Citizens of Philadelphia, beware: You may see a grown man whizzing by you on a skateboard, doing 20 mph. That would be PopSci staff photographer John Carnett, and in case you don’t get a good look, it’s a souped-up, motorized board he built from the ground up.
Carnett wanted to create a motorized skateboard that would be superior to commercial models—a fast, hot-looking board that ran on all terrains. He started by cutting a shiny 44-inch-long aluminum deck and bending the ends and side rails. So that it could move easily from pavement to trail, he outfitted it with durable axles and eight-inch inflatable knobby tires.
Then there was the matter of installing a disc-braking system and a 500-watt electric motor. And since no wheel bearings existed that fit both the truck axle and his custom drive system, Carnett had to cobble together and weld an aluminum adapter plate to make everything fit. Then he attached a box to the underside that holds the motor controller and four batteries; when the first two die, the board can go another eight miles on the backups. Or he can let the board do the climbing work, and then power it off and freewheel downhill. Either way, it’s the sweetest ride on the road—or off it.
The incredible innovations, like drone swarms and perpetual flight, bringing aviation into the world of tomorrow. Plus: today's greatest sci-fi writers predict the future, the science behind the summer's biggest blockbusters, a Doctor Who-themed DIY 'bot, the organs you can do without, and much more.