Build a ringing or knocking machine - Fun at-home activities for Kids.

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Build a ringing or knocking machine

Build a simple ringing or knocking machine using cardboard, rubber bands, small motor or crank, and a bell or mallet to explore mechanical motion.

Table of contents

Step-by-step guide to build a ringing or knocking machine

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4 Sound Science Experiments for Kids

What you need

Cardboard sheet, rubber bands, small hobby motor with battery pack and aa battery, small bell or lightweight mallet, wooden skewer or craft stick, tape, scissors, paperclip, glue, adult supervision required

Step 1

Gather all the materials on a clear workspace so you can reach everything easily.

Step 2

Cut a cardboard rectangle about 20 cm by 12 cm to use as the base.

Step 3

Cut a small cardboard strip about 4 cm by 6 cm and fold it into a U shape to make a motor holder.

Step 4

Tape or glue the motor into the U-shaped holder so the motor shaft sticks out past the edge of the base.

Step 5

Tape the battery pack to the base near the motor and connect the battery wires to the motor terminals.

Step 6

Bend a paperclip into an L shape with a short nub to make an off-center cam.

Step 7

Push the short nub of the paperclip cam onto the motor shaft so it sits off-center.

Step 8

Tape the bell or mallet securely to the end of the wooden skewer or craft stick to make the striker.

Step 9

Stand the striker upright on the base and tape it so the cam will swing into it as the motor turns.

Step 10

Hook a rubber band from near the top of the striker to a taped anchor point on the base so the rubber band pulls the striker back after each hit.

Step 11

Turn on the motor by connecting the battery to make the cam spin.

Step 12

Listen carefully to see whether the cam hits the striker and makes the bell knock each rotation.

Step 13

If the striker does not knock, turn off the motor before touching any parts.

Step 14

Move the striker or rotate the cam position slightly and secure it so the cam makes a gentle knock once per rotation.

Step 15

Take a photo or short video and share your finished ringing or knocking machine on DIY.org

Help!?

What can we use if we don't have the small motor, battery pack, bell/mallet, or wooden skewer listed?

You can substitute the small motor with a vibrating motor from an old toy or a DC motor from a broken toothbrush, use an AA battery holder or a 9V battery clip instead of the battery pack, tape a metal washer or bottle cap to the end of a popsicle stick or pencil in place of the bell/mallet and replace the wooden skewer with that popsicle stick or pencil.

Why might the cam spin without knocking the striker, and how can we fix it?

If the cam spins but doesn't hit the striker, turn off the motor, then push the paperclip cam further onto the motor shaft so it's truly off-center, secure the U-shaped motor holder and base tape so nothing shifts, and adjust the striker position or rubber band anchor tension so the cam makes a gentle knock each rotation.

How can this activity be changed for younger kids or for older kids who want more challenge?

For younger children have an adult pre-cut the 20×12 cm cardboard base, fold and tape the U-shaped motor holder, and pre-connect the battery wires, while older kids can solder the battery wires, add a small on/off switch, experiment with multiple paperclip cams, and vary striker length to change rhythms.

What are simple ways to improve the sound or make the machine more interesting after it works?

Decorate and label the cardboard base, try different-shaped paperclip cams or add extra cams on the motor shaft to produce rhythms, attach different bells, washers, or bottle caps to the skewer for varied tones, and add a speed control or switch between the battery pack and motor to change tempo.

Watch videos on how to build a ringing or knocking machine

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Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

4 Fun Sound Science Experiment That Anyone Can Do!

4 Videos

Facts about simple machines and mechanical motion

🔔 Bells can be ancient — some of the oldest bells date back thousands of years and huge church bells can weigh several tons!

🤖 Small DC electric motors can spin at thousands of revolutions per minute and are the same kind used in many toys and simple machines.

🪢 A stretched rubber band stores elastic energy that can be released to make things move — toy planes and cars have used them for propulsion!

📦 Corrugated cardboard is lightweight but very strong for its weight, which is why it's great for building prototypes and kid projects.

🎨 Rube Goldberg drew funny, complicated machines to do simple tasks — people still build chain-reaction machines for contests and creativity.

How do you build a ringing or knocking machine?

Start by sketching a simple design: a sturdy cardboard base with a mounted motor or hand crank. Attach a short axle or skewer to the motor/crank and secure a rubber band or cam to convert rotation into a back-and-forth motion. Fix a lightweight mallet or bell arm to strike a bell or washer as the cam turns. Use tape, glue, or hot glue to secure parts, adjust alignment, and test slowly. Supervise closely to prevent pinches and loose parts.

