Tricycle

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A tricycle (often abbreviated to trike) is a three-wheeled vehicle.Tricycles generally follow one of two layouts: delta, with two wheels at the back (of which one or both may be driven) and one steered wheel at the front; and tadpole, with two steered wheels at the front and one (usually driven) wheel at the back.

Not all trikes fall into one of these two classes. For example, some early pedal tricycles used two wheels in tandem on one side and a larger driving wheel on the other. It is common for tricycles to have front and rear wheels of different sizes.

History

The word tricycle has been in use since the early 19th century and stems from the Greek tri (treia), meaning three, and kyklos, meaning a circle or wheel. The first recorded usage is apparently in 1828, signifying a "three-wheeled horse-drawn carriage." Tricycles have evolved to include various forms of propulsion including pedals, steam and internal combustion engines. The abbreviation trike has been in use since 1883.

            Trike motorbike

Similar to motorcycles, some tricycles are motorized. Some of the earliest prototype automobiles were steam tricycles. However, motorcycles with sidecars are not considered tricycles, nor are the three wheeled automobiles such as the Morgan).

A motorized tricycle's wheels may be arranged in either configuration: delta or tadpole. Occasionally, rear wheel steering is used, although this increases the turning circle and can affect handling (the geometry is similar to a regular trike operating in reverse, but with a steering damper added). Thrust SSC used a rear-steer tadpole layout (technically, Thrust SSC was not a tricycle; it had four wheels two at each end. The rear steering wheels (2) were mounted very close together).

Tadpoles are more stable under braking and more likely to slide instead of roll; front braking hard on a delta requires the vehicle to steer almost straight to avoid tipping. The balance of friction patches and rolling resistance also means that tadpoles tend to understeer and deltas oversteer.

Motor trikes are attractive for those with mobility or balance problems, for carrying multiple passengers on a motorcycle licence, or to avoid helmet use regulations. These machines are generally custom-built and often finished to a very high standard. A common arrangement is to fit chopper-style ("ape hanger") front forks to a VW Beetle engine and transaxle, popular because it is largely self-contained on a single subframe.

Mass-manufactured motor tricycles include the Piaggio Ape (Bee) delivery trike; trikes used by municipal authorities in the USA; and, historically, vehicles such as the Scammell Scarab railway dray, a common sight around post-war British railway stations.