Gibbs engineers outfitted the Quadski with a modified automotive dual-wishbone suspension. To ensure that the fiberglass V-shaped hull has enough ground clearance, they repositioned the upright shaft, which attaches to the wheel, below the wishbone arms instead of between them.
The Quadski's wheels will not retract unless it is in at least three feet of water. To make sure the water level is high enough, an optical sensor in the rear monitors the refraction of light through water; until the central computer receives the correct signal from that sensor, the wheels remain locked in road mode.
The driver pushes a button to initiate retraction. A control module disconnects the differential to prevent the wheels from turning. Servomotors, similar to those on aircraft landing gear, retract the wheels. Sensors on each motor detect the angle of the wheels; when they're 15 degrees above the horizontal, the motors shut off.
A thumb-operated throttle controls the four-cylinder, 140-horsepower engine. Torque passes through a pulley-and-belt-driven output shaft to the Quadski's wheels or a larger-than-normal seven-inch water jet. In marine mode, the five-speed transmission remains in third gear. On land, the rider uses a shifter to toggle between gears.
In the past, amphibious vehicles used displacement hulls, which push water aside rather than lift a craft above it. Instead, the Quadski has a V-shaped hull, which forces the craft up and out of the water when it accelerates, allowing it to plane in about 3.5 seconds.
Top Speed: 45 mph
Transition Time: 5 seconds
This article originally appeared in the May 2013 issue of Popular Science. See the rest of the magazine here.