How to make a simple Orrery

Описание: This is my very simple design for a working orrery.
Orreries show the relative positions and movements of the planets (and some of their satellites) around the Sun and are named after the Earl of Orrery who commissioned rather splendid (and very expensive) orreries to be made for him. Examples can be seen in the Science Museum. Orreries were also built by much older civilisations such as the Greeks.
My version is much simpler and only shows the Sun, the Earth and the Moon. The Sun should be much larger than the Earth. The Earth does not spin on its axis the correct number of times per orbit of the Sun and should be at an angle. Similarly the Moon does not orbit the Earth enough times per solar orbit but nevertheless this model is still useful when teaching 'the Earth in Space' as it reinforces the key points: the Sun, Earth and Moon are separate spherical bodies. The Earth orbits the Sun (and takes a year to do so). The Earth spins on its axis (and takes a day to do this). Finally, the Moon orbits the Earth and takes about 27 days.
The model can also be used with a torch or desk lamp to demonstrate eclipses.
Its available as a kit or as a classpack - see my website at www.slstc.southwarklea.org.uk for more details.