The Gama Goat was a

six-wheel drive Six-wheel drive (6WD or 6×6) is an all-wheel drive drivetrain configuration of three axles with at least two wheels on each axle capable of being driven simultaneously by the vehicle's engine. Unlike four-wheel drive drivetrains, the configurat ...

semi-

amphibious Amphibious means able to use either land or water. In particular it may refer to: Animals * Amphibian, a vertebrate animal of the class Amphibia (many of which live on land and breed in water) * Amphibious caterpillar * Amphibious fish, a fish ...

off-road vehicle An off-road vehicle, sometimes referred to as an overland or adventure vehicle, is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with de ...

originally developed for use by the US military in the

Vietnam War The Vietnam War (also known by #Names, other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vie ...

. The Goat uses an articulated chassis, so that from distance it appears to be a four-wheel drive vehicle pulling a two-wheel trailer, but it is a single six-wheel vehicle with a

four-wheel steering Steering is a system of components, linkages, and other parts that allows a driver to control the direction of the vehicle. Introduction The most conventional steering arrangement allows a driver to turn the front wheels of a vehicle using ...

arrangement with the front and rear wheels turning in opposite directions. It was famous for its ability to travel over exceptionally rough and muddy terrain. The vehicle's nickname came from two sources: "Gama" from the name of the inventor of its powered articulated joint, Roger Gamaunt, and "Goat" for its mountain goat-like off-road ability. Its military designation was M561, 6×6 tactical 1¼-ton truck. There was also an ambulance version known as the M792. The vehicle was replaced by a variety of Commercial Utility Cargo Vehicles (CUCV) and

Humvee The High Mobility Multipurpose Wheeled Vehicle (HMMWV; colloquial: Humvee) is a family of light, four-wheel drive, military trucks and utility vehicles produced by AM General. It has largely supplanted the roles previously performed by the or ...

s (HMMWV)

History

The concept for the vehicle came when the French Army reported that the

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trucks provided to them were woefully inadequate for the terrain in Vietnam. In 1959, ARPA (now known as DARPA) funded a research project called Project "Agile" to develop a new tactical truck for the Southeast Asia theatre, as well as other projects of interest to the then-looming

. Of 50 companies solicited for XM561 proposals, six entered the competition, including

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General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...

and

LeTourneau Technologies LeTourneau Technologies, Inc. was an American manufacturer of heavy construction equipment founded by R. G. LeTourneau. In 2011, the company was acquired by Joy Global. History R. G. LeTourneau, also the founder of LeTourneau University, founded ...

, but on 15 March 1963, the research & development contract was awarded to Chance Vought division of

LTV Aerospace LTV may refer to: Television * Lagos Television, a TV channel in Nigeria. * Latvijas Televīzija, Latvian Television * LRT televizija, formerly LTV, Lithuanian National Television * LTV Ethiopia, a private satellite TV channel in Ethiopia * Lumie ...

Dallas, Texas Dallas () is the third largest city in Texas and the largest city in the Dallas–Fort Worth metroplex, the fourth-largest metropolitan area in the United States at 7.5 million people. It is the largest city in and seat of Dallas County ...

,Gama Goat Contract Data by R.F. Keller, Assistant Comptroller General of the United States
Washington, D.C., 6 October 1970, p. 487. best known for their combat aircraft (though, actually the company did have some experience in designing ground vehicles, particularly, a predecessor of Gama Goat, but they didn't have the truck assembly lines and production experience comparable to those of the mentioned car manufacturers). The principal competitor to the Goat was a tracked XM571

Articulated An articulated vehicle is a vehicle which has a permanent or semi-permanent pivot joint in its construction, allowing it to turn more sharply. There are many kinds, from heavy equipment to buses, trams and trains. Steam locomotives were sometim ...

Utility Carrier developed by Canadair Ltd. of

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(yet another aerospace company,) which eventually lost the contest. The research and development contract for the Goat was completed by LTV at cost of about $8.7 million, over three times more expensive than when it had been awarded. The vehicle weighed almost three times as much as originally requested by the military and specified by the

operational requirement An Operational Requirement, commonly abbreviated OR, was a United Kingdom (UK) Air Ministry document setting out the required characteristics for a future (i.e., as-yet unbuilt) military aircraft or weapon system. The numbered OR would describe ...

s (). Field testing had not been completed before the mass production order had been issued. During the field tests, it had not been able to go without a breakdown. Final construction of the vehicles was conducted by the Consolidated Diesel Electric Company (CONDEC) at their factory in

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(on 11 June 1968, the Army awarded them a 3-year contract for 15,274 vehicles, 13,516 Army and 1,758 Marine Corps, at a total price of about $132.1 million, on the same day Detroit Diesel Division of

received $30 million 3-year contract for the engines). CONDEC also had factories in

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, where the Gama Goat was originally manufactured, and in

Greenwich, Connecticut Greenwich (, ) is a town in southwestern Fairfield County, Connecticut, United States. At the 2020 census, the town had a total population of 63,518. The largest town on Connecticut's Gold Coast, Greenwich is home to many hedge funds and othe ...

