Kinetic Chain Sculpture Built From a Bicycle

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About: Eric J. Wilhelm is the founder of Instructables. He has a Ph.D. from MIT in Mechanical Engineering. Eric believes in making technology accessible through understanding, and strives to inspire others to lear...

Intro: Kinetic Chain Sculpture Built From a Bicycle

I took an old bike, scavenged a 12-volt car seat-motor from another project to power it, and ran chain around the rear rim. I find it so mesmerizing it's almost dangerous to turn it on; I might spend an hour watching the various shapes travel through the moving chain. I didn't realize how cool this project would be until I had actually built and tested it.



Though this phenomenon is probably best described by pages upon pages of differential equations, my best simple explainantion is this: Think of a length of chain hanging and not moving. If you hit it, something like a wave will propagate away from the point at which you struck. Now fix yourself to a point on the chain, start it moving, and hit it again. From your perspective the wave propagates as before, at equal speed in both directions, yet from the perspective of a fixed external observer, the wave's speed and the chain's speed add in one direction along the chain, and subtract in the other. So for chain speeds close to the wave speed, waves will appear to sit at the same relative position or to move slowly along.

This "slowing down" effect is one of the reasons why I am so fascinated. In the moving chain, shapes that would otherwise change too fast to enjoy can be clearly seen.

The Exploratorium has a similar exhibit called the Lariat Chain.


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    22 Discussions

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    sgt_eldridge

    10 years ago on Introduction

    might I suggest using some sort of rod to manipulate the chain instead of your fingers. hate to see them sliced off. other than that very very cool.

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    ewilhelmsgt_eldridge

    Reply 10 years ago on Introduction

    Not a bad suggestion, but the low-wattage motor tended to stall easily and really couldn't do any harm.

    These are great, my local science museum has a 10 foot one with thicker chain.

    I made one out of knex once but the chain can only form shapes in one plain so it's not as impressive.

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    michaelgohjs

    7 years ago on Introduction

    read the comments..dont you guys think making it work with black light would be cool..its like everything is dark except a glowing chain with weird patterns

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    michaelgohjs

    7 years ago on Introduction

    COOL !!
    love the way it looks slow motion
    whats the rpm of the wheel?

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    ozetzioni

    9 years ago on Introduction

    Hey, I am building a pedal generator bike with a battery. at the end of the day i want to transfer the electricity i made of riding into a bigger battery and then use it for lighting equipment... anyone knows of a method to transfer the electricity from one battery to a bigger one without losing voltage or too much energy???

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    hlumbard

    10 years ago on Introduction

    What type of chain is that? I've seen similar things in a smaller scale using string in a hand held device.

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    ewilhelmhlumbard

    Reply 10 years ago on Introduction

    It's the chain that looks like a bunch of small hallow balls connected by straight pieces of metal. You can just make it out in the slideshow images.

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    BeanGolemewilhelm

    Reply 9 years ago on Introduction

    You can usually find this stuff at bathroom hardware type stores. I've seen it labeled "shower curtain" chain, because many sliding-track shower mounting systems use it to hang the curtain... I think. Other than that, though, i think "hollow-ball-straight-pieces-of-metal" is a more functional title.

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    They have one of these at the Science Museum of MN. Its really fun to play with.

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    you know what the waves make me think of, in both the way you describe them and the way they look in the pictures. sound waves from a car. as the car gets closer the waves are closer to gether and as the car gets farther away, the waves spread out and the pitch sounds deeper. i bet you could paint on some IR reflective paint and use it for a synth of some kind.

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    Gene Hacker

    10 years ago on Introduction

    I saw a huge one of these in the exploritorium. Very cool project indeed.

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    crapflinger

    10 years ago on Introduction

    does it make wild random shapes on it's own? maybe hook up some kind of cam or something off of the wheel hub that would introduce a "wave" randomly as the thing churned along? nifty! i really wish i had the time and space to set up some stuff like this....my dad would sit in a room for a month without moving if he had something like that

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    GorillazMiko

    10 years ago on Introduction

    ewilhelm, you look cool :-) was this instructable filmed and done at the instructables office/ workshop/ place? :-)

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    ewilhelmGorillazMiko

    Reply 10 years ago on Introduction

    I wanted to share the project, but I didn't take step-by-step photos, only pictures and video of the final things, so I made a Slideshow.