Off-road vehicle

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Mercedes-Benz Unimog in the Dunes of Erg Chebbi in Morocco. Note the high ground clearance due to portal gear axles. S404-300TDI-erg-chebbi.jpg
Mercedes-Benz Unimog in the Dunes of Erg Chebbi in Morocco. Note the high ground clearance due to portal gear axles.

An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. [1] It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks.[ citation needed ] Other vehicles that do not travel public streets or highways are generally termed off-highway vehicles, including tractors, forklifts, cranes, backhoes, bulldozers, and golf carts.[ citation needed ]

Contents

Off-road vehicles have an enthusiastic following because of their versatility. Several types of motorsports involve racing off-road vehicles. The most common use of these vehicles is for sight seeing in areas distant from pavement. The use of higher clearance and higher traction vehicles enables access on trails and forest roads that have rough and low traction surfaces.

History

Nicholas II's Packard Twin-6 with Kegresse track Kegresse tsar17.jpg
Nicholas II's Packard Twin-6 with Kégresse track

One of the first modified off-road vehicles was the Kégresse track, a conversion undertaken first by Adolphe Kégresse, who designed the original while working for Czar Nicholas II of Russia between 1906 and 1916. [2] The system uses an unusual caterpillar track which has a flexible belt rather than interlocking metal segments. It can be fitted to a conventional car or truck to turn it into a half-track suitable for use over rough or soft ground.

After the Russian Revolution of 1917, Kégresse returned to his native France where the system was used on Citroën cars between 1921 and 1937 for off-road and military vehicles. The Citroën company sponsored several overland expeditions with their vehicles crossing North Africa and Central Asia.

A huge wheeled vehicle designed from 1937 to 1939 under the direction of Thomas Poulter called Antarctic Snow Cruiser was intended to facilitate transport in the Antarctica. While having several innovative features, it generally failed to operate as hoped under the difficult conditions, and was eventually abandoned in Antarctica.

After World War II, a huge surplus of light off-road vehicles like the Jeep and heavier lorries were available on the market.[ citation needed ] The Jeeps in particular were popular with buyers who used them as utility vehicles. This was also the start of offroading as a hobby. The wartime Jeeps soon wore out, though, and the Jeep company started to produce civilian derivatives, closely followed by similar vehicles from British Land Rover and Japanese Toyota, Datsun/Nissan, Suzuki, and Mitsubishi. These were all alike: small, compact, four-wheel-drive vehicles with at most a small hardtop to protect the occupants from the elements.[ citation needed ]

From the 1960s and onward, more comfortable vehicles were produced.[ citation needed ] For several years they were popular with rural buyers due to their off-road and load-lugging capabilities.[ citation needed ] The U.S. Jeep Wagoneer and the Ford Bronco, the British Range Rover, and the station wagon-bodied Japanese Toyota Land Cruiser, Nissan Patrol and Suzuki Lj's series were all essentially just station wagon bodies on light truck frames with four-wheel-drive drivetrains. Later, during the 1990s, manufacturers started to add even more luxuries to bring those off-road vehicles on par with regular cars. This eventually evolved into what we call the SUV today. It also evolved into the newer crossover vehicle, where utility and off-road capability was sacrificed for better on-road handling and luxury.

Technical

Swedish Hagglunds Bv206 with wide rubber tracks US 5055th Range Squadron M973 SUSV.jpg
Swedish Hägglunds Bv206 with wide rubber tracks

To be able to drive off the pavement, off-road vehicles need several characteristics: They need to have a low ground pressure, so as not to sink into soft ground, they need ground clearance to not get hung up on obstacles, and they need to keep their wheels or tracks on the ground so as not to lose traction. Wheeled vehicles accomplish this by having a suitable balance of large or additional tires combined with tall and flexible suspension. Tracked vehicles accomplish this by having wide tracks and a flexible suspension on the road wheels.

Russian GAZ-34039 (ru) GT-SM at Vankorskoe oilfield.jpg
Russian GAZ-34039 (ru)

The choice of wheels versus tracks is one of cost and suitability. A tracked drivetrain is more expensive to produce and maintain. Wheeled drivetrains are cheaper and give a higher top speed. The tracked drivetrain has greater off-road capability.

