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O’Reilly’s Toy Story
Mechanical engineer turns playthings into instruments of higher learning
by Mark Frauenfelder
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ME professor Oliver O’Reilly discovered the value of toys as teaching tools as a graduate student at Cornell in the 1980s. Toys, he says, provide “a way to develop an appreciation for mathematical methods and mathematical models.”
AARON WALBURG PHOTO
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What is it about colorful spinning tops, kinetic sculptures, model motorcycles, even a penny rolling across a tabletop that makes a professor’s heart thump and deepens his students’ grasp of core engineering principles? Why toys, of course.
“Toys may seem simple, but looking at the principles of physics that govern how they behave can lead to deep insights and the unraveling of scientifically intriguing historical threads,” says mechanical engineering professor Oliver O’Reilly. “I see toys as a pathway to understanding science. They’re a way to develop an appreciation for mathematical methods and mathematical models. The fact that these toys have such a variety of interesting mechanics is extraordinary.”
The table opposite O’Reilly’s desk is loaded with what appears to be booty from a shopping spree at Toys “я” Us. O’Reilly reaches for a clear plastic sphere about the size of a tennis ball, called a Dynabee. It has a smaller, green–colored ball inside that can freely spin inside its plastic enclosure, like a globe in a stand. He takes a length of string, winds it around a groove in the green ball, and gives it a yank, just as you would power up a lawn mower. Holding the sphere in one hand, O’Reilly slowly rotates his wrist. The smaller green ball starts spinning faster. In a matter of seconds, the green ball is a humming blur.
O’Reilly’s students become intimately familiar with this sound, because their assignment is to develop a mathematical model to explain how the energy from their wrist movement is translated to the green ball. O’Reilly says most of them have no idea how to begin to attack the problem. “It’s almost a quantum leap beyond their understanding of dynamics,” he says.
O’Reilly hands over the Dynabee, sold as a wrist exerciser for about $20, so others can feel what’s happening. It exerts a force on your hand that you counteract by moving your wrist in the opposite direction. “They are feeding energy into the system,” says O’Reilly. What’s intriguing, he says, is that the green sphere is rotating much faster than their wrists are.
“The faster it spins, the easier it is to keep rolling—it’s more stable,” says O’Reilly. This phenomenon, in which speed is proportional to stability, can be found in satellites orbiting the earth. “Certain satellites are ‘spin-stabilized,’” he says. “You get what’s called resonance capture.”
With a pleasing brogue, an easy smile, and a love for mechanics that borders on the infectious, Irish-born O’Reilly discovered the value of toys as teaching tools while a graduate student at Cornell University in the late 1980s. It was there that he met Frank Moon, a mechanical engineering professor. “He was very much into demonstration experiments,” says O’Reilly. “He had an enthusiasm for toys and helped foster a culture of looking at toys and developing mathematical models for toys.”
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“Toys seem to make things more interesting for students,” says O’Reilly (left), seen here with graduate students Tim Wheeler (center), Patch Kessler, and their “spolling” Euler’s Disk. O’Reilly teaches a graduate seminar on rotation and occasionally a freshman seminar on special effects in the movies.
AARON WALBURG PHOTO
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O’Reilly swivels round in his chair to grab a shiny disk sitting on top of a round mirror the size of a dinner plate. He picks up the disk, which resembles a chrome-plated hockey puck, and gives it a gentle spin on the mirror. For the next 60 seconds, the disk “spolls” (spins and rolls) on the slightly concave surface of the mirror, whirring as it goes. It looks like it’ll never stop, until suddenly it begins tilting downward and spinning faster. The frequency of the whir increases rapidly and then—clink! It comes to a dead stop.
The physics describing the motion of the disk—which is sold as a science toy called Euler’s Disk—turns out to be very complex. O’Reilly and one of his graduate students, Patrick “Patch” Kessler, wrote a lengthy paper describing their analysis of the toy. They believe, but are not certain, that the “clink” sound at the very end occurs because the disk loses all contact with the mirror the instant before it stops spinning and drops flat on the mirror.
