4x4, 4WD or QuadTrac is a vehicle with a drive that allows the engine torque all four wheels at the same time. It simultaneously feeding all 4 wheels to ensure that the vehicle is in better control of the road. The term describes the four more "truck-like" 4x4 cars where the driver can manually switch between the shipment on 2 wheels for the ordinary road or on 4-wheel traction for low values such as ice, snow, loose gravel, slippery surfaces or hills area.
When 2 wheels are driven simultaneously, the wheels rotate at different speeds when the car takes a turn. This problem is even greater when all four wheels driving. A designer who does not mind this ensures that the 4x4 cars do not behave well in curves because the wheels tend to get slip.
A differential ensures that an axle, 2 axes with different speeds heading. The differential distributes the torque evenly, while distributing the angular velocity (running speed) is equal to the average of the two axes. Each drive shaft required to power a difference between the left and right sides to distribute. When all four wheels are driven, third differential can be used to the torque between the front axle and rear axles to distribute.
The true inventor of fourwheel drive is not known. In 1893, before the creation of the modern automotive industry, the English engineer Joeseph Bramah Diplock patented a four-drive system for a tractor, including a four-wheel steering direction and three differentials, which later were actually built. Ferdinand Porsche designed and built a four-driven electric vehicle for the Hofwagenfabrik "Ludwig Lohner & Co." in Vienna in 1899. This vehicle was presented to the public during the World Exhibition of 1900 in Paris. The vehicle was driven by an electric hubmotor at each wheel. Although clumsy and heavy, the vehicle proved to be a powerful sprinter. Unfortunately for Ferdinand, the world did not recognized this as the first four wheel driven car. In 1903 the Dutch brothers Jacobus and Hendrik-Jan Spijker from Amsterdam presented the 60 HP Spyker, the first four wheel drive car with internal combustion engine. This 2-seater sports car, which also was the first car with six cylinders ever, is now exhibited at the National Automobile Museum in Raamsdonksveer, Netherlands.
Any self-respecting car manufacturer will bring a 4WD / 4x4 car on the market. Very well-known brands are the Jeep and Land Rover, but also the 4WD Toyota and the Mercedes Benz, BMW, etc. still doing good business.