Fifth Wheel

The fifth wheel is mounted over the rear axle of the truck-tractor. It has locking jaws in it center where the semi-trailer's kingpin fits. The fifth wheel assembly couples the truck-tractor and the semi-trailer. It serves as a pivot point between the units and supports the weight of the fron of the semi-trailer. The tractor (typically) hs 3 axles: One front (“steer” axle); 2 rear (“drive” axles) with a pair of dual wheels on each side. Most tractor configurations have 10 wheels. The trailer (typically) has 2 axles: 2 rear with a pair of dual wheels on each side, or 8 wheels on the trailer. Total length is 50 to 70 feet, with a typical weight limit 80,000 lbs.

Van Trailer

A van trailer is fully enclosed with a a permament top and sides to keep the inside of the trailer dry. At the rear is a large door which may swing opn or roll up. This trailer is primarily used for small non-palletized cargo, sensitive equipment, mail, and cargo that is weather sensitive. Dry vans are ubiquitous on Interstates throughout the US. When people think about trucking, the image that pops into their mind is most likely a dry van. Their purpose is to keep goods protected from the elements (hence the “dry” in the name) and shielded from road damage.

Typically constructed as a solid, enclosed box, a dry van can be loaded from the rear or, in some cases, from the side. Generally, a loading dock is needed to enable efficient loading and unloading. Rather than being a separate container loaded onto a flatbed trailer, the dry-van box is connected directly to the tractor and the truck operates as a single unit.

Highboy

The highboy, flatbed, or stake trailer [aka Kentucky trailer] is designed for cargo that cannot fit through the dooors of a van trailer. This type of trailer has removable side stakes. Side rails. May be removed by securing to the front wall with straps in order to haul larger cargo item. To install the rails, place all of the stabilizing posts in the slots, slide the rails between the posts from top to bottom, and ensure both sides of the rails are inserted in the rail guides on each post. Blind spots are concerns due to the mounted rails on the front of the bed. The largest blind spot is on the passenger side almost parallel with the fifth wheel, and on the driver’s side just behind the cab.

Lowboy

A lowboy trailer is often referred to as a low-bed, double drop, low loader, or a float depending on what part of the world you are in. It is a trailer manufactured for the primary purpose of carrying heavy equipment on a flat-surfaced deck, which deck is at a height equal to or lower than the top of the rear axle group. A lowboy trailer has two drops in the deck, the first drop is right behind the gooseneck and the second drop is right before the wheels, this allows the trailer to sit extremely low to the ground. The drop in the trailer is designed to allow the ability to ship oversized items or equipment that exceeds normal height restrictions for transportation (which is typically any freight over 8' high).

The maximum weight for a two axle lowboy trailer is 40,000 pounds, but the weight limit can be increased up to 80,000 pounds total weight of trailer, and load depending on the number of axles required.

Long low-bed trailers have always presented a problem in negotiation of sharp curves due to the tendency for the trailer to cut the corner and follow the path of least resistance in relation to the towing vehicle. When the trailer makes sharp turns it wears on the tires. If the trailer is loaded, sharp turns could snap the axle or blow a tire due to the skidding effect.

Customarily, the towing vehicle or tractor is equipped with the well-known fifth wheel pivotal coupling which allows hitching up to and separation from the trailer gooseneck drawbar as well as pivoting of the gooseneck relative to the tractor horizontally or from side-to-side when negotiating turns. In order to concentrate the weight of the trailer through the gooseneck most advantageously over the rear axle assemblies of the tractor, it has always been deemed necessary to place the pivot of the trailer relative to the tractor on the strategically located fifth wheel assembly.

Gooseneck

The hydraulic detachable gooseneck [HDG] trailer or removable gooseneck [RGN] trailer is often referred to as a drop neck. It is designed so that the gooseneck can be removed, leveing the front of the frame resting on the ground ready for loading. The detachable front allows the trailer to be dropped on the ground, creating a ramp for convenient loading of heavy freight. This adaptable unit can haul and carry freight loads up to 150,000 pounds. It can be expanded from 3 axles to more than 20 for the heaviest shipments.

The stretch removable gooseneck trailer, or stretch RGN, is specially designed to carry and haul loads that are too long for the standard type of RGN. Depending on the weight of the load, this trailer can be adapted with 3 or more axles. The heavier loads would use additional axles. Stretch RGN or Removable Goosenecks maximum freight weight is 42,000 pounds to 150,000 pounds or more.