Penny-farthing

A late nineteenth-century bicycle with a very large front wheel, a much smaller rear wheel, and pedals attached directly to the front-wheel hub. Its height and direct-drive design made it fast but difficult to mount and stop.

Direct-drive mechanism: A drive system in which pedals turn the driven wheel without an intervening chain or gears. The pedals turn the large front wheel directly, making wheel size determine distance traveled per pedal revolution.
Velocipede: An early human-powered wheeled vehicle, especially a precursor to the modern bicycle. The penny-farthing developed from earlier velocipedes with pedals driving the front wheel.
Safety bicycle: A bicycle with two similarly sized wheels and a chain-driven rear wheel, forming the basis of the modern bicycle. Its lower frame and rear-wheel drive addressed the high-wheel bicycle's mounting and falling hazards.
Bicycle safety: The design and practices that reduce injury risks while riding bicycles. The penny-farthing's height and forward pitching risk made safety a central design concern.
Bicycle gearing: Systems that alter the relationship between pedal rotation and wheel rotation. Unlike later geared bicycles, the penny-farthing has no gearing to separate pedal cadence from wheel speed.
Michaux-Perreaux steam velocipede: A nineteenth-century steam-powered two-wheeler built by Louis-Guillaume Perreaux and associated with the Michaux firm. It belongs to the earlier French velocipede tradition from which high-wheel bicycles evolved.
Tricycle: A human-powered vehicle with three wheels, usually arranged for greater stability than a bicycle. Some riders chose three wheels rather than face the balance demands of a penny-farthing.
Bicycle boom: A period of rapid growth in bicycle use and manufacture, especially during the 1890s. The safer bicycle that followed the high-wheel era helped cycling reach a much larger public.
Center of gravity: The point at which an object's mass can be treated as concentrated for analyzing balance. The rider's high position over the front wheel contributes to the danger of pitching forward.
James Starley: An English inventor and bicycle manufacturer known for major improvements to high-wheel bicycles. His 1870 Ariel helped establish the characteristic large-front-wheel design.

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