I played around with cardboard, tape, glue and marbles a lot as a kid, making tracks and ramps and such just for fun.
I had been wanting to make one of these for years, just to see what I could come up with now that I'm a little older. The main thing I'd been wondering about was how I could get the marbles back to the top with some sort of mechanism made from simple, available items.
The whole thing turned out pretty well, and surprisingly, the motor/conveyor belt system I came up with works perfectly, although the initial version was really fast (see the video in step 6).
I made a few changes to slow down the conveyor, and the final painted version is shown here.
Step 1: Supplies
I used lots hot glue, along with some wood glue and white glue in a few places.
Step 3: Original motor assembly
The electric motor is out of an old printer. The drive is made from a section of cardboard tube, along with MDF glued to the inside, and rubber bands placed on the outside to give traction to the conveyor belt.
The motor was hot glued directly to the base, and the geared end of the motor was pressed against a rubber band on the conveyor drive. The power comes from four double-A batteries in a holder from Radio Shack.