Big horsepower on the coal makes for a contented Mack owner
If you are ever travelling south on the Princes Highway from Sydney you’ll find Mount Ousley covering the foothills of Mount Keira, about four kilometres northwest of Wollongong township.
As the road crosses the Illawarra escarpment the terrain changes to provide a challenging climb northwards to a height of around 800 metres from sea level. Obviously, for those travelling south, the descent is equally challenging, especially when driving a tipper and quad dog trailer grossing 57.5 tonnes under PBS approval.
Greg Watt of Watt-Trans faces the climb and descent of Mount Ousley very often on a daily basis, and, with many years spent behind the wheel, both as a company driver and as an owner/operator, he reckons he now has the right truck and trailer for the job.
Through his driving career Greg has operated a Western Star Constellation with a C15 under the bonnet, a Kenworth SAR, and, in the early, days a Ford Louisville, but nothing handles his daily workload quite the same as his current truck and trailer combination, a Mack Super-Liner.
Powered by the Mack MP10 engine with a power output of 685 hp, the 16-litre puts out an impressive 3150 Nm (2300 ft-lb) of torque through from 1000-1500 rpm. Combined with the 12-speeed mDrive automated manual transmission and with a rear diff ratio of 3.42:1, the truck/trailer combination literally does power up the hill, making the ascent to the summit look typically very easy.
What goes up, must come down, and the Mack with its Sloanebuilt quad-dog trailer is equally impressive as it makes the descent towards Wollongong, with the Mack PowerLeash engine brake combining with the exhaust brake to hold the rig in check with just very occasional service brake application.
Throughout the descent there’s none of the traditional Jake-brake roar as local council requirements include minimising noise levels. The Mack PowerLeash combined engine brake and exhaust brake generates a total retardation ability of up to 570 hp (425 kW).
The Super-Liner is obviously the latest in a line of trucks Greg has either driven or operated and it is standing up well to the relatively harsh operating conditions of working in the coal haulage industry.
With 16-litres, the MP10 engine takes on the daily challenge of Mount Ousley without any complaints, covering the route with ease.
“Grossing 57.5 tonnes and with 685 hp it’s more than a match for a good 550 hp truck at 50-tonnes. I drive it most of the time with the gear selector in auto and get better fuel consumption, averaging 1.9 km/l at full 57.5 tonnes in the city. In country areas that consumption improves to 2.3 km/litre.
“This fuel economy would be comparable with my previous Kenworth SAR T408 I operated fitted with a 550 ISX EGR engine. There’s not a lot of difference in fuel but a lot more power, and I am carrying an additional 7 tonnes. The SAR was not set up for PBS,” said Greg.
“There’s just no comparison between this truck with the mDrive and my previous CAT-powered Western Star Constellation with an 18-speed manual gearbox hauling a three-axled Sloanebuilt dog trailer.
“I bought the MACK back in April 2013 and moved to full PBS accreditation with Sloanebuilt Trailers and the quad dog trailer. From a financial perspective there is an immediate $50-$60,000 advantage per year, and I have the flexibility to work on asphalt, aggregates and coal.
“We run with a 31.5 tonnes payload when not on Mass Management, and that can be increased to 38.5 when on Mass to achieve a further 7 tonnes payload. The PBS application together with all the combination spec was organised by Sloanebuilt to give me maximum length of 19 metres. That’s the beauty of running a four-axled dog rather than a five-axled dog trailer.
“We chose a 5500 mm wheelbase as a better option than a 5700 mm wheelbase, which was an alternative at the time. If it was 200 mm longer in overall length I would have had to shorten the drawbar, which can influence the ease of jackknifing the truck and trailer.
“One of our own ideas in conjunction with Sloanebuilt was to fit a spill tray on the rear of the trailer for when we work on asphalt. That just bolts on and we put it on when we arrive on site and take it off when we leave. Because of the extreme axle measurement you need 700 mm overhang on the trailer from the apex of the tyre when you back up to the paver machine. You already have 700 mm overhang on the truck and we have a manual over-ride control that maintains the rear dump height.
“As far as maintenance is concerned, with the Mack we run our oil drain intervals at 40,000 km with standard mineral oil, twice the distance when compared to an SAR at 20,000 km. The MACK’s certainly quieter and much more relaxing to drive.
“Changing gear with a manual is what you did when you first came into trucking, but, as far as going back to driving a manual transmission, I don’t think that I would be interested these days. It took a little while to get used to the mDrive, but once you got your head around it I found it works well.
“With EBS and ABS it’s a small job to adjust the drum brakes throughout the truck and trailer combination. I prefer drum brakes for this particular application, especially when working on coal as the wheels are regularly passing through a wheel wash and you don’t have to worry about calliper seizing or contamination.
“The choice of Hendrickson INTRAAX suspension for the trailer comes down to the reliability and support of having a one-million-kilometre warranty. These are also fitted with the magnet bearing monitors.
“For added safety we run with a rear-vision camera on the truck and trailer, plus a reverse warning buzzer as these are safety features required when working on RMS and rail work. We can monitor all our loading through on-board weighing with a display readout inside the cab that covers all truck and trailer axles with the exception of the steer axle.
“With other features we have burst protection valves on the EDBRO hydraulic rams, we use JOST ball-race turntables, and a rotating pin Ringfeder coupling which has its own jackknife alert. The bins are lined with rock sheets to make them as versatile as possible,” said Greg.
The Mack Super-Liner was supplied by Mack Trucks of Huntingwood through sales manager Michael Inzitari.