In the Exhibit Shop

Six months after The Science of Nature, opened I am starting on final fabrication on the next exhibition. There will be many interesting gadgets in this one and I am working on one of the more complex pieces right now.  This Rube Goldberg contraption has many features that allow the visitor to guide a wooden ball through a series of mechanical obstacles.   The next component I am working on involves a disc that carries a wooden ball from one track to another-- sort of like a Ferris wheel.  The Ferris wheel is actually  built up from a stack of discs.  I cut the discs out of black foamed PVC sheets.  Making discs is pretty basic fabrication but I thought I would go over the process for non-shop folk who may be reading.

A trim router is attached to a strip of plywood.  I drilled the plywood to accept flat head screws into the factory holes in the router base.  The strip of plywood (circle jig) can be used over and over.  A hole is drilled in the jig at the point that marks the exact radius of the disc I would like to make.  In this case I wanted a 10" disk so the hole was drilled five inches from the router bit.  

The jig is screwed to the material with a single screw through the hole you drilled and the router bit touching one edge of the material.  A waste board (some piece of plywood you don't care about) is placed under the setup before cutting begins.   You have to brace the jig and router really well when turning it on because the bit is already in contact with the material.  But once you are powered up it is a simple matter of rotating the jig and router around the center screw.

Depending on the thickness or hardness of the material and the length of your bit, you may have to make at least two passes to cut the discs.

In minutes you will have some snazzy disks that are about as close to perfect as you can get with hand tools.  The screw hole marks the center of the discs. for me this was a benefit because I needed to drill a hole in the center of the Ferris wheel for a 1/2" shaft.

You can see I used an old router jig from a previous exhibit as my waste board.  In minutes I cut four perfect plastic discs-- pretty cool.

Thanks for checking in.  Full steam ahead.