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### Topic: Cycloids doodle on a coffee cup sleeve (Read 1 time)previous topic - next topic

#### liuzengqiang

##### Mar 19, 2012, 06:25 pm
Not very related to arduino. I was drinking a cup of Einstein bros coffee today over lunch and noticed the doodle on the sleeve was like cycloids (had to google a few time to get this exact term ).

Until recently I didn't know a whole a lot about these cycloid curves, although I briefly talk about it in my intro physics in rolling (I knew enough for brief mentioning ). I thought I should investigate these curves a bit more. After some more serious investigation, I think:

The top doodle is when you are skidding on ice and put your car on reverse then slam on the gas.
The bottom doodle is when you are skidding on ice and slam on the gas trying to power through the icy road.

Here's a simulation. There is no way to reverse the rotation of the wheel in the simulation so you can't get the top doodle.

http://www.cut-the-knot.org/pythagoras/cycloids.shtml

I guess you learn something everyday, even during some routine things.

To relate to arduino, I wonder if anyone has made an arduino project to keep an object upright when it is on a rotation wheel, like some counters on a bus wheel, always upright, so it won't make these cycloids.

Any others want to comment on cycloids or unexpected learning experience?

#### focalist

#1
##### Mar 20, 2012, 02:40 pmLast Edit: Mar 20, 2012, 02:43 pm by focalist Reason: 1
Classic Cycloid based toy.. I'm POSITIVE you had one.

"Spirographs" are based upon Cycloid motion and math

Cycloids are also good things to run with a plotter that's pen-down all the time.  Cool patterns for little code; the demo videos of my Frankenbotic Thinganator, it's drawing a cycloid on a dry erase board!