da Vinci Designs’ Independent Coasting System (ICS) allow the captain
and stoker to pedal at their own speed. Traversing obstacles is easier
and more efficient because the captain and stoker can coordinate avoiding
the obstacles while maintaining forward momentum. Asynchronous pedaling
decreases strain on the final drive train. The main component of da Vinci
Designs’ ICS is an intermediate drive shaft six inches in front of
the rear bottom bracket. The intermediate shaft has two single-speed freewheels
on the left side that are independently driven by the cranks at twice
the rotating speed and half the torque.
On the right side of the shaft, four Hyperglide cogs drive the bike.
The chain rings are half the size as those on a conventional tandem because
of the double rotation of the intermediate shaft. The combination of 12-,
18-, 24-, 30-tooth driving gears equals 24-, 36-, 48-, 60-tooth chain
rings. The combination of the small 6-tooth gap, doubled rotation and
the Hyperglide cogs gives da Vinci Designs’ tandems these technical
advantages: Smooth and fast front shifting – The closer the chain
rings are to the same size, the easier it is to shift. Other tandems,
and even single bikes, are forced to use a 12-tooth gap between chain
rings.
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