There is an old military proverb that states, "Amateurs talk about strategy, professionals talk about logistics." But logistics are boring, and not nearly as interesting as watching a battle unfold. But without those transports that never see action, no battle can ever be won. Take for example the massive tank battles of World War II. War movies and newsreels of the day focus on combat, not the need to prepare for the fight. Tanks are seen as invulnerable behemoths, but in fact, they are quite fragile over the long haul. When traveling over long distances cross-country, tanks are subject to dozens of mechanical failures especially to their treads, chassis, sprockets, and drive train. And so, there was a need for hauling tanks over great distances which was met by a specialized vehicle, the tank transport. You will never see it in a war movie (remember, logistics are boring), but the tank transport made armored warfare possible. It was designed with a low body (today called a "lowboy") for easy onloading and offloading as well as a rigid steel framework that could withstand the dead loads from a loaded tank. Driven by a powerful diesel engine, these vehicles would provide attached ramps that allowed the tank to be driven on and off the flatbed.
In the post-war world for over half a century, similar vehicles have provided similar services for civilian heavy equipment. Certain types of heavy equipment (larger dozers, soil compactors, long reach excavators, etc.) are in the same size and weight class as a battle tank. And like the tank, these kinds of equipment are subject to wear and tear when used over distances longer than the operational area of a typical work site. Certainly, no one would ever think to drive a tractor-tread-equipped excavator cross-state to a new job site.
But while these equipment transports provide the same function and in general are of similar design to their military counterparts, technological innovation continues and new improvements occur yearly. These include changes to the design that allow for safer and more efficient handling of these heavy equipment payloads; improved loading and unloading features and procedures that make for safer transport and easier operation; upgraded safety features that utilize electronic sensors and in-cab CCTV cameras; and "smart" trailer systems (air latches for tilts, tire inflation equipment, galvanized steel frames, etc.). Many of these improvements are driven by the fact that the equipment is getting bigger. The choices of newer large equipment sizes have additional features in order to handle greater earthwork productivity.
Trailer Designs for Handling Heavy Equipment Payloads
All designs have to meet structural, safety, and performance standards. The design of hauling trailers is no different. In most industries, there is an industry compliance group representing the interests and setting the standards for its members. The National Association of Trailer Manufacturers (NATM, mission statement: “Promote trailer safety and the success of the trailer manufacturing industry through education and advocacy”) compiles the guidelines governing the recommended manufacturing practices. These practices and standards apply to lightweight and medium-weight trailers. The NATM is the industry’s umbrella group, setting standards for both performance and safety, including a series of updates to its guidelines in 2019/2020.
Their “Guidelines” provide a simplified and easy to follow explanation of federal requirements in regards to the manufacture of trailers. Though these are industry standards and practices, the federal government regulations that they are based on are not optional. However, these regulations are massive in both number and scope and intricate in detail. The NATM's Guidelines document provides a much-needed service by offering its simplified and easy to follow guidelines providing a succinct synopsis of compliance requirements. These compliance requirements are taken and consolidated from multiple agencies (both federal and private sector): the U.S. Department of Transportation, the Society of Automotive Engineers Inc., the American Association of Motor Vehicle Administrators, the Recreational Vehicle Industry Association, the Traffic Safety Administration, the Maintenance Council, and the National Electrical Manufacturers Association. They are kept current by annual updates, the most recent of which includes a heavily updated Compliance Quick Guide.
Trailer types in general are defined by weight. Light trailers have traditionally been categorized as trailers whose total weight simply did not exceed the car’s unladen weight. Generally, lightweight travel trailers are considered 6,000 pounds or less. Medium trailers are defined as trailers with GVWR of 14,000 pounds. The heavy-duty trailer is classified as a trailer with GVWR up to 20,000 pounds (Source: Federal Register).
Choosing the Best Safety Features
The single most important safety concern is the trailer’s load capacity or concentration (the length of the deck that can handle the rated weight). Next come state laws and regulations, such as bridge laws and kingpin-to-axle distance guidelines. Suppose a lowbed has a 50-ton loading capacity and is 25 feet long. The entire deck can be rated for 50 tons, or only a 20-foot span of the deck, or only half the deck length.
