Build a waving machine
Build a hand cranked waving machine from cardboard, craft sticks, straws, and string to make an arm wave and explore simple machines.
About this activity
Build a hand cranked waving machine from cardboard, craft sticks, straws, and string to make an arm wave and explore simple machines.
What you need
Step by step
- 1
Step 1
Gather all the Materials Needed and clear a flat workspace so you have room to build.
- 2
Step 2
Use the ruler and scissors to cut a rectangle about 20 cm by 12 cm from the cardboard to make the base.
- 3
Step 3
Cut two straw pieces about 3 cm long each to use as axle supports.
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Step 4
Tape the two short straw pieces to the base about 3 cm from one short edge and about 6 cm apart so they line up as axle supports.
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Step 5
Slide the pencil or wooden skewer through the straw supports so it rests across the base as the axle.
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Step 6
Cut a 3 cm length of straw to make a crank sleeve.
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Step 7
Glue the 3 cm straw sleeve to the center of one craft stick to make a crank hub and let the glue dry.
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Step 8
Slide the crank craft stick with its straw sleeve onto the pencil axle so the stick sits on the axle and can turn.
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Step 9
Mark a pivot spot on the base about 8 cm from the axle on the opposite side so the arm will have space to wave.
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Step 10
Push the paper fastener through one end of another craft stick to prepare the arm pivot.
- 11
Step 11
Push the fastener through the marked pivot spot on the base and fold the fastener legs under so the craft stick can rotate as the waving arm.
- 12
Step 12
Tie one end of the string to the free end of the craft stick arm with a secure knot.
- 13
Step 13
Tie the other end of the string to the crank craft stick about 2 cm from the straw sleeve so the string is slightly slack when the arm is down.
- 14
Step 14
Slowly turn the pencil axle by hand to make the crank pull the string and watch the arm wave; adjust the string knot if the motion needs more or less travel.
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Step 15
Share your finished waving machine on DIY.org.
Fun facts
How do you make a hand-cranked waving machine?
Cut a sturdy cardboard base and attach a vertical support. Build an “arm” from craft sticks glued or taped together with a straw as a pivot sleeve. Make a crank from a stick or dowel and attach it to the base so it turns freely. Tie a short length of string from the crank’s offset peg to the arm so turning the crank pulls the arm up and lets it fall, creating a waving motion. Test and adjust link lengths for smooth movement.
What materials do I need for a hand-cranked waving machine?
You’ll need cardboard for the base and supports, several craft sticks or small wooden dowels, plastic drinking straws for pivots, string or thin twine, tape and school glue, scissors, a pencil or small wooden dowel for the crank, and a hole punch or sharp tool to make peg holes. Optional: markers or paint for decoration, paper or foam for a hand shape, and extra cardboard for reinforcement.
What ages is the waving machine activity suitable for?
This hands-on project suits children aged about 6–12. Younger kids (6–8) will need close adult help with cutting, punching holes, and tying knots. Older children (9–12) can design link lengths and improve stability, exploring mechanical concepts more independently. Adapt complexity: make a simpler glued design for younger kids or add gearing and multiple linkages for older kids to extend the challenge.
What safety tips should I follow when building the machine?
Supervise children when cutting cardboard or using sharp tools. Use child-safe scissors and have adults handle hot glue or awl work. Watch for small parts and loose string—avoid long loops near the neck. Secure pivots so the crank doesn’t slip and test slowly to find points of strain. Encourage wearing safety glasses if you poke holes, and tidy up debris to prevent choking hazards for younger siblings.
Watch & Learn
Need help?
What can we use instead of the 3 cm straw pieces or a wooden skewer if those materials are hard to find?
If you don't have the 3 cm straw supports or sleeve, substitute short tightly rolled cardboard tubes (from paper or tape) for the straw pieces and use a pen, chopstick, or thin dowel instead of the pencil or wooden skewer for the axle.
My crank won't turn or the arm won't wave smoothly—what should I check and fix?
If the crank binds or the arm doesn't move enough, make sure the two short straw pieces taped to the base are aligned and not pinching the pencil axle, trim or loosen the tape on the supports, and adjust the string knot tied about 2 cm from the straw sleeve to add or reduce travel.
How can I adapt this waving machine activity for younger or older kids?
For younger children, pre-cut the 20 cm by 12 cm cardboard base and the straw pieces and let them tape, tie, and decorate, while older kids can measure and cut the base themselves, hot-glue the 3 cm straw sleeve for a stronger crank hub, or add extra craft-stick arms to explore motion changes.
What are some ways to extend or personalize the finished waving machine?
To extend the project, decorate the cardboard base, attach additional craft-stick arms at different pivot spots for more complex motion, or replace the hand-turned pencil axle with a small DC motor for continuous waving.