Wide load follows

In July 2023, Tech Topics9 MinutesBy Gavin MyersAugust 9, 2023

Few trailers hide as much sophistication in their outwardly simple appearance as widening low loaders and house removal trailers. These flat-deck cousins are also – simply – cool. We went to TRT’s recent low-loader event to discover what lies beneath the coaming rails.

The intrigue of what’s following a couple of pilot vehicles always leads to great excitement for truck enthusiasts. But how much thought is given to the design and engineering that goes into building one of those multiple-row mammoths?

TRT’s head office in Hamilton is also home to its 33,000m2 manufacturing site, which produces a range of trailers and cranes to ISO 9001:2015 standards, and supports customers with service facilities, rebuilds and parts support.

Glen Harnett, TRT general manager sales – capital whole goods, explains that the build process begins within the TRT design office, where the design and sales team work together to provide a solution for the customer. Once sign-off has been confirmed, manufacturing drawings are provided to the steel processing and fabrication shops to start the manufacturing process of the trailer.

1) A new three-rows-of-eight Swing Wing widening trailer for Gill Construction, Blenheim, featuring fully compensating hydraulic gooseneck, double-acting suspension and telescopic delineators. Swing Wing allows it to widen to 4.2m.
2) Two configurations of widening low loaders.

The actual manufacturing process starts in the steel processing division. Raw steel, most of which is high-tensile steel sourced from SSAB in Sweden, is processed by the CNC machines and steel plasma cutter, resulting in precisely machined individual components.

On using Hardox AR450 wear plate, Harnett says: “All our low loaders have AR450 Hardox decks. We now use 5mm or 6mm steel that provides a strong hard-wearing deck, as well as minimising the tare weight.

Harnett explains that TRT does as much in-house manufacturing as possible. “We have control and flexibility in how we manage our jobs. We’re a lot more efficient and we can ensure the quality is maintained.”

Every steel component for each trailer is machined, profiled or pressed and sent into the fabrication process on a steel pallet or forklift dolly. This ensures that the fabrication team receives all the parts required to build that particular weldment of the trailer.

At the fabrication shop, a couple of house trailers are being built. “We’ve changed our design a little,” says Harnett. “We’ve developed a fabricated double-box trombone that is lighter by approximately 40kg per metre, and is stronger and stiffer than more traditional designs. That’s important for house-movers, as they don’t want the trailer flexing overly much, causing damage to the house or structure they are transporting.”

TRT also employs a CNC line-boring machine and a robotic welder to aid in manufacturing and assembly. The line-boring machine replaces the old process of machining a boss and welding it into place. “These days we don’t even use machined bosses. For example, we weld a block on the end of the swing arm and the line borer drills straight through. It’s incredibly accurate,” says Harnett.

Gary the robot welder – affectionately named after Gary Webber who was the lead in getting it up and running – adds capacity and aids the welding technicians for certain components.

Eventually, all parts reach the paint shop. TRT operates a sand-blasting booth and two electrostatic paint booths. “Every item on a trailer is blasted and painted separately to ensure complete coverage. We blast at 50 microns and within a few hours the primer and top coat are applied. Its important that our customer is provided with a product that has the correct paint coverage to ensure the longevity of the trailer,” Harnett comments.

3 & 4) Some house trailers in various stages of manufacturing and fitout.

Finally, we get to final assembly where components such as lights, wiring, hydraulics, braking and steering are fitted. Harnett takes the opportunity to detail TRT’s electronic steering system. Commonly fitted to platform and house trailers, ESS allows for maximum manoeuvrability of multiple-axle units. We explored the system in detail when we hopped aboard PBR’s Peterbilt 389 for the October 2020 issue but, in brief, the system works through a ball race slew ring on the gooseneck. Inside that, two encoders signal each steering ram to set the radius and follow the line of the truck. The system offers 35° steering on house trailers and 45° on platform trailers.

“The steering geometry is accurate to the radius you’re going around. The trailer will follow the truck as much as it can until it gets into an obstructed position. Then an operator can individually steer each axle by remote control to manoeuvre the trailer.”

ESS is also electronically configurable when operators add or remove axles via TRT’s Quick Connect clip-on modular system, whether the trailer is extended or widened. The operator simply configures the ESS via an in-cab display screen and the trailer’s pivot point is adjusted to suit.

“With mechanical linkage platform trailers, every single linkage on every single axle would have to be changed when adding axle modules. Changing a 12-line platform trailer could take two guys two days. A Quick Connect module can be added in 30 minutes to 90 minutes depending on whether it’s a house or platform trailer.”

We’ve managed to condense up to two months of design work and about 4000 hours of fabrication and assembly into these pages. However, that’s all for creating the right product for the customer. “We offer our customers an option against our competitors – we don’t want to just give them the same; we want to be able to provide a better product. We need to thank our loyal customers who have helped us push the envelope on design,” concludes Harnett.

1) PBR ESS house trailer. Deck height lifts from 880mm to about 2.8m. TRT fifth-wheel push-pull slider ram provides 1500mm stroke. Two Quick-Connect modules extend this unit to six (30m) or eight (33m) rows – about the limit for a house trailer.
2) A truck deck fit out for Horotiu Cartage and Hire out, featuring liftable Hendrickson steer tag axle, full-depth low-loader style coaming rail and nine-tonne winch. Capacity up to 20 tonnes.
3) Nikau Contractors ESS modular platform trailer extends from four to six, eight or 10 rows and widens from 3090mm to 4390mm. Suspension can be raised from 850mm by 650mm, with a 600mm stroke at the gooseneck.