But the trailer's loading capacity is only one factor that goes into its overall safety rating. This number is a comprehensive evaluation of the trailer's inherent safety while transporting equipment and it factors in shocks and stresses from traveling over uneven ground or even off-road when it arrives at the job site, hitting potholes even on otherwise smooth pavement, being jostled by bumps and railroad track crossings. It essentially takes the normal dead weight load and spikes it with live load shocks. In short, it indicates how much stress from rough usage a trailer can handle. This is far more important than the load capacity since trailers are often driving over rough terrain even if most of its journey was made on smoothly paved freeways. Accidents, overturning, or loss of equipment at a rugged job site can be as disastrous as similar occurrences on a roadway. The industry standard is for magnification of the load capacity by a factor of 1.8 to derive the safety rating. So, the same 50-ton trailer described above would need a 90-ton (1.8 x 50) when bouncing over rough surfaces.
The 1.8 is an average, a rule of thumb. During transport, trailers can be subject to force multipliers far more than the standard 1.8. Trailer design needs to take into account these eventualities with a design that builds in a factor of safety against extreme shocks. Generally, the trailer industry considers a force multiple of 2.5 to be sufficient. But just because you can doesn't mean that you should. Though technically the 2.5 multipliers could allow a 125-ton load, at no time should the multiplied value be used to carry a heavy overload. Overloading a trailer should be avoided at all costs since load dynamics and static force distribution through the trailer can change with increased loading. This could lead to overstressing the frame members. Even if a failure does not occur on a particular trip, repeated stressing of the frame can cause weakening and eventual breakage in the future.
In addition to weight and load ratings, trailers have speed ratings that have to conform to the speed limits imposed by the states that the trailer will be traveling through. Most manufactures have either a 65 mph or 55 mph speed limit imposed on equipment hauling trailers. The speed of movement could be limited to as low as 10 mph when moving across the job site. In any case, it is important to match the trailer's speed rating with anticipated transport and operational speeds.
In addition to carrying the massive weight of heavy equipment, trailers have to provide equipment with the means to load and unload them easily and efficiently. These tasks are often performed with a power ramp system that is either air, electric, or hydraulically operated. Pneumatic (air) operations are "greener" than others with systems that can run off any truck with an air pump. The safest to operate, these systems are easy to maintain with easily replaceable parts. Electrically powered ramps are often more efficient than pneumatic and generally safer than hydraulic systems, though they require a dedicated specific truck battery or back up battery. Hydraulic lines can leak hydraulic fluid, making them less environmentally friendly and more expensive to maintain.
The first safety task is always a thorough pre-trip inspection of every inch of the trailer. A complete walk-around including visual observations is required, and a video recording with a cell phone is recommended to provide a visual record of the trailer's condition.
Second, make sure every piece of equipment is rated for the anticipated load. There is not much point in having a properly sized and designed trailer deck if the straps are substandard. Load ratings for ancillary equipment are typically printed right on them for easy reference.
Mechanical systems come next, from hydraulic brakes to automated ramp controls to turn signals. Last but not least are the tires. The operator needs to ensure that they are not under-inflated or over-inflated for the anticipated haul load weight.
Check brakes and confirm that the tires are properly inflated to the recommended psi. Over- or under-inflated tires won’t have the proper load rating so they won’t carry the weight like they should, which adds stress to the trailer. Traveling with improper tires can also cause a blowout when hauling heavy loads. Drivers can typically find the psi, size, ply, and load rating on the manufacturer’s VIN tag.
(Note: A detailed list of inspection requirements refer to the Federal Motor Carrier Safety Administration’s part 396 webpage and the Driver-Vehicle Inspection Report.)
What New and Improved Technology is Being Employed?
Trailer design is subject to the law of incremental improvements. That is, small improvements to multiple aspects of the design over time have a synergistic effect with the cumulative overall improvement being greater than the sum of its parts. As such, there are multiple systems providing areas of improvement and advancement:
Camera-based monitoring systems (CMS) improve on the vision provided by traditional rear-view mirrors—or can replace them entirely. The NHTSA asked the NATM to investigate the potential of this new technology. While mostly on board with the positive aspects of this new technology (night vision from infrared, use of echolocation sensors, the ability to pan across the trailer swing, wider angle view, and generally safer operational efficiency), they also noted potential drawbacks from too heavy a dependence on CMS. Most importantly, the camera view can be obstructed by build-up debris, mud, or even the trailer structure itself.
