# Double Pendulum



## bob shutt (Dec 24, 2014)

Latest project  Double Pendulum
 [ame]https://www.youtube.com/watch?v=neQugok-wUU[/ame]


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## rleete (Dec 24, 2014)

Video is private.


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## Ken I (Dec 25, 2014)

I tried to build a very small one mounted in a vacuumed tube - rather hoped to get the chaotic motion that it demonstrates in a "snow globe" type desk ornament.





"D" cell is for size comparison.

As it stands it doesn't work and I've kind of given up on it.

Your design has given me a couple of new ideas to try - if that doesn't work I'm definitely going to build a bigger one like yours.
Thanks for the inspiration.

Well executed model - did you use ball bearings or plain ?

Anyone else out there ever built a small one ?

Regards,

      Ken


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## bob shutt (Dec 25, 2014)

Hi Ken, I used ball bearings. The best thing I can tell you is to as much of the weight (mass) into the pivot and the end piece.


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## kquiggle (Dec 25, 2014)

Bob - nicely done. It's amazing how long these things will go once they get started. I notice you have it clamped to the table - do you plan to make a heavier base?

Note to Ken: I've never made one of these, so I am just guessing here, but it looks to me like your design has too much mass in the pendulum "rod" and not enough in the "bob." No doubt bearing friction is also a factor; ball bearings must certainly be a big benefit, if not a requirement (at least for a small version). Let us know if you get it working.


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## AussieJimG (Dec 25, 2014)

Looks like a good project to add to the list of potential gifts.

Jim


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## Ken I (Dec 26, 2014)

I've been playing with my "snow globe" double pendulum (it turns on small ball bearings) and made the pendulums more pendulous and it is working much better - but it decays too quickly - hence the reason for the vacuum (which I haven't applied yet) in order to eliminate aerodynamic drag.

However what should have been blindingly obvious from the get-go is that small pendulums move very fast and its hard to follow the chaotic movement without slowmo.

Ah well.

Regards,
            Ken


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## Speedy (Jan 4, 2015)

headphones on and pumping some tunes, click the video and my eyes light up! 
but I suppose pendulums work well with rhythm


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