​​Why is it called a semi-truck? (9 types)

In today’s article, we will discuss: ​​Why is it called a semi-truck? We will explain what a semi-truck is and the difference between a trailer and a semi-trailer truck. We will also review the types of semi-trucks. 

​​Why is it called a semi-truck?

A semi-truck is short for a semi-trailer truck, and it is called that way because its structure is composed of a semi-trailer for carrying the cargo and a semi-tractor for the engine power. 

The term semi-trailer derives from the fact that the vehicle unloads part of its weight on its axles and starts on the fifth wheel of the road tractor that pulls it; therefore, from a physical point of view, it is only half towed.

The semi-trailer is a vehicle without an engine intended to be towed by a road tractor with which, in combination, it forms a vehicle complex called an articulated lorry. Typically its construction is made of a frame with one or more wheel axles (the most common configuration is the 3-axle one), also twinned, located at the rear.

What are the types of semi-trucks?

There are currently nine types of semi-trucks categorised according to their purpose. We describe them in the table below. 

Purpose of the semi-truckDescriptionAdvice on use
For the transportation of bulk goodsThis semi-truck has a high load capacity.Quick and practical, the loading/unloading steps are done by tilting the vehicle’s rear or the side, using a jack.This model is perfect when loading times are long and is well suited for transporting waste.
For rear unloadingThe floor of this semi-trailer is made of aluminum slats. These blades move from the front to the rear of the vehicle, allowing cargo to be unloaded from the rear of the dumpster. Therefore, no tilting device is necessary. The moving floor enables the loading of bulk materials or pallets.If you want to transport bulk materials that can be unloaded from the vehicle’s rear, this body will be a great fit. It is ideal for transporting large volume products in agriculture or even wood.
For tall goodsThis semi-trailer is used when the goods to be transported are unlikely to be damaged under the effect of rain or unfavourable weather conditions. There are so-called “low-loaders” flatbed trailers.As its name suggests, it then has a lower part allowing the loading of high-rise parts such as industrial parts.
For long goodsThis body is ideal when the goods are particularly long. It can indeed lengthen by sliding or extension.This type of bodywork is ideal if the goods need to be protected but traditional tarpaulin is restrictive and time-consuming.
For great versatilityThis semi-truck consists of a platform already covered with sidewalls/posts and bars, this body can be completely dismantled, which avoids having to face the inconveniences associated with unblocking.If you transport a variety of goods, this type of body could be particularly suitable for you. 
For transporting liquidsCertain semi-trucks are used when transporting goods in the form of liquids, pearls or even granules. They can consist of a single tank or of several compartments.The loading is carried out above the truck. Unloading is done by compressor or tilting (using a jack and counting on gravity).
For refrigerated goodsIt is equipped with a refrigeration unit that lowers the temperature inside the vehicle body to reach -20 ° C when the outside temperature is + 30 ° C. 
Of course, it all depends on the body’s insulation, the power of the cooling device and the intended application. It can be used for transporting fruit and vegetables, for example.
It is important to check the temperature inside the refrigerated truck to ensure that the products will not deteriorate during transport (health risk in the event of thawing, for example).
For multimodal transportationIntended as its name suggests for the transport of containers, the container carrier is available in a version for heavy but not fragile goods (the platform semi-trailer) and in a “skeleton chassis semi-trailer” version.This body is well suited for multimodal transport and has the advantage of being able to accommodate a wide range of different goods.
Box trailersThis type of trailer or semi-trailer is intended to protect the goods transported thanks to its rigid walls. Watertight and fitted with tail lifts, some models are equipped with sliding panels for loading from the side.If the goods are likely to attract thieves, this type of trailer is a good protection solution, while remaining quite versatile in handling the goods transported.

What is the difference between a trailer and a semi-trailer truck?

The difference between a trailer and a semi-trailer is in the way they are built, their carrying capacity and their purpose of use. 

Thus, trailers are vehicles without an engine, which are towed or pulled by a tow vehicle (rigid truck). Semi-trailers are vehicles without an engine hooked or coupled on the 5th wheel of a tractor head resting part of its weight on it.

As we can remember, a trailer is a non-self-propelled vehicle that will need another to move. Semi-trailer: a non-self-propelled vehicle designed and conceived to be coupled to a car on which part of it will rest, transferring a substantial part of its mass to it.

In fact, the trailer and the semi-trailer are structures generally designed in the form of a closed, dry or refrigerated box. They are used to transport goods or equipment over long or short distances. The size of the trailer and the semi-trailer may vary, but must nevertheless comply with the standards of the law. Depending on their size, these types of trailers can be towed by a truck, with or without a berth.

We highlight more differences between trailers and semi-trailer trucks in the table below:

CriteriaTrailerSemi-trucks
Distinct structuresThe trailer can have two to four axles and is stable when unhitched. This must be paired with a bi-train semi-trailer, or a tractor truck to move. 
The trailer can be fixed or tilted, depending on its use.
The semi-truck, on the other hand, has wheels only at the rear of its structure. 
The tractor truck thus supports most of the semi-trailer’s weight thanks to a platform called a fifth wheel.
DimensionsStandard dimensions can be: Length: 28 to 53 foot. Width:96 to 102 inches. Height: 12.6 to 13.6 ftStandard dimensions can be:  Length: 48 – 53 feet Width: 8.5 feet Height: 13.5 feet (162 inches)
CouplingThe trailer must be attached to a carrier truck by means of a tow bar. This then locks to ensure safe transport. 
In order to prevent the cargo from shifting during transport and causing the trailer to sway, the load should be distributed evenly, depending on the weight.
The semi-trailer, for its part, is supported on a tractor truck thanks to a part called a fifth wheel. These can be fixed or adjustable, to better distribute the weight on the front and rear axles of the truck. 
This platform is located on the rear axle of the tractor truck and should be checked regularly to ensure that it is working properly. Since much of the weight of the semi-trailer rests on the tractor truck, the tractor must be sturdy and strong.

Conclusions

The standard semi-trailer truck is an 18-wheeler made up of three main components. These are the engine, the cab, and the trailer. The size of the truck requires the installation of three axles for smooth handling. A semi-truck is called that way for convenience. 

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FAQ on ​​Why is it called a semi-truck?

What wind speed can flip a semi?

Wind speed near 60 mph can flip a semi.  Driving in moderate to strong wind conditions can be very dangerous. It is even more so when it comes to bulky vehicles such as trucks, as they are more sensitive to crosswinds due to their size and shape.

What is the best brand of American trucks?

The motto of the Americans is “The bigger the truck, the better.” This can be seen perfectly reflected in the best American truck brands such as Kenworth, Mack, Freightliner, Western Star, Peterbilt or International Trucks.

What are straight trucks?

Straight trucks are also known as box trucks, and they are vehicles with fixed trailers.  They have all the amenities for passengers to travel comfortably. In addition, the rear box allows a greater load capacity than any trunk.

What are truck tractors?

A truck tractor is a set of vehicles made up of a tractor unit and a semi-trailer. What distinguishes a semi-trailer from a normal trailer is that these vehicles are designed to be coupled to the tractor.

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