Tires play a significant role for any off-road vehicle equipped with wheels, as they ensure optimal traction required to keep it moving. The off-road tire tread types vary depending on the terrain type. The most common types of off-road tires are A/T (stands for "All Terrain") and M/T (stands for "Mud Terrain"). While the A/T tires perform excellently on the sand, they are barely usable in the mud. There are also unique Sand Blaster and Mud bogging tires used for the most challenging terrains such as dirt, sand and even water to maintain traction at extreme angles and high speeds (off-road motorsport). [3]

Most off-road vehicles are fitted with especially low gearing. This allows the operator to make the most of the engine's available power while moving slowly through challenging terrain. An internal combustion engine coupled to a normal gearbox often has an output speed too high. The vehicle often has one of two things, either a very low ("granny") first gear (like the all wheel drive Volkswagen Transporter versions) or an additional gearbox in line with the first, called a reduction drive. Some vehicles, like the Bv206 in the picture on the right, also have torque converters to further reduce the gearing.[ citation needed ]

Many wheeled off-road vehicles provide power to all wheels to keep traction on slippery surfaces. For a typical four-wheel vehicle this is known as four-wheel drive. Vehicles designed for use both on and off-road may be designed to be switched between two-wheel drive and four-wheel drive so that the vehicle uses fewer driven wheels when driven on the road.

Criticism of off-road vehicles

Safety

SUVs are built with higher ground clearance for off-road use and thus have a higher center of gravity, [4] therefore increasing the risk of rollover. When an SUV turns, the vehicle's mass resists the turn and carries the weight forward, thus allowing the traction from the tires to create a lateral centripetal force as the vehicle continues through the turn. The conflict between the top weight of the SUV's desire to go straight while the friction of the tires on the road cause the bottom of the vehicle to move away and out from under the vehicle during a turn.

SUVs are more likely to be in rollover accidents than passenger cars. According to a study conducted in the United States, SUVs have twice the fatality rate of cars and have nearly triple the fatality rate in rollover accidents. [5] Of vehicles in the United States, light trucks (including SUVs) represent 36 percent of all registered vehicles. They are involved in about half of the fatal two-vehicle crashes with passenger cars, and 80 percent of these fatalities are to occupants of the passenger cars. [5]

Environment

In the United States, the number of ORV users since 1972 has climbed sevenfold—from five million to 36 million in 2000. [6] Government policies that protect wilderness but also allow recreational ORV use have been the subject of some debate within the United States and other countries. [7]

All trail and off-trail activities impact natural vegetation and wildlife, which can lead to erosion, invasive species, habitat loss, and ultimately species loss [8] [9] [10] decreasing an ecosystem's ability to maintain homeostasis. [11] ORV's cause greater stress to the environment than foot traffic alone, and ORV operators who attempt to test their vehicles against natural obstacles can do significantly more damage than those who follow legal trails. [12] [13] Illegal use of off-road vehicles has been identified as a serious land management problem ranked with dumping garbage and other forms of vandalism. [14] Many user organizations, such as Tread Lightly! and the Sierra Club, publish and encourage appropriate trail ethics. [15]

ORVs have also been criticized for producing more pollution in areas that might normally have none. In addition to noise pollution that can cause hearing impairment and stress in wildlife, [16] according to the U.S. Forest Service, old-style two-stroke engines (no longer a component of new off-road vehicles, although some are still in use) "emit about 20 to 33 percent of the consumed fuel through the exhaust" and "discharge from two-stroke snowmobile engines can lead to indirect pollutant deposition into the top layer of snow and subsequently into the associated surface and ground water." [17] [18] In 2002, the United States Environmental Protection Agency adopted emissions standards for all-terrain vehicles that "when fully implemented in 2012... are expected to prevent the release of more than two million tons of air pollution each year—the equivalent of removing the pollution from more than 32 million cars every year." [19] [20]

Common off-road vehicles

Common[ where? ] commercial off-road vehicles include four-wheel-drive pickup trucks like the Ford F-Series, Chevrolet C/K, Dodge Ram, and Toyota Tacoma.[ quantify ] A number of military vehicles have also seen civilian use, including the Jeep CJ and the AM General Hummer. Some, like the early Land Rovers, were adapted to military use from civilian specifications. Specialised commonly available[ where? ] off-road vehicles include ATVs (All Terrain Vehicles), dirt bikes, dune buggies, rock crawlers, and sandrails.

