Abstract: A planetary gear speed reducer includes a gear bracket having a center hole and first, second and third locating portions arranged in parallel along the center hole, a sun gear mounted in the center hole of the gear bracket, first gears rotatably mounted in between the first and second locating portions of the gear bracket and meshed with the sun gear, second gears rotatably mounted in between the second and third locating portions of the gear bracket and meshed with the sun gear, and two annular gears respectively meshed with the first gears and the second gears. Enabling the two annular gears to mesh with the first and second gears respectively avoids installation inconvenience due to phase difference between the first and second gears and eliminates interference during rotation of the two annular gears. By means of changing the number of teeth of each gear, the planetary gear speed reducer can provide a low, medium or high reduction ratio.

Abstract: A folding bicycle with a telescopic rod includes a bicycle body, a folding switch and the telescopic rod. The bicycle body includes front and rear frames that are foldable against each other. The telescopic rod has two ends respectively and pivotally connected to the front and rear frames, and has an engaging position thereof. The folding switch is disposed on a lateral side of the bicycle body to fix the front and rear frames together or release from each other. When the bicycle body is unfolded, the telescopic rod is driven to extend, and the folding switch fixes the front and rear frames together. When the bicycle body is folded in half, the telescopic rod is driven to retract and fixed in the engaging position. Thus, the present invention has advantages of enhanced rigidity of the bicycle body, easily movability, auxiliary positioning, simply rapid folding and lower costs.