, where the parts for the Gama Goat were produced. In the early 1960s, the company moved to Waterbury, Connecticut for a few years, then closed their plants in New York and Connecticut to move to Charlotte, North Carolina for cheaper labor and facilities. The Gama Goat was replaced in the late 1980s by a variety of CUCVs and "Humvees" (HMMWV).

Description

Overall, some 14,274 Gama Goats were built at a cost of US$8,000 each (1965 dollars; ); this was considered quite high at the time. 12,516 were slated for the US Army and 1,758 for the USMC. While the Gama Goat had exceptional off-road ability, its quirky

steering Steering is a system of components, linkages, and other parts that allows a driver to control the direction of the vehicle. Introduction The most conventional steering arrangement allows a driver to turn the front wheels of a vehicle using ...

made it hard to handle on pavement, and its tendency to flounder in amphibious operations required drivers to have special training in order to operate it. This meant that it could not be the "general purpose" vehicle the Army had hoped for, and production was halted after the original contract expired. The air-cooled engine used in the original prototypes overheated in use, and was replaced in the production vehicles with a liquid-cooled Detroit 3-53

Diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-cal ...

. Due to the high-intensity noise from the two-stroke Diesel engine, the drivers required hearing protection. The

double hull A double hull is a ship hull design and construction method where the bottom and sides of the ship have two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is some dist ...

construction and complex articulated

drivetrain A drivetrain (also frequently spelled as drive train or sometimes drive-train) is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the drivetrain is the components o ...

made maintenance difficult (the lubrication order alone took around six hours). In service in Vietnam, Gama Goats would often be sent out ahead of other vehicles in order to arrive at their destination at the same time. While technically listed as

, the Gama Goat's swimming capability was limited to smooth water crossings of ponds, canals and streams due to the very low

freeboard In sailing and boating, a vessel's freeboard is the distance from the waterline to the upper deck level, measured at the lowest point of sheer where water can enter the boat or ship. In commercial vessels, the latter criterion measured relativ ...

and the lack of a propeller. Propulsion in the water was supplied by the six spinning wheels, and

bilge pump A bilge pump is a water pump used to remove bilge water. Since fuel can be present in the bilge, electric bilge pumps are designed to not cause sparks. Electric bilge pumps are often fitted with float switches which turn on the pump when the bilge ...

s were standard equipment. Drivers had to remember to close the hull's drain openings before swimming the vehicles. Some models had extra equipment installed that made them too heavy to swim, such as heavy-duty winches, communications shelters that made them top heavy, or

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

gear. It was designed to be air-transportable and droppable by

parachute A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, w ...

Typical problems and malfunctions

In May 1972

Fort Hood Fort Hood is a United States Army post located near Killeen, Texas. Named after Confederate General John Bell Hood, it is located halfway between Austin and Waco, about from each, within the U.S. state of Texas. The post is the headquarter ...

cited the following problems as a result of examining 566 vehicles:

Additional specifications

Articulation

* Roll at center axle: ± 15 degrees * Roll at rear axle: ± 30 degrees * Pitch at rear axle: ± 40 degrees * Wall climb (vertical): 18 in (460 mm) * Angle of approach: 62 degrees * Angle of departure: 45 degrees * Hump angle: 140 degrees

Suspension

* Front and rear independent coil springs at each wheel * Center single leaf spring and swing axle

Steering system

* Type: Mechanical front and rear simultaneously operated * Steering ratio: 24:1 * Turning radius: 29 ft (8.8 m)

Variants

* M561 :* Cargo / personnel (eight troops) carrier ;* TOW ATGM team carrier (originally intended to be a dedicated Anti-Tank variant with its own TOW launching platform) :* Communications (separate shelter installed in the cargo compartment) :* Mortar carrier :* Radar (counter-mortar/artillery system) :* Radar (FAAR System) * M60 Machine gun and mount on passenger fender * M792 :* Ambulance

References

* SNL G874 * *

External links

M561 Gama Goat page on olive-drab.com
{{Post-WWII US Soft Vehicles Articulated vehicles Military trucks of the United States Off-road vehicles Military vehicles introduced in the 1970s