Amphibious vehicle

An amphibious vehicle (or simply amphibian), is a vehicle or craft, that is a means of transport, viable on land as well as on water – just like an amphibian.

This definition applies equally to any land and water transport, small or large, powered or unpowered, ranging from amphibious bicycles, ATVs, cars, buses, trucks, RVs, and military vehicles, all the way to the very largest hovercraft. Classic landing craft are generally not considered amphibious vehicles, although they are part of amphibious assault. Nor are Ground effect vehicles, such as Ekranoplans. The former do not offer any real land transportation at all – the latter (aside from completely disconnecting from the surface, like a fixed-wing aircraft) will probably crash on all but the flattest of landmasses.

Wheeled

Unarmored

ATVs

Amongst the smallest non air-cushioned amphibious vehicles are amphibious bicycles, (see also) and ATVs. Although the former are still an absolute rarity, the latter saw significant popularity in North America during the 1960s and early 70s. Typically an amphibious ATV (AATV) is a small, lightweight, off-highway vehicle, constructed from an integral hard plastic or fibreglass bodytub, fitted with six (sometimes eight) driven wheels, with low pressure, balloon tires. With no suspension (other than what the tires offer) and no steering wheels, directional control is accomplished through skid-steering – just as on a tracked vehicle – either by braking the wheels on the side where you want to turn, or by applying more throttle to the wheels on the opposite side. Most contemporary designs use garden tractor type engines, that will provide roughly 25 mph top speed on land.

Constructed this way, an AATV will float with ample freeboard and is capable of traversing swamps, ponds and streams as well as dry land. On land these units have high grip and great off-road ability, that can be further enhanced with an optional set of tracks that can be mounted directly onto the wheels. Although the spinning action of the tires is enough to propel the vehicle through the water – albeit slowly – outboard motors can be added for extended water use. Current AATV manufacturers are Argo, Land Tamer, MAX ATVs and Triton.

Articulated-body designs in this category were the Coot and the very similar TAG Croco.

Recently some efforts have been made toward amphibious ATVs of the straddled variety. Gibbs Technologies plans to begin production of the Quadski High-Speed Amphibian in late 2010. Part ATV, part personal watercraft, Gibbs has said the Quadski will be capable of 45 mph on land or water http://www.thedetroitbureau.com/2010/07/carboat-stalled-gibbs-to-launch-amphibious-atv/. Others include the add-on inflatable pontoon kit, that can be installed on any quad-bike ATV with front and rear metal frame racks and at least 14" water fording ability.

Cycles

An Amphibious Cycle is capable of operation on both land and water. The design which has probably received the most coverage is Saidullah’s Bicycle.[5] This has been featured on both the Discovery Channel and BBC News. The bike uses four rectangular air filled floats for buoyancy, and is propelled using two fan blades which have been attached to the spokes. Moraga’s Cyclo Amphibious uses a simple tricycle frame to support three floaters which provide both the floatation and thrust. The wings on the powered wheels propel the vehicle in a similar way to a paddle wheel.

The most recent attempt, featured in the Southern Daily Echo (5 June 2008) and The Daily Telegraph (6 June 2008) is that of seven engineering students at the University of Southampton. The Amphibious Cycle combines a recumbent frame with separate floats, and is propelled using a paddle wheel. A speed test on water achieved an average speed of 1.12 m/s. The cyclist was able to transition the cycle both into and out of the water unassisted. This elegant prototype has a real application in urban areas of flooding, as well as applications in the leisure industry.

Trucks and barges

With more than 20,000 units produced, the DUKW was the most successful amphibious truck of World War II. This 31-foot (9.4 m) 6x6 truck was deployed in the Pacific theatre to establish and supply beachheads. It was designed as a wartime project by Sparkman & Stephens, the famous yacht design firm who also designed the hull for the Ford GPA 'Seep'. During the war, Germany produced the Landwasserschlepper and Schwimmwagen, and in the '50s, the Soviets developed the GAZ 46, BAV 485, and PTS.

During the Vietnam War, the US Army used the amphibious articulated Gama Goat and the larger Caterpillar 'Goer' truck-series to move supplies through the canals and rice paddies of Southeast Asia. The latter was based on a 1950s civil construction vehicle and became the US Army’s standard heavy tactical truck before its replacement by the HEMTT. Although the vehicles' wheels were mounted without suspension or steering action, and land speeds over 20 mph were ill-advised, its articulated design provided it with good maneuverability and helped it to keep all four wheels firmly in touch with uneven ground. Coupled with its amphibious capability, in the Vietnam War (especially during raining season), the M520 Goer developed a reputation of being able to go where other trucks could not.

For taking vehicles and supplies onto the beaches the US used the 1950s designed LARC-V and the huge LARC-LX or "BARC". At 63 feet (19 m) long and 27 feet (8.2 m) wide the latter is one of the largest wheeled amphibians to date. It could carry up to 100 tons of cargo or 200 people, but a more typical load was 60 tons of cargo or 120 people. The vehicle was powered by four V8 diesel engines positioned in the sides of the hull, each driving a single 8-foot (2.4 m) wheel.

History

Some of the earliest known amphibious vehicles were amphibious carriages, the invention of which is credited to the notorious Neapolitan Prince Raimondo di Sangro of Sansevero or Sir Samuel Bentham (1781).

The first known self-propelled amphibious vehicle, a steam-powered wheeled dredging barge, named the Orukter Amphibolos, was conceived and built by United States inventor Oliver Evans in 1805, although it is disputed to have successfully travelled over land or water under its own steam.

Although it is unclear who (and where and when) built the first combustion-engined amphibian, in all likelihood the development of powered amphibious vehicles didn't start until 1899. Until the late 1920s the efforts to unify a boat and an automobile mostly came down to simply putting wheels and axles on a boat hull, or getting a rolling chassis to float by blending a boat-like hull with the car's frame (Pohl, 1998). One of the first reasonably well documented cases was the 1905 amphibious petrol-powered carriage of T. Richmond (Jessup, Iowa, USA). Just like the world's first petrol-powered automobile (1885, Carl Benz) it was a three-wheeler. The single front wheel provided direction, both on land and in the water. A three-cylinder petrol combustion-engine powered the oversized rear wheels. In order to get the wheels to provide propulsion in the water, fins or buckets would be attached to the rear wheel spokes. Remarkably the boat-like hull was one of the first integral bodies ever used on a car (Pohl, 1998).
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