope Precession: https://m.youtube.com/watch?v=vGun5athdfg

When the two gyroscopes are spinning in the same direction, the apparatus can be rotated and the arms tilt up or down.

My question is, when the gyros are spinning in opposite directions, and the base is rotated, the arms do not move but their forces cancel out. Will this cause an upward force on the system? As in, will the apparatus weigh less if placed on a scale and then rotated?

(I am not a physics expert, I don’t know a lot of the terminology)

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To see what will happen in the case that you describe think of that same setup, with one of the gyroscopes removed.

If you release the gyroscope then it will settle in steady precessing motion, gradually sagging down because of the non-zero friction at the central pivot. (I bought the particular model of gyroscope that you see in the video, I very much enjoyed playing around with it.)

You can replenish the energy lost to friction by giving the precessing gyroscope a little push in the precessing direction.

Now the bit that answers your question: if you push a bit more, making the precessing gyroscope go around a bit faster than the natural precessing motion, then the gyroscope will climb.

Overview:
The friction at the central pivot act as a mild counterforce, preventing the gyroscope from precessing at the natural precessing speed, causing the gyroscpe to sag. Conversely, if you push in the direction of precessing motion, then you make the gyroscope rise.

In the two-gyroscopes setup the other one will have the same response to pushing to faster-than-natural-precessing: it will tend to rise.

Given that the two gyroscopes are on a rigid rod the tendency to rise will transfer to the center. So yeah: a scale will show a lower weight.

Of course, this does not provide a way to get lift for free: in order to push you need leverage; your feet need to be firmly on the ground. (Compare pushing a large piece of furniture: if your feet don't have grip then you will only push yourself backward instead of moving that piece of furniture.)

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  • $\begingroup$ Thank you for the answer! I’ve been looking everywhere, where can I buy that model of gyroscope? $\endgroup$
    – Tdoggo
    Mar 7 '20 at 17:21
  • $\begingroup$ @Tdoggo That model is called 'super precision gyroscope'. Compared to other gyroscopes very expensive, Quality: very high. The base set comes with a small electric motor, powered by 4 AAA batteries. When I took the set of ouf the box after a couple of months not having used it I found battery leakage had damaged that battery box beyond repair. Now when I want to spin up the gyroscope I use a dremel. (The dremel set came with a 10mm diameter cilindrical rubber thingy.) $\endgroup$
    – Cleonis
    Mar 7 '20 at 17:49
  • $\begingroup$ Thank you :). I appreciate it! $\endgroup$
    – Tdoggo
    Mar 7 '20 at 19:45
  • $\begingroup$ Ok, just to be clear. Let's say I have a spaceship floating in zero gravity. It has two long wings, each one with a gyroscope at the end. If the gyros are turning in the same direction, and I rotate their bases, the spaceship will roll. But if the gyros are turning in opposite directions and I rotate their bases, will the spaceship move straight up or down? As in, can the arrangement mentioned in my first question provide thrust? $\endgroup$
    – Tdoggo
    Mar 8 '20 at 6:42

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