THE DEFINITIVE TRUCKING SITE

September 2008

 

In the July 2008 FleetWatch special report on overloading, attention was given to the self-regulation initiative gathering momentum in the timber and sugar industries. Known as the RTMS (Road Transport Management System), the initiative is based on ‘selfregulated’ processes within the trucking industry, ensuring ‘best practice’ in such mission-critical areas as overloading, driver/vehicle fitness and safety. Under the auspices of the RTMS is the current testing of timber rigs exceeding the permissible maximum length of 22 metres, capable of carrying a payload in excess of 45 tons. Based on a regulation principle known as PBS (Performance-based Standards), these rigs have much to offer in the way of improving payload efficiency and overall operating costs, writes Paul Collings.

Established timber hauliers who have already qualified for RTMS accreditation will have the opportunity to run PBS trailers once the pilot project has been fully vetted by government. Reaping the benefits means full, ongoing compliance and accurate reporting of load masses.

The expression ‘ongoing improvement’ may sound like something of a cliché bandied about by management consultants drafting all manner of plans to help improve the way people work. However, in truck transport – and PBS specifically – the ‘ongoing improvement’ referred to focuses on the truck trailer and what Des Armstrong of Mondi defines as ‘payload efficiency factor’ or PEF. Exceeding 56 GCM tons doesn’t necessarily spell danger, it seems. 

From down under 

Designing better vehicles is what automotive engineering is all about and the trucking arena has some of the sharpest brains on the planet when it comes to producing vehicles that are safer, more economical and more profitable. Often, what drives trucking’s R&D process is a specific need, emanating from a particular application, be it mining, construction or agriculture. 

Successfully rolling out in Australia and New Zealand, PBS is an approach to vehicle regulation that focuses on how the vehicle behaves on the road, rather than how big and heavy (length and mass) it is, through a set of safety and infrastructure protection standards (in SA, the RTMS). In other words, PBS governs what a vehicle can do (performance criteria), not what it should look like (prescriptive dimension-based criteria). 

South Africa’s timber industry is a prime example of how big corporations drive engineering innovation, not least when it comes to trucks. Mondi and Sappi, for example, are at the centre of the PBS pilot project currently underway in Kwa-Zulu Natal, along with the KZN DoT and several of our leading trailer manufacturers and component suppliers. 

Leading the Mondi PBS project is Des Armstrong who, over the years, has made a name for himself as something of a visionary when it comes to finding smarter ways to move a load by truck. 

“Heavy-duty truck tare mass has, through innovative approaches to trailer design, been reduced significantly over the last 20 years by over 12 tons,” says Armstrong. “The Mondi PBS logging trailer currently under trial is a 24-metre rigid-drawbar combination capable of carrying 45.3 tons with a combination tare mass of 19 010kg and a GCM of 64 tons.” 

What it’s got 

A vehicle of this nature, in order to meet the PBS (and RTMS) criteria, needs to have the requisite performance and safety characteristics. The truck tractor, a V8 6x4 Mercedes-Benz LWB Actros 33.50/45 provides 370kW of power and 2400Nm of torque for the demanding extra-heavy in-field and on-road work. 

In order to keep tare mass at a minimum, the 12.5m/7460kg five-axle drawbar Evans trailer (imported from New Zealand) is fitted with light but strong BPW Eco Plus axles with mechanical suspension systems that effectively lower the trailer height and thereby improve its centre of gravity. 

“This improves overall vehicle stability and handling, despite higher payloads,” Armstrong adds. Additional weight-saving is achieved using Alcoa aluminium rims and lightweight Mondo bolsters from ExTe. 

The ‘innovation’ underpinning the PBS Actros/Evans combination is the fact that despite its 64 ton GCM, none of its eight axles exceeds the current permissible axle mass restrictions, dispelling the fear of damage to bridges and road surfaces. 

To assist in the RTMS compliance process, all trailers have on-board weighing systems to not only ensure loading is kept within the PBS/RTMS parameters but also to log all loads for comparative purposes with standard Actros logging rigs. The Merc CANbus system is used to measure fuel consumption. 

“A Central Tyre Inflation unit helps prolong tyre life and improve vehicle safety and efficiency,” Armstrong says. “Also being benchmarked are foundation brake, drawbar coupling and suspension wear. Recording vehicle speed and tracking ability on forestry roads is also part of the pilot programme.” 

These graphs illustrate the cost benefits of longer trailers given tonnage and lead distance parameters – clockwise from top left: Six fewer rigs are needed to move the contracted load; fewer trucks means less harmful emissions; a total cost saving of almost R12m per annum; a fuel saving of over R4m per annum.

Myriad benefits

With a mere two extra metres added to the length of the vehicle, the Mondi PBS rig has proven itself to be exceptionally efficient in a number of areas, with advantages not only for the logistics chain but for the public too. 

“Apart from the issue of improved transport efficiency, the PBS unit positively addresses a number of serious issues facing this country,” explains Armstrong. “An increase in the number of heavy trucks on our roads has led to rapid deterioration of the road network, which costs the tax payer billions and causes thousands of accidents every year. With the PBS rig carrying around seven tons more than a standard unit, less trips are required to move the contracted payload and as a result, less fuel is used, fewer vehicles and drivers are needed, effectively reducing traffic congestion. 

“While overall vehicle operating costs are lowered, road safety is improved and environmental impact is reduced. It’s quite simple – everyone scores!”
 

Check all those axles! Trailer  length and other design elements can be stretched beyond the existing legal stipulations, if the vehicle meets stringent performance criteria. In KZN, this PBS timber truck runs daily trips along the N2, but only because its operator plays by the book.