All-terrain vehicle

The ATV is commonly called a four-wheeler in Australia, New Zealand, South Africa, the United Kingdom and parts of Canada, India and the United States. They are used extensively in agriculture, because of their speed and light footprint. Four wheeler.jpg
The ATV is commonly called a four-wheeler in Australia, New Zealand, South Africa, the United Kingdom and parts of Canada, India and the United States. They are used extensively in agriculture, because of their speed and light footprint.

An all-terrain vehicle (ATV), also known as a quad, quad bike, three-wheeler, or four-wheeler, or RZR is defined by the American National Standards Institute (ANSI) as a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles. Although it is a street-legal vehicle in some countries, it is not street-legal within most states and provinces of Australia, the United States or Canada.[ citation needed ].

UTV (Utility Vehicle) is very similar to ATV.

Off-road motorcycle

There are various types of off-road motorcycles, also known as dirt bikes, specially designed for off-road events. Compared to road-going motorcycles, off-road machines are simpler and lighter, having long suspension travel, high ground clearance, and rugged construction with little bodywork and no fairings for less damage in spills. Wheels (usually 21" front, 18" rear) have knobby tires, often clamped to the rim with a rim lock.[ citation needed ]

Commercial, military and less common off-road vehicles

European militaries and utilities have used Land Rover Defenders, Haflingers, Pinzgauers, Volvo L3314, and Mercedes-Benz Unimogs for all-terrain transportation. The Portuguese UMM Alter is less common.[ citation needed ]

The military market for off-road vehicles used to be large, but, since the fall of the Iron Curtain in the 1990s, it has dried up to some extent. The U.S. jeeps, developed during World War II, coined the word many people use for any type of light off-road vehicle. In the U.S., the Jeeps' successor from the mid 1980s was the AM General HMMWV series. The Red Army used the GAZ-61 and GAZ-64 during World War II. The Eastern Bloc used the GAZ-69 and UAZ-469 in similar roles.

See also

Related Research Articles

Sport utility vehicle Type of automobile

A sport utility vehicle or SUV is a car classification that combines elements of road-going passenger cars with features from off-road vehicles, such as raised ground clearance and four-wheel drive.

All-terrain vehicle Light off-road vehicle

An all-terrain vehicle (ATV), also known as a light utility vehicle (LUV), a quad bike, or simply a quad, as defined by the American National Standards Institute (ANSI); is a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles. Although it is a street-legal vehicle in some countries, it is not street-legal within most states, territories, and provinces of Australia, the United States or Canada.

Electronic stability control Computerized safety automotive technology

Electronic stability control (ESC), also referred to as electronic stability program (ESP) or dynamic stability control (DSC), is a computerized technology that improves a vehicle's stability by detecting and reducing loss of traction (skidding). When ESC detects loss of steering control, it automatically applies the brakes to help steer the vehicle where the driver intends to go. Braking is automatically applied to wheels individually, such as the outer front wheel to counter oversteer, or the inner rear wheel to counter understeer. Some ESC systems also reduce engine power until control is regained. ESC does not improve a vehicle's cornering performance; instead, it helps reduce the chance of the driver losing control of the vehicle.

Four-wheel drive Type of drivetrain with four driven wheels

Four-wheel drive, also called 4x4 or 4WD, refers to a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges.

Ford Explorer Range of SUVs manufactured by Ford Motor Company

The Ford Explorer is a range of SUVs manufactured by Ford Motor Company since the 1991 model year. The first four-door SUV produced by Ford, the Explorer was introduced as a replacement for the two-door Bronco II. Within the current Ford light truck range, the Explorer is slotted between the Ford Edge and Ford Expedition. As with the Ford Ranger, the Explorer derives its name from a trim package previously offered on the Ford F-Series pickup trucks.

Automobile handling and vehicle handling are descriptions of the way a wheeled vehicle responds and reacts to the inputs of a driver, as well as how it moves along a track or road. It is commonly judged by how a vehicle performs particularly during cornering, acceleration, and braking as well as on the vehicle's directional stability when moving in steady state condition.

Transfer case

A transfer case is a part of the drivetrain of four-wheel-drive, all-wheel-drive, and other multiple powered axle vehicles. The transfer case transfers power from the transmission to the front and rear axles by means of drive shafts. It also synchronizes the difference between the rotation of the front and rear wheels, and may contain one or more sets of low range gears for off-road use.

