Dept.: You Built What?!
Tech: Homemade jet power
Time: 10 days
Practical | | | | | Popcorn
Some folks like to take their time on the can. Not Paul Stender. When the 43-year-old former pit mechanic feels the need for speed, he straps himself into his jet-engine-equipped toilet and roars off, trailing flame. Stender was running superfast snowmobiles on the drag-racing circuit when he saw his first jet-driven funny car. He liked it so much he bought one, and started building his own outlandishly overpowered vehicles: a jet motorcycle, a jet pickup, a jet school bus. Then one day at a show in Texas, he saw a windstorm blow portable toilets across the tarmac, and it was Newton's apple all over again.
Powered by a 50-year-old, 750-pound Boeing jet turbine that Stender bought for $5,000, the "Port-O-Jet" can top 46 mph with a tailwind. "It's not real aerodynamic," he allows. That said, he's beaten buddy Tim Arfons's jet barstool two of the four times they've raced [see the barstool at turbinegroup.com].
During his shows at drag strips, arenas and airports across the country, Stender runs the outhouse up and down in front of the crowd, popping the burner and shooting out 30-foot fireballs before making a final high-speed run. (A burner pop happens when Stender hits the afterburner switch while the engine is running at high rpm's-it dumps volatile JP-8 fuel into the rear burner pipe, which burns quickly, causing a loud explosion. If the engine is running at low rpm's, hitting the switch sends out a long, loose, yellow fireball.)
On Stender's blackboard is a jet-powered beer truck with a 24,000-horsepower F-16 engine. His advice to wannabe jet-engine hobbyists: Be careful. "So many things can go wrong," he says. "You suck in a piece of garbage, it's going to explode-and
you're going to go with it."
Dimensions: Seven-and-a-half feet tall, four feet wide, four feet deep
Weight: About 600 pounds
A. Shell is a Country Classic portable toilet from the Hampel Corporation of Germantown, Wisconsin. "It's heavy and looks like fake wood," Stender says, "like an outhouse should."
B. Welded scrap metal tubing reinforces the chassis.
C. Driver sits on the original throne and looks out through a hole in the door. (Stender tried to keep the toilet paper, but it kept getting sucked into the engine.)
D. Handle bar-with lever for the rear hydraulic brakes and twist throttle for acceleration-is attached to a shaft that connects directly to the wheel spindles.
E. Six-inch rubber Goodyear tires are from a go-kart.
F. Four-gallon tank attached to a CO2 cartridge holds pressurized JP-8 fuel for the afterburner.
G. Twelve-gallon tank holds JP-4 fuel for the engine (funneled in through the original urinal).
H. The muscle: Stender cut the back half off an old Boeing 502 turbine (which once powered a pump on a Navy minesweeper) and welded a cone on the back to channel what he guesses is a few hundred pounds of thrust.
JET ENGINES 101
A jet turbine uses many thin blades whirling at high speeds to compress incoming air, which is burned with highly combustible jet fuel in a central combustion area. Another set of blades in the rear extracts power from the hot gases emerging from the chamber. Some turbines use those rear blades to send power to a drive unit through an output shaft, and vent the hot gases as exhaust. Stender removed the drive unit so that the hot gases instead funnel through a tail cone to generate thrust. At full power, these thin blades can be moving at supersonic speeds. If the engine sucks in something large enough to break one of them, a catastrophic chain reaction of disintegration can follow.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.