Introduction: Propeller-Powered Zipline Racers
Please message me to report broken links. All of these materials are used in my other Instructables for kids, so your purchases can be used across multiple projects.
- Craft sticks
- Propellers with plastic mount
- Card Stock
- Long rubber bands
- Masking tape
- Hot glue gun with safety nozzle
- Kite string
How It Works
It's simple. Winding the propeller will store energy in a rubberband by twisting it. When released, the propeller rapidly unwinds and generates thrust, which pulls the craft along a low-friction zipline. However, the torque from the unwinding propeller can cause the entire racer to flip upside down. To counter this force, another force is introduced: drag. By attaching a paper cutout, drag perpendicular to the side of the racer is created, which helps prevent inversions.
Safety and Tips
- CAUTION! Pulling downward on the racer while it is hooked onto the zipline may cause it to be flung off the line upon being released. This can be dangerous when the propeller is rapidly unwinding. Be sure to directly supervise each student at least once as they attempt to launch their racer for the first time. Be sure to correct anyone who pulls on the zipline before a launch.
- Make sure the zipline is either highly visible or above everyone's head.
- Young students (grades 1-3) may need extra guidance while bending the paperclips, attaching the rubberbands, and properly launching the racer.
- Encourage your students to experiment, especially if they're in grades 4 and up - I'm always amazed by their innovations and improvements.