<p>The principle is almost exactly the same as a watch or clock, but instead of three concentric axles, you need 9 for the planets.</p>

<p>Have a google for Orrery kit - there are loads available. It is really all simple maths - you just need to know relative orbital periods in order to calculate cog sizes.
<img src="https://i.sstatic.net/wHjjr.jpg" alt="enter image description here">
(picture from <a href="http://www.curiousminds.co.uk/large-fergusons-orrery" rel="noreferrer">curiousminds.co.uk</a>)
For moons, you do add a little complexity in the form of a transmission to support the Earth, so that the difference in movement can move the Moon. </p>

CC BY-SA 3.0
2014-01-12T14:25:45.127Z
Okay! Well after a whole lot of googling, I wasn't able to come upon a resource that would give me the gear ratios. Where do I get these from?
Ranveer
CC BY-SA 3.0
2014-01-12T14:31:51.127Z
You can work them out pretty easily from orbital periods: 0.24 0.62 1 1.88 11.86 29.46 84.01 164.8 for Mercury to Neptune.
Rory Alsop
CC BY-SA 3.0
2014-01-12T14:45:35.707Z
Also, a quick google for Orrery gear ratio comes up loads of results, including a set of spreadsheets with all the info you need.
Rory Alsop
CC BY-SA 3.0
2014-01-12T14:21:46.913Z
2014-01-12T14:21:46.913Z
Rory Alsop
<p>Orrery is a clockwork model of the solar system. I am trying to emulate one in 2D. Now, to emulate, I need to know what goes on inside. Can someone please explain the basic principle behind the clockwork? Or direct me to a resource that will explain all the machinery inside a simple Orrery.</p>

CC BY-SA 4.0
2020-12-29T00:20:10.423Z
orrery-related posts: [The Jupiter Effect Book](https://astronomy.stackexchange.com/q/39194/7982) and in Math SE [How to predict the incidents of synchronization for multiple oscillations.](https://math.stackexchange.com/q/1812124/284619)
uhoh
<solar-system><n-body-simulations><orrery>
Emulation of an Orrery
Ranveer
# Emulation of an Orrery

(Asked by: username_0 on 2014-01-10)

Orrery is a clockwork model of the solar system. I am trying to emulate one in 2D. Now, to emulate, I need to know what goes on inside. Can someone please explain the basic principle behind the clockwork? Or direct me to a resource that will explain all the machinery inside a simple Orrery.

**Tags:** solar-system, n-body-simulations, orrery
> **Comments:**
> **username_1**: orrery-related posts: [The Jupiter Effect Book](https://astronomy.stackexchange.com/q/39194/7982) and in Math SE [How to predict the incidents of synchronization for multiple oscillations.](https://math.stackexchange.com/q/1812124/284619)  

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## 1 answers

### Answer by username_2 on 2014-01-12. Score: 8 | Accepted answer

The principle is almost exactly the same as a watch or clock, but instead of three concentric axles, you need 9 for the planets.

Have a google for Orrery kit - there are loads available. It is really all simple maths - you just need to know relative orbital periods in order to calculate cog sizes.
![enter image description here](https://i.sstatic.net/wHjjr.jpg)
(picture from [curiousminds.co.uk](http://www.curiousminds.co.uk/large-fergusons-orrery))
For moons, you do add a little complexity in the form of a transmission to support the Earth, so that the difference in movement can move the Moon.

> **Comments:**
> **username_0**: Okay! Well after a whole lot of googling, I wasn't able to come upon a resource that would give me the gear ratios. Where do I get these from?  
> **username_2**: You can work them out pretty easily from orbital periods: 0.24 0.62 1 1.88 11.86 29.46 84.01 164.8 for Mercury to Neptune.  
> **username_2**: Also, a quick google for Orrery gear ratio comes up loads of results, including a set of spreadsheets with all the info you need.  

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