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Off-road vehicle

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File: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. It is generally characterized by having large Tire with deep, open treads and a flexible Suspension (vehicle), or even Caterpillar track. Other vehicles that do not travel public streets or highways are generally termed off-highway vehicles, which would include Tractors, Forklifts, Crane (machine)s, Backhoes, Bulldozers and Golf carts.

Off-road vehicles have an enthusiastic following because of their many uses and versatility. Several types of Motorsports involve racing off-road vehicles. The three largest "4 wheel vehicle" off-road types of competitions are Rally, Desert Racing, and Rockcrawling. The three largest types of All Terrain Vehicle (ATV) / Motorcycle competitions are Motocross, Enduro, and also Desert Racing like Dakar Rallye and Baja 1000. The most common use of these vehicles is for Sight seeing in areas distant from Pavement (material). The use of higher clearance and higher traction vehicles enables access on Trail and Forest roads that have rough and low traction surfaces.

HistoryEdit

File:Kegresse tsar17.jpg
Nicholas II' Delaunay-Belleville 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 Tsar Nicholas II of Russia between 1906 and 1916. The system uses an unusual Caterpillar track which uses 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. Conventional front wheels and steering are used.

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.

After World War II a huge surplus of light off-road vehicles like the Jeep and heavier lorries were available on the market. The Jeeps in particular were popular with buyers who used them as Utility vehicles. This was also the start of off-roading 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, Datsun/Nissan, and Japanese Toyota and Mitsubishi. These were all alike; small, compact four wheel drives with at most a small hardtop to protect the occupants from the elements.

From the 1960s more comfortable vehicles, later called SUVs, were produced. First they were popular for many years with rural buyers due to their off-road and load-lugging capabilities. The U.S. Jeep and the Ford Bronco, the British Range Rover and the Station wagon-bodied Japanese Toyota were early SUV examples, essentially a station wagon body on a Light truck frame with Four wheel drive Drivetrain.

TechnicalEdit

File: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 not to sink in 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 to not lose traction.

Wheeled vehicles accomplish this by having a suitable balance of large or additional tires and tall and flexible suspension.

Tracked vehicles accomplish this by having wide tracks and a flexible suspension on the road wheels.

The choice of wheels versus tracks are one of cost and suitability. A tracked drivetrain is more expensive and costly in terms of maintenance. Wheeled drivetrains are cheaper and give a higher top speed. For pure off-road capabilites the tracked drivetrain has the edge.

Most off-road vehicles are fitted with especially low gearing. This allows the operator to make the most of the Engine's Power (physics), while moving through challenging terrain slowly. A Combustion engine coupled to a normal low gearing often has a too high output speed to be usable. 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 has a Torque converter to further reduce the gearing .

Common off-road vehiclesEdit

File:Offroad Jeep 05760 2.jpg
Jeep in action

Common commercial off-road vehicles include four wheel drive Pickup trucks like the Chevrolet Silverado, Ford F-Series, GMC Sierra, Toyota, Dodge Ram and similar. Also common are light trucks with Station wagon-like bodies, which have been very popular since the 1980s. These include Chevrolet Blazer, Dodge Ram, Ford Bronco, Jeep, International Scout, Land Rover, Land Rover and Range Rover and Toyota's Toyota and Toyota.

A number of Military vehicle have also seen civilian use, including the Jeep and AM General Hummer. Some, like the early Land Rovers, were adapted to military use from civilian specifications.

Specialised commonly available off-road vehicles include ATVs, or All Terrain Vehicles, Dirt bikes, dune buggies, rock crawlers and Sandrails.

Commercial, military and less common off-road vehiclesEdit

European militaries and utilities have used Land Rovers, Haflingers, Pinzgauers and Mercedes-Benz Unimogs for all-terrain transportation. Less common is the Portuguese UMM Alter.

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

Criticism of Off-Road VehiclesEdit

SafetyEdit

SUVs are built with higher ground clearance for Off-roading use and have a higher center of gravity, therefore increasing the risk of rollover. Research has shown that whenever an SUV turns, the vehicles mass resists the turn and carries the weight forward 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.

Pickup truck and SUVs are more likely to be in rollover accident than passenger cars. Pickups have twice the fatality rate of cars and SUVs have nearly triple the fatality rate in rollover accidents. Of vehicles in the US, Light trucks (includes SUVs) represent 36 percent of all registered vehicles. They are involved in about half of the fatal two-vehicle crashes with passenger cars, 80 percent of these fatalities are to occupants of the passenger cars. Trails and off trail activities impact the natural vegetation and wildlife leading to Erosion and Invasive species, Habitat loss, and Species loss, which decreases the environment's ability to maintain Homeostasis. ORVs cause greater stress to the environment that foot traffic alone. Some ORVs operators like to test themselves and their vehicles against natural obstacles and do significantly more damage then driving the established Trail. Most operators stay on designated areas but some who do not cause severe damage. Illegal use of off-road vehicles (ORV) has been identified as a serious Land management problem ranked with dumping garbage and other forms of Vandalism. Many user organizations publish and encourage appropriate Trail some of the more active are Tread Lightly and Sierra Club. In 30 years the number of U.S. ORV users has climbed sevenfold- from five million in 1972 to 36 million in 2000. In 2002, the U.S. EPA 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."

See alsoEdit

  • Amphibious vehicle
  • Off highway vehicle
  • Off road park
  • Off roading
  • Tread Lightly
  • Ramp travel index
  • SUVs

ReferencesEdit

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