Homemade Roller Coaster: Jeremy Reid; Oklahoma City

On a 10-acre plot southwest of Oklahoma City, Jeremy Reid built an unexpected

addition to his parents’ backyard: a roller coaster. “I thought it would be great to have a small one to piece together and ride,” he says. “Once I started taking college engineering courses, I realized I could probably build one on my own.” And so began a monumental project that included 2900 board feet of southern yellow pine and 7000 assorted screws and nails. For the next four years, Reid conjured up ways to raise dozens of supports for the hills, laminate the track and piece it all together.

Riders—limited to close friends and family because of liability concerns—sit in a single-seat cart built from an abandoned stadium seat, which is winched up the first hill by a 1-hp electric motor. A 16-foot drop propels the car to 18 mph; the rider then zips over another hill, down the sloping backyard and around a 50-degree bank that pulls 2 g’s. Nearly 1 minute and 450 feet after the initial drop, the car returns to the lift. Reid estimates he spent $10,000 on the project—though it paid off by helping him lock down a post-college job with coaster design company Arrow Dynamics (now S&S Arrow). In fact, the project was such a success, it’s worth wondering if the married engineer will build another one in his own backyard. Or maybe not. “Once was definitely enough,” he says.

Video From The Stratosphere: James Ewen, Barry Sloan, Garrett Sloan; Edmonton, Alberta

A decade ago, a group of amateur radio enthusiasts picked up on the growing hobby of sending balloons into near space. Recently, they came back with a YouTube sensation. “We posted video of the flight online, and it went viral,” says 44-year-old James Ewen, who leads tracking operations for the group. This isn’t the first time they’ve made news: Three years ago, the friends sent a Nikon Coolpix to 117,597 feet, and it came back with photos of the upper atmosphere. That success prompted a mission to launch the next logical piece of electronics, an HD video camera. So last August, they built a Styrofoam box to house a Canon iVIS HF20 camcorder. They outfitted the box with an APRS tracker, a GPS receiver and 10 lithium batteries. After clearance from Canada’s civil aviation authority, the group launched its balloon from an Edmonton-area park; the payload touched down 89 miles away. The balloon burst at 107,145 feet, 21,234 feet shy of the record, but the camera captured some of the first amateur HD video of the arc of the Earth. In the future, the group plans to include an RC plane to its balloon payload and fly the camera home.

Tandem Unicycle: Corbin Dunn and Louise Lovelle; Los Gatos, Calif.

When Corbin Dunn first met his future wife, Louise, he was intrigued by her mountain unicycling; she by his homemade treehouse in a grove of California redwoods. He soon took his tinkering to Apple, where he worked on the first-generation iPhone; she taught aerial silks at the circus. He arrived at their wedding via homemade zipline. “My dad built our house from the foundation up. I’d help him hammer nails,” Dunn says. “My parents always encouraged me to build things.” It comes as little surprise, then, that as Dunn picked up Louise’s passion for off-road unicycling, he headed into his shop—and emerged with a unicycle for two. Dunn introduced a pair of salvaged Huffy mountain bikes to a Sawzall, a 4.5-inch angle grinder and a MIG welder. After severing the bikes’ front halves, he remounted the main drive hub and welded the rear triangles together around the wheel. He reinstalled the sprockets and hubs and put in a pair of chains. “I spent a week trying to machine a special transmission,” Dunn says, “but then I realized the stock components would work fine.” So far the 20-pound tandem has been used mainly on special occasions—usually, Dunn admits, for short bursts of time. “We’re still learning how to ride it.”

Loki Home Robot: Dave Shinsel; Portland, Ore.

Dave Shinsel’s latest robot may look like WALL-E—but it takes after the Jetsons’ Rosie. “I was just going to attach a webcam to a mobile pedestal, but then I figured I should make it more personable,” says the longtime engineering manager at Intel. “Then I decided it should at least pick up the pet toys.” What Shinsel ultimately created was the 4-foot-tall Loki—named for the Norse god of mischief, partly for its unpredictable AI responses in “conversation mode,” and partly for the 40-pound bot’s early predilection for running into walls. The aluminum chassis is loaded with two dozen sensors, 11 servos, a pair of webcams for eyes and 70,000 lines of custom code. Thanks to the OpenCV vision program, Loki can recognize people, identify CDs, count cash—and, yes, pick up objects from the floor. Microsoft Speech API allows Loki to respond to voice commands. A digital map of the house, along with a compass and odometer, helps the robot navigate between rooms. Next task for the $2000 droid? Tackling the refrigerator’s tricky vacuum seal. “I’d love for him to grab me a beer.”

