The Cardboard Marble Run

Step 1 of 5 · 15 min

Collect & flatten

Raid the recycling bin. You want three medium boxes with clean, unbent faces. Flatten them along the folds and cut away any taped or torn panels. Flat, stiff cardboard is what makes tracks roll smoothly.

Tip: Cereal boxes are too thin for tracks, but perfect for curved side walls.

Step 2 of 5 · 25 min

Cut the tracks

Cut strips 6 cm wide and as long as your box allows. Score a line 1.5 cm from each edge and fold the sides up to make a U-channel. Each channel is one section of track, and you need six to eight of them.

Tip: An adult should handle the box cutter; kids can do all the scoring and folding.

Step 3 of 5 · 30 min

Build the frame

Stand the largest box on its side; this is your tower. Hot-glue the track channels in a zig-zag down the face, each one tilted just enough that a marble keeps moving. Test the angle with a dry fit before gluing.

Tip: Shallower angles are more fun to watch. Aim for lazy, not fast.

Step 4 of 5 · 20 min

Test the run

Send a marble down. It will fly off somewhere, and that is part of it. Add cardboard bumpers at every crash site and re-test until the marble survives the whole run three times in a row.

Tip: Film the fails in slow motion. They make the best shorts.

Step 5 of 5 · 30 min

Paint & decorate

Now everyone gets a brush. Acrylics cover cardboard beautifully. Paint each track section a different color and let everything dry for an hour before the grand opening run.

Tip: Paint before final assembly if you want crisp edges between sections.

Finish · Back to project