

Paradoxical Gear Sets - dayyan
http://jacquesmaurel.com/gears

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jacquesm
That's beautiful stuff. Gears are fascinating in their own right, these gears
doubly so. As a kid I would disassemble (for the most part, sometimes I
managed to put things back together again) all kinds of stuff and my favorites
were alarm clocks and regular clocks. I must have destroyed what today would
be worth a small fortune of clocks. Gears always fascinated me, they look so
simple and yet they're quite complex.

The beginnings of the industrial revolution were grounded to some extent in
the clock making industry, to aid the sea going nations. Cutting the gears for
those clocks required a degree of precision that had not been seen for a long
time and from that clock making industry we got to portable clocks (watches),
mechanical computers and so on.

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nraynaud
They just love it in French engineering schools. They bring it on the day of
the test, if you make an odd number of sign error you completely miss the
trick, if you check your results for general coherency you'll never believe
they are rotating in the same direction and you'll loose quite some time
checking your stuff.

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Someone
See also: [http://www.shapeways.com/model/458290/magic-
gears.html](http://www.shapeways.com/model/458290/magic-gears.html). 3
identical gears that, depending on the way they are assembled on their axes,
behave like normal gears or paradoxically.

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cousin_it
Oh, I see. Normal gears can be flat, but paradoxical gears have to be 3D,
they're like a pair of corkscrews driving each other. Right? Is there friction
at the points of contact?

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ZoF
Paradoxical gears both rotate in the same direction.(e.g. both clock-wise)

Normally gears rotate in opposite directions, meaning the gear on the left
rotates counterclockwise and the gear on the right rotates clockwise(or vice-
versa). It just so happens that any paradoxical gear has to be "3D"(no 2D
solution), there are "normal" gears that are 3D though.

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stefantalpalaru
Are they still gears if they are powered independently and the only connection
between them is that they may come in contact without blocking each other's
rotation?

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taejo
I think that one is driving the others (in the first video it looks like the
motor is only powering the middle gear)

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mcv
The "Paradoxical Gears Explained" video shows a belt behind the gears. That
suggests it's not really the gears driving each other.

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nkurz
They are driving each other. Although not well explained, the belt is just
used to demonstrate how the angles are determined. This is a little clearer
(although still hard to follow) if you watch the "Standard Gear Explanation"
video first:
[http://www.youtube.com/watch?feature=player_embedded&v=lWuKl...](http://www.youtube.com/watch?feature=player_embedded&v=lWuKl4rG2HA)

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stefantalpalaru
You're right. These 3D printed gears are clearly driving each other:
[http://www.youtube.com/watch?v=qGAnmRb66s0](http://www.youtube.com/watch?v=qGAnmRb66s0)

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twiceaday
Imagine screwing in a screw. Rotation makes lateral movement. Imagine pushing
in a sharp-ended screw into something soft. Lateral movement makes rotation.
What I believe is happening here is that one screw is being rotated,
generating a lateral force on the other screw, rotating it.

