Gear shifting system for derailleur equipped bicycle

Apparatus for controlling the gear ratio of a bicycle having a plurality of front chainwheels and a plurality of rear sprockets, front and rear derailleurs controlling the position of a bicycle chain on selected ones of said chainwheels and sprockets comprising:

• means for generating a first electrical signal corresponding to the velocity of the bicycle;
• means for generating a second electrical signal corresponding to the crank speed of said bicycle;
• a microcontroller responsive to said first and second electrical signals for calculating the actual gear ratio and comparing it with preset values to see if it is within a first set of limits, if within said first set of limits the microcontroller then determining whether the crank speed is within limits, the microcontroller generating a third signal if the crank speed is below limits and the bicycle is moving at a speed above a threshold value;
• and
• means for controlling said front and rear derailleurs in response to said third electrical control signal whereby said bicycle chain is downshifted to the next lowest gear.

Apparatus for controlling the gear ratio of a bicycle having a plurality of front chainwheels, a plurality of rear sprockets and first and second wheels, first and second pedals, front and rear derailleurs controlling the position of a bicycle chain on selected ones of said chainwheels and sprockets comprising:

• sensor means operatively mounted adjacent said first wheel for generating a first electrical signal corresponding to the velocity of the bicycle;
• sensor means operatively associated with said first pedal for generating a second electrical signal corresponding to the crank speed of said bicycle;
• a microcontroller responsive to said first and second electrical signals for calculating the actual gear ratio and comparing it with preset values to see if ti si within a first set of limits, if within said first set of limits the microcontroller thereafter determining whether the crank speed is within a second set of limits and generating a third electrical signal if the crank speed is outside said second set of limits;
• and
• means for controlling said front and rear derailleurs in response to said third signal to shift said bicycle chain whereby said cadence is within said second set of limits, said controlling means comprising first and second servomotors.