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THIS IS THE TEST SITE OF EUROBRICKS! ×
THIS IS THE TEST SITE OF EUROBRICKS!

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Posted

Hi all, Here is my latest kinetic art piece:

The nine pods all oscillate at slightly different speeds, so the pattern is always changing, and repeats about every 5 minutes.

The two at the ends are directly geared in a 9:10 ratio.  The others are driven by differentials which successively average the speeds.  This means that the speeds are in the ratios 72:73:74:75:76:77:78:79:80.

At various times, it produces 1 wave, 2 interlacing waves, and 3 synchronized color sets.

Enjoy!

Posted

I've enjoyed the video, so mesmerising.

3 hours ago, aeh5040 said:

speeds are in the ratios 72:73:74:75:76:77:78:79:80

I would love to see gear setup picture for such close ratio. Simply to understand how you achieved this.

Posted

Thanks!  You should be able to see the gear setup pretty clearly at 1:50.  Let me know if any something is unclear.

Understanding why it works is a different question.  As I said, the two ends pods are geared directly from the motor, with 1:2 x 3:5 and 1:3 ratios, giving 9:10 or equivalently 72:80.  Then the middle pod is driven by the cage of a differential connected to the ends, so its speed is the average of the ends, or 76.  Then another differential averages the 72 and 76 to give 74, and so on.

Posted (edited)
2 hours ago, aeh5040 said:

Thanks!  You should be able to see the gear setup pretty clearly at 1:50.  Let me know if any something is unclear.

Understanding why it works is a different question.  ...

As to understanding why it works, it's just few sinewaves (projection of blob trajectory onto horizontal plane) whose frequencies are slightly off ... at times they're in phase, at others not, and then anything in between. I'm tempted to do an LDD model and would appreciate few static shots. 

 

A while back (~10 years) I bought 10 differentials from Lego.edu with big hopes/dreams to do something useful with them. This project is just it. Where else can you use that many differentials? Well, maybe this marvel and the Lego Antikythera (can't find the link now)

Edited by DrJB
Posted (edited)
37 minutes ago, DrJB said:

As to understanding why it works, it's just few sinewaves (projection of blob trajectory onto horizontal plane) whose frequencies are slightly off ... at times they're in phase, at others not, and then anything in between. I'm tempted to do an LDD model and would appreciate few static shots.

That's right.  I was referring more to how the actual gearing works, which tends to baffle people.  I'll take a few photos soon.

My first attempt had the differentials arranged differently.  One linking pods 1,2 and 3, the next linking 2,3,4, etc.  Theoretically this gives exactly the same effect, but it did not work at all.  A combination of friction and gear lash meant that it just locked up.  The current version (with diffs between 1,5,9;  1,3,5;  5,7,9;  1,2,3;  3,4,5;  5,6,7;  7,8,9) works very smoothly.  It's not so easy to explain the big difference.

37 minutes ago, DrJB said:

A while back (~10 years) I bought 10 differentials from Lego.edu with big hopes/dreams to do something useful with them. This project is just it. Where else can you use that many differentials? Well, maybe this marvel and the Lego Antikythera (can't find the link now)

Yeah, diffs are awesome, and I would like to find more applications.  Here's something else I used them for a while ago:

http://www.brickshelf.com/cgi-bin/gallery.cgi?i=4756066

 

Edited by aeh5040
Posted

This reminds me of sitting at a traffic light in a turn lane with my blinker on and watching as the frequency *almost* matches the car in front of me but then becomes syncopated.  It is pretty mesmerizing.

Are those X-pod lids?  Where in the world did you get so many?  When I was trying to get some for building Arvo brothers' Kaneda bike, they were impossible to buy at any price.

Posted

This is a simply beautiful, mesmerizing motion, similar to the (slightly annoying) effect that Blakbird mentioned above of two flashing lights with not-quite-synced frequencies, so sometimes they both flash at the same time and sometimes alternately, but most of the time somewhere in-between. Only difference being, you've got 9 swaying pods instead of two lights.
You could put quite a display together now of unusual LEGO contraptions...

Posted (edited)

Thanks everyone for the kind remarks.  I guess I too have always been fascinated by things gradually going in and out or phase like this.

13 hours ago, Blakbird said:

Eric is correct (or should that be 90% correct?).  They are X-Pod bottoms (in pairs).  No special method for collecting them - several orders, patience, etc.

It worked pretty well at the two consecutive shows I just did.  On the positive side: it runs incredibly smoothly - no problems at all, and not even any detectable ABS dust after six solid days of running.  The negative: it's not necessarily the easiest for spectators to appreciate.  If they walk past during the more random phase, they may not notice that the pattern is changing, and thus quickly tune it out.  On the last day I added a little sign saying "The pods synchronize about every 5 minutes", which helped.  Quite a few people waited to see it and were happy!

I'll probably make an LDraw file at some point...

Here are some static pictures as requested (see bricksafe for more)

800x600.jpg

800x600.jpg

Edited by aeh5040
  • 5 weeks later...
Posted

I have seen other pieces of your kinetic art, but this is the first time seeing this one.  Wonderful job......I especially love the piece selection (color selection?) for the disks at the top

  • 3 weeks later...
  • aeh5040 changed the title to [MOC] Synchro Pods kinetic art - now with instructions

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