I've currently moved over to blogging at http://mathcraft.wonderhowto.com/

Here I will be posting about 4 times per week and will have a project every week with more in depth information and a how to component and templates. There will also be a user forum for people to submit pictures and ideas.

Thanks! I hope to see you there!

Copernican Planetary Orrery (Gears for Mercury)

I've always been fascinated with astronomy, gears, and building things out of wood.... So....

I've started building a model solar system out of wood (a wooden orrery). There will be some metal parts but the gears are made from wood. It has 6 of the planets all the way out to Saturn. I'm building it from these plans, and I'll be doing pretty much all of the cutting using my scroll saw. It's probably going to take me a while. If I build it successfully, I'll probably purchase a few other plans from the same site. Some of the wooden gear clocks are amazing! But of course for those accuracy is going to be very important. We'll call this project practice.

So far all I've completed is the gears for Mercury. The drive system is set up so that the 2 gears for Earth have the same number of teeth. The drive gear for Mercury has 54 teeth and the gear connected to Mercury has 13. So the ratio is 13/54. If you multiply this by 365.2425 days (need to take into account leap years!) you get a period of 87.93 days. Mercury's orbital period is actually 87.97 days. So it's off by 1 part in about 2200. I think I can live with that sort of accuracy! So anyways, here's the first gears. There's still some sanding to do.

The 54 tooth drive wheel out of 1/2 inch plywood. Penny for scale.

The 1/4 inch pegs are for the main drive crank which will be vertical (90 degrees to the gears)

The full gearing for running Mercury.


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