What materials do I need to build a ringing or knocking machine?

You'll need cardboard or a small wooden board, a low-voltage hobby motor or a simple crank, rubber bands, a bell or small metal washer and mallet (or craft stick), wooden skewers or dowels for axles, tape, glue or hot glue, a battery pack with wires (if using a motor), scissors, and pliers. Optional: clothespins, cardboard gears, and safety goggles. Substitute a hand crank for a motor to avoid batteries and wiring for younger kids.

What ages is this ringing machine activity suitable for?

This project fits ages about 6–12 with adult help; older children and teens can handle motors, wiring, and more precise builds independently. Preschoolers (3–5) can join if an adult does cutting, wiring, and hot-gluing, and they focus on testing and decorating. Always supervise when tools, small parts, or batteries are involved. Adapt complexity: simple crank and tape for younger kids; added gears, speed control, or multiple mallets for older builders.

What are the benefits, safety tips, and variations for the ringing machine?

Building a ringing machine teaches cause-and-effect, basic mechanics, fine motor skills, and creativity. Try variations: change cam shapes, add multiple mallets, vary rubber band tension, or build a percussion ensemble to explore rhythm. For safety, use low-voltage motors, insulate connections, avoid sharp edges, and secure moving parts. Encourage experimentation and note how changing speed or cam shape alters sound. This activity also supports STEM thinking and cooperative play.

Ready to create?

All Activities

Build a ringing or knocking machine

Build a simple ringing or knocking machine using cardboard, rubber bands, small motor or crank, and a bell or mallet to explore mechanical motion.

Table of contents

Step-by-step guide to build a ringing or knocking machine

0:00/0:00

Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

4 Sound Science Experiments for Kids

What you need

Step 1

Gather all the materials on a clear workspace so you can reach everything easily.

Step 2

Cut a cardboard rectangle about 20 cm by 12 cm to use as the base.

Step 3

Cut a small cardboard strip about 4 cm by 6 cm and fold it into a U shape to make a motor holder.

Step 4

Tape or glue the motor into the U-shaped holder so the motor shaft sticks out past the edge of the base.

Step 5

Tape the battery pack to the base near the motor and connect the battery wires to the motor terminals.

Step 6

Bend a paperclip into an L shape with a short nub to make an off-center cam.

Step 7

Push the short nub of the paperclip cam onto the motor shaft so it sits off-center.

Step 8

Tape the bell or mallet securely to the end of the wooden skewer or craft stick to make the striker.

Step 9

Stand the striker upright on the base and tape it so the cam will swing into it as the motor turns.

Step 10

Hook a rubber band from near the top of the striker to a taped anchor point on the base so the rubber band pulls the striker back after each hit.

Step 11

Turn on the motor by connecting the battery to make the cam spin.

Step 12

Listen carefully to see whether the cam hits the striker and makes the bell knock each rotation.

Step 13

If the striker does not knock, turn off the motor before touching any parts.

Step 14

Move the striker or rotate the cam position slightly and secure it so the cam makes a gentle knock once per rotation.

Step 15

Take a photo or short video and share your finished ringing or knocking machine on DIY.org

Help!?

What can we use if we don't have the small motor, battery pack, bell/mallet, or wooden skewer listed?

Why might the cam spin without knocking the striker, and how can we fix it?

How can this activity be changed for younger kids or for older kids who want more challenge?

What are simple ways to improve the sound or make the machine more interesting after it works?

Watch videos on how to build a ringing or knocking machine

0:00/0:00

Here at SafeTube, we're on a mission to create a safer and more delightful internet. 😊

4 Fun Sound Science Experiment That Anyone Can Do!

4 Videos

Facts about simple machines and mechanical motion

🔔 Bells can be ancient — some of the oldest bells date back thousands of years and huge church bells can weigh several tons!

🤖 Small DC electric motors can spin at thousands of revolutions per minute and are the same kind used in many toys and simple machines.

🪢 A stretched rubber band stores elastic energy that can be released to make things move — toy planes and cars have used them for propulsion!

📦 Corrugated cardboard is lightweight but very strong for its weight, which is why it's great for building prototypes and kid projects.

🎨 Rube Goldberg drew funny, complicated machines to do simple tasks — people still build chain-reaction machines for contests and creativity.