How to make a cardboard marble run (using tubes and tape)

A cardboard marble run is one of those projects where you can spend 30 minutes building and hours playing. It's also a quiet lesson in testing, fixing and trying again, since the marble will tell you right away whether your design works.

What you need

• Cardboard tubes (paper towel and toilet paper rolls are ideal)
• Masking tape or painter's tape (it won't peel paint off a wall)
• Scissors
• A marble, or a small ball or bead that fits through the tubes
• Optional: cardboard box, paper cups, a tray or a plastic tub to catch the marble

How to build it

1. Choose a surface. A wall, a door, the side of a cardboard box or a table edge all work. A wall with painter's tape is the easiest for beginners.
2. Start at the top. Tape the first tube at a slight slope, with the high end at the top.
3. Test it. Drop the marble in. Does it roll all the way through? Change the slope until it does.
4. Add the next tube. Overlap the end of the first tube a little, so the marble drops into the next one. Tape it down.
5. Test again. Every time you add a piece, test it. It's much easier to fix one tube than five.
6. Add turns and tricks. Cut a tube in half to make an open channel, add a cup as a catch, or use a funnel.
7. Finish with a landing. A bowl, a tub or a paper cup at the bottom stops the marble from rolling across the room.

Tips for a run that works

• Slope is everything. Too flat and the marble stops. Too steep and it flies off. A gentle slope usually works best.
• Test one tube at a time. Every wobble is a clue, not a failure.
• Overlap generously. Gaps between tubes are the number one reason marbles get stuck.
• Use plenty of tape. Loose tubes move, and the marble goes the wrong way.
• Cut a few tubes in half. Open channels are easier to see into and fix.
• Let them be the engineer. Hand them the tape and let them choose where each piece goes.

Make it more interesting

• Race two marbles. Build two tracks side by side and see which is faster.
• Add obstacles. Zigzags, a tunnel or a jump from one tube to another.
• Use a different object. Try a pom-pom or a small ball and see how each behaves.
• Add a challenge. Can the marble take at least ten seconds to get to the bottom?
• Build it bigger. Add a second wall, or extend it across the room.

Safety

• Marbles are a choking hazard for young children. If anyone in the room still puts things in their mouth, save this project for later, or keep the marbles with an adult.
• Keep the run away from stairs and anywhere the marble could roll underfoot.
• Pick up marbles at the end of the game.

What to say

I wonder if we could make a marble go all the way down without touching it. Shall we try?

If it stalls

If the marble keeps getting stuck, try just one tube and one marble. A simple one-slope run is a fine finish. If they lose interest in the building, let them be the engineer and hand you the tape. Test one thing at a time, and treat each fix as a discovery.

Why it's worth it

Building a marble run teaches planning and patience, and shows that getting it wrong is part of getting it right. It also builds fine motor skills as kids tape, cut and position pieces.

More ideas

Try our paper plate masks, floor is lava, or browse our full list of things to do with kids.