Smart trailer systems help the operator and owner to keep up with the trailer's maintenance requirements and service schedules. It allows for movement tracking while on remote transport operations. Overall, it can track and evaluate trailer assets, determining which ones are being used the most efficiently. Internally, they can serve as onboard scales, registering the weight of the equipment being hauled.
CAD-CAM systems are now fully used for the design and strength analysis of trailer frames. The design can use software to accurately and efficiently evaluate multiple load situations and weight distributions throughout the trailer frame. In doing so, the designer can adjust the frame layout, adding members for strength or removing them for weight reduction. Conversely, they can redesign the cross-sectional area, size, or connections of individual spans. Such analyses can also be used to evaluate the requirement for securely installing mechanical systems such as winches, providing rated hitch weight allowances.
Tires and other drive train components can be improved as well. Self-oiling hubs may seem like a small thing, but they can greatly reduce maintenance requirements and ensure consistency of lube applications. This is especially helpful for high usage fleet trailers. Automated tire inflation systems use the same principles of reduced labor requirements and improved consistency. The result is improved gas mileage and reduced wear and tear on the trailer tires. The use of disc brakes ensures shorter braking distances and longer operational lifetimes.
Loading the equipment requires adherence to strict safety procedures, and improvement in the mechanical loading systems can greatly improve overall safety. That is where air latches for tilt trailers come in. Their use eliminated pinch points like those in manual latches—a significant source of injury. They also automatically prevent having only one side locked down, a situation that could damage the tilt bed.
For more than 30 years, Interstate Trailers Inc. has been a manufacturer and supplier of heavy equipment transport vehicles. With 275 nationwide dealers, they can meet localized and customized transport needs across the country. The specialized manufacturing capabilities allow them to meet specific customer demands for even the oddest heavy equipment types. Their structural frame designs are based on the use of pierced main beams. These allow for the use of deeper manrails and cross members while maintaining a lower deck height. Piercing also creates a unitized, inter-locking frame for added strength. Each design, no matter how unique, comes with a rated-at capacity that eliminates the guesswork concerning the trailer's true capability. The frames themselves consist of cold-formed "A" frames that avoid cutting notches from drawbar angles which could compromise their strengths by creating stress points. Control and electrical systems are based on modular wiring in a PVC jacket harness which allows the repair of wiring damage by simple modular replacement. Lastly, the trailers utilize Hutch 9700 suspensions with equalizers that distribute load weight evenly to axles. Having 44,800 pounds of total spring capacity on dual tandems prevents complete spring deflection under extreme load.
Interstate provides a wide range of products that meet variable applications and weight requirements. At the lighter end is their RBS Series, which utilize Dexter Torflex axles (standard throughout) and have an 83-inch load width and weight range in capacity from 6-ton to 9-ton. Their BST series are single tire deck over trailers that range from 6-ton to 9-ton capacity and utilize 12-inch manrails and oak decking. The somewhat larger BST/S is designed for directional boring machines and similar equipment, with capacities ranging from 6-ton to 10-ton. Larger still are their DT/DTA Series with 9- to 12-ton capacities, with standard Hutch 9700 suspensions and 6-inch I-beam cross members on most models (gooseneck design optional). Lastly is the DLA Series which include 20-ton two-axle and 25-ton three-axle versions with available options such as an airlift axle and air or hydraulic ramps.
