Semi-truck tractors are by far the most popular motive power used by truckers carrying large loads across the USA. These mighty beasts have earned an important place in American road culture. In many ways, the USA is a country dominated by its relationship with roads and road-faring people. The semi-truck, the muscle car, and the motorbike all hold special symbolic significance in this environment.
This article is a very quick guide to some of the components that all semi-trucks share.
One of the most obvious differences between American semi-trucks and their European equivalents is the inclusion of a large sleeper cabin that sits behind the driver’s cab. The reason for this inclusion is simple. The United States of America is vast, and much of the shipping work found on load boards like Shiply involves huge, multi-day journeys. Therefore, truckers need a good place to relax between shifts.
During these long trips, many truckers would rather call their trucks home instead of having to find and pay for a motel every night. A comfortable sleeper cabin is essential for any trucker that wants to have a true ‘home on the road’. Many owner-operators customize their sleeping cabins to make them more reflective of their own comfort levels. A sizable industry has developed around craftspeople that customize sleeper cabins for truckers looking for a more luxurious moving home.
While small non-commercial vehicles use brakes powered by hydraulic fluid, semi-trucks use air brakes. Hydraulic fluid can be lost in a leak and needs to be replaced regularly in commercially utilized vehicles. Air, however, can be compressed within the truck itself and is far more reliable for stopping heavy loads. An engine-mounted compressor distributes a flow of high-pressure air to chambers. When the driver compresses the brake pedal, the air is vented from these chambers into valves which actuate disc calipers and slow the truck down. Older semi-trucks sometimes have drum brakes instead of disc brakes. Instead of a caliper being forced onto a disc, brake shoes are actuated onto the inner edge of a drum that is securely fastened to the wheel.
The fifth wheel is not, as the name might suggest, a wheel. Instead, it is the connection that receives the kingpin of a trailer. The fifth wheel on most semi-trucks can be adjusted to compensate for unusual weights and load distributions, so that they can be articulated safely and efficiently. The correct coupling of a tractor and trailer can mean the difference between a safe ride and a disaster. Truckers need to learn how to calculate the correct coupling distance to use for each load so that they can adjust their fifth wheel accordingly before a journey.
Early trucks had chains that connected the engine to the driving axles. Chains were found to be less than ideal for high-speed driving, which led to the adoption of drive shafts. These cylinders efficiently transmit torque using a series of yokes.