Spokeless Bicycle: Yale University Mechanical Engineering 489 class: Henry Misas, Sean McCusker, Jordan Carter, Nicholas Tsouris, Gregory Brown, Trevor Hines, Derek Zhao, Stephen Miehls and Aaron Fuchs

In the nearly 150 years since the bicycle debuted, its operation has remained remarkably consistent. That is, until this year, when a group of mechanical engineering students at Yale created what might be the first spokeless bicycle. Redesigning something so fundamental was bound to be difficult. So Vern Van Fleet, a Sikorsky test engineer who taught the course, broke his students into three groups (frame, drivetrain and wheel) to tackle the challenge. The result? An 8-pound frame, made from sheet aluminum, which holds the spokeless rear wheel in place. Inside the wheel housing, rollers fit into grooves carved into the wheel rim to prevent wobbling and to provide support. In place of the normal rear hub, the team added teeth along the inner rim of the wheel to spin a small gear behind the pedals. That gear ratio, however, is lower than first gear on most 10-speeds. So the team improved performance by connecting an 18-tooth rear cog to two 53-tooth chain rings. An outside vendor who was supposed to machine the bike’s wheels fell through, forcing the students to focus solely on the rear wheel to get things done quickly and inexpensively. “That was a good lesson,” Van Fleet says. “You’ve got to have contingency plans.”

Self-Propelled Movie Theater: Rodger Cleye; Aliso Viejo, Calif.

When electrical engineers get into the Halloween spirit, there’s no telling what might happen. Last year Rodger Cleye outdid himself with a creation as simple as it was elegant: a radio-controlled home theater on wheels that displays video of a flaming head while blaring Rockwell’s 1984 song “Somebody’s Watching Me.” The heart of the system is an electric wheelchair he bought off eBay; Cleye tapped into the chair’s control box and converted it to remote operation. “Suddenly I could puppet around any 300-pound object,” he says.

On top, Cleye stacked a DVD player, a marine battery and a 300-watt projector. The image bounces off a mirror and splashes across a 5-foot screen from Target. “It’s a shower curtain. ‘Frost,’” he says. “It has excellent optical properties.” A separate 12-volt battery powers a 100-watt speaker system and a two-channel amp, which are attached to a simple steel frame from a shelving unit. “We had a blast sending it down the street after the children,” he says. Not only did neighbors enjoy the handiwork, but Cleye says there was an unexpected safety benefit: Drivers who would otherwise have sped by slowed down for a look at the video puttering down the street beside them.

Wooden Mechanical Calendar and Orrery: Clayton Boyer; Kauai, Hawaii

Clayton Boyer was inspired to build wooden clocks by plans he saw in Popular Mechanics 45 years ago. Since building his first clock, Boyer has designed more than 50 extraordinary timepieces. But his recent wooden creation, the majestic Celestial Mechanical Calendar and Orrery, doesn’t tell time at all. “This is driven by clockworks,” the retired chiropractor says. “But I’ve got other things that tell time.” This 42 x 26–inch machine, however, is remarkable for its comprehensive attention to other details. Powered by 14 gears, a 5-pound drive weight and three counterweights, the Baltic birch device shows the day of the week; the day of the month; the month; the zodiac sun sign; the phase of the moon (represented by a ball that rotates to reflect the moon in the night sky); the equinox and solstice; cross-quarter holidays such as Groundhog Day; and the synodic rotations and retrograde cycles of Mercury, Venus and Mars. Boyer says it took only a week or two to build—but four months to plan. “This is like building two or three clocks at once,” he says, “but it’s just step by step. Start with the frame, then add this wheel, then that wheel, then the levers, then the weights. It just takes a little stick-to-it-iveness.”

