Patent ID: 7753182

Claim:
A gravity driven vehicle, said gravity driven vehicle comprising: a chassis; a front axle assembly mounted to said chassis, said front axle assembly including at least one wheel on at least one front axle; at least one rear axle mounted to said chassis, the at least one rear axle directly connected to and rotatable with rear wheels mounted at ends of the at least one rear axle; and a speed restrictor engaging the at least one rear axle to control the rotation speed of the at least one rear axle of the rear axle assembly, said speed restrictor comprising: a sealed housing mounted to said chassis; a fluid sealably disposed in said housing; at least one rotor mounted on the at least one rear axle within said housing, said at least one rotor having an outer periphery surface facing an inner surface of said housing, said rotor having a plurality of blades disposed around and normal to an axis of the at least one rear axle, said plurality of blades defining a plurality of fluid channels therebetween; said housing having a first section and a second section, said at least one rotor mounted on the at least one rear axle within the first section of said housing, wherein the first section is in fluid communication with the second section; a plate disposed in said housing around the at least one rear axle and having first and second surfaces disposed normal to the axis of the at least one rear axle, said first surface of said plate being disposed adjacent to the plurality of blades and separating the first section from said second section, and said plate having at least one hole extending through said plate from said first surface to said second surface adjacent to said plurality of blades wherein said at least one hole in said plate permits fluid to pass between the first section to the second section; wherein fluid circulates between the first section and the second section through at least one hole in the plate; and wherein rotation of the at least one rear axle slows in response to resistance caused by fluid being forced against the inner surface of said housing during rotation of the at least one rear axle.