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Mack Metroliner takes Hansons mining to a new level

Hanson and Mack have created a concrete agitator specifically designed for the most extreme underground conditions

Half an hour north east of Bendigo in Victoria, you’ll find the Fosterville Gold Mine. It’s an all-underground mine that runs all year round.

Hanson’s super-customised Mack Metroliner is playing a key role in helping transport concrete at the mine.

Hanson’s Concrete Plant Manager Matthew Bray knew from the start that conditions in the mine are extreme, and that any truck going down there needed to be tough enough to handle it.

“It’s a harsh, incredibly dusty environment that often turns to mud and slurry the moment it is exposed to water from the water carts or mining machines,” says Bray.

“The temperature down the bottom can get up to 50 degrees centigrade. Truck filters clog up quickly which compound into a vast array of truck faults.”

Hanson installed all heavy-duty fittings on the Metroliners, including extra layers of paint and rust-proofing, large custom external trays and a single conveyor guard over the drive wheels with additional bracing to handle the bumpy and steep conditions.

“We go through about 10 tyres a month so the single guard will give us more room to change the tyres out. The single guard allows us to mount larger external trays on top, which hold the chutes and some custom wheel chocks we’ve had manufactured,” says Bray.

“When the floor is underwater conventional chocks can float away, and if we’re on an extreme gradient they can slip. Having these handy around the truck gives us a bit of reassurance and prevents the truck sliding.”

Bray and his team worked closely with the Mack engineers to customise all aspects of the Metroliners, using an agile development process that saw them making changes on the fly as new truck data came to hand from the mine. A good example is keeping the trucks slow enough to stay in control.

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“The track is a steep and narrow tunnel that reaches a 7-to-1 gradient in places,” says Bray. “Slowing the truck down enough on the descent is a major safety issue, especially when the roads are wet. If the driver sits on the air-brakes all the way down the compressor can’t keep up and you risk running out of air and not being able to stop. Besides the obvious potential damage caused to the truck, sliding into the tunnel wall could also cause large safety and structural concerns, so this was a large challenge we worked with Mack to engineer out.”

To get around this problem, Hanson imposed a speed limiter of 30 km/h on the engine, installed a transmission retarder to reduce the need for braking, and lowered the diff ratio so the retarder cuts in earlier than usual at low speeds.

“Ideally, we want the drivers to be able to get down there without using the brakes much at all,” says Matt, “the retarder is crucial to that, it’s the way we’re expecting to control the descent, especially when the roads are slippery. The drivers are super-excited about it, they’ve had the experience of hubs overheating from riding the brakes and the seals blowing, and we’re confident this approach will solve that.”

Mack saysHanson’s mining Metroliner is a great example of how Mack’s engineers can customise a truck to make it perfectly fit-for-purpose, and Bray expects them to put in a solid performance.

“We’re looking to run them for at least five years,” says Bray. “And the Mack driver trainers are coming down to help our drivers get the most out of them. It’s a complete package, and Mack really pulled out all the stops to build exactly what we were after.”

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