The
sulky is the light, two-wheeled
cart used in
harness racing. It is derived from a single-seat cart for pleasure driving. In its modern form, the sulky consists of a U-shaped shaft mounted on two
wheels, with a
seat for the driver at the bowl of the U. When first used for
harness racing in the early 19th century the sulky weighed about 125 lbs. Through the addition of ball bearings, pneumatic tires and other technological refinements, the sulky, as currently employed in harness racing, weighs only about 1/5 that original weight.
Source: Encyclopedia Britannica http://www.britannica.com