We've been thinking about rockets and spaceships this week at 123D and we had some cool glow-in-the-dark filament for a Makerbot Rep2, so naturally: GLOW IN THE DARK SPACESHIPS!
This is a quick weekend project, and perfect for teaching a kid how to be careful with Krazy Glue. (I've been scraping KG off my thumb for 3 days now.)
Step 1: Print your models
The rocket models came directly from the 123Dapp.com gallery, but the planets, star-shaped end caps and filament points I quickly modeled in Tinkercad (free). Because the rockets were taller than would fit on a Makerbot, I imported them into MeshMixer (free) to chop them in half with the Slice tool. Slicing them also allowed for printing without support material. With a little glue, you get more size options.
The trickiest part of a mobile is (perhaps obvious) is the balancing of all the elements - both physically and visually. I printed a couple different sizes of rockets and planets, with varying infills so that I would have options when I started assembling it. Only after printing the last rocket did I realize I could have just modeled the eyelets, but there you have it. In total, the project cost about $15 in parts and materials: monofilament, eyelets, dowels and krazy glue.
Step 2: Experiment with your options
I dove in without a lot of pre-planning, just making different size/weight options. I don't think planning would have really helped, unless you went so far as to calculate weights.
I did make the connection points with the ability to slide/balance, which made it much easier. When you reach 'stasis' just drop a dab of glue to hold it in place.
Play with cantilevers - I made it so that one part can actually spin under another. Just remember that heavier objects on the short side will balance lighter objects on the longer side.