The pogo stick, once just a springy toy that helped kids hop a few inches off the ground, has evolved into high-performance equipment for extreme athletes, capable of launching people eight feet or more into the air. And arguably the most extreme of these new sticks is the “BowGo,” developed at Carnegie Mellon University’s Robotics Institute.
The top pogo athletes in the world will have their annual gathering in Pittsburgh this month at a four-day extravaganza, Aug. 19-22, called Pogopalooza. Several will be aboard newly built versions of BowGo that get their bounce from a fiberglass bow of high tensile strength.
“It’s the smoothest ride of any of the extreme pogo sticks,” said Nick Ryan, the organizer of Pogopalooza and a rising junior majoring in both English and public policy at Carnegie Mellon. “Athletes riding BowGos are favored to win the high jump event, possibly clearing 9 or 9 ½ feet.”
Ben Brown, a Robotics Institute project scientist who invented BowGo, said his pogo stick is particularly energetic because the fiber-reinforced composite bow can store as much as five times the elastic energy per unit of mass as a steel coil spring. The bending bow also precludes the friction that results when coil springs buckle sideways. Its efficiency is further enhanced by using rollers to guide the stick’s plunger, rather than the usual plastic bushings.
“This feels very different from other pogo sticks, including the extreme sticks now on the market that use elastic bands or air springs,” Brown said. “It’s very smooth and you can jump really high.” The BowGos now being delivered for the Pogopalooza competition have bows made with S-glass, a type of fiberglass with greater tensile strength than the E-glass used in earlier versions.
The story of the BowGo begins in the early 1980s, when Brown was working in the lab of Marc Raibert, then a faculty member in the Robotics Institute. They were studying dynamic balance and developed a series of one-legged hopping robots. The hoppers had power-hungry hydraulic legs and were tethered to external power sources and computer controls.
The hoppers were successful in demonstrating that legged robots could be agile and speedy. In 2008, Carnegie Mellon inducted the Raibert Hopper into its Robot Hall of Fame, now part of the roboworld exhibit at the Carnegie Science Center in Pittsburgh. But Brown couldn’t help but wonder if a dynamic leg could also be efficient, so that a running, hopping robot could operate without a power tether.
Working in the late 1990s with Garth Zeglin, then a graduate student and now a project scientist, Brown fashioned a cheap, low-tech bow leg out of piano wire. They found it was quite efficient, capable of releasing 80 percent of the energy that was stored when the bow was bent.
But these were just small robots, weighing a few pounds. To test whether the technology scaled up, they and Illah Nourbakhsh, associate research professor of robotics, in early 2000 developed a human-size bow leg — the BowGo.
The development of the BowGo coincided with the development of the Flybar, an extreme pogo stick built by SBI Enterprises, the original maker of pogo sticks. “Extreme pogo really took off at that point,” Ryan said, “and Carnegie Mellon and Ben Brown were at the forefront of this movement.”
The BowGo is not yet commercially available, though the technology is patented and discussions are under way with a possible marketer, Brown said.
The leg technology meanwhile is being used in a climbing robot developed in the Manipulation Laboratory headed by Matt Mason, director of the Robotics Institute. Called Parkour, after the physical discipline associated with getting over obstacles, the device has two opposed bow legs and climbs between two adjacent walls by hopping between them. Ultimately, Brown hopes to see the bow legs used to build a running, hopping robot capable of covering long distances and rough terrain.
To hear a podcast about BowGo, visit http://www.cs.cmu.edu/video/Brown-SpicePodcast8-6-09.mp3
For information about Pogopalooza 6, visit http://www.pogopalooza6.com/