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ITSA General Assembly: December 5th - 12th

Author Topic: Centrifugal tops  (Read 1393 times)

Jeremy McCreary

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Centrifugal tops
« on: March 16, 2016, 11:07:18 PM »

EDIT moderator: I split this thread from Eames "Tops" film from 1969.

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I really love the little sliver-ball-fringed-tassel-top at 3:33.

A LEGO version of the tassel top at 8:30...

https://www.youtube.com/watch?v=nTNyuuhw04s
« Last Edit: March 18, 2016, 11:21:20 AM by ta0 »
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Playing with the physical world through LEGO

ta0

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Re: Centrifugal tops
« Reply #1 on: March 17, 2016, 09:03:22 PM »

Wow! I finally watched the whole video. I lost count of how many "centrifugal tops" you show!
I specially loved the circular scissor linkage tops.

The RPM of these tops should not decrease the same way as regular tops. The spin should remain more constant while it is contracting. I would like to see a graph of the spin decay  ;)
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Jeremy McCreary

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Re: Centrifugal tops
« Reply #2 on: March 18, 2016, 01:54:25 AM »

Wow! I finally watched the whole video. I lost count of how many "centrifugal tops" you show!
I specially loved the circular scissor linkage tops.

The RPM of these tops should not decrease the same way as regular tops. The spin should remain more constant while it is contracting. I would like to see a graph of the spin decay  ;)

Thanks, ta0! This video includes ~1/3 of the centrifugal tops I've made to date.

Yes, the dynamics get pretty interesting when a top can deform reversibly under centrifugal force. Next time I have a willing assistant, I'll record some spin decay curves.

Available observations: The mechanisms on the flyball tops at the beginning of the video can be locked in any desired position. In all cases, spin times are longest when locked in the fully extended position and shortest when locked in the fully contracted position. Unlocked mechanisms always give intermediate spin times.

These findings make some sense if you consider how CM height and the axial and transverse moments of inertia change as an unlocked mechanism contracts during spin-down. Changes in air resistance may also play a role.
« Last Edit: March 18, 2016, 06:58:53 PM by Jeremy McCreary »
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collectop

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Re: Centrifugal tops
« Reply #3 on: March 18, 2016, 05:48:21 PM »

I never knew Lego's could be so fun ,loved the color changes on the last one
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Jeremy McCreary

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Re: Centrifugal tops
« Reply #4 on: March 18, 2016, 07:51:35 PM »

I never knew Lego's could be so fun ,loved the color changes on the last one

Thanks, Michael! Unfortunately, LEGO tops are generally not tough enough to throw, but they're a lot of fun as finger tops and also work well with various spin-up tools. Better yet, they're a ton of fun, design, engineer, and tinker with.

If you liked the color changes, check out my color-mixing tops at http://www.moc-pages.com/moc.php/421944. One example below...




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collectop

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Re: Centrifugal tops
« Reply #5 on: March 19, 2016, 11:03:56 PM »

I checked out the link and it was very informative .   Thanks michael
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