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The Magnetic Marble Roll Portable marble roll
A few years back I was teaching children's carpentry and science and a friend lent me a small wooden marble roll to use in class. It consisted of two upright 1 X 4's connected by sloping, grooved troughs. The marbles rolled down the troughs, reversing direction in a zig-zag fashion, to the bottom.

The kids loved it! They would roll one marble down by itself, then two or three, then a whole handful. Over and over and over again. They used it so much it began to bother me. What could they possibly be learning?

Portable marble roll, another view A friend mentioned that the Museum of Science and Industry in Vancouver, B.C. had a giant velcro ball roll. I went to look and discovered a large wall covered with velcro. Beside the wall was a box of small troughs made from plastic plumbing pipe split lengthwise. Each trough was fastened to a velcro-backed L-bracket. The troughs could then be placed anywhere on the velcro wall. By moving the troughs around, an infinite number of paths could be made... this was great, children could desing their own marble roll.
I made a scaled down version with a 3' X 5' sheet of velcro. It worked fine at first but gradually the velcro sheet wore out and the troughs would fall off.

What about using magnets instead of velcro? I replaced the big velcro sheet with a piece of sheet metal and the velcro on the back of the troughs with sheet magnet. It worked great and didn't wear out either.

And by the way, I don't actually use marbles with this marble roll (the name seemed to stick). If you use marbles kids are always running all over chasing them. I use the little rubber (Kiosh) balls with rubber spikes sticking out of them. They roll much slower.

You will not believe how much fun kids have with this. Cate Melcher, director of the Children's Museum in Mount Vernon, WA, says, "Children (and adults) have a GREAT time playing with the Marble Roll! It is fun for all ages, and the opportunity for creativity is endless. It has been an excellent addition to the museum."

MATERIALS
  • A refrigerator or freezer door. More on size later. I really like the idea of using a refridgerator door but eventually I started using galvanized sheet metal. Attached to a piece of plywood. Its easier to move and doesn't scratch so badly as the door. More expensive however.
  • 3' X 7' 1/8" door skin (thin plywood) to cover up the back of the fringe door
  • 7' of 2" white plastic plumbing pipe.
  • 2" plumbing pipe connectors: four 90°, four 45°, two tee's, two sleeve
  • 40 3/8" X 7 flat heat screws
  • 32 1/2" sheet metal screws
  • Contact cement
  • Ten 5" X 8" magnetic sheets with adhesive backing cut into 1 1/2" strips
  • Eleven feet of 5/16" thick by 1 1/2" wide soft wood such as pine or cedar, for the wood pieces to mount the pipe troughs and connectors. These need to be flat, in order to accept the magnetic sheet, light so they're not too heavy for the magnets, and of uniform thickness so the troughs will line up when mounted on the door.
  • A small box approximately 2" X 3" to catch the balls. This could be wood, cardboard, plastic or something fancier like a band saw box. It needs to be light.
  • A box to hold all the pieces about 12" wide 4" deep and 16" long. Cardboard works but a wood box adds a nice touch.
  • Ping pong balls, jack balls and mini Kiosh-type balls. The kiosh-type balls are nice, especially on hard floors, because they don't roll all over the room.
  • 100 grit sandpaper for smoothing up the plastic pipe

TOOLS
  • An electric drill, battery powered is fine. A hand drill will work.
  • Drill bit for screw pilot holes and larger bit (3/8") for countersinking screws
  • Screwdriver bit for drill
  • Screw driver to match screws
  • A vice to hold wood while cutting is nice but not absolutely necessary.
  • Hot glue gun and glue
  • Hand saw
  • Metal file
Fridge door marble roll

CONSTRUCTION

THE FRIDGE DOOR

Locate a refrigerator door at an appliance repair shop. If you show how the door is to be used you may get it for free, so take a few troughs to demonstrate. Choose a big door but not so big it's difficult to move around. I used a freezer door, 35" X 68", and it's a little heavy and awkward to move around.

The door can be painted but it is hard to find a paint that won't scratch from the constant rubbing of the troughs. The enamel that comes on the door is harder than most paints you'll find but it, too, will scratch. Epoxy paint might work. Or use galvanized sheet metal attached to plywood.

Here is how to prepare the door:

  • Remove the plastic trays, egg holders, etc., from inside the door.
  • Make a stand to support the door by cutting two half circles of 3/4" plywood with an 18" radius (could be smaller for a smaller door) and bolting them through the sides of the door. Angle the door back just a little before attaching these side braces. Carve some of the foam away on the inside of the door at the points where the bolts come through the side of the fridge.
  • Cut, fit and fasten door skin to the back of fringe door. This will protect the foam insulation from being chipped away.

PIPE

Cut the pipe down the center lengthwise and then it cut into lengths

  • four 10" lengths
  • eight 6" lengths
  • eight 8" lengths
Although it is hard to hold, the pipe can be cut with a fine tooth hand saw. A band saw will do the job quickly. Sand the edges of the pipe smooth.

WOOD

Cut the 5/16" thick by 1 1/2" molding into lengths to match the pipe. Ten 6" pieces for the 6" pipe and 8" lengths for the 8" and 10' pipe. Sand smooth.

ASSEMBLY

  • Fasten the sanded split pipe to the wood pieces with screws and hot glue. File screws flat if they stick through the wood.
  • Fasten pipe connector pieces to wood backing pieces. File screws flat if they protrude.
  • Cut and fit magnet sheet for the wood on the back of each pipe piece (troughs and connectors). Apply contact cement to the back of each wood piece and after it dries remove the protective backing from the adhesive side of the magnetic sheet and fasten magnetic sheet to back of wood pieces.
  • Attach wood and magnetic sheet to the small box same as above.
  • Glue closed-cell foam to the bottom edge of door with contact cement. This will keep the edge of the door stable when in use.
  • Find kids and test!

Kid-built marble rolls are described in my book Woodshop for Kids. The Woodshop gallery page has an example.

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