As you know, for different road conditions: descents, climbs — many types of bikes use a block of sprockets of different diameters for changing torque to the rear driving wheel. These mechanisms are relatively complicated, high cost structure, which does not allow to use the foot brake. But torque can be adjusted by changing the length of the connecting rod! And their mess is easy to exercise at home on all road bikes.
Figure 1 shows a “three-speed” rod. Every Dauch levers regular pedals securely welded steel plate with three blind holes. On the threaded end of the shaft nahodou pedals tightly screwed steel sleeve with a diameter of 18 mm, freely included in any of the three blind holes (with a gap of 0.3—0.5 mm). Every pedal is equipped with a homemade tulipson (see “modelist-Konstruktor” No. 5’2000), densely pressing to her foot. Remove the legs from tulips while riding and stops you do not need; if you need to “switch gears”, the cyclist removes his foot from pedal to the side, bringing a sleeve from one hole lining, and easily and quickly brings it (with end of chamfer 1,5×45°) and an adjacent hole, changing the torque. Then the same actions are taken with the left foot. The whole process takes no more than five seconds. When you stop any foot is on the ground with the pedal. Tulips besides help pull the pedal up, increasing the capacity of the drive.