Making Optical Illusion Spinners

Doug Schamel and John Lahr showing Fairbanks grade school children how to make optical illusion spinners from CD-ROM disks donated by local radio stations. This is a technique that Ronald Bonnsetter of the University of Nebraska developed and demonstrated at the September, 1997, POLARIS teacher's conference in Anchorage, Alaska.

Making CD-spinners was just one of many activities available for families during the October opening of the Science Exploratorium Center set up in Denali Elementary school by Doug Schamel and Debbie Rockney.

For this project, first get a bunch of unneeded CD's from local radio stations. They toss out lots of demo CD's. Some of the lyrics are in poor taste, so I microwave the CD's for a few seconds to eliminate any possibility of actually listening to them.

Holding the edge of a penny with pliers, heat the other edge in a propane flame for about 10 seconds

Heating the penny.

Press the penny into the center hole of the CD, making certain that it stands straight up.  The penny will melt the plastic as it is pushed into position.

I use a board with a slot just wide enough for a penny.  The slot should be about 3 mm deep, so that the penny will protrude about this far below the disk.

 Alternatively, rest the penny on the burner of an electric stove set to medium heat for a few seconds.  Then grab it with pliers and press it into the CD's center hole.  The plastic of the CD melts and then sticks to the penny as soon as it cools. This is now a well balanced disk that will spin for a long time on a hard smooth surface.

A safer way, with no burn hazard, to make a CD spinner is to glue a disk of cardboard to the center of the CD.  Then drill or poke a hole for a short doll rod that has been sharpened on one end.

Here is a gif image of the spiral design.  The spiral and Benham's disk designs are available in PDF format and in MS-Word97 format.   They are also posted on the Exploratorium's web site (spiral design and Benham's disk design).  Print out copies reduced so that they will just fit on a 4.75-inch diameter CD. With a short slit in the center that fits over the penny, these patterns can be easily spun.  The Benham's disk generates colors.   If you fix your eyes for a minute or so on the spinning spiral pattern that appears to shrink and then look a something else, such as someone's head, it will appear to be expanding.

Handout and Patterns used at the Corvallis da Vinci Days celebration.

An excellent site with detailed instructions for making Benham's disk spinners from CD's or cardboard disks is:  http://faculty.washington.edu/chudler/benham.html

Downlaod a small, interactive program from UC Davis that allows one to experiment with a Benham's disk display, right on the PC computer's screen!

More things to do with CD's


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