A few months later, Brian, a charismatic marketing executive, announced that he’d found an investor. He handed his father a check for $10,000.
Roused by the engineering challenge, Bruce Spencer dove into the project with such zeal that his wife often found him awake at night trying to unravel some pogo-related physics problem.
His first prototype was a Rube Goldberg mishmash of PVC irrigation pipe from Home Depot, truck tire valves, and pistons he machined in his garage. He found a polyurethane shock absorber at an off-road supply store and bolted it to the foot of the pogo to cushion landings. He pressurized the irrigation pipe to about 50 pounds per square inch with an air compressor.
When I asked Spencer for an everyday example of an air spring, he stood up from his desk chair and plopped back down. The seat dipped an inch or so under his weight, then rebounded, thanks to pressurized air in its support column. “It’s core technology,” he told me. “And no one had really made it work in a pogo stick.”
Spencer’s first prototypes worked, but the plunger recoiled with such vehemence that he felt as if he were riding a jackhammer. To sell his sticks commercially, he’d need a smoother ride.
He’d studied Boyle’s law in college and recalled that volume and pressure were inversely proportional: Compress air to half its original volume and the pressure doubles; compress volume by another half and pressure doubles again.
If you tried to squeeze air into anything smaller than a quarter of its original volume, Spencer discovered, you got the jackhammer effect. The only way to keep the “compression ratio” low while still producing enough thrust to lift an adult rider was to use the entire length of the pogo cylinder as an air spring. Once he demonstrated this insight, examiners at the U.S. Patent Office certified the novelty of his invention.
He spent the next year experimenting with tube materials, pressure seals and lubricants. To make sure the pogo cylinder could withstand enormous pressures, he drove to a local park in the early mornings, dropped a tube inside a 55-gallon steel drum, and slid the whole rig into a batting cage. He put in earplugs, took cover behind a concrete water fountain and cranked up the pressure in the tube with a nitrogen tank until the tube exploded.
“Then I’d pick up the pieces, throw everything in the trunk and drive away before the cops came,” he told me, half jokingly. He found that the cylinder could withstand pressures of nearly 800 pounds per square inch, more than three times what an adult rider was apt to produce.
The Spencers took 16 prototypes of their stick—the Vurtego, they called it—to the Ice Village at the 2002 Olympics in Salt Lake City. They were a hit with tourists, visiting athletes and TV cameras. “When I came home, I thought I’d have people champing at the bit to invest in the company,” Bruce said. “It didn’t happen.”