Trikes and 3 Wheelers
A tricycle (often abbreviated to trike) is a three-wheeled vehicle. While tricycles are often associated with the small three-wheeled vehicles used by pre-school-age children, they are also used by adults for a variety of purposes. In the United States and Canada, adult-sized tricycles are used primarily by older persons for recreation, shopping, and exercise. Human-powered trikes are usually powered by pedals, although some models have hand cranks. Motorized trikes can be powered with a variety of methods, including motorcycle engines, smaller automatic transmission scooter motors, and electric motors. Scooters are motor vehicles that can vary significantly in design and capability, but are generally derived from a traditional design combining a step-through frame with front fairings and floor boards, inner fairing storage, small wheels (10" to 16" in diameter), and a rear swingarm-mounted engine suitable for light duty. The classic scooter design features a step-through frame and a flat floorboard for the rider's feet. Most newer scooters use a continuously variable transmission (CVT). While most scooters have two wheels, some scooters are three-wheeled scooter trikes.Most scooter trikes have two rear wheels which are the drive wheels and a front wheel which is used for steering. Some first decade of the 21st century-era scooter trikes such as the Piaggio MP3 are reverse trikes, with two wheels in front and one in the back. The MP3 leans like a 2-wheeled bike, with the front wheels moving independently in a scissors action.