Trailer manufacturer replaces conventional steel HSS tube frame components with HSLA, reduces weight, increases durability

Situation

XL Specialized Trailers, Manchester, Iowa, sought a way to reduce the weight of one of its products, a bottom-dump trailer. A manufacturer of heavy-haul trailers for commercial, construction, agricultural, wind energy, oil and gas, and custom transportation applications, the company has a competitive interest in weight reduction. Reducing a trailer’s weight is a productivity enhancement, providing the opportunity to carry larger, heavier loads within the legal load limit.

After XL was purchased by Bull Moose Tube in 2016, it had a partner with a vested interest in improving its products. Bull Moose Tube has a niche in tube production, using a high-strength, low-alloy (HSLA) steel and forming square and rectangular hollow structural sections directly from strip. By forming the shape directly rather than forming it round as an intermediate step, the process minimizes cold-working, which changes steel’s characteristics. Through this process, Bull Moose has created Stratusteel®, an HSLA that is about 2.5 times stronger and three times harder than conventional steel tubing.

In 2016, the two companies pursued a proof of concept, whereby the proprietary alloy would be used for the frame of the company’s 60 BD bottom-dump trailer.

Resolution

While the XL team worked on new designs, Bull Moose Tube’s engineering team provided input and advice in three areas. First was finite element analysis, providing computer-aided structural design optimization and checks on stresses and loads related to various design concepts. Second was welding. Bull Moose provided a thermal analysis with instructions for keeping the weld temperatures down to prevent altering the steel’s characteristics. The Bull Moose team also weighed in regarding a testing regimen.

For the initial proof of concept, XL and Bull Moose opted not to alter the current XL 60 BD design, but rather to simply replace the steel. All other design elements were kept constant.

The proprietary alloy allows XL to use far less material. The substitution removed 1,100 pounds from the 5,500-lb. frame, for a 20 percent reduction in the frame weight. The total (unloaded) weight of the trailer was reduced from 12,900 lbs. to 11,800 lbs. Given an 80,000-lb. legal load limit for over-the-road use, this new trailer allows operators to haul 1,100 lbs. more per trip, equivalent to one free haul for every 50 fully loaded hauls.

Another benefit is the material’s hardness, which increases its impact resistance, keeping it looking newer longer.

Through a distribution partner, Midco Sales LLC, XL identified an enduser, Arizona-based Gila River Sand & Gravel, that was eager to use the new trailer. The test trailer operated out of Gila River’s Maricopa plant, hauling eight to 12 loads of rock and concrete sand to and from a concrete producer over more than a half mile of dirt and more than 10 miles of highway each way. In addition, Gila River took the trailer to construction sites, hauling aggregate base course material on road projects.

Driver reports on the trailer were good regarding tracking and ride. Most notably, the owner found no evidence of wear in the frame, the fifth-wheel pin or plate, brakes, or air systems, which are areas of concern for Gila River.

The weight savings balanced well with the investment cost. Getting one free load for every 50 loads resulted in a three-year return on investment (ROI) for Gila River Sand & Gravel. The test trailer is expected to be robust and durable enough to yield an overall life span of seven to 10 years, well beyond the three-year ROI period.

Bull Moose Tube Co., 1819 Clarkson Road, Chesterfield, MO 63017, 636-537-2600, www.bullmoosetube.com