Three-wheeler

Diagram showing an initial velocity vector for three vehicles and the corresponding angular displacement from the initial wheel positions required to change the direction of the initial velocity vector by the same value when turning using various three-wheeled car steering mechanism configurations

A three-wheeler is a vehicle with three wheels, either "human or people-powered vehicles" (HPV or PPV or velomobiles) or motorized vehicles in the form of a motorcycle, all-terrain vehicle (ATV) or automobile. Other names for three-wheelers include trikes, tricars and cyclecars. The term tricycle is used somewhat interchangeably, but the term three-wheeler is more often applied to motor vehicles. They can be legally classed as either automobiles or motorcycles.

Many three-wheelers which exist in the form of motorcycle-based machines are often called trikes and often have the front single wheel and mechanics similar to that of a motorcycle and the rear axle similar to that of a car. Often such vehicles are owner-constructed using a portion of a rear-engine, rear-drive Volkswagen Beetle in combination with a motorcycle front end. Other trikes include ATVs that are specially constructed for off road use. Three-wheeled automobiles can have either one wheel at the back and two at the front, (for example: Morgan Motor Company) or one wheel at the front and two at the back (such as the Reliant Robin).

Due to its superior safety when braking, an increasingly popular form is the front-steering "tadpole" or "reverse trike" sometimes with front drive but usually with rear drive. A variant on the 'one at the front' layout was the Scott Sociable, which resembled a four-wheeler with a front wheel missing.^[1] Not illustrated is the Thebis rear-steered delta from Sidney, British Columbia

Three-wheeler cars, usually microcars, are often built for economic reasons: in the UK for tax advantages, or in the US to take advantage of lower safety regulations, being classed as motorcycles. As a result of their light construction and potential better streamlining, three-wheeled cars are usually very economical to run.

Three-wheeler transport vehicles known as Auto Rickshaws are a common means of public transportation in many countries in the world. Auto rickshaws are an essential form of urban transport in many developing countries such as India, and a form of novelty transport in many Eastern countries.

History

Early car pioneer Karl Benz developed a number of three-wheeled models.^[2] One of these, the Benz Patent Motorwagen,^[3] is widely regarded as the first purpose-built automobile. It was built in 1885.

In 1896, John Henry Knight showed a tri-car at The Great Exhibition.^[2]

In 1897, Edward Butler (inventor) made the Butler Petrol Cycle, another three-wheeled car.

A Conti 6 hp Tri-car competed in (but did not complete) a 1907 Peking-to-Paris race sponsored by a French newspaper, Le Matin.^[4]

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  A photograph of the 1885 Benz Patent Motorwagen.

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  Davis D-2 Divan, at the National Automotive and Truck Museum, Auburn, IN

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  Davis 494, at the National Automotive and Truck Museum, Auburn, IN

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  Velorex was a manufacturing cooperative in Solnice, Czechoslovakia, formed in 1936 to satisfy demand for small, inexpensive city cars.

Configurations

Two front

Trihawk, a Tadpole-type trike manufactured in California during the 1980s

A configuration of two wheels in the front and one wheel at the back presents two advantages : it has improved aerodynamics, and that it readily enables small lightweight motorcycle powerplant and rear wheel to be used. This approach was used by Messerschmitt kr200 and by the BMW Isetta. Alternatively, a more conventional front-engine, front wheel drive layout as is common in four-wheeled cars can be used, with subsequent advantages for transversal stability (further front location of CG) and traction (two driven wheels instead of one).

For the lowest wind resistance (which increases fuel efficiency), a teardrop shape is desirable.^{[citation needed]} A teardrop is wide and round at the front, tapering at the back. The three-wheel configuration allows the two front wheels to create the wide round surface of the vehicle. The single rear wheel allows the vehicle to taper at the back. This approach is used by the Aptera 2 Series. It is also used by Myers Motors for both its single passenger NmG and upcoming 2-passenger Duo.

Two rear

Bond Bug at Silverstone

Having one wheel in front and two in the rear for power reduces the cost of the steering mechanism, but greatly decreases lateral stability when cornering while braking.

Lateral stability

Crashed Reliant Robin

The disadvantage of a three-wheel configuration is lateral instability - the car will tip over in a turn before it will slide. This can be prevented in 3 different ways: - By placing the centre of mass is much closer to the ground. (This is easiest for electric three-wheelers that can lower the center of mass by placing the heavy battery pack as low as possible) - By placing the center of the mass closer to place with the 2 wheels. - By increasing the track width is to be much wider than a similar four-wheel vehicle.

