Updated videos with rotation corrected:
Rolling a magic can:
Sorry I have to figure out how to rotate the iphone video or reshoot but for now this should give you the idea of what we are talking about.
You can use just about any can but since I was doing three of these as gifts for grandchildren I wanted them to neat and clean so I went to Lowe's hardware and got paint cans. I also made one out of a peanut butter clear jar so you can see how it works, you know the "Magic".
I used a nut but other weights will work. Here is a shot of most of the parts you need. I was going to tape the nut on but changed my mind and went to a zip tie. The tape was still used to mark the center of then ends of the cans.
The following are a few shots of the assembly details not that you will need them since it pretty simple stuff:
And while I only got to see one grandson play with his it was a big hit. It got a lot more use and play time then anything else at the birthday party.
The rubber bands do wear out so expect to have to replace them from time to time.
If the mystery is not clear in your mind I'll do a video of the clear version so you can see it in action.
This was not my idea, saw it on a tv show a while back, forgot the guys name but he does/did science shows.