Lowboy Trailers: Designed with Flexibility in Mind

Updated: Sep 17, 2019

Since about the mid-1920s, the “lowboy” trailer (aka “low-loader,” “low-bed,” or “float”— depending on where in the world it’s used) has been an indispensable piece of equipment in the construction industry.

By Construction Equipment Magazine

Key Insights for Buyers

  • Lowboys are designed to transport a varied range of large, heavy, tall pieces of construction equipment.

  • Although most manufacturers have a wide selection of “standard” models, most will work with buyers to design a trailer that helps achieve maximum safety, compliance, and productivity.

  • If regulations governing load weight require extra axles, most manufacturers meet requirements by adding a rear spread axle or a multi-axle “jeep dolly” at the front, under the trailer’s gooseneck.

Overview of lowboy trailers

The lowboy—so named because of the low height of its deck (load-carrying area)—is a semi-trailer with a deck configuration that drops down in front of the rear axles and maintains a low profile (perhaps 18 inches—or less—from the ground) until it attaches at the front of the trailer to a “neck” or “gooseneck” that rises to meet the tractor’s fifth wheel.

Lowboys are extremely strong—some able to carry loads in excess of 100,000 pounds concentrated in a relatively short linear space on the deck. The XL Specialized XL-110 Low-Profile HDG, for example, has a capacity of 110,000 pounds in 12 feet. Lowboy construction typically uses multiple, massive, longitudinal steel beams, which are reinforced with cross-member beams that might be positioned on 24-inch centers.

The lowboy’s low deck height and its ability to handle heavy loads combine to make these trailers the most expedient way to transport a varied range of large, heavy, tall pieces of construction equipment. In most instances, loads are kept low enough to clear overhead obstructions on the way to a new job site. If the load is especially wide, many lowboys have a series of cantilever-type outriggers along each side of the deck that can be folded out and fitted with planks to provide extra deck width.

The neck at the front of the trailer can be fixed, which necessitates loading from the rear of the trailer via ramps, or “detachable” (removed from the trailer). The detach mechanism, which came along in the late 1950s, can be either mechanical or hydraulic. With the gooseneck removed, loading can be more conveniently done from the front of the trailer, which drops low to the ground and has heavy-duty fold-down ramps to facilitate the process. Many lowboys in today’s market have hydraulically actuated detach mechanisms, with hydraulic flow provided either from the tractor or via a hydraulic power pack on the trailer.

In addition, some lowboy models have a smaller deck positioned above the rear wheels, allowing ancillary equipment or perhaps small machines to be transported on this upper deck, which is typically accessed via a “transition” ramp in front of the axles. (Some detachable-gooseneck models also allow loading over the rear of the trailer via ramps.)

Depending on the rated capacity of lowboy trailers and the configuration of the loads they haul, axle configurations can vary, typically from two to four, with the last axle sometimes designed to flip up when the trailer is running empty. If regulations governing load weight or distribution of load weight require extra axles, most manufacturers can meet the user’s requirements by adding a rear spread axle or a multi-axle “jeep dolly” at the front, under the trailer’s gooseneck, the dolly thus becoming the attachment between the trailer and the tractor. Axles typically are fitted with low-profile tires.

Suspension Systems

Suspension systems for lowboy trailers vary, and some manufacturers have proprietary systems designed to effectively cushion the ride and reduce stress on the trailer. Typical suspension types might include spring, air-ride, and hydraulic, the latter sometimes designed to transfer hydraulic fluid throughout the system to equalize axle loading.

Trailer Configurations

The lowboy can be designed in either a “level-deck” or “drop-side-deck” configuration. XL Specialized Trailer’s Matt Schattgen, director of sales, explains.

“A drop-side trailer’s center deck is higher than the sides,” says Schattgen. “The lower sides allow for equipment to ride lower, because the machine’s tracks or tires are resting below the main structure. Some trailers, however, are designed with the entire deck lower, which results in greater versatility. A level-deck can still haul equipment with tracks and tires, yet is not constrained by the higher center deck, meaning more loads can ride low on the trailer.”

Decking Options

Lowboy decks typically are covered with wood planks, 1.75 to 2.0 inches thick. Planks often are Apitong, a hard wood (mostly from the Philippines) having mechanical and physical properties that yield an excellent strength-to-weight ratio, an important factor in lowboy design. Oak decking also is fairly common, and steel plates are sometime used as decking, although weight is a detriment to their use.

Design Matters

The discussion so far has touched on the basic design and capabilities of the lowboy, but important to note is that most manufacturers, although they might have a wide selection of “standard” models, are ready and willing to work with buyers to design the trailer—its basic configuration and features—to meet the customer’s exact needs.

