Paper Marble Run

Checked in code for this build

Nobody can fold paper inside a computer, so the first real build of each run is the true test. Send us yours!

The standard

• 16 mm glass marble — the classic size
• 22 mm channel floor: the marble plus 3 mm of play each side for paper seams
• 12 mm walls: higher than the marble's centre (8 mm), so it can't hop out on curves
• 6.5° downhill everywhere: steeper than 5° so it never stalls on a seam, gentler than 10° so it doesn't fly off the curves. On curves the inner edge is 8.8° and the outer edge 5.1°.
• 15 mm connector lip on every outlet tucks into the next piece's inlet
• 12-sided towers (54 mm across): curves wrap them with the inner wall glued flat to the tower faces. Towers come in 80, 140 and 200 mm.

The kit

• Straight ramps · curved ramps (90°) · switchbacks (180°) · spirals (360° and 540°)
• Funnel (92 mm wide) + hexagonal drop tube (28 mm inside)
• Start cup · catch cup · finish bell
• Towers: 80 · 140 · 200 mm

Print at 100% on cardstock (65–110 lb). Check the 5 cm line on each page before you cut.