The amount of work O’Reilly and his students have put into analyzing Euler’s Disk is beginning to pay off. O’Reilly recently looked into the problem of squeaking brakes. He found similarities between the way Euler’s Disk makes noise as it spolls and the way brakes squeak when the calipers pinch the rotating disk. “Sound doesn’t cost that much energy,” explains O’Reilly. Just as a tiny fraction of the energy in a spolling disk is lost via sound, a minuscule amount of the energy in a braking car is converted into a squeal. Despite O’Reilly’s knowledge of the subject, he says his own car’s brakes produce a nasty sound.
O’Reilly and Kessler’s interest in vehicles extends beyond brakes. They have developed a clever motorcycle navigation system for BMW using a whirling pendulum to supplement a gyro sensor. And recently, one of O’Reilly’s students told him about an impressive one-wheeled vehicle invented by a relative’s father, the late Charles F. Taylor, a self-taught engineer from Colorado.
Taylor designed his all-terrain mono-wheel vehicles in the pre-microprocessor 1950s and 1960s, so the feedback systems were all mechanically based, a feat O’Reilly marvels at. “The number of mechanisms he came up with to get this thing to work in harmony—it’s just mind boggling!” he says. A team of students, including Tim Wheeler and Bernice Yen, are studying Taylor’s ingenious use of gyroscopes for steering and stability.
Taylor’s work comes to life when O’Reilly pops a DVD into his laptop computer and a scratchy black-and-white 8-mm film starts playing. It’s Taylor and his vehicle in action. “It truly is a remarkable sight to see this bizarre looking one-wheeled contraption zipping down a deserted prairie highway, tilting and slaloming in response to turns of the steering wheel. You might suspect trick photography was involved had you not been told otherwise,” says O’Reilly.
When the film ends, O’Reilly picks up a multicolored plastic globe that looks vaguely like a geodesic Buckminster Fuller Sphere. But this toy, called a Hoberman Sphere, is collapsible and has become a source of fascination for O’Reilly, who studies theories of deformable bodies. O’Reilly’s wife gave him a Hoberman Sphere for Christmas. “It was on the mantelpiece in our house when one of my former students, Tom Nordenholz, walked in and said, ‘That’s an example of a pseudo-rigid body.’ I thought about it, and said, ‘Oh my God, you’re right! It’s an expandable sphere—a homogeneous deforming body.’”
It also turned out to be an excellent instructional aid. O’Reilly wanted to teach his students how to calculate three-dimensional rotation using quaternion multiplication. (As the name implies, a quaternion consists of four numbers: w, x, y, and z.) Quaternion multiplication is commonly used in navigation schemes for satellites and in computer graphics applications, but O’Reilly couldn’t think of a good way to introduce the method. He saw the Hoberman Sphere on his desk and thought, “That’s it! The four numbers determine the orientation and expansion of the Hoberman Sphere!” Much to his surprise, O’Reilly later found that the sphere’s motion was discussed in an 1820s paper written by the famous mathematician Gauss. Now O’Reilly’s students are as much fans of the sphere as their instructor.
Always on the lookout for toys that possess some quality that makes them special to a mechanical engineer, O’Reilly finds the search a great excuse to take his three-year-old daughter to toy stores. “A really good toy doesn’t come up that often,” he says. “It’s pretty rare. At first, you’re totally stumped by it, and then you slowly start to figure it out. You discover the essence of the toy. You unravel the puzzle. And that’s really a great feeling.”
MARK FRAUENFELDER is a writer and illustrator in Los Angeles. Founder of Boing Boing.net and editor-in-chief of MAKE magazine, he also wrote Mad Professor: Concoct Extremely Weird Science Experiments; The World's Worst: A Guide to the Most Disgusting, Hideous, Inept and Dangerous, People, Places and Things on Earth; and The Computer, a Visual History. |