“We recognize the unique needs of customers and the challenges they face,” says Troy Geisler, vice president of sales and marketing, Talbert Manufacturing. “Where these trailers haul, what they haul, and how they haul varies, and manufacturers must partner with customers to develop the package and design that best meets their needs.

“That doesn’t always mean a completely new model,” says Geisler, “but it does lead to new packages and configurations that helps customers achieve maximum safety, compliance, and productivity. Each trailer starts with a base model, and we work up from there, taking into account every variable from the load to the road. Operator needs are as diverse as the state and federal laws regulating hauling.”

Talbert’s 60CC 55SA-LD trailer has a capacity of 55 tons in 10 feet with four axles close-coupled, 55 tons in half the deck length in a three-axle or “3+1” spread-axle configuration (the latter meeting the requirement in some states for the fourth axle to be at least 14 feet 1 inch from the third axle), and 60 tons in half the deck length with four axles close-coupled. The four-beam trailer features an 18-inch deck height.

XL Specialized’s Schattgen echoes that approach to trailer design and manufacturing.

“Equipment continues to get bigger and regulations tighter,” says Schattgen, “with many areas requiring curfews for permitted loads. Due to the challenges of the loads they haul, our customers are needing more custom-specified products. As a manufacturer, we must accommodate these unique spec requirements, while still also offering many versatile standard products in the lineup.”

According to a number of lowboy-trailer manufacturers, design issues that their engineers must take into account at present include overall trailer weight, the manner in which the trailer distributes its weight (an accommodation to varying state regulations), and even clean-air regulations.

Talbert’s Geisler cites the company’s 60CC/55SA-LD trailer as an example of a design approach that helps users meet variable weight/weight-distribution regulations and that adds overall versatility to the trailer. The design, he says, gives customers the flexibility to switch between 60-ton and 55-ton configurations, using three axles, four axles close-coupled, or a “3+1” spread-axle configuration.

Air-quality concerns and their impact on trailer design, says Geisler, are reflected in California’s Sustainable Freight Action Plan and Clean Air Initiative, which is aimed at reducing fuel consumption and, subsequently, emissions. The legislation is having a major impact on over-the-road freight-hauling operations, he says, and is “tricking all the way down to trailers—such as requiring low-rolling-resistance tires, aluminum wheels, and fairings.” These regulations have not yet reached the heavy-haul industry, says Geisler, but lowboy manufacturers are watching carefully.

Another customer request being voiced more often today, says Nathan Uphus, sales manager for Felling Trailers, concerns equipment transport heights.

“As construction equipment continues to get larger,” says Uphus, “requests for lower-profile, level-deck models are becoming more common. Level-deck models allow a wider variety of equipment to be hauled, as opposed to drop-side models. The level-deck, however, won’t completely replace the drop-side in all situations.”

Uphus cites Felling Trailer’s SL (Super-Low) model lineup, which presently has capacities from 35 to 60 tons, as “achieving somewhat comparable deck heights to drop-side models,” he says.

Felling Trailer’s X-Force HDG Super Low Series, such as this XF110-3HDG-SL model, features a cambered deck with 16-inch main beams and 10-inch cross members on 24-inch centers.

“Low deck height has become extremely important,” says XL Specialized Trailer’s Schattgen. “Carriers and contractors are taking on more challenging jobs every day—jobs that require more versatile trailers. Lower-deck-height trailers can transport more loads, in more areas, with fewer permits.”

To that end, says Schattgen, the company’s XL-110 Low-Profile HDG, a “flat-deck” model, is designed with a 15-inch, loaded deck height.

The XL-110 Low-Profile HDG trailer from XL Specialized Trailers has a loaded deck height of 15 inches, allowing “this flat-deck lowboy to accommodate loads that might otherwise require a drop-side trailer,” says the company. The trailer has a capacity of 110,000 pounds in 12 feet, uses air-ride suspension, and is designed to accommodate a fourth axle.

Impacts of Driver Shortage

Of course, as in any sector of the trucking industry today, challenges are not all design-related.

“In our current economy, with construction booming in almost every market, the need for lowboy trailers to haul equipment is very strong,” says Felling Trailer’s Uphus. “Among the major issue hitting the trucking industry as a whole right now, however, is driver shortage—which isn’t impacting the construction market as bad as over-the-road, but still remains an issue.”

This Rogers MH25 is custom-built, 25-ton-capacity, rear-loading, fixed-neck, “carry-all” lowboy that features four-spring suspension and 10-inch-deep cross members “pierced through” the main beams to provide a lower deck height.

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