The XR311 was a prototype military vehicle of US origin that was procured in limited numbers during the

1970s File:1970s decade montage.jpg, Clockwise from top left: U.S. President Richard Nixon doing the V for Victory sign after his resignation from office following the Watergate scandal in 1974; The United States was still involved in the Vietnam War ...

. It was originally developed as the ''High Mobility Combat Vehicle'', or HMCV (not to be confused with the

JGSDF The Japan Ground Self-Defense Force ( ja, 陸上自衛隊, Rikujō Jieitai), , also referred to as the Japanese Army, is the land warfare branch of the Japan Self-Defense Forces. Created on July 1, 1954, it is the largest of the three service b ...

MCV, which was also called the "HMCV" for a short time).

Development

Development of the XR311 commenced as a private venture in 1969, with the first of two prototypes being completed in 1970. The vehicle was developed as a possible replacement for the by that time over ten years old M151 jeep, years prior to the

Lamborghini Cheetah The Lamborghini Cheetah was an off-road prototype built in 1977 by the Italian carmaker Lamborghini. History The Lamborghini Cheetah was Lamborghini's first attempt at an off-road vehicle. It was built on contract from Mobility Technology Inter ...

and other competitors, including

AM General AM General is an American heavy vehicle and contract automotive manufacturer based in South Bend, Indiana. It is best known for the civilian Hummer and the military Humvee that are assembled in Mishawaka, Indiana. For a relatively brief period, ...

's design for the HMMWV, which was eventually selected. As a result of the trials of these two prototypes the

US Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...

purchased ten improved or second generation models in 1971. Of these ten vehicles, four had a

TOW missile The BGM-71 TOW ("Tube-launched, Optically tracked, Wire-guided") is an American anti-tank missile. TOW replaced much smaller missiles like the SS.10 and ENTAC, offering roughly twice the effective range, a more powerful warhead, and a greatly ...

installation for use in the anti-tank/AFV role, three had an M2HB machine-gun for use in the reconnaissance role and three had 7.62mm M60 machine guns and the crew armor kit for use in the escort/security role. These trials were completed in 1972. They were then tested by the 2nd Armored Division. In 1974 they were also tested in the 2nd Armored Reconnaissance Scout Vehicle competition along with a number of vehicles including the original

FMC Technologies FMC Technologies, Inc. was a North American company that produced equipment for exploration and production of hydrocarbons. FMC Technologies was incorporated in 2000 when FMC Corporation divested its machinery businesses. It exists today as a par ...

and Lockheed Martin designs. It has been stated that an XR311 with

installation cost around $50,000. The XR311 was designed to carry out a wide variety of roles including anti-tank, reconnaissance patrol, convoy escort,

command and control Command and control (abbr. C2) is a "set of organizational and technical attributes and processes ... hatemploys human, physical, and information resources to solve problems and accomplish missions" to achieve the goals of an organization or en ...

, medivac,

military police Military police (MP) are law enforcement agencies connected with, or part of, the military of a state. In wartime operations, the military police may support the main fighting force with force protection, convoy security, screening, rear rec ...

, mortar carrier, internal security and forward air defense communications vehicle.

Variants

There were several models of the XR311: * Support: A 106 mm Recoilless rifle mounted above the crew compartment, and a total of six rounds of ammunition, * Anti-tank: TOW installation with a total of 10 TOW missiles * Reconnaissance: Fitted with a ring-mounted .50cal M2HB machine gun with a 360 degree traverse * Convoy Escort/ Security Vehicle: This could be provided with a pintle-mount 5.56mm or 7.62 mm

GPMG A general-purpose machine gun (GPMG) is an air-cooled, usually ammunition belt, belt-fed machine gun that can be adapted flexibly to various tactical roles for light machine gun, light and medium machine guns. A GPMG typically features a quick-c ...

's,

XM174 The XM174 is a mounted automatic 40mm grenade launcher heavily based on the M1919A4 machine gun and the M79 grenade launcher, but fed from an ammo can. It was used in the Vietnam War as a tripod mounted crew-served weapon and as a weapon mounted ...

automatic grenade launcher An automatic grenade launcher (AGL) or grenade machine gun is a grenade launcher that is capable of fully automatic fire, and is typically loaded with either an ammunition belt or magazine. These weapons are often mounted on vehicles or helicopt ...

s and various other similar weapons. These weapons could also be mounted on the reconnaissance model on the ring mount. The following kits were available for the basic vehicle: crew compartment armor kit, consisting of a high-hardness steel doors, side body panels, toe panel, firewall, bulletproof windshield and bulletproof side windows, armored radiator, armored fuel tank, top and door kit (waterproof fabric with plastic windows and hinged doors) various communications installations, high output alternators (100 and 180 amp), litter-carrying kit, jump seat for two additional passengers, explosion-resistant reticulated foam fuel-tank filler,

radial tire A radial tire (more properly, a radial-ply tire) is a particular design of vehicular tire. In this design, the cord plies are arranged at 90 degrees to the direction of travel, or radially (from the center of the tire). Radial tire construction ...

s or foam-filled run-flat tires, extreme climate kits for winterization or desert temperatures, tool kit and portable

fire extinguisher A fire extinguisher is a handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies. It is not intended for use on an out-of-control fire, such as one which ha ...

