At some point in time, you may be presented with load proportions just barely it above the legal parameters that constitute an over-dimensional shipment. Before resigning yourself to the arranging the painstaking details of an over sized shipment, consider employing a double drop trailer. This type of trailer is best described as a flat bed that is modified to legally carry taller freight. You may hear them referred to as drop-frame trailers or lowboys in some trucking circles.
There are other flavors of drop frame trailers, such as the single drop (beaver tail) but double drops are arguably considered the best. While not without their disadvantages, they are preferred because they achieve maximum legal load heights by bringing the height of the cargo bed as low as 18 inches off of the ground. This adds a considerable 3 feet to height clearance; a remarkable improvement considering the complications saved from avoiding an over-dimensional shipment. This brings the legal height limit of your shipment to 11 feet and 6 inches. The trailer also has the added benefit of much lowered center of gravity compared to standard flatbeds. Drivers often find this safer and therefore preferential.
Essentially, double drop trailers have the same applications as flatbeds with the added height allowance. This includes shipments that:
- are large and heavy,
- have abnormal proportions, particularly height,
- need to be loaded by crane,
- and are impervious to the potentially harsh environment of transit, such as prolonged sunlight, wind, rain, and/or snow.
Even if your shipment is also too large in width, double drop trailers should not go unconsidered for over-dimensional shipments. Some of these trailers are equipped with extra features which make them a more attractive choice for an over-dimensional shipment. One such feature is the addition of outrigger flaps, which simply unfold to add more width to the cargo bed. This is generally preferred to the practice of extending a standard flatbed’s width by using a platform or several planks. Other models include an extendable cargo bed, which is very useful for pushing the length capacity of the trailer.
Unfortunately, the use of double drop trailers can severely complicate loading operations. Standard forklift dock-loading is completely out of the question considering the height of the trailer. It may be possible for some forklifts to load cargo onto the bed from the side, but this typically requires a large loading area. Many models of double drop trailers have a removable gooseneck, the component which connects the trailer to the tractor. After this piece has been removed, a forklift could potentially drive onto the trailer from the ground. Lastly, if the object is truly large, it might be best loaded with even heavier lifting equipment such as a crane. It is notable, however, that most double drops are prone to the standard 45,000 pound weight limit or less. This is an unavoidable weakness in the design.
Also remember to consider the low ground clearance as a possible complication for the driver. Eighteen inches is probably low enough to be caught by many obstacles, particularly tracks in a loading area.