### Spiro Gear Drawing Apparatus

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Published on October 21, 2011

#### Description

This project is what inspired my Gear O' Clock gear profile. A very simple continuous .075 radius. Formula below for making your own...

Print out all or a few of the gears.

Grab a mechanical pencil, Sharpie Pen, or an similar fine drawing utensils.

Hold outer gear, place utensil in any one of the inner gears and draw many shapes.

Feel free to use my design to make any new gear designs you wish. I only ask that you share working ones and upload them as derivatives. The designs can be endless. Squares, ovals, rectangles, blob shaped and any combination can be made.

The diameter of the gear teeth is .15 inches. (See drawing.)
You must calculate pi by first determining how many teeth you want.
So basically 31 teeth x 2 = 62
62 x .15 = 9.3" which = The Circumference
9.3"/ pi = 2.962 which = the diameter to base your teeth off of.
The diameter refers to the pitch circle or center of diameter of your gear teeth.

#### Instructions

I WANT YOU to make more designs and post them as derivatives!

The units are inches so don't complain they are not the proper size!

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Warning! Impossible overhangs in the assembly plate. I didn't notice and made a PLA mess :(

Since the separate 3" wheel does not have the overhangs, it and the smaller gears can be combined into a overhang free plate, I am trying that now in my ultimaker. Wish me luck! :D

Nope. They can't fit together without the overhang :(
I conclude that this thing can't be printed without support and that the separate 3" wheel does not fit.

I had a spirograph about forty years ago.  Loved it.  Wanted to see the tech used for some other stuff, such as a large version that a wood router could fit into so that you could engrave a rosette in a hardwood board.

Super cool thing!

Watching the video... it looks like using the inner gear upside-down would make it even easier :)

Couple of questions: Is the outer gear cut in sections? Do this sections safely fit into a cupcake (92mmx92mm)?

(I guess: yes
&
amp; yes)

Great work, thanks for sharing!!