How Komatsu trucks auto braking system make easy (and safe) work on a steep downhill quarry run

The automatic engine braking system on Komatsu HD325-7 dump trucks is helping a Wellington quarry safely and efficiently handle some of the steepest downhill haul roads in the business – even when fully loaded.


GBC Winstone’s Belmont Quarry, near Lower Hutt, supplies high-grade aggregates for roading and construction throughout the wider Wellington region.

Unlike most quarries, which win material from a pit, Belmont is currently extracting its material from the top of a hill, then carting it downhill to the crushing and processing plant.

According to Belmont Quarry Manager Shane Hagai, this downhill haul road is one of the steepest in the business.

“We’ve got two inclines, one of around 8% and the other 10-12%, so good braking on the trucks is key to our process,” he said.

The haul distance is 1.4 km, with around a 15-minute turnaround time.

About three years ago, Belmont Quarry opted to replace its previous haul trucks with two Komatsu HD325-7 trucks – based primarily on their unique braking capabilities.

The HD325-7s – along with others in Komatsu’s mechanical dump truck range – feature an Auto Retard Speed Control (ARSC) system, that give unrivalled braking power when travelling downhill, even when fully loaded.

ARSC allows the operator to simply set the downhill travel speed and go down slopes at a constant speed, allowing the operator to concentrate on steering.

Speeds can be set at increments of 1 km/h, to match the optimum speed for the slope.

In addition, since the retarder cooling oil temperature is always monitored, speed is automatically lowered if the oil gets too hot.

“With that built-in engine braking, the trucks handle our inclines really well, absolutely without a doubt,” said Shane.

“The operators just select the maximum travel speed to come down the hill safely, and they’ll come down at that precise speed. When I’m following them down the hill, the brake lights never even come on; the guys and girls only need to touch the brakes when approaching the bins to tip off.”

In addition to the two HD325-7s, Belmont also runs a Komatsu HM400-3 articulated dump truck, which Shane brought in from GBC Winstones’ Otaki quarry – where he’d previously been manager – in late 2016.

“The HM400 has an auto retarder system, and that works fine here.”

Komatsu’s auto retarder system on the HM400 works off the accelerator pedal so when the operator takes pressure off the accelerator pedal, the auto retarder works immediately to slow the truck, no matter what speed it’s doing.

Retardation is cancelled simply by applying pressure back on the accelerator pedal, so that operators often only need to use the gas pedal for retarding.

“We’d had that truck at Otaki when I was managing it, but I could see the need for it here at Belmont, based on its braking power,” Shane said.

“We’ve had many articulated trucks here at Belmont over the years, but we found they just weren’t safe for our conditions, even with exhaust brakes. But there’s no concerns with the HM400.

“While the articulated truck is mainly helping with carting from the main pit, it also gives us good opportunities for stockpile work, with its manoeuvrability and ability to climb stockpiles.”

For the past few years, Shane has worked closely with Komatsu and its Wellington region service agent, Machinery Specialists.

“We have a very close relationship with Machinery Specialists, originally in Palmerston North, and now down in Wellington. Rob Myers and his team there are very good,” he said.

“We’re still getting very good reliability with the trucks here; if anything comes up, it’s just little things, nothing major. And if we need something, Machinery Specialists’ and Komatsu’s Porirua branch is only about 40 minutes away with a phone call, so that works out really well.”

Shane and his operational team at Belmont also find the KOMTRAX remote monitoring system useful, not only for preventive maintenance, but also to assist with operating efficiency.

“Certainly we use KOMTRAX for monitoring the trucks operating data and component health, but we also get the emails showing us how we are going from an efficiency point of view.

“We use these in our toolbox talks, and have a bit of banter about who’s got the greatest idle times, and that sort of thing,” said Shane.