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Dad Field Manual · Field card 27 · Indoor & Rainy DayIdea · not yet tested

Cardboard marble run on the wall or a box

A marble run is a rainy afternoon of real engineering: build, test, watch it fail, fix it. In about 90 minutes you go from a pile of recycling to a run that drops a marble into a cup.

Time
90 min
Cost
About $10
Ages
5 to 12
Where
A bare wall or a big box

What you need

  • Cardboard tubes (paper towel, toilet paper, wrapping paper) and a big box
  • Painter's tape or masking tape
  • Kid scissors
  • A box cutter or utility knife, adults only
  • A handful of marbles
  • A paper cup or bowl to catch the marble

Before you start

  • Marbles are a choking hazard. Federal rules label them not for children under 3. With a baby or toddler in the house, count marbles out and count them back in.
  • The box cutter is yours. Cut on the floor, away from your body, and close the blade every time you set it down. Kids use kid scissors.
  • Test the tape. Stick a strip somewhere hidden and peel it off before taping up the whole wall. If paint lifts, build on a box instead.
  • Marbles roll underfoot. Run it over a rug or towel and round up strays before anyone walks through.

Steps

  1. Gather and sketch. Gather cardboard and sketch a zigzag path from a high start to a cup at the bottom.
  2. Cut the pieces. Adult cuts tubes in half lengthwise and makes cardboard ramps with folded-up edges.
  3. Tape the first ramp. Tape the first ramp up high, tilted a little downhill, and test it with a marble.
  4. Add one piece, test, repeat. Add one piece under the end of the last, then test. Ask what went wrong before fixing.
  5. Fix the trouble spots. Add walls where it flies off, flatten slopes where it's too fast, tip pieces where it stalls.
  6. Land it and time it. Tape the cup at the bottom, time three runs, then try to make the run slower.

If it stalls

  • If they get frustrated, shrink the goal: three pieces that work, then race it and celebrate.
  • If tape won't hold, build on a big flattened box leaned against the couch. Tape sticks better to cardboard.
Pieces in the run · slowest time
Signed off: can do this.Signed by Date