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Old 06-17-20, 11:09 AM
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Seattle Forrest
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SRAM invents rotating 3 FD system

It sounds like this would give the bike a slightly cleaner look, and still not work. Next year, there will be a rotating 1x system.

All of the design’s front shifting mechanisms are built into the crankset. There’s nothing – zero – mounted to the frame. The system includes a wireless receiver, battery, and one motor, all of which enable three separate derailleurs. It’s all tied together with linkages and cams and pivots and springs and sensors in a symphony of electro-mechanical action. I’ll skip over most of the internal fiddly bits, and focus on how shifting actually works.

...

SRAM engineers found a way around this, but it adds significant complexity to the system. Sensors know the rotational position of the cranks, so the downshifting elements only move into shift position when they’re between about 6:30 and 11 o’clock. When one downshift element approaches 11 o’clock, it encounters the side of the chain, and pushes the chain inward and down to the small ring. That’s why there are two downshifting elements: press a shift button, and the system waits until one of them is in the right spot. That means two shift periods per pedal stroke.




https://cyclingtips.com/2020/06/radi...g-derailleurs/
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