Solar system model (aka Orrery)

[jhllt67]

Hi guys,
There was some discussion in another thread about making a model of the solar system. I was looking for something to do with gears that was a little more interesting than a basic clock, so this seemed like the perfect project.

I've gotten the arm with the earth on it working pretty well, and that seems like it is one of the more complex planets so I may be able to get a model of the inner planets and moons running before to long. Here are a few pics.

IMG_20120728_205427.jpg (171.59 KiB) Viewed 6803 times

IMG_20120728_205403.jpg (190.18 KiB) Viewed 6803 times

So when this arm is mounted in the completed orrery the gear on the right with the sun on it will be stationary and the arm will pivot around it. The big gear on the far left has the moon on it and rotates 12 times for each revolution of the arm. There is a shaft through the middle of the moon gear that turns the earth 30.25 turns for every moon cycle, or 363 days a year (as close as I could get with the gear ratios).

It is not really accurate enough to be useful but it should be a good conversation piece. I am also thinking of hooking a stepper motor up to it and using it as a kind of clock due to the 12 to 1 ratio of the arm and moon.
I hope to start working on Mercury and Venus next, which should be easier as they have no moons.

Let me know if you guys have any ideas.

[Improbable Construct]

Have you thought about using a synchronous motor? They run off of the frequency cycle of your AC power. That would simplify your timing enormously. You can buy them with gear reductions built in.

[jhllt67]

Ah good point. That would be a lot easier than a stepper/driver/arduino set up.

[Digitalmagic]

Cheap and convenient, but this happens http://www.msnbc.msn.com/id/43532031/ns ... BVRzEJRfmE

Frequency variation is about 0.5Hz average.
In winter, when power grid is very loaded, the frequency can decrease significantly. (Operator starts thermal plants up to supply more, can take some time).

[jhllt67]

I'm not super concerned with the accuracy as the clock function is just kind of an extra, but I still might just use a stepper for testing because I have an extra along with an easy driver. Have to see how that goes.

Anyway I've got a rough design for the Mercury and Venus arms. 26 gears total and about that many bearings. Not sure if I'm gonna do Mars because the complexity is really going up rapidly.

Orrey.jpg (70.54 KiB) Viewed 6745 times

Hopefully I'll be able to start cutting parts next weekend.

[DanMc]

Ahh but the complexity is what makes it so interesting

[jhllt67]

Ha, that's true. I'll have to see how these next pieces turn out.

[jhllt67]

Well its been a while but I did "finish" this little project a few weeks back, just hadn't got around to taking the pics and such.
I decided to use an extra stepper motor I had though it isn't the most cost effective solution. I used an easy driver from sparkfun and a 555 timer circuit to generate the step pulses, all running off of a 9 volt wall wart.
Mechanically it works pretty well, I leave it running pretty much all the time (it did take a lot of tuning to get it that way though). It is a bit noisy, probably due to vibration from the stepper motor.

IMG_20120930_111714.jpg (314.13 KiB) Viewed 6489 times

IMG_20120930_111616.jpg (315.13 KiB) Viewed 6489 times

There are 28 gears and about 25 bearings. Also a lot of loctite and superglue.
I'm not planning on painting or staining it, but I do need to get the electronics mounted inside the base at some point.

Let me know what you think.

[fito]

Wow! That looks fantastic. Any chance for video of it running.

[Aaron Seltzer]

Very nice build! Nice looking, and a lot of work. Cudos.