Tilting option

A Honda Canopy used for delivery service

To improve stability some three-wheelers are designed as tilting three-wheelers so that they lean while cornering like a motorcyclist would do. The tilt may be controlled manually or by computer.

A tilting three-wheeler's body and or wheels tilt in the direction of the turn. Such vehicles can corner safely even with a narrow track.

Wheel configurations

Several configurations are practical. Two front wheels and one rear, where all three wheels tilt, use the acronym 2F3T (i.e. two front three tilt). Other variations include 1F1T, where only the front wheel tilts, an example being the Vandenbrink Carver, made in the Netherlands.

Active or passive tilt control

Tilting can be actively controlled by applying force between the paired wheels. A "free leaner" is balanced by steering, like a single track vehicle. This still leaves some advantages in traction, and the tilt can be locked for parking faster than a stand can be deployed.

Topology

Propulsion may be on one, two, or three wheels, tilted or not. Many possible arrangements require particularly flexible U-joints, which favours the other possibilities.

Use of 'extra' wheel

Tripendo recumbent tricycle, a tilting three-wheeler

Vandenbrink Carver

Any extra laterally spaced wheel can benefit the vehicle by providing stability gains if there is a mechanism to lock the laterally spaced wheels at any given moment relative to the road plane. In some countersteered vehicles this benefit is generally only available when stopped.

In other types where the tilt angle is directly controlled this additional stability is constant at all speeds.

In a countersteered vehicle a loss of traction will result in a fall whereas in a tilt controlled design a fall may not occur.

Various electric and hydraulic systems have been employed to modify TTW behaviour, with notable success on the Carver.

Due to the tilting, there is not necessarily any load transfer between the wheels in cornering, so the rule about tadpoles (2F or "reverse trike") understeering and Deltas (1F or standard trike) oversteering does not necessarily apply

Registration

In the U.S the National Highway Traffic Safety Administration defines and regulates three-wheeled vehicles as motorcycles.^[5] Licensing requirements vary on a state-by-state basis. In other jurisdictions, such as British Columbia, Canada, and Connecticut, a three-wheeled vehicle with an enclosed passenger compartment or partially enclosed seat is considered an automobile.

Safety

When the single wheel is in the front (the "delta" form, as in a child's pedal tricycle), the vehicle is inherently unstable in a braking turn, as the combined tipping forces at the center of gravity from turning and braking can rapidly extend beyond the triangle formed by the contact patches of the wheels. This type, if not tipped, also has a greater tendency to spin out ("swap ends") when handled roughly.

With two wheels in the front (the "tadpole" form or "reverse trike") the vehicle is far more stable in braking turns, but remains more prone to overturning in normal turns compared to an equivalent four-wheeled vehicle, unless the center of mass is lower and/or further forward. Motorcycle-derived designs suffer from most of the weight being towards the rear of the vehicle.

Due to the incidence of injuries related to their use, a 10-year ban was placed on the sale of new three-wheeled ATVs in the United States in January 1988.^{[citation needed]}

In popular culture

1932 Morgan Aero 2-Seater Sports

One of the most famous three-wheeled cars is the dirty yellow Reliant Regal Supervan III from the British TV series Only Fools and Horses.

In the British TV series Mr. Bean, a Reliant Regal three-wheeler was often driving around town. The car was sort of a nemesis to Mr. Bean, as he would drive in such a manner as to cause the car to roll over and even refused a ride from the three-wheeler when hitchhiking.^[6]

Examples

Folding City Car: Zaschka Three-wheeled car, 1929. Engelbert Zaschka, German inventor, and his folding three-wheeler

See also

• Auto rickshaw
• Bubble car
• Cabin cycle
• CityEl
• CLEVER
• Corbin Sparrow
• Cushman
• Davis Motorcar Company
• Egy-Tech Engineering
• Electric trike
• Feet forwards motorcycle
• Goliath (car)
• Harley-Davidson Servi-Car
• Motorized tricycle (Philippines)
• Myers Motors NmG
• Piaggio MP3
• Steam tricycle
• T-Rex (automobile)
• Tri-Magnum
• Tuk-tuk
• Volkswagen 1-litre car
• Volkswagen GX3

References

External links

• All about 3-wheeled ATVs
• Online A-Z of 3-wheeled cars
• Article on three-wheeled ATV safety at The American Academy of Pediatrics
• Gallery of Japan three-wheelers
• Theory and Practice of Three Wheel design (English & Français)
• Photo catalog of past and present three-wheel motor vehicles (street driven)
• "Three Wheel Cars; Primary Factors that Determine Handling & Rollover Characteristics" at Robert Q. Riley's website
• History of the Three Wheeler
• Link index for three-wheeled cars as well as other types