To power up a mountain, you need a stiff bike frame that transfers pedaling force straight to the wheels. But zooming downhill without jolts or spills calls for more cushioning. So Kona’s Coilair bikes feature a lever that automatically shortens the shock when you pedal and lengthens it when you coast. The lever also pushes the seat closer to the ground, lowering the center of gravity to match the stability of a dedicated downhill racing bike.
On an ordinary bike, the chain stay [A]—the bar connecting the rear wheel to the rest of the bike—is fixed to the frame. But on the Coilair, the chain stay attaches to a pivoting link [B] under the shock [C]. The link lets the angle of the shock and frame change.
Pedaling pulls the rear wheel forward and brings the chain stay along with it. The chain stay, in turn, pushes the link, locking it in an upright position [left]. This makes for a stiffer, easier-to-pedal frame.
When you stop pedaling, the rear wheel can move backward when it hits a bump, yanking the link back with it. This lets the link bounce against a secondary shock [D] that provides extra cushioning. The tilting link also pushes the seat tube [E] down to lower the bike’s center of gravity and provide better stability.
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.