Long before a single load is booked or any wheels turn, someone — usually an equipment manager — needs to determine exactly what is going to separate the road and the load.
There’s a lot to keep in mind with this decision, because there are many factors that go into choosing the right trailer with the appropriate capacity needed for the carrier’s operations. Two of the main aspects for determining capacity are load concentration and load distribution. Load concentration refers to a considerable amount of weight within one specific portion of the trailer. Shorter load concentrations require maximum strength trailer beams or the load will cause frame cracks and prematurely wear the trailer. Load distribution, also known as load balancing, is how the products are distributed throughout the trailer bed and it’s effects on the carrier’s handling of the trailer, traction and speed options and trailer life.
For utility contractors, these factors are especially important due to frequent hauling of large units such as excavators and trenchers, as well as skid steers and loaders. Selecting a manufacturer that understands how to calculate capacity, while considering load concentration and load distribution, is the key to getting the right customized trailer to the jobsite safely and on time. And, a trailer that matches the size of the load will provide the greatest lifespan and deliver the highest possible return on investment.
For our purposes, let’s take a closer look at load concentration and load distribution of a 50-ton lowbed. Keep in mind, though that there are many styles and designs, so not all trailers are created equal.
Load Concentration: Half Deck, Full Utilization
There are more than 50 manufacturers of lowbed heavy-haul trailers in North America, and they apply several methods to rate their trailer capacities. Since there is no industry-set or government-mandated system, it’s up to every buyer to be in tune with the method each manufacturer uses before making a purchase decision.
A key difference between manufacturers’ ratings comes in load concentration, or the length of the deck that can handle the rated weight. Obviously, a 26-ft, 50-ton lowbed can haul 50 tons. But how much deck space those 50 tons occupy is just as important as the weight itself. Whereas one trailer might need the entire length of the deck to be rated at 50 tons, another can be rated for 50 tons in a 16-ft span, and another can handle that same weight in half the deck length.
For example, a 26-ft, 50-ton lowbed might be rated for the trailer’s entire span with equal weight distribution. In that case, the trailer would need to be hauling materials that run the entire length of the trailer, such as long steel poles, lumber or concrete culvert sections.
However, if the payload is a 50-ton excavator that’s only 13 ft long, a trailer rated for the entire deck length, or even for 16 ft, won’t be right for the load. Even though the load is only 50 tons, that trailer will be overloaded because the weight will not span the entire length of the deck, making it too concentrated for the area the excavator covers. For a trailer that’s rated at full deck length, or 16 ft, to safely handle the excavator, it would likely need to be rated at 55 or 60 tons.
So again, using the 13-ft, 50-ton excavator as the payload, the ideal trailer will be one rated at half the deck length. Trailers rated for half the deck length can carry a specified load in just that, half the length of the deck. These ratings give a more realistic indication of the concentrated loads the trailer will be able to handle safely and without structural failure. In addition, manufacturers who build trailers with half-deck ratings often do so with a two-point rigid load base specifically for the tire spacing, or hot spots, of large equipment and heavy machinery.
Load Distribution: Scaling Out
How a load is distributed over the deck and the axles can be just as important as the overall weight rating. However, even though the trailers will be operating in the United States, the states are not very united when it comes to axle weight laws and regulations.
All across the country, the laws and regulations related to weight vary from state to state. Equipment managers need to be aware of, and plan for, variances between states and regions where their trailers will be used. Be sure to have the proper trailer configuration to make the load distribution work for a fleet’s particular area of operation.
Manufacturers bear some responsibility, too, and should work with buyers to define not just the best trailer for the cargo those buyers will be carrying, but also the best axle configurations for maximizing the load in every one of the states they’ll be hauling through.
Clearly, it’s impossible to max out a trailer’s capacity in every state, but the goal of most interstate heavy-haul carriers is to get a trailer as close to the maximum as possible across all the states where the carrier intends to operate.
There are many ways to achieve the best possible weight distribution over the axles. It might be as simple as adding a fourth flip axle or as complicated as adding two or three axles and spreading them apart to ensure they can support an equal amount of weight from the payload. There are also other possibilities in between depending on the specific state’s regulations, components and the nature of the load. Keep in mind that the trailer needs to be designed for additional axle and component capability in order to handle these changes.
For example, carriers can vary gooseneck lengths in the front to achieve the proper steer weight and drive axle weight. Carriers also can alter the distances between axles and axle groups to hit max weights and remain in compliance with various state laws. With an East Coast trailer, for example, they can add shims to a rigid spread bar or, if the trailer has a nitro version of a spreader bar, use hydraulics to vary the weight distribution. Yet another way is to move the load closer to one end or the other to properly distribute weight over the axles. And, finally, a carrier can use a Jeep dolly to add extra axles, thereby lowering the per-axle weight distribution.
Help To Be Had
It can be tempting to look at a trailer’s capacity rating and stop there. However, for a true sense of how much a trailer can handle and how it will hold up under the stresses of a specific operation, with its individualized loads, geographies, weights and other variables, fleet managers need to consider everything that goes into that rating.
Purchasing the right trailers for updating a fleet can be complicated and, clearly, the decision is an important one — but there is help available. Many manufacturers have sales people who know capacity from top to bottom and can help equipment managers select exactly the right trailer with the optimal combination of load concentration and load distribution for specific utility applications and load types.
Having that depth of understanding about each specification will help ensure an investment that leads to a long, smooth ride.
Troy Geisler is the Vice President of Sales and Marketing for Talbert Mfg.