Unicycle

Table of contents

1 Introduction
2 Construction
3 Riding
4 History
5 Recent developments
6 Variations
7 External links

Introduction

A unicycle is a one-wheeled human powered vehicle. Unicycles are similar to, but less complex than, bicycles.

Unicycles comprise a few key parts: the wheel and axle, the frame, the seat, and crankss and pedals. The wheel is the main part of the unicycle; it is essentially a bicycle wheel with a special hub so that the frame and cranks can attach to the side. Unicycles use direct drive, with the crank's rotation directly connected to that of the wheel. The frame sits above the wheel, and the seat is located on top of the frame.

Riding

Unicycles are more difficult to ride than bicycles. They require the rider to maintain balance in two dimensions rather than one, and with their slower speeds their motion has less gyroscopic assistance for maintaining stability.

Balancing a robotic unicycle forms an interesting problem in control theory.

History

Unicycles are thought to descend from the penny-farthing bicycles of the late 19th century. These bicycles had a large wheel in front, to which the pedals were attached, and a much smaller wheel behind for balance. When these bicycles hit a bump, the rear wheel would come off the ground, forcing the rider to balance on one wheel. Early unicycle photographs, which show unicycles with very large wheels, support this explanation.

Recent developments

Unicycles have traditionally had circus connotations, but in recent years unicycles have gained a following as a means of everyday transportation. Unicycling has also gained popularity as a sport. The bi-annual world championship UNICON holds Unicycle races. Riding a unicycle in off-road conditions is known as mountain unicycling, which is similar to mountain biking. In unicycle trials the unicyclist aims to negotiate a series of obstacles without any part of the rider touching the ground. Freestyle Unicycling contains a style of tricks seen in skateboarding, aggressive in-line skating, BMX, and freestyle biking including jumps, spins, and grinds.

Variations

Giraffe unicycles: tall, chain-driven unicycles.
Mountain unicycles: unicycles made for the sport of mountain unicycling.
Kangaroo unicycles: unicycles with an off-center wheel and cranks that face the same direction. The rider of a kangaroo unicycle appears to be hopping about like a kangaroo, hence the name.
Ultimate wheel: a unicycle with no frame or seat, just a wheel, cranks, and pedals.
Impossible wheel: a wheel with pegs sticking out for the rider to stand on. Theoretically, this works like log-rolling.
Multi-wheeled unicycle: Still a unicycle since the wheels are stacked on top of each other so only one touches the ground. The wheels are linked together by chains or friction.
A quick list of other variations: Tandem, Recumbent, Hydraulic Giraffe, Unibike, Motorized
Monowheel: a large wheel in which the rider sits inside (like a hamster wheel) and either pedals an internal drive or is motorized. It is not plagued by the normal unicycle balance problems because of the greater gyroscopic properties and lower center of mass.