Overview

The XR311 is built around a tubular-steel frame safety roll-cage which protects the passenger compartment if the vehicle rolls over. This cage is covered by a heavy-gauge sheet metal forming the skin of the vehicle. An internally mounted electrical extraction winch with a capacity of can be mounted at the front of the vehicle if required, and the 2-piece windshield can be removed to provide greater visibility and protect from flying glass fragments. The glass halves are stored in a mounting bracket on the hood until needed again. The passenger compartment is in the center of the vehicle with the driver on the left and the passenger seat to the right. There is space for of cargo behind the passenger seats. The engine and transmission are at the rear of the hull and there is an external load-carrying platform above this which can take a maximum load of . The minimum ground clearance is 11 inches, and a full length skid pan protects the hull and drivetrain, which allows the vehicle to slide over obstacles. The transmission is a Chrysler A-727 "

TorqueFlite TorqueFlite (also seen as Torqueflite) is the trademarked name of Chrysler Corporation's automatic transmissions, starting with the three-speed unit introduced late in the 1956 model year as a successor to Chrysler's two-speed PowerFlite. In t ...

torque converter A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power ...

automatic, with three forward and one reverse gears. The XR311 is a full-time 4WD vehicle. "Trak-lok" limited-slip differentials with a 5.89:1 drive ratio are used front and rear, and a lockable center differential ensures traction to all wheels. The fully independent suspension uses modified Dana 44 centersections, and used many off the shelf parts from the

front wheel drive Front-wheel drive (FWD) is a form of engine and transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitu ...

Oldsmobile Toronado The Oldsmobile Toronado is a personal luxury car manufactured and marketed by the Oldsmobile division of General Motors from 1966 to 1992 over four generations. The Toronado was noted for its transaxle version of GM's Turbo-Hydramatic transmissio ...

Cadillac Eldorado The Cadillac Eldorado is a luxury car manufactured and marketed by Cadillac from 1952 until 2002 over twelve generations. The Eldorado was at or near the top of the Cadillac line. The original 1953 Eldorado convertible and the Eldorado Brougham ...

(e.g., CV joints and boots, spindle and bearings, and 11 inch disk brakes), and is of a

double-wishbone A double wishbone suspension is an independent suspension design for automobiles using two (occasionally parallel) wishbone-shaped arms to locate the wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the knuckl ...

design with a

torsion-bar A torsion bar suspension, also known as a torsion spring suspension, is any vehicle suspension that uses a torsion bar as its main weight-bearing spring. One end of a long metal bar is attached firmly to the vehicle chassis; the opposite end term ...

spring and hydraulic telescopic shock absorber at each station. A stabilizer bar is provided for the rear suspension to limit body roll. Maximum speed is 80-90 mph for vehicles with the 318ci engine, dropping to 67 mph at full load. Acceleration was 12 seconds 0-60 mph time, falling to 10 seconds with the 360ci engine. The steering is power-assisted and the

tubeless tire Tubeless tires ( also spelled as tubeless tyres in Commonwealth English) are pneumatic tires that do not require a separate inner tube. Unlike pneumatic tires which use a separate inner tube, tubeless tires have continuous ribs molded integra ...

s feature a special high-pressure inner tire tube, which provides a built-in backup in case air pressure is lost from the main tire itself, as well as providing lateral support to eliminate leakage from the

tire bead Tire bead is the term for the edge of a tire that sits on the wheel. Wheels for automobiles, bicycles, etc. are made with a small slot or groove into which the tire bead sits. When the tire is properly inflated, the air pressure within the tire ...

during high speed cornering. The tires are self-cleaning, meaning mud and other materials are flung free from the tread grooves by centrifugal force, rather than sticking to the tire (more commonly known as a "mud tire"). Disc brakes are fitted on all four wheels. The electrical system is 24V DC, and two batteries with a capacity of 45 Amp/Hr are provided. The alternator is of the integral rectifier and regulator type. The XR311 is provided with a heavy duty towing pintle as well as a trailer wiring harness receptacle. It is air-transportable and can be air-dropped.

References

{{reflist

External Links

The XR311 Story, a Prototype of the Military Hummer , Wayback Machine

* http://svsm.org/gallery/xr311

February 2013 Backward Glances - MotorTrend

FMC XR311 patent US3709314

FMC XR311 patent US3858901
Military vehicles of the United States All-wheel-drive vehicles Off-road vehicles Military light utility vehicles FMC Corporation

Development

Variants

Overview

See also

References

External Links