Their next product line, tilt bed trailers, range in size from 5 to 8 tons for the TST series to the 15- to 25-ton TDL series. The medium-range TDT/TDA series includes a 4-foot stationary deck for hauling backhoes and similar equipment. The specialized APC models are specifically designed with the paving contractor in mind. Low incline ramps and roller deck options make for easier loading. The heavy-duty TDL series features dual tilt cylinders, standard 4-foot stationary deck, and available air operated bed lock with an NHTSA approved underride is also standard
An assortment of gooseneck and lowboy trailers fill out their product line. The LBG/PRC Series consists of fixed neck lowboys ranging from 25–50 tons with an operational full width gentle slope neck and extended air or hydraulic ramps. Their PHT Powertail trailers range from 35 to 50 tons and come with a 12K winch, 14-degree load angle air ride suspension, and 35-inch loaded deck height, all standard. The SDGN Series are detachable neck 35- to 60-ton with 4 beam constructions, apitong decking, and air ride suspension. Optional features include airlift 3rd axle and 13 hp Honda power pack.
Since 1983, Indiana-based Talbert Manufacturing has been providing a wide variety of commercial, military, government, aerospace, and energy applications as well as inner plant and material handling movers and manufacturing systems. Experts in providing safe standard and unique solutions to multiple transport needs, Talbert is a complete system solution provider for hauling the heavy loads. Always an innovative company, their list of firsts is impressive: lowbed removable gooseneck trailer, hydraulic removable gooseneck (non-ground engaging), trailer manufacturer to use high strength heat-treated steel (T1A), trailer manufacturer to design and incorporate air suspensions, trailer to use self-steering axles, and their patented 10- to 30-ton-capacity Tag-A-Long Series.
Their product lines based on custom-built manufacturing serve a wide variety of industries: commercial, construction, towing and recovery, transportation, military, agriculture, oil field, etc. The designs include fixed, mechanical and/or hydraulic removable goosenecks; extendable and modular setups; and low bed series. Their air tilt design models include the Hydraulic trail series (35- to 50-ton capacity), Traveling Axle designs, and Double Drop Series (25 to 55-ton capacity).
XL Specialized Trailers Inc. are custom trailer experts providing heavy haul and specialized trailers for both conventional and custom transportation markets.
Their heavy haul and specialized trailers (XL Specialized Trailers XL 110 Low-Profile HDG 18-Inch Deck Height Lowboy) provides solutions for transporters moving tall equipment under low bridges. It provides an 18-inch loaded main deck height and 6-inch ground clearance to help operators meet bridge clearance laws without needing a drop-side or beam deck. The hydraulic detachable lowboy features a payload capacity of 110,000 pounds in 16-feet concentrated, making it a versatile option for hauling construction equipment. Their companion XL 110 Low-Profile HDG offers maximum swing radius, deck length, and axle spacing in a 53-foot-long trailer. The main deck is constructed of 12-inch cross member spacing for additional support under the apitong wood deck and a full 26 feet in the well. The deck comes standard with seven bend D rings per side, 13 chain drops per side, and swing-out outriggers adding versatility for tying down loads of various widths and shapes. The XL 100 has a 13-foot-long detachable hydraulic gooseneck and a 51-inch fifth wheel height, 110-inch and 84-inch swing clearance, with 16-inch and 42-inch kingpin settings. With a five-position variable ride, the gooseneck allows the operator to adjust the neck’s fifth wheel height and deck height depending on the load being carried and the tractor being used. The XL100 trailer is spreader bar and power booster capable.
XL manufactures its trailers from galvanized steel frames. This protects against rust and corrosion, extending the operational life of the trailer by a factor of 3. It can withstand harsh weather conditions, road salt, and harsh road conditions. Scratches on its surface will self-repair and seal out corrosive elements while requiring little in the way of maintenance. The galvanizing process includes full submergences in hot zinc. The result is a chemical- and abrasive-resistant finish that extends the life of the trailer while minimizing maintenance costs.
At the smaller end of the scale are their XL HDE Mini-Deck Extendable trailers. Smaller than other trailers, they have a capacity rating of 110,000 pounds overall and 100,000 in 10 feet when the trailer is closed. It has a low and long main deck with a loaded deck height of only 14 inches while utilizing a 10-inch beam design.
Further versatility is provided by their low-profile hydraulic detachable gooseneck with the main deck that extends from 27 feet to 47 feet with a 14-inch loaded deck height (4-inch ground clearance). Greater capacity can be provided by a detachable wheel area allowing for additional deck sections. Ease of maneuverability is enhanced by a 52-inch hydraulic assist flip neck and axles that automatically rotate to keep the trailer behind the truck at all times.