ROBOTS ALIVE!: RoboFlyers
Motorized balloons, gas-powered model helicopters, tail sitters and other unusual designs were among the contenders in the Fifth International Aerial Robotics Competition. The challenge? Have the robot locate and pick up a metal puck and drop it off at a designated spot. Student teams tried their best to achieve success (in previous years, robots flew but could not pick up the pucks). As you see on FRONTIERS, the U.S. Department of Defense Global Positioning System (GPS) provides a strategic edge.
Activity 1: Rotating Wing: Going Up?
Activity 2: Spinning Stability: Going Down?
For Further Thought
Flying High (Show 603): "Build and Race a LTAV" and
"The Ultimate LTAV Challenge"
ACTIVITY 1: ROTATING WING: GOING UP?
Unlike most aircraft, a helicopter does not have a stationary or fixed wing. Instead, the spinning rotor blades atop the craft function as a lift-generating wing. As the blades turn, they produce the upward force needed to counterbalance the downward pull of gravity. When the lift is greater than the weight of the craft, the helicopter rises.
Using a straw and a small strip of paper, you can build a simple rotary-wing craft, similar to an ancient toy propeller designed by the Chinese centuries ago. Customize your wing to produce the most efficient rotary blades.
Observe how rotating wings produce lift.
- thin cardboard or poster board
- straws or small round dowels
- tape (if necessary)
- modeling knife or a hole punch
- Cut out a thin strip of cardboard about 2 1/2 cm wide by about 12 1/2 cm long.
- Make two small snips in the cardboard strip as shown at far right.
- Use a hole punch or modeling knife to carefully make a small hole in the center of the cardboard strip (rotor).
- On each side of the center hole, bend the cut end of the blade upward to form the leading edge.
- Insert the straw into the hole. If the fit is not snug, use tape to secure the straw to the blade. (But remember, tape will add weight.)
- Place the straw (blades on the top) between the palms of your hands. Rapidly move one palm across the other and release the spinning prop. What happens? (Note: If the prop dives, change the direction in which you move your palms.)
- Can you create a better rotor design? Experiment with the different variables in the construction of this device (rotor size, shape, placement of cuts, number of cuts, angle of bends, length of straw, etc.) to develop the highest-flying rotor blades.
- What is the effect of different angles (pitch) on real helicopter blades?
- Explain more about the ways helicopters produce lift; compare to the way a fixed-wing plane produces lift.
Hold a contest to test your designs. Which designs produce the highest- and longest-flying craft? Draw "blueprints" of the winning aircraft and use these illustrations to discuss effective aviation design.
SPINNING STABILITY: GOING DOWN?
The teams of college students participating in the Aerial Robotics Competition used sophisticated (and, in some cases, expensive) technology. They spent many months creating and perfecting their designs. But even with the most high-tech devices, their designs required an understanding of the basic principles that govern helicopter flight. These simpler activities provide an opportunity to learn more about rotating wings -- without having to program a flying helicopter.
If you've ever spun a top, you know that rotating objects gain stability from their twirling motion. This type of balance is also seen in objects that spin as they fall through the sky. You can observe this gyroscope-like stability in a rotating glider made with a sheet of paper and a paper clip.
Experiment with rotating wings and helicopter aviation. Observe the relationship between stability and spin.
- sheets of 81/2-inch x 11-inch paper
- small paper clips
- Cut one sheet of paper lengthwise into thirds. Each strip (about 28 cm by about 7 cm) becomes a "wing."
- Cut about two-thirds of the way down the center of each strip (wing) as shown by the dotted line.
- Make two horizontal cuts about 2 cm deep along the dotted lines as shown.
- Fold and crease the wings in opposite directions as shown in the drawing.
- Fold in the bottom leaves as shown. Secure the three-layer fold with a paper clip.
- While holding the wings out, release the glider from a height of about six feet.
- Experiment with using different weights of paper or shorter or longer wings, and releasing the rotating glider from various heights.
Observe the direction of the rotation. Alter the craft so that it spins in the opposite direction.
Change the design so that the craft rotates as fast as possible.
FOR FURTHER THOUGHT
- You can read about the Aerial Robotics Competition in "Magnificent Men (Mostly) and Their Flying Machines," Scientific American, September 1995.
- A flying propeller toy like the one illustrated in Activity 1 for RoboFlyers can be purchased from Edmund Scientific.
- For rules, videos of the competition and to see what other schools are doing in the "ultimate collegiate competition," go to the Association of Unmanned Vehicle Systems International (AUVSI) Web site at avdil.gtri.gatech.edu/AUVS/IARCLaunchPoint.html.
- AUVSI also sponsors a high school contest. Any interested robotics clubs should see the contest description and rules at avdil.gtri.gatech.edu/AUVS/97IARC/1997HSOpenRules.html .
- Find out more about the winning entry and how it used GPS technology at www.gtri.gatech.edu:80/res-news/AERROB.html.
Massachusetts-based science writer Michael DiSpezio contributed these activities. DiSpezio is the author of several recent books of science activities, including Visual Foolery (Planet Dexter Division of Addison-Wesley, 1995), Critical Thinking Puzzles (Sterling, 1996) and The Science of HIV, part of a curriculum package for NSTA.
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