Twenty years ago, the wacky, waving inflatable tube—also known as a sky puppet or air dancer—made its debut as a decoration at the 1996 Olympics in Atlanta. Since then, it’s become most famous as an advertising gimmick at used-car lots.
Goofiness aside, there’s a lot of science going on inside that tube. In 1883, British scientist Osborne Reynolds developed a theory that predicted how fluids, such as water or gas, would flow through pipes and ducts based on the ratio of speed to viscosity. Blow air through the flexible tube of a sky puppet, and it will flow smoothly, up to a certain point. When the air speed increases enough, the flow becomes turbulent and chaotic, turning the cylinder into a dancing decoration.
Once you’ve found the ideal tube dimensions to achieve turbulent air flow, you can craft your own sky puppet. Popular Science‘s version is 5 feet tall, and it takes only an afternoon to build.
Stats
- Time: 2 hours
- Cost: $25
- Difficulty: Easy
Tools
- Hammer
- Hot-glue gun
- Scissors
- Safety glasses
Materials
- 130-cubic-feet-per-minute or larger 12- to 18-volt DC electric blower with a 3-inch opening
- 3-inch to 11⁄2-inch PVC reducing fitting
- 2-inch packing tape
- 2 12-by-12- by-3⁄4-inch pieces of wood
- 2 11⁄2-inch-long nails
- 2 No. 10 round-head wood screws, 3⁄4-inch long
- 30-gallon plastic garbage bag
- 3⁄4-inch roll of clear adhesive tape
- 2 alligator test leads
- Battery or other power supply
Instructions
- Connect the outlet of the electric blower to the wide end of the PVC reducing fitting using hot glue and packing tape.
- Build a stand by nailing the end of one board to the center of the other. Use the screws to attach the blower to the vertical board so the PVC fitting points up.
- Cut the garbage bag into two pieces, each 3⁄4 inches wide and 2.5 feet long. Seal each piece into a skinny tube with the adhesive tape.
- Use the adhesive tape to connect the pieces into one longer tube. Leave both ends of the tube open.
- Connect one end of the tube to the 1.5-inch opening of the PVC fitting.
- Give your tube personality—tape or glue ribbons, googly eyes, or other decorations to the top.
- Don safety glasses. Use alligator clips to connect the positive and negative terminals of the power supply to the appropriate wires on the blower.
- If the tube isn’t waving enough, change the voltage to decrease or increase the air flow. You can also try adjusting the tube’s length or width.
This article was originally published in the September/October 2016 issue of Popular Science, under the title “Annoy Coworkers with This DIY Sky Puppet.”
