Aerobie

History of the Aerobie

Lots of toys are invented by someone stumbling onto a design or idea. Not so with the Aerobie. Inventor Alan Adler worked for years to perfect the design and find the right materials to create this flying ring, which can be thrown several times farther than a flying disc such as a Frisbee. Adler, an engineering professor at Stanford University, used his knowledge of aerodynamics to design the Aerobie. Before he invented the Aerobie he invented the Skyro, which set a Guinness World Record in 1980 when it was thrown 857 feet. The Aerobie beat that record when Scott Zimmerman chucked one 1,257 feet in 1986. Scott's throw set the world record for the longest throw of an inert, heavier-than-air object. Although the record was bested a few years later, it remains the world record for an "object without any velocity-aiding feature."

How Aerobies Work

To understand how a flying disc or ring flies, read about the Frisbee (page 52). Aerobies are different from Frisbees in several ways. Whereas a Frisbee has a blunt edge to create turbulence and reduce lift at the leading edge, the Aerobie has a unique lip, or spoiler, on its outer edge to create stability. Its slender profile presents much less drag surface than a flying disc. Less drag allows it to travel farther.

The Aerobie also differs from the Frisbee in that, as a ring instead of a disc, it has an opening in the center. In flight, air moves through the opening so that the inside edge is also a leading edge, which generates more lift.

You can make your own version of the Aerobie and determine how much of a spoiler is needed to get a good flight.

Inside the Aerobie

By looking at a cross section of the Aerobie, you can see features that may have otherwise eluded you. Cut through one side of the Aerobie, as shown here. A coping saw or another saw with a slender blade works well.

Check out the shape. It looks like a wing, which it is. The odd part of the design is the lip, or spoiler, on the outside edge. That spoiler was the breakthrough design feature.

Another problem Professor Adler had to overcome was making the outer edge soft enough that it wouldn't hurt someone who might be hit by it, yet keeping the toy rigid enough to fling. That's why you'll find a dark polycarbonate backbone in the middle of the softer and lighter outer material.

If you want to put your Aerobie back together, glue the cut edges back together with plastic glue. Reinforce the weld by gluing a craft stick to the underside, across the glued edge. It looks a bit odd, but it will fly fine.

Build Your Own

Cut out the centers of several thick paper dinner plates. Fling your "rings" to see how they fly. A few brands of paper plates are made of heavier material; they make for rings that fly well without modifications. Most paper plate rings, however, require some help.

Mount two plates upside down on top of a third, right-side-up plate to form a flying saucer–like toy, and tape them together. Check how this flies. To improve the flying characteristics, try affixing four metal washers or pennies at even intervals along the outer edge. Now try out your creation. Next, try bending up the edges of the plates to make a lip like that of the Aerobie. Adjust the position of the lip until your ring flies level. Then try adding more evenly spaced weights to your ring. The goal is to create a ring flyer that travels far. It should fly level, without either side rising.

You can also create a ring flyer by cutting out the center of an empty pie pan. Adjust its flight by bending the outer edge up or down.

Resources

Teachers wanting to incorporate Aerobies and Frisbees into classroom learning opportunities should look at Ed's book Loco-Motion: Physics Models for the Classroom (Zephyr Press, 2005).

Air Hog

History of the Air Hog

The idea of a toy plane that's driven by air pressure and a piston came from inventors in England. The inventors were unable to sell their idea to big toy companies — they hadn't yet made a flying prototype — but they found interest in a young Canadian company, Spin Master. Following the success of two previous toys, Spin Master invested a half-million dollars to develop the idea into a product. Beginning in 1998, sales — like the planes themselves — took off.

How Air Hogs Work

Like all Air Hogs toys, an Air Hogs car has a pneumatic motor. Air pressure — you provide the energy by pumping air into a pressurized reservoir — pushes on a piston. The piston is attached to a crankshaft that converts the linear motion of the piston into the rotary motion of the wheels. Add some gearing and a flywheel to keep the spin going through angular momentum, and the car is ready to go. To control air flow to the piston's cylinder, there are intake and exhaust valves. Each has a tiny black ball that you can see (and easily lose if you take the car apart!).

The car comes with a pump to fill the reservoir. Air enters the reservoir through a ball valve, supported by a spring, that lets air into the reservoir, but not out. When the reservoir is filled and you're ready to play, you spin the left rear wheel (or the propeller, if you have a plane or helicopter). As it rotates, it turns the crankshaft (attached through the gears). The crankshaft pushes up on the piston, which is connected to a spring. The spring lifts the bottom of the second valve to let air into the chamber, driving the piston down.

The crankshaft is attached to a metal gear with eight teeth. It drives a plastic gear with 22 teeth, and that gear drives a third gear with 52 teeth that is attached to the wheel. When a small gear drives a larger gear, which in turn drives an even larger gear, these gears in series slow down the rotation speed (from small to large) but increase the torque, or turning force, that powers the wheels.

Once we took apart the car we were able to estimate that for every turn of the big wheel, the piston completed six or seven cycles. This estimation was validated when we calculated the gear ratio, which is 52/8, or 6.5. (The biggest gear has...