Construction - Friction
Hole size
This is a no brainer. I drilled a hole in a long piece of MDF and then tried swinging it on different size arbors. I thought I might have to accurately measure how long it took to slow down, but it was so obvious that the greater the play the longer the pendulum swung. Wobble was a bit of a problem as it was difficult to release the pendulum without any sideways movement, but again the smaller the arbor diameter the less the wobble.
So I will stick with the initial sizes and use a metric bit, rather than the slightly smaller imperial one.
Contact area
The MDF flooring is made as a sandwich of a top layer of melamine with aluminum oxide particles which makes it extremely durable, the inner MR MDF and a backing made from cellulose paper that has been saturated with melamine plastic resins (not quite so hard as the top layer).
Again it is a no brainer to over bore the holes, so that only the top layer (and perhaps a touch of the inner layer) is in contact with the arbor. This means that I must place the Minute wheel support on the back of it, rather than the front (as my original design) to help reduce the wobble as much as possible.
Wear
To test this I need to make a couple of wheels and then coat half the teeth with hardener.
I can then hopefully see if it introduces extra friction by doing spin-blow tests and see where the wheels stop.
I can then have a long run as a destruction test to check the wear.
This will also give me more practice before I start the proper construction - I'm sure I need it!.
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