The rider-problem of a multi-sprocket bicycle is that the rider needs to manage chain-shifting apparatus that is not visible in the riding position. Safe and satisfactory riding involves shifting a chain to an appropriate set of sprockets in anticipation of speed change, terrain differences and future startup.
Derailleur mechanisms are mounted to guide chain travel onto front and rear sprocket sets, as specified by cable-command from non-standard hand-operated apparatus. Misjudgment in guiding the chain onto appropriately-sized sprockets is initially irritating; and sustained erroneous operation can induce knee injury.
Modern bicycles offer 7 to 21 chain-and-sprocket ratios. When pedalling seems too stiff, or too soft, the rider is expected to make sprocket-ratio adjustments. Cable adjusting apparatus is mounted within rider's vision on handlebars or bicycle frame.
Prior art for an automatic bicycle transmission (U.S. Pat. No. 4,598,920) sensed the angular velocity of the rear bicycle wheel, and guided the chain onto a smaller driven sprocket as angular velocity increased. This velocity-sensing system is independent of rider's variation in pedal-drive pressure.