What is a trailer?
To put simply, a trailer is an unpowered vehicle that is towed by a powered vehicle. It facilitates the transportation of goods all over the country. A semi-tractor-trailer truck is the combination of a tractor unit and one or more semi-trailers. The semi-trailer attaches to the tractor with a type of hitch called a fifth-wheel (quick release coupling device). The trailer can also be attached using a turntable hitch at the rear of the towing engine.
Note that the truck trailer cannot move by itself because it only has wheels at the rear end. It requires a forward axle, provided by the towing engine, to carry half the load weight.
Trailer Safety and CANbus
In the United States, the trailer lights mostly have a shared light for brake and turn indicators. Some vehicles can be fitted with Controller Area Network (CANbus) networks – which is a vehicle bus standard that allows microcontrollers and devices to communicate with each other’s applications without a host computer. The CANbus network is used to connect the tow bar electrics to various safety systems and controls. A separate wiring kit that can interact appropriately must be used for vehicles that use CANbus for activating towing-related safety systems. With the towbar wiring kit, the vehicle can detect the trailer and activate safety features such as trailer stability program.
Let us now look at the types of trailers and their uses.
Dry Van (Enclosed) Trailer
Dry Van is one of the most common type of trailer used in the United States. This type of trailer can be best explained as rectangular containers made of galvanized metal, packed and sealed from every side. Due to this nature, the Dry Van is regarded as a secure choice of trailer. It is mainly used to transport equipments and pallets of cargo. Dry Vans do not provide the flexibility of temperature control. Moreover, most Dry Vans have hardwood flooring that makes it prone to moisture if precautionary measures aren’t taken. Hence, this trailer is not an ideal option for hauling freight that contains perishable items. However, the nonperishable goods are protected from bad weather, theft, and other conditions.
It is an ideal choice for truckload as well as less-than-truckload (LTL) shipments. LTL shipping allows the shipper to only use part of the truck space. This makes it an economic option as it saves cost through shipment consolidation.
Models vary from double to triple axel. The dimensions of a typical dry van trailer are 53 ft. x 8 ft. 6 inches x 8 ft. 6 inches. The average weigh handling capacity of a Dry Van is approximately about 45,000 pounds or cargo of 26 standard pallets. Unlike the Flatbed trailers, oversized freight cannot be transported by this type of trailer.
Flat Beds, as the name suggests, this type of trailer is entirely flat. It has no roof or sides. The physical characteristics offer its advantages and disadvantages. It is easier to load freight on a Flat Bed trailer. The load is secured by manually using ropes. It does require skill and experience to be able to secure load on a Flat Bed. If not done properly, the load is susceptible to shed in transit. It is an ideal option for heavy loads that are not weather sensitive or delicate in nature.
The nature of this type of trailer doesn’t provide any security for loads. Flatbed are hence used in more specialized cargos like construction, light or abnormal loads like machinery, lumber loads, etc.
Typical dimension of a Flat Bed trailer ranges from 48 ft. to 53 ft. with a width of either 96 or 102 inches. On an average, a Flat Bed weighs around 32,000 lbs without any load and can carry average load of 24,200 Kilograms.
Also known as double-drop, the Lowboy trailers have two drops in deck height 1. Right after the gooseneck, 2. Right before the wheels. This helps in Lowboy trailers to be extremely low in comparison with other trailers. It also has permissible load capacity of up to 12 ft. tall (3.66 m), which other trailers don’t. Introduced first in 1920s, the Lowboy trailer featured a riveted gooseneck and solid rubber tires. In 1958, detachable goosenecks were introduced.
Lowboys are tall and wide and tend to be an ideal choice for transporting heavy equipment and machinery, such as excavators, bulldozers, and other large construction equipment. The maximum weight for a two-axle lowboy trailer is 40,000 pounds. This limit can be increased up to 80,000 pounds total weight of trailer and load (depending on the number of axles required). Dimensions of a typical Lowboy trailer would be length being 29 feet, width is 8.5 feet, and height as 11.5 feet.
