The Earth-Moon Orrery: a quick status update.

My ultimate goal is to recreate the 3D printed object in brass, creating a small little tabletop Orrery for display. That means, of course, cutting gears.

So there has been a little bit of a pause while I order the correct things for gear cutting. Ultimately my goal is to set up a Sherline mill as a gear cutting system. I have 32DP gear cutters on order–which means I’m going to be resizing the machine I make even smaller than its current 3D printed size. And that means a lot of waiting and tinkering–since I’m a complete noob when it comes to metal working. But my goal is to learn along the way.

I also have some plate aluminum on order; my theory is learn on the cheap stuff–though I bet I’ll waste a lot of (more expensive) engravers brass when it comes time to cut the final gears.

Meanwhile, I do have a 7″ lathe and mill, both from these guys, which I bought a couple of years ago (but circumstances in my life meant they got to sit around gathering dust), and it’s time to cut the gear arbors.

I’m using something I first saw on Clickspring. The principle of cutting a gear is more or less the same: cut a roughly circular blank out of sheet metal, super-glue it to a gear arbor, then true the blank to the correct diameter. Mount on the Sherline (and yes, I know; this means a lot of fiddling to re-center the blank), align the cutters, and start cutting gears.

So today I’m making my superglue gear arbors.

For our orrery we need three arbors: one that is 1.5 inches in diameter (to hold the 52-tooth wheels), one that is 0.75 inches in diameter (to hold the 26- and 29-tooth wheels), and one that is 0.375 inches in diameter (to hold the 14 tooth wheels).

Each are made from aluminum stock I have on hand; the 0.375 inch arbor was turned on a lathe down from 1/2 inch diameter aluminum stock. And while my arbors may not have the same fit and finish as the Clickspring arbors, hey; I’m still learning how to do this stuff. My hope is that by the time I get to working with brass, I’ve learned enough from working with aluminum to get the fit and finish right.

As a footnote, since I’m using 32DP gear cutters (which has the nice property that they should work well with stock gears from Sparkfun,) this means in the future if I get interested in doing some robots work, I’m well equipped to cut my own custom gears in case I need a custom tooth ratio.

But it does mean going through and resizing the gear parameters in Kythera for the Earth-Moon Orrery.

After doing a little research I decided to cut the gears from 1/16″ thick brass sheet and 1/8″ thick brass sheet. A little fiddling with the settings for the document, but setting the gear and layer thickness to 1/16″ and 1/8th”, respectively, and I’ve come up with a tentative update to the Earth-Moon orrery design, which you can download here.


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