30 Mar 2008 The Swirling Brain   » (Master)

Shrinky Dink Gears

I found some ShrinkyDinks paper that can be run through an inkjet printer. I thought it looked like great fun, so I bought some on ebay. It took a while to arrive so I ran down to Hobby Lobby and picked up a couple of packs of it too. The two packs of it at Hobby Lobby were cheaper than one pack of it on ebay!

I then wrote some code in Postscript to draw gears on paper. I downloaded ghostscript and gsview so that I could code and view postscript on my computer screen instead of doing lots of printouts to test outputs. I was able to make a function to draw gears of a calculated size based on the tooth number and size. On each gear I put a number for the number of teeth each has to help me not have to count all the teeth each time.

I found out the hard way that the shrinky dink paper is not 8.5x11 inches but rather 8x10 inches and of course I printed on the wrong corner and wasted a sheet. So I adjusted my placement and all worked ok for the next sheet. grr.

I made the lines at 50% gray because when they shrink they get darker and if I start out at 100% black it doesn't dry and the lines smear.

Here's what my postscript gears output looks like:

Notice the output is all crammed in the upper left hand corner because this image is with 8.5x11 inch regular paper but the shrinky dink paper is really 8x10 inch size. You probably can't tell it from the picture but the lines are 50% gray.

I then carefully cut out the gears to just the outside of the black lines (so you still see the lines). I punched the center hole with a leather belt punch I had laying around. A regular paper hole punch is too big for my purposes. Them I put the cut out gears in my toaster oven at 300 degrees. It's fun watching them shrink! The small ones with teeth sizes of 12 or less work great and shrink with no problems. The bigger ones like 24 or 32 teeth came out egg shaped. I figured out that it was because it was sticking to the foil so I sprayed the foil with cooking spray and the next one came out round.

The gears always come out bowl shaped so I got a cassette case of all things and pushed them flat while they were still hot and malleable out of the oven. On one gear I smashed it too hard and it sort of squished out like squishing a marshmallow and ruined it. So I must be careful to flatten but not flatten too hard!

The process makes hard plastic gears about 1/16 inch thick. Thought about stacking three gears and gluing together for the pinion gear to make them match up to the bigger gear easier.

Here's some sample gears I created:

I then got a couple of push pins and put the gears on the wall for my test. I was able to spin the gears very well.

Here's an example of the gears on the wall with push pins:

You can kind of get an idea of the size with the push pins for your reference and from the 8.5x11 inch paper picture above to see how far they shrink. They shrink about 50%.

I hope to try making a pendulum clock if it is possible.

I hope you enjoyed this fun info. Try the buffet, we'll be here all week. Come again!

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