Lowboy trailer is facilitates in hauling freights that exceed the legal height requirements of transportation by a Flat Bed trailer.
Refrigerated trailers or Reefers are primarily designed for hauling perishable items and other materials that needs to be stored at a specific temperature. The Reefers must not be confused with simple insulated or ventilated trailers that are used to transport commodities like fruits – these aren’t equipped with any cooling apparatus.
A Reefer can be ice-cooled, equipped with mechanical refrigeration, or utilize the carbon dioxide as a cooling agent. Mostly, the interiors have aluminum coating that helps in temperature control. Reefers used in the long-distance hauls are done in articulated trucks pulling refrigerated semi-trailers.
Some reefers are equipped with a water-cooling system. This can be used if the reefer is stored below deck on a vessel without adequate ventilation to remove the heat generated. Maximum dimensions for a Refrigerated trailer in the United States is: length 48 ft. – 53 ft., width 8 ft., and height 7.5 ft. The maximum load weight should always be lesser than 44,000 pounds.
At present, there are about 500,000 refrigerated trailers on the road in the USA.
Extendable Flatbed Trailers
As the name suggests, the flatbed trailers are extendable to an extent for appropriate placing and transporting longer and unevenly sized freight. Including all those characteristics of a flatbed trailer, the extension facilitates increased efficiency of the trailer. From long parts of windmills to heavy loads, the extendable feature helps in efficient handling and transportation. The minimum bearable weight of the extended trailers may vary. The average weight for the same is 43,000 pounds.
Dimensions of the extendable flatbed stretch trailers are 48 ft to 80 ft in length. The width is 8.5 ft and the permitted legal height for transportation is 8.5 ft. Axle quantity is 2 and spacing is approximately 49 inches.
With the best load-bearing and extendable feature, the product or the materials would not get damaged due to overhanging.
Step Deck Trailers – Single Drop Trailers
Similar to the Lowboy trailer, the Step Deck trailer is used to haul tall cargo that exceeds legal height limits when transported on other trailers. Step deck trailers have two decks: an upper, and a lower. Some step deck trailers also have ramp capabilities that makes it easier to load and unload equipment.
The trailer’s lower height allows forklifts to easily access cargo as they’re closer to the ground. Depending on the type of freight and loading/unloading needs, options can be fixed-neck, gooseneck, and removable gooseneck (RGN), etc. Fixed-neck trailers have limited options for loading and unloading. The RGNs can be loaded on either the front or back. The average dimensions of Step Deck trailers are measured as 48 ft. and 53 ft. These trailers contain a two-piece welded main beam that is about 28” long. The average minimum capacity of the Step Deck trailer is 50,000 lbs. These trailers weigh about 48000 lbs.
Moving heavier loads sometimes require extra permits. The larger and bigger the load, the more technical it gets when it comes to the hauls. The Removable Gooseneck Trailers, or RGN, carries the loads lower – which means the loads are held closer to the ground, allowing taller objects to be hauled easily. A RGN is also called as double lowboy or double drop trailer. It is an ideal choice of trailer to move large equipments.
The RGN trailer has a drop in the middle. It provides a margin for taller objects. The taller objects can be placed in this area – which is called as the well, and use the raised beds for equipment that isn’t too tall. The well is usually 29 feet long. Objects as tall as 12 feet can be placed in well without violating any rules and regulations about maximum heights.
The frontend of the RGN is detachable. It allows heavy equipment like a bulldozer to drive directly onto the trailer making loading and unloading quite convenient and fast.
As the name suggests, Specialty trailers are built for specific purposes. These are usually custom-built and are not available otherwise. The make and model of these trailers highly depend upon the purpose of the trailer. For example, trailer made for moving massive quantities of liquid will be different than a trailer built for medical equipment. These trailers usually require a special permit. The driver may also need to have a special license to be able to haul this type of trailer. The weight limit for specialty trailers can be as much as (approximately) 200,000 pounds.