Abdul Rauf  ·  Age 14

Pakistan Science Club

I wanted to learn how to use stored energy to power a vehicle. A rubber band stores mechanical energy when wound up, and I thought it would be interesting to use that energy to spin a propeller — combining propulsion science with simple recycled materials.

• Bottle caps (4 pieces)
• Straws
• Ice cream sticks
• Kabab sticks
• Paper clips
• Beads
• Disposable cup
• Rubber bands
• Glue gun
• Knife cutter
• Scissors

Step 1 — Car Body: Join ice cream sticks together to make the car base. Attach a vertical stick, then join two more to form the frame. Step 2 — Propeller: Cut two equal fins from a disposable cup. Attach to ice cream stick with tape. Make a hole in the centre. Step 3 — Hook: Straighten a paper clip, bend top 90 degrees. Pass through propeller hole and fix with glue. Add beads and straw. Make a hook at the other end. Step 4 — Propeller Attachment: Attach propeller to car body at a tilted angle. Step 5 — Axle: Cut two straws, glue to bottom of car. Insert kabab sticks as axles. Step 6 — Wheels: Mount bottle caps as wheels. Add hot glue if loose. Step 7 — Rubber Band: Attach one end to propeller hook, other to car base. Step 8 — Test: Place on smooth surface and release.

The trickiest part was making propeller fins equal in size — unequal fins caused the car to spin in circles. I also had trouble keeping wheels aligned while glue hardened. I experimented with different rubber band lengths and found medium tension gave the best distance without snapping.

This project demonstrates elastic potential energy converting to kinetic energy. The wound rubber band stores elastic energy. When released it spins the propeller. The spinning blades push air backwards (Newtons Third Law) creating forward thrust. The project also uses axle and wheel simple machines and friction reduction principles.