The solar system mobile tutorial

A shaky, badly lighted Youtube-video of a self build solar system mobile attracts more visitors to this blog than I ever expected.

Welcome, you solar system builders!

Since 2012 a lot of questions have reached me about how it´s been build and what materials were used.

On this page I want to bring all the hints and tips together which I have given over the years and offer an substantial guide of how to build a solar system mobile.

If you are wondering what I´m talking about, you probably didn´t see the video yet. So here it is:



A few things to say before we start
Building a model of the solar system seems to be a practical teaching content in schools around the globe.
For the case you are a kid and want to build one for school, here is a safety warning before you start: If you are unexperienced in handling tools, ask a grown up to help you. For building this mobile, tools have to be handled that can cause serious injuries if not used in the right way.

It takes a lot of time to finish this kind of mobile. If you are a trained home constructor you may have it done in one weekend.

It is quite an investment for all the materials that are needed. Most expensive are the styrofoam balls which I used for the planets. I didn´t find a cheaper way to get round shaped planets in a diameter of 40 cm. If you don´t want to have planets as big as 40 cm diameter, balloons covered with paper mache is a good option for small budgets. Over all I spent about 100 Euros for the materials.

You don´t need to build one to own one. If you´re incapable of manual work or simply lazy, Authentic Models is offering a well done, ready made mobile for a reasonable price. Have a look at the "Globes Collection" on their website. 

If you are not daunted by now, lets get on!

1. MATERIALS

Planets
As mentioned above, I used Styrofoam/Polystyrene balls for the planets.
Pro: they are perfectly round shaped, lightweight and you get them in several diameters from very small to very big. The bigger ones come in two parts which is perfect for applying the Saturn rings.
Con: they are quite expensive. They need to be covered with paper mache, otherwise paint will not stay on the surface.
Alternative: balloons, covered with paper mache. Balloons are an option for small budgets but the more you blow them up, the less ball shaped they will be. So if you want to have really big, spherical planets you should use Styrofoam balls.

Hanging, balancing and fixing
A simple hook in the ceiling (like the ones you use to hang lamps) is the main hanging.
The hanging line will twirl and allows the mobile to spin.

Any string that is strong enough to carry the weight of the planets can be used as hanging line. The thinner, the better. A clear nylon string (fishing line) is doing this job perfectly.

You need special screws for hanging Styrofoam balls. You will get them in well sorted art and craft shops or on the internet.
They look like this: 
A special screw for hanging Styrofoam objects.
Pro: they are build for this purpose and can hold a lot of weight, durable, the hanging line is easy to attach because it´s open on one side.
Con: you have to know that they exist.
Alternative: bend some hangers with stable wire (straight, triangle-shaped kink, straight) and fix it with glue and paper mache. This should work fine but needs to be well fixed to hold the the weight of bigger planets.

Beveled glass beads in several sizes to create the rests for the rods on the main string and for balancing the mobile in the end. You will need more of the bigger ones.
Pro: they sparkle and twinkle a little bit like the night sky.
Con: very, very, very expensive!
Beveled Glass beads in the sizes of 10 mm, 8 mm, 6 mm and 4 mm.
Alternative: led split-shot sinkers from the fishing supplies work very good as balancing weights, wooden beads are good for fixing the rods on the main hanging line.

Framework / Rods
Round wooden strips/rods (from the DIY-shop) and aluminium tubes.
You can get them in different diameters. Get an aluminium tube with 8 mm inner diameter and wooden rods with 8 mm outer diameter. You need 6 wooden rods, each with a length of 1 meter and about 30 cm aluminium tube.

To be complemented ...


2. BUILDING AND PAINTING

Framework / Rods
Cut the aluminium tubes into 10 cm long pieces with a metal saw. Hit a hole through the middle by using a nail and a hammer. You have to fix the tube to do this.

Stick the wooden strips into each side of the tube, about 5cm deep. Sand the end if it does not fit in. It has to sit firm.

Planets

To be complemented ...


3. ASSEMBLING AND BALANCING

To balance the planets on the rods is a laborous task: you need to figure out an equal weight on each side of the rod. 
Some examples: 
two planets of about the same size with about the same distance from the middle, 
or 
a group of small ones on one and a big one on the other side with about the same distance from the middle, 
or 
a small one far away from the middle and a big one very close to it, ... 

It is helpful to lay all your planets and rods on the floor in the order you want to have them hanging. It might be necessary to hang some of the planets half way "under" other ones, to fit them all on the rods. 

When you have figured out the layout, measure the length of every planet´s hanging line and attach it to the planet. 
Knot a lug on the end of every planet´s hanging line. Make the lug big enough to be able to quickly put the planet on and remove it from the rod. You´ll be happy for that later. 

Now temporarily hang the planets and planet groups on the dedicated rod in the distance, you have layed them out. 
Be sure to have a lot of glass beads of different sizes or split-shot sinkers from the fishing supplies at hand. 

Balance the planets by adding weight where it is needed. Simply thread the beads on the planet´s hanging line and retry the hanging. You might need to put a lot of extra weight on some planets! 

Mark the spots on the rod where the planets are in balance. 

Unhang them and cut a notch in the rod where your marks are. That will help keeping the hanging lines in place when you assemble the whole thing. Otherwise they will be slipping off very easily. 

Go on like that separately with every rod. 

After you have balanced every rod, start to assemble the mobile from down to top. 

The main hanging line is the one with the sun on it. It has to carry the whole weight so you better take a bundle of four strings to be on the save side. 

Knot a bead closely above the sun.

Thread the rod for the inner planets on the main hanging line and again knot a bead above it. 
You will need to unhang the whole thing for doing that. 
This bead will define the distance where the next rod will be. 

Now thread the next rod on the line and knot the next bead above it where the next rod shall rest. 

Hang all planets and make sure that the planets do not touch each other or any hanging line while they spin around themselves and while the rods spin. 

If the planets do touch, redo the balancing on that particular rod with a greater distance from the middle. You will need to take off and on the planets very often. 

When everything is in balance, Your mobile is ready for the final hanging. 

Congratulations!