After spending a lot of time talking about things like tires and cabs, we want to make sure we aren’t leaving other parts of the truck (and trailer) out. Although what you’re driving and how you’re rolling are important, what you’re hauling pays the bills.
The fact is, the freight needs to go somewhere, and that somewhere is through a trailer’s doors and onto the floor, nice and secure. Let’s take a deeper look at one of the unsung heroes of trucking technology: doors.
The main function of your trailer doors is to keep the freight secure. There are two different types of trailer doors: swing and overhead. Each has advantages and disadvantages.
Swing doors are relatively simple and provide ample interior space for cargo loading. Once the doors are secured, they add stiffness to the trailer’s structure.
Swing doors must be able to withstand interior forces of up to 10,000 pounds. This force must be uniformly spread across the doors to simulate shifting cargo.
Sandwich-type panels should be faced inside and out with metal and treated with an ASTM compliant coating tested to last at least 12 years. Steel panel swing doors should be coated in a layer of zinc and then properly painted. Aluminum doors should be strength tested and painted.
One drawback to swing doors is their poor ease of use. Truck drivers must stop and get out of the cab to swing the doors open. The doors then need to be hooked against the sidewall before backing into the loading dock.
Once the cargo is loaded and the truck driver pulls away, he or she must again get out of the cab and manually close the doors. For street deliveries, swing doors are susceptible to obstructions like trees, poles, and parked cars.
Overhead doors are more commonly referred to as roll-up doors. They can be quickly opened and closed while the trailer sits against the dock. They are also less liable to come up against any rear or side obstructions.
Truck drivers can get their loads in and out more efficiently with overhead doors. Time saved on each delivery adds up, especially if you’re being paid by the mile.
Overhead doors are not relegated to just the rear, either. They can also be used on the sides, although in most applications single-panel doors are used on the trailer’s side walls.
Overhead door panels should be made of three-and-a-quarter inch APA Group 1, Structure 1 plywood. Alternate approved materials, such as foam core-with-metal skin sandwiches, are required to display similar strength and performance characteristics as their wood counterparts.
Each panel must be 11 to 11.5 inches tall and 2.25 inches wide, including the door panel. The top panel should be a minimum of 9 inches.
Although they have many advantages, overhead doors are not without their limitations. They take up quite a bit of space at the rear, and along the ceiling of, the trailer. Overhead doors also more difficult to install and come with more moving parts.
Which to Buy?
In the end, both types of doors carry advantages and disadvantages. Door choice should include factors such as the type of truck, trailer, and cargo. The route should also be factored. The strength of the trailer doors is even more important if the truck will be climbing steep mountain passes.
If you are thinking about cost, it’s important to remember that both types of doors can be built from a variety of materials. It is possible to meet a low cost aim without compromising on durability and long life.
Still, never skimp on safety to meet cost goals. Keep in mind that these doors will need to keep your livelihood secure. The last thing you want is for your cargo to go spilling out on to the road as you hit an incline.
As truck manufacturing ramps up and embraces technological innovation, expect new materials to continually displace old ones. In the past 10 years alone, ply-metal doors have been replaced by plate doors, primarily because plate is more durable. For now however, what lies ahead for the evolution of the door is anybody’s guess.