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Converter dolly trial draws Toll plaudits

ATA points to benefits highlighted by data from latest tests


Nearly two years after being unveiled at the 2019 Brisbane Truck Show, the rigid drawbar converter dolly prototype is edging closer to hitting the market, with its latest test run hailed by the Australian Trucking Association (ATA).

A trial to measure its performance has showcased industry innovation, demonstrating superior capabilities when compared to other units, ATA notes.

The prototype was developed following concerns raised regarding dynamic issues with hinged drawbar converter dollies, in particular brake reactivity and tyre wear.

The new unit removed the pivot point of a hinged drawbar, making a dramatic difference in the brake system control. 

It was developed in partnership with industry suppliers and manufacturers MaxiTrans, Bridgestone, Hendrickson, Jost, Wabco and Alcoa, and has since undergone informal trials with operators across the country. 

Delivered by ATA’s Industry Technical Council (ITC) and Toll Group, a formal trial has evaluated the converter dolly’s performance and acquired measurable data using inertial measurement units (IMUs), strain gauges and GPS. 

“We were looking to complete back-to-back testing of the rigid drawbar dolly and a standard hinged drawbar dolly when used in an A-double combination, comparing the lateral force accelerations seen in each of the vehicle units to determine which is better,” ITC Member and Smedley’s Engineers managing director Rob Smedley says. 

The IMUs were placed above the axle group in the lead trailer, the converter dolly and the trailing trailer to measure roll, pitch and yaw, and lateral, longitudinal and vertical acceleration.

How the converter dolly first hit the road, here

Strain gauges were fitted on the converter dolly fifth wheel pedestals and towing eyes to measure correlation of forces and comparative stresses, while GPS recorded positioning and speed.

“Initial observations left me really surprised at how severely the hinge drawbar pitched and danced around on the road in comparison to the rigid drawbar.

“It will be very interesting to examine the final data of the difference in performances between the two.” 

Toll Group national equipment manager Ian Lipplegoes says improving safety for all road users is a high priority for Toll, with the company proud to support the trial. 

“The trial has been valuable and early outcomes are encouraging. We eagerly await the final results which will help demonstrate the safety benefits of making the dollies accessible to all,” Lipplegoes says. 

With the data gathered during the trial now being evaluated, MaxiTrans engineering support manager Greg Brown says the project is about building a safer, better performing dolly than those already on the market. 

“With the support of the project partners, we have seen this project evolve from concept to reality, and based on the success of the prototype, MaxiTrans have since manufactured and sold a number of these dollies,” Brown says. 

“It performs and handles better than other dollies and this trial has proven it, providing a direct comparison between the rigid drawbar and a hinged drawbar dolly to see the performance differences on the same route.” 

The ITC chair and Kel Baxter Transport managing director, Kel Baxter, had the opportunity to trial the dolly as it made its way around the country, and says he was immediately convinced it was a “superior piece of equipment”. 

“I was immediately sold on the idea and have since had a dolly manufactured with another one on the way,” Baxter says. 

“Our drivers have been very impressed as the whole setup makes the combination feel like a single unit, with no pitching.

“This dolly has better handling than both airbag and spring hinged drawbar dollies.”

ATA chief engineer Bob Woodward says the difference in the vehicle’s stability when using the converter dolly during the trial was incredible. 

“Visually, the trial demonstrated how much more settled the combination with the rigid drawbar converter dolly was on the road, tracking and in corners,” Woodward says. 

“It’s amazing to see what can be achieved in our industry when the talent and expertise can be brought together to deliver real outcomes.

“The team is excited to see what the data produces. 

The prototype dolly will be trialled by one final operator in South Australia for further analysis before being sold. 


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