Take the tour ×  Has anyone ever designed or manufactured and
automatic transmission (automatic shifter?) for cycling?  I
imagine such a device would automatically change the gearing to
allow the rider to maintain constant cadence or constant torque
on the cranks.  I used to daydream about the existence such a
system many years ago when riding my first (battered,
secondhand) racer as it was such an ordeal to change gears.
share|improve this question Wondering about that, and about what
you said you wondered, I think the act of shifting is the
problem, but the right to choose the exact gear you want, and
the time of shifting, that is invaluable (imagine the bike
"arbitrarily shifting" when you don't expect or don't want).
Regarding that, shifting systems have become more and more
ergonomic, and there are some good attempts to build CVT
transmission for bikes, for example the NuVinci hub. – 
heltonbiker Jul 17 '12 at 23:09 Automatic gearboxes tend to be
heavier and have more friction (i.e. you would have to pe