The Gama Goat was a six-wheel-drive semi-amphibious off-road vehicle originally developed for use by the US Military in the Vietnam War. The 'Goat used 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 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 Gamount, and "Goat" for its mountain goat-like off-road ability. Its military designation was M561, 6×6 tactical 1-1/4-ton truck. There was also an ambulance version known as the M792 that could carry four litters.
The concept for the vehicle came when the French Army reported that the US Army 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 Vietnam War.
Several companies bid for the contract, including Clark, General Motors and LeTourneau, but the contract was awarded to Ling-Temco-Vought (LTV) aerospace, best known for their A-7 Corsair II aircraft. Final construction of the vehicles was conducted by Consolidated Diesel Electric Company (CONDEC) at their factory in Charlotte, North Carolina. CONDEC also had factories in Schenectady, New York, where the Gama Goat was originally manufactured, and in Greenwich, Connecticut, 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.
Overall, some 15,274 Gama Goats were built at a cost of US$8,000 each; this was considered quite high at the time ($8,000 in 1965 is $54,700 in 2010). While the Gama Goat had exceptional off-road ability, its quirky steering 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 it could not be the "general purpose" vehicle the Army had hoped for, and production was halted after the original contract expired. This is somewhat ironic, as some[who?] claim the problems were largely due to cost-cutting modifications made at the request of the U.S. Army.
The air-cooled engine used in the original prototypes overheated in use, and was replaced in the production vehicles with a Detroit 3-53 diesel engine. The high intensity noise from the 2-stroke diesel engine resulted in a warning to all operators that hearing protection was required while driving the vehicle. The double hull construction and complex articulated drive train made maintenance difficult (the lube 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. Their loud engine noise made them much less than stealthy. The 'Goat is prized among military vehicle collectors because it is so unusual and in short supply. The vehicle was replaced by the CUCV and HMMWV.
The Gama Goat was 226.6 inch (5.76 m) long; had a curb weight of 7,300 pounds (3,300 kg); had a payload capacity of 2,900 pounds (1,300 kg); and was powered by a Detroit Diesel 3-53 three cylinder, two-stroke engine that produced 101 hp (77 kW) at 2,800 rpm with a 159.3 in³ (2,610 cc) displacement. It could travel at 55 mph (90 km/h) on paved surfaces and traverse almost any terrain. A simple exhaust baffle was used instead of a muffler, so they could easily be heard before seen. It was designed to be air-transportable and droppable by parachute.
While technically listed as amphibious, the swimming capability was limited to smooth water crossings of ponds, canals and streams due to the very low freeboard and the lack of a propeller. Propulsion in the water was supplied by the six spinning wheels, and bilge pumps were standard equipment. Drivers had to remember to close the hull's drain openings before swimming the vehicles. Some models had extra equipment installed which made them too heavy to swim, such as heavy-duty winches, communications shelters that made them top heavy, or radar gear.
- Length 226.6 in (5.76 m)
- Width 83.80 in (2.13 m)
- Height 90.80 in (2.31 m)
- Reducible height 65 in (1.65 m)
- Tread 72 in (1.83 m)
- Ground clearance 15 in (380 mm)
- Pintle height 22 in (560 mm)
- 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
- Front and Rear Independent coil and springs at each wheel.
- Center Single leaf spring and swing axle.
- Type Mechanical front and rear simultaneous operated.
- Steering ratio 24:1
- Turning radius 29 ft (8.8 m)
- Cargo / personnel (eight troops) carrier
- Communications (separate shelter installed in the cargo compartment)
- Mortar carrier
- Radar (counter-mortar / artillery system)
- Radar (FAAR System)
- Ambulance (M792)
- Carolinas Aviation Museum - Fully restored and in running condition - currently in storage.
- Mexican Navy - In service
- Fort Snelling Military Museum - M561 & M792 Both restored and in running condition.
- Muckleburgh Collection - Running condition, available for visitor rides.
- Military Museum of North Florida - Running condition, recently restored, and on display.
- U.S. Space & Rocket Center - Two on display on facility.
- In Stripes, several Gama-Goats are used as stand-ins for Soviet vehicles due to their "foreign" look. Bill Murray drives one up to a Soviet base in Czechoslovakia dressed as a Soviet soldier to rescue his friends from captivity.
- In McHale's Navy, several Gama Goats are seen driving back and forth in the terrorists' compound.
- Movies showing brief views or scenes featuring Gama Goats:
- SNL G874
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