A faster, safer snowmobile, a fish-friendly tidal turbine, a gun sight that keeps soldiers safe and more top Popular Science's list of the year's most ingenious garage inventions.

A Faster, Safer System for Snowmobiles

Nobody would have expected the biggest innovation in modern snowmobiling to come from a self-taught engineer, a broken-down all-terrain vehicle, and a drag strip. No one except for those who know Shawn Watling.

In 2005, Watling bought a scrapped ATV for $250 and retrofitted it with a 130-horsepower snowmobile motor and transmission for fooling around on his local drag strip. But what started as a lark became an obsession when a dynamometer test, which measures power and torque, revealed that his Frankenstein road vehicle was delivering 85 percent of its engine power to the ground, a major jump over a conventional snowmobile’s 55 percent.

The surprising results led him to discover that front-drive snowmobiles are inherently inefficient, because the way they pull their rubber track compresses the rear suspension and increases rolling resistance. RAD (Rear Axle Drive) Technology was born.

RAD employs Watling’s innovative “cradle scissor” geometry, which capitalizes on an independent suspension arm to maintain consistent track tension even while negotiating rough terrain. When one area goes slack, the other tightens. With this design, the snow-contact area of the sled’s 121-inch-long track is boosted by 43 percent versus a conventional sled, which translates into improved power transfer, control and fuel economy.

A Fish-Friendly Tidal Turbine

W. Scott Anderson spent the past five decades creating complicated machines for manufacturing, including a lipstick labeler and a plastic-straw maker. So when two years ago the 77-year-old industrial engineer invented a fish-friendly underwater turbine that looks like a giant screw, it seemed a cruel twist of fate that every manufacturer he approached said it was too complex to produce economically. But that didn’t stop him.

There are a handful of companies using windmill-like turbines to capture the untapped energy in tidal streams, bays and inlets and convert it to electricity. But these projects tend to be huge and expensive, and require permanent installations that can disrupt marine life.

Anderson’s ECO-Auger is based on a much different design, enabling it to access energy that regular water turbines can’t. Rather than using blades, it produces power when the current spins a drill-shaped device called an auger, which has tapered ends that don’t harm fish. Instead of using gears to drive an attached generator, a hydraulic pump in the nosecone pumps high-pressure oil to turn a generator outside the water.

The arrangement lets the turbine capture energy in shallow waters, and to tether to bridges and other structures so that the auger is relatively easy to lift out of the water for maintenance. Whereas most bladed turbines need at least 30 feet of water to operate, Anderson’s smallest units need only 10.

A Box That Keeps Plants Hydrated in the Desert

Dutch flower exporter Pieter Hoff often spent nights in his beloved lily fields to monitor them. One evening, he noticed that the first droplets of morning condensation were collecting on the leaves of his lilies well before midnight.

The plants lost heat to the air at night, and the cool surface of the leaves sucked water droplets from the warm, humid air. Nature’s watering system, Hoff thought, is incredibly efficient. So in 2003, he sold his business and began developing a planter that could capture water the same way plants do and foster saplings in the harshest conditions.

Today, one third of the world’s population lives where water is scarce or of poor quality, a number that’s expected to jump to two thirds by 2025. Making matters worse, in some areas deforestation and overfarming have led to eroded soil that can no longer support many crops.

Hoff designed his Groasis Waterboxx with this in mind -- it’s a plant incubator that’s made from plastic or a biodegradable material and designed to cool faster than the night air, like his lilies. The box is coolest at its top, the part that has the most contact with the open air. Water condenses on the cover and flows down into a small holding tank, where it’s trapped, along with any rainwater. The collected water and the box itself keep the plant and its roots hydrated and protected.

A Gun Sight That Keeps Soldiers out of Danger

The Rolling Green hills of Sonora, California, no longer lure prospectors with the promise of gold, but for Matthew Hagerty the draw is just as powerful: They’re a secluded hideaway ideal for perfecting his military invention, called SmartSight.

Ten years in the making, SmartSight is a gun-cam system that allows a soldier to see around corners and shoot targets without putting himself in the line of fire. It consists of a wireless video camera mounted to the rail of an M4 or .308 SOCOM carbine, a small computer worn on a military vest, and a thumbnail-size color head-up display affixed to a pair of protective glasses.

In effect, SmartSight turns the muzzle of an assault rifle into a third eye -- a soldier can crouch behind a blockade, stick his weapon over his head, and shoot his target with the same accuracy as if he were taking aim normally. “No other weapons sight can do that,” Hagerty says. “What you see is what you get.”

Miniaturizing the hardware found in news broadcasting equipment, Hagerty devised a way to beam live, uncompressed high-quality video from the 1.5-pound camera at a speedy 30 frames per second; meanwhile, custom software overlays the shooter’s red target dot in the head-up display so that the view appears exactly as it does through the gun’s conventional scope, all with no delay. Former Navy SEAL captain Larry Lasky, who has demoed SmartSight, says this capability could transform warfare, especially in urban environments.

A Bridge That Keeps Guitars Always in Tune

In a small engineering studio in Bronxville, New York, Cosmos Lyles and Paul Dowd eagerly take turns at the dry-erase board, sketching out diagrams of springs, levers and tension curves. This may not seem very rock ’n’ roll, but what they’re creating will let the musicians on their current client list, including Slash and Rob Zombie’s guitarist John 5, shred harder than ever: a bridge that keeps the instrument continuously in tune.

Guitar strings need constant tension to stay tuned, but they’re easily loosened or tightened if the temperature changes, the instrument gets knocked around, or the guitarist just plays too hard. In an EverTune-equipped guitar, the bridge, which holds the strings in place, contains six spring-and-lever contraptions, one at the end of each string. These keep the strings’ tension constant even if the tuning pegs get turned or the strings become loosened or tightened accidentally.

Each string is attached to a lever, which is in turn attached to a spring. To tune up, the guitarist tightens an adjustor screw at the bridge that alters the position of its corresponding spring, changing its leverage to obtain the right tension. If the guitar string loosens or tightens after being set, the lever shifts, but it is counteracted by the spring so that it holds the desired tension, until it needs to be replaced. (The guitarist can change the tuning anytime simply by readjusting the screws.)

For musicians, this elegant design translates to less time spent fiddling with guitars, and more time onstage and in the studio. While recording, Dowd says, “everyone talks about being annoyed waiting for the guitarist to tune up. They’ll tune every take.” And during live shows, guitarists may swap out for a new guitar with every song.

For more for more details and the remaining 5 best inventions of 2010, see the full list of the year’s best at PopSci.com