Locking differential Forcing two transaxial wheels to spin together

A locking differential is designed to overcome the chief limitation of a standard open differential by essentially "locking" both wheels on an axle together as if on a common shaft. This forces both wheels to turn in unison, regardless of the traction available to either wheel individually.

Weight transfer

Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects:

Off-roading Activity of driving on unsurfaced roads or tracks

Off-roading is the activity of driving or riding a vehicle on unsurfaced roads or tracks, made of materials such as sand, gravel, riverbeds, mud, snow, rocks, and other natural terrain. Types of off-roading range in intensity, from leisure drives with unmodified vehicles to competitions with customized vehicles and professional drivers. Off-roaders have been met with criticism for the environmental damage caused by their vehicles. There have also been extensive debates over the role of government in regulating the sport, including a Supreme Court case brought against the Bureau of Land Management.

Vehicle rollover Car accident in which the vehicle tips or rolls over

A rollover is a type of vehicle crash in which a vehicle tips over onto its side or roof. Rollovers have a higher fatality rate than other types of vehicle collisions.

Ford Bronco American sport-utility vehicle

The Ford Bronco is a model line of sport utility vehicles manufactured and marketed by Ford. The first SUV model developed by the company, five generations of the Bronco were sold from the 1966 to 1996 model years; a sixth generation of the model line is an upcoming vehicle to be sold for the 2021 model year. The nameplate has been used on other Ford SUVs, including the 1984-1990 Ford Bronco II compact SUV and the Ford Bronco Sport compact CUV.

Toyota FJ Cruiser Motor vehicle

The Toyota FJ Cruiser is a retro style, mid-size SUV. Introduced as a concept car at the January 2003 North American International Auto Show, the FJ Cruiser was approved for production after positive consumer response and debuted at the January 2005 North American International Auto Show in final production form.

Drive wheel

A drive wheel is a wheel of a motor vehicle that transmits force, transforming torque into tractive force from the tires to the road, causing the vehicle to move. The powertrain delivers enough torque to the wheel to overcome stationary forces, resulting in the vehicle moving forwards or backwards.

A beadlock or bead lock is a mechanical device that secures the bead of a tire to the wheel of a vehicle. Tires and wheels are designed so that when the tire is inflated, the tire pressure pushes the bead of the tire against the inside of the wheel rim so that the tire stays on the wheel and the two rotate together. In situations where tire pressure is insufficient to hold the bead of the tire in place, a beadlock is needed.

Jeep Patriot Motor vehicle

The Jeep Patriot (MK74) is a front-engine five-door compact crossover SUV manufactured and marketed by Jeep, having debuted with the Jeep Compass in April 2006 at the New York Auto Show for the 2007 model year. Both cars, as well as Dodge Caliber shared the GS platform, differentiated by their styling and marketing, with the Patriot exclusively offering a four-wheel drive system, marketed as Freedom Drive II.

Jeep uses a variety of four-wheel drive systems on their vehicles. These range from basic part-time systems that require the driver to move a control lever to send power to four wheels, to permanent four-wheel systems that monitor and sense traction needs at all four wheels automatically under all conditions.

Spare tire

A spare tire is an additional tire carried in a motor vehicle as a replacement for one that goes flat, has a blowout, or has another emergency. Spare tire is generally a misnomer, as almost all vehicles actually carry an entire wheel with a tire mounted on it as a spare rather than just a tire, as fitting a tire to a wheel would require a motorist to carry additional, specialized equipment. However, some spare tires are not meant to be driven long distances. Space-savers have a maximum speed of around 50 mph (80 km/h).

Front-engine, four-wheel-drive layout

In automotive design, an F4, or front-engine, four-wheel drive (4WD) layout places the internal combustion engine at the front of the vehicle and drives all four roadwheels. This layout is typically chosen for better control on many surfaces, and is an important part of rally racing, as well as off-road driving. In terms of racing purposes, whether it be on-road or off-road, can be described as followed, "A team that pursues the Weak LS4WD architecture will minimize the development cost of the front-wheel drive system at the expense of having a larger rear powertrain. The Weak architecture produces a vehicle with a large powersplit between the front and rear powertrains, while the Strong architecture recommends a vehicle with more similar power and torque requirements for the front and rear."

All-wheel drive

An all-wheel drive vehicle is one with a powertrain capable of providing power to all its wheels, whether full-time or on-demand.

References

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