If you want to make truck driving your career (and who wouldn’t?), you need to know everything there is to know about the vehicle you intend to drive. And although you may drive a number of different kinds of commercial motor vehicles (CMV) at any point throughout your career, there are some common terms that you need to know.
First we are going to start with the most basic terms. These are the terms most people will have heard of. In later Parts, we will delve deeper into certain aspects of these terms, but for now, let’s lay the groundwork.
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Tractor. Otherwise known as the truck, rig, or semi, the tractor is essentially the power unit that is used to pull a vehicle or series of vehicles, whether it is a trailer, semi-trailer, flatbed, tanker and so on. There are essentially two types of tractors in existence today, the conventional and cab-over-engine design.
Conventional. A conventional tractor is one where the vehicle cab is located behind the engine, which is under a hood at the front of the vehicle, much like a passenger car or truck. Conventional tractors are used in applications that require longer time in the vehicle.
Cab-over-engine: This layout is relatively self-explanatory. Here, the front of the tractor is flattened and the cab sits above the engine. These designs are used primarily for regional and city-based applications.
Once you have isolated the type of vehicle you will be driving, there are certain terms that will immediately come to mind. These terms will be used to describe other aspects of the vehicle later on.
- Steering axle: This is the front axle of the vehicle and is responsible for controlling the vehicles direction.
- Drive axle: This is the axle – or series of axles – that is powered and pulls the load.
- Tandem axle: An assembly of two axles, whether on the tractor or the trailer.
- Duals: A pair of wheels mounted together on the same side and axle.
Now that you understand how axles will be referred to, it’s time to move on to the other, most crucial part of the configuration.
Trailer. The cargo, in whatever form or configuration, is stored in the trailer and pulled behind the tractor, hence: tractor-trailer. There are two types of trailer configurations: full and semi.
- Full trailer: A full trailer will rest on its own axles and bear its own weight, independent of the towing vehicle.
- Semitrailer: The front of a semitrailer will rest on the fifth wheel of the tractor. When a semitrailer is disconnected from the tractor, it will generally rest on legs commonly referred to as ‘landing gear’.
So now you are probably wondering what a fifth wheel is. This is another very common term related to CMVs that doesn’t actually refer to a wheel, per se.
Fifth wheel. The fifth wheel is located at the rear of the tractor’s frame. It is the coupling device used to join the front of the trailer with the tractor. It can be best described as a flat metal plate with a notch in the middle in the shape of a “V”.
Although the setup is mainly referred to as a tractor-trailer, there is an official term for it, for which there are also subcategories, which we will get into later.
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Combination vehicle. This official term is what a trailer attached to a tractor is referred to. The subtypes of combination vehicles that we will get into later include:
- Rocky mountain double;
- Turnpike double;
- Triple trailers.
Now that you know the basic trucking terms, it’s time to dig a little deeper. Join us in Part II of our series when we delve into vehicle control systems.