Pedal-powered four-wheel vehicle

Claim 1

A pedal-powered four-wheel vehicle, comprising: a. a left side two-wheel bicycle and a right side two-wheel bicycle attached in a side-by-side relationship, each bicycle having a frame member including a chain wheel, a head tube, an incline crossbar, an incline down tube, a steering post, a front fork for attaching to a front wheel and a stay seat for attaching to a rear wheel; b. a handlebar securely attached to said steering post of said left side bicycle for steering said four-wheel vehicle; c. a dummy handlebar clamped on said incline crossbar of said right side bicycle; d. an elongated upper front horizontal bar and an elongated lower front horizontal bar located adjacent and parallel to each other and respectively clamped between said incline crossbars and said incline down tubes of said left and right side bicycles for rigidly securing and stabilizing said left and right side bicycles together; e. a steering system having an elongated horizontal tie rod with two opposite ends, each coupled to a mounting plate which is clamped to a respective one of said steering posts of said left and right side bicycles for jointly operating both said steering posts; f. a differential axle mounted between said left and right side bicycles and having a central sprocket and two opposite ends which are coupled to rear wheel shafts of said left and right side bicycles through respective half-axles so that said rear wheels can rotate at different speeds; g. an intermediate driving shaft mounted between said rear wheels of said left and right bicycles and located parallel and adjacent to said differential axle, the intermediate driving shaft having a central sprocket and two opposite ends, each end having a freewheel affixed to a speed control hub, where each speed control hub is supported by two support shafts extending from a respective one of said stay seats of said left and right side bicycles; h. two gear control chains each linking said chain wheel and said freewheel of a respective one of said left and right bicycles, where an individual pedalling power of said left side bicycle and an individual pedalling power of said right side bicycle are transmitted by its respective gear control chains to said intermediate driving shaft through said freewheels respectively; i. a drive chain linking said sprocket of said differential axle and said sprocket of said intermediate driving shaft, where a rotational power transmitted through said freewheels drives said intermediate driving shaft, which in turn drives a propelling gear of said differential axle; j. a unified braking system for simultaneously applying brakes on at least two parallel ones of said wheels of said left and right side bicycles so that said left and right side bicycles can be evenly braked to stop said four-wheel vehicle; and k. an elongated cover member mounted between said left and right side bicycles for covering said differential axle and said intermediate driving shaft and further securing and stabilizing said left and right side bicycles together; l. whereby said individual pedal powers are combined to transmit combined power to said intermediate driving shaft, which then transmits the combined power to said differential axle, which in turn evenly distributes the combined power to said rear wheels of said left and right side bicycles.