Family Home Built Into A Cavern: William, Deborah, Kian, Perry and Wesley Sleeper; Festus, Mo.

Seven years ago, William and Deborah Sleeper found a choice piece of property just west of the Mississippi River. The defining element? A 17,000-square-foot sandstone mine that at one time housed a roller-skating rink and a concert hall. “We loved it,” William says, “but the property is just 3 acres and a hole. No one wanted to finance it.” The family bought the property themselves, but were cash-strapped when it came to building there. “One wall was a lot cheaper than four,” William says. So he incorporated nearly three dozen orphaned sliding-glass doors into a 45 x 45–foot outer wall at the mouth of the cave. Inside the 2000-square-foot front chamber, the Sleepers—including daughter Kian, 16, and son Perry, 14—spent four years building a sprawling kitchen, an office and three bedrooms with recycled hardwood floors. A stairwell gently spirals through the home’s three levels. “I had a bit more confidence than common sense,” William says. “I wasn’t intimidated by the project. But that stairwell took me six months.” The doors’ double-paned, insulated glass provides passive solar heating to bring the cave’s temperature to 70 degrees, year-round. Three industrial-grade dehumidifiers pull 300 gallons of water from the air daily, keeping the living space between 60 and 70 percent humidity. Interior roofs and umbrellas shield sensitive areas such as the kitchen from the sand that sheds from the walls. The Sleepers worked with the city of Festus every step of the way to build evacuation routes and meet building codes. “Some people can’t imagine that cooperation, but the politicians all roller-skated here as kids,” William says. “Three generations of folks have enjoyed this property.” And maybe more to come: These underground geniuses refinanced in March 2009 for the long haul—right after a doctor visited the home to deliver their third child, Wesley.

Space Station Radio Call: Gino Cunti, Paul Je, Kevin Luong, Patrick Neelin; Toronto, Ontario

Last year, four Humber College students working on their senior project became the first college students to contact the International Space Station (ISS) on a radio they built themselves—to NASA specifications. “When they first suggested doing it, I almost laughed,” says Mark Rector, an electronics engineering professor at Humber and their mentor for the project. “Maybe they could achieve nuclear fission while they were at it.” He quickly learned how serious his students really were. While ham operators—like Neelin’s grandfather—have long contacted astronauts through NASA’s Amateur Radio International Space Station program, no other group of college students had built a system from scratch. Over 22 months, the students designed and constructed the system, which included a transmitter, VHF transceivers, a pair of antennas and their own adapted tracking system and software that would allow them to reach the ISS as it traveled at 17,000 mph, 250 miles overhead. With a $4000 budget, the NASA-approved radio squawked to life on Feb. 2—and flight engineer and science officer Sandra Magnus answered.

Homebuilt Personal Semisubmersible: Cal Giordano; Juneau, Alaska

Building a personal submarine may seem as fanciful as a DIY jet pack—but Cal Giordano proved that with a little ambition, and a recycled 500-gallon propane tank, most anything is possible. “After drawing a zillion sketches, it occurred to me I could actually make this,” the longtime boat mechanic says. The 32-foot semi-sub, which is fashioned from an industrial buoy cockpit welded to the propane tank, dives by pitching its 4-foot-long bow planes forward. The front half submerges about 8 feet, while the engine continues breathing air, guiding the sub through Auke Bay at a leisurely 10 knots. If the boat drops below 3 knots, it loses the forward momentum necessary to force the craft underwater, and it pops back to the surface. (Should some malfunction pull the 3000-pound boat into too steep a dive, the rear prop would leave the water, eliminating thrust—and popping it back to the surface.) An electric snorkel cycles fresh air through the cockpit, and a video camera mounted on the top deck allows Giordano to steer when visibility gets hazy. “Around here, once you hit the deep water, it all just gets green,” he says. For wintertime, he affixed a blade to the bow that can plow through 4 inches of ice. Giordano also attached small wheels to the semi-sub’s keel, so that running aground was no longer a threat. In fact, it’s convenient: The boat can drive onto the beach after an outing and requires no trailer to transport. And what about the Dahlgren cannon mounted on the bow? “I only fire that on the Fourth of July,” he says. “And maybe my birthday.”