Our Nantwich member, Peter has been busy constructing this rare orrery:
‘While browsing the web I came across an orrery which I believe is in the Museum of the History of Science in Oxford. It was an unusual design showing the stars visible in the sky for every night of the year as well as the phase of the Moon. There were no details of it’s construction but I figured I could build one.
At the same time I had been developing my CNC skills and wanted to try producing cycloidal gear wheels on my CNC mill. I can cut involute gears with a set of standard cutters and my stepper motor driven rotary table, but cycloidal gears are a different kettle of fish. They require an impractical number of cutters if you wish to cut a wide range of teeth. Some initial tests of machining Module 1 gears in 1.5 mm brass sheet using a 1 mm slot drill proved successful. The photo of the 8 tooth pinions with different addendum profiles shows what is possible. For scale the smallest central hole is 2 mm diameter.
So I planned to produce all the parts for the orrery on the CNC machine, using cycloidal wheels and lantern pinions.
The star chart I also produced on the CNC mill. This is engraved on black anodised aluminium using a spring loaded diamond stylus in place of the slot drill.
I have yet to source a suitable base for it so it is temporarily mounted on a block of hardwood.
I hope the photos are self explanatory.’
