In the United States, a commercial driver's license is required to drive any type of commercial vehicle weighing 26,001 lb (11,794 kg) or more. In 2006 the US trucking industry employed 1.8 million drivers of heavy trucks.
The basics of all trucks are not difficult, as they share common construction.They are generally made of chassis, a cab, an area for placing cargo or equipment, axles, suspension, road wheels, and engine and a drive train. Pneumatic, hydraulic, water, and electrical systems may also be present. Many also tow one or more trailers or semi-trailers, which also vary inmultipleways but are similar as well.
Unfortunately for the trucking industry, their image began to crumble during the latter part of the 20th century. As a result, their reputation suffered. More recently truckers havebeen portrayedas chauvinists or even worse, serial killers.The portrayals of semi-trailer trucks have focused on stories of the trucks becoming self-aware. Generally, this is with some extraterrestrial help.
The rise of technological development gave rise to the modern trucking industry.There a few factors supporting this spike in the industry such as the advent of the gas-powered internal combustion engine.Improvement in transmissions is yet another source,justlike the move away from chain drives to gear drives. And of course the development of the tractor/semi-trailer combination.
The first state weight limits for truckswere determinedand put in place in 1913.Only four states limited truck weights, from a low of 18,000 pounds (8,200 kg) in Maine to a high of 28,000 pounds (13,000 kg) in Massachusetts. The intention of these laws was to protect the earth and gravel-surfaced roads. In this case, particular damages due to the iron and solid rubber wheels of early trucks. By 1914 there were almost 100,000 trucks on America's roads.As a result of solid tires, poor rural roads, and amaximumspeed of 15 miles per hour (24km/h) continued to limit the use of these trucks tomostlyurban areas.
In order toload or unloadbotsand other cargo to and from a trailer, trailer winchesare designedfor this purpose. They consist of a ratchet mechanism and cable. The handle on the ratchet mechanism is then turned to tighten or loosen the tension on the winch cable. Trailer winches vary, some are manual while othersare motorized. Trailer winches are mosttypicallyfound on the front of the trailer by towing an A-frame.