Build a unique jumping robot that uses rotating bottle caps and rubber grip to create motion. This clever STEM project demonstrates how friction, grip, and stored energy combine to produce jumping movement and forward motion.
Difficulty Level: Advanced
Concepts: Robotics, Electronics
Materials List
- TT gear motor
- 2 lithium batteries (in series)
- Wires
- Bottle caps (2)
- Rubber strip (for grip surface)
- Rubber band (for top tension)
- Wooden dowels or thick skewers (~4mm diameter) (legs)
- Large craft sticks / tongue depressors (feet)
- Glue (hot glue recommended)
- Tape
Steps
- Build the leg structure
- Use wooden dowels or thick skewers (~4mm) to create angled legs.
- Attach the feet
- Fix large craft sticks or tongue depressors at the bottom for stability.
- Mount the motor
- Attach the motor between the legs, slightly tilted forward.
- Add bottle cap wheels
- Glue bottle caps onto both ends of the motor shaft.
- Add rubber grip
- Attach a rubber strip on part of each bottle cap’s outer edge.
- Attach top rubber band
- Connect a rubber band from the top frame to the motor to create upward pull.
- Connect batteries
- Wire two lithium batteries in series and attach them securely.
- Turn it on
- Watch the robot grip, release, and jump forward step by step!
Science Behind It
This robot works using a clever grip–release cycle.
Grip Phase (High Friction) 🛞
The rubber strip on the bottle cap touches the legs and creates strong grip, pulling the body slightly downward.
Energy Storage
As the robot is pulled down, the rubber band stretches and stores energy.
Release Phase (Low Friction)
When the smooth part of the cap rotates:
- Grip disappears
- Stored energy is released
Jump Motion 🦘
The rubber band snaps back, lifting the robot and causing a jump.
Forward Movement ➡️
Because the legs lean forward, each jump pushes the robot ahead.
Key Concept
Friction + Elastic Energy + Timing = Controlled Motion
Troubleshooting Tips 🛠️
Not jumping? >>> Increase rubber band tension
Slipping too much? >>> Improve rubber grip
Too aggressive? >>> Reduce rubber band strength
Falling over? >>> Adjust leg angle and base width
Uneven motion? >>> Align bottle caps properly
Watch the video!
Keywords: jumping robot project, friction robot DIY, STEM robotics for kids, elastic energy experiment, rubber band robot, bottle cap robot, physics motion experiment, kids engineering project, creative robotics activity
