Intermediate axis demo top

[ta0]

We have discussed the intermediate axis theorem, also called the tenis racket theorem. See these:

Finger-top spinnability and a CONTEST!

Intermediate axis theorem

And I have shown the top I got from Philippe Dyon to demo it:



Now, Grand Illusions offers one. But look to the end for a big surprise:

https://www.youtube.com/watch?v=pPy6c4D148M

It clearly shows the T-handle reversing effect, or Dzhanibekov effect (discovered by that Russian cosmonaut in 1985) that we discussed on this thread:

Gyros and tops in space

I had tried in the past with my Dyon top free falling and I had not seen it. But now I tried again and filmed it in slow motion: it flips back and forth! But the flipping is very fast and both sides of the axle have the same color so I didn't realize it was doing it! I'll be out of the house the rest of the day, but I'll make a video when I can.

[ta0]

Here is a video of the Dyon top in a 1.8 m free fall showing the Dzhanibekov effect.

https://www.youtube.com/watch?v=e-a2nkTFWNc

I wish I had spun the the second video with less wobble, but I didn't want to continue risking the phone in a free fall.

[ortwin]

Very nice find ta0! Thank you for the video.
But what is taking Jeremy so long to show us the Lego version?

[Iacopo]

Here is a video of the Dyon top in a 1.8 m free fall showing the Dzhanibekov effect.

https://www.youtube.com/watch?v=e-a2nkTFWNc

I wish I had spun the the second video with less wobble, but I didn't want to continue risking the phone in a free fall.

There are 4 inversions in the first part of the video and 6 inversions in the second part.  It seems that the frequency of the inversions is more rapid when there is more wobble, which intuitively makes sense to me.  Nice video. 

[ortwin]

"There are 4 inversions in the first part of the video and 6 inversions in the second part.  It seems that the frequency of the inversions is more rapid when there is more wobble, which intuitively makes sense to me."."


Do you think the starting "speed" is the similar enough for the two runs to be comparable?

[Iacopo]

Do you think the starting "speed" is the similar enough for the two runs to be comparable?

I am not totally sure. I tried to see the video frame by frame but even so it is difficult to measure the speeds.  A mark at the side of the Dyon top would help.

[ta0]

"There are 4 inversions in the first part of the video and 6 inversions in the second part.  It seems that the frequency of the inversions is more rapid when there is more wobble, which intuitively makes sense to me."."


Do you think the starting "speed" is the similar enough for the two runs to be comparable?

The starting speed on those two above is similar. But now I recorded a fast and slow start to see the difference it would make: the faster it spins, the faster it flips back and forth:

https://www.youtube.com/watch?v=HoMiCNj8egk

[Iacopo]

the faster it spins, the faster it flips back and forth:

I would expect the ratio between the spin frequency and the flip frequency to be relatively constant, at the changing of the spin speed. But my guess is that if there is some wobble, this could lower the ratio, (making the flip frequency faster relatively to the spin frequency). 

[ta0]

the faster it spins, the faster it flips back and forth:

I would expect the ratio between the spin frequency and the flip frequency to be relatively constant, at the changing of the spin speed. But my guess is that if there is some wobble, this could lower the ratio, (making the flip frequency faster relatively to the spin frequency).

Yes, that's also my intuition and what the experiments seem to show.

[ortwin]

Especially under those conditions -no gravitational force i.e. free fall, no contact to any surface- I find it hard to grasp what is meant by "wobble". Maybe the angle of the initial alignment of the rotation axis relative to a principal axis of the top?

[ta0]

Especially under those conditions -no gravitational force i.e. free fall, no contact to any surface- I find it hard to grasp what is meant by "wobble". Maybe the angle of the initial alignment of the rotation axis relative to a principal axis of the top?

Yes, the angle of the initial alignment of the rotation axis relative to a principal axis of the top.