Abstract: A bicycle includes a frame, a pedaling device, a sprocket device, a stepping device and a clutch device. The pedaling device is furnished on the frame for a rider to perform pedaling operation. The sprocket device includes an axle pivotally coupled to the frame and a front sprocket rotatably mounted on the axle. The stepping device is connected between the pedal device and the sprocket device for transmitting power from the pedal device to rotate the axle and increasing moment of force of the pedaling operation by a reciprocal stepping operation. The clutch device is furnished on the frame for performing a first position to engage with the front sprocket so that the front sprocket is driven together with the axle by the stepping device to rotate, and a second position to disengage from the front sprocket so that the front sprocket is free from driven by the stepping device.

Abstract: An improved connecting mechanism includes a rotary frame, a connecting seat, and a tightening device. The rotary frame is a substantially inverted U-shaped frame having frame wings on both sides provided with symmetrical wing holes. The connecting seat is a substantially curved structure having a front end seat and a rear end seat, the front end seat being disposed between the two frame wings and formed with a through front axial hole in a transverse direction. The front axial hole has two ends each of which is provided with a recess that is further communicated radially with a groove and a sector-like end recess. Springs are fitted into the recesses, respectively, such that a spring end at one end of each of the springs is inserted into the groove, with a spring coil extending from a spring post at the other end passing through one of the end recesses to connect to one of the frame wings. The tightening device includes a shaft passing through the two wing holes, the two springs, and the front axial hole.