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.
Step 4: Conveyor belt
A cardboard guiding track was built around the conveyor belt. This V shaped track keeps the balls centered on the belt. A thin piece of wood was built into the track under the belt which keeps the belt from sagging.
I added little triangular pieces of cardboard to the front of each nail and "flag" which keep the marbles in place on the track while they are being pushed along.
Step 5: Track
I made up the layout of the track as I went along. It took a lot of trial and error to create all the various sections of track that curve, dip, rise, etc. The trick is to build and test with a marble as you go, and if it works, great--if not, take it apart and try something else.
If you're interested in making a marble coaster but are somewhat scared by the complexity of my project, take a look at these instructions for building simple marble tracks (shared by user Covo).
Step 6: Video of original version
Step 7: Upgrades!
I dug around for more parts I had kept from the old printer and found a small rubber belt along with a bunch of gears. These were put to use to slow the lift down to a nice, roller coaster-appropriate pace.
I modified the cardboard drive cog to accept the new motor belt, and added a tower to house the motor, gears, and battery pack.
Because of the slower lift, I had to make some adjustments to the positioning of the upper portion of the track which receives the ball off of the lift. This slowed down the track somewhat, so I also had to switch to using steelies (heavier metal marbles).
Prior to painting, the tower looked a lot like a prison yard guard tower. That was unintentional.
Step 8: And another video
As a parting note, I have a couple of balls out of old computer mice--they are heavy and rubber coated. They are silent as they go down the track, and very lively. My track wasn't built with these heavier balls in mind, so they tend to fly right off in a couple of spots.
If I ever build one of these again, I'm going to build it to be used with an old mouse ball, and I would recommend anyone interested in building one of these try them out. They create a really cool effect.
Let me know what you think!