DOUBLE REDUCTION IN THE DUST

In Kenworth, Aussie Angles, July 20219 MinutesBy Howard ShanksAugust 12, 2021

The Goldfields region of Western Australia is one of the most inhospitable and hottest places in the country. In fact, since the late 1800s, it is often referred to as one of the loneliest of “God’s acres”. And that makes it one of the best places to investigate how Sisu hub-reduction rear axles survive in the arduous heat (and dust).

The Sisu axles in this Kenworth C509 originated half a world away in the cool climate of Southern Finland, a far cry from where they operate today. My Western Australian journey begins at Leahy Haulage’s West Kalgoorlie depot. I’d arranged to catch up with owner Murray Leahy to discuss the advantages of specifying the Sisu hub- reduction final drive axle for his operation.

Out in the heart of the Goldfields, one of Murray’s C509s is toiling hard in the intense summer heat. If you can find a bit of shade anywhere to stand under, you’ll quickly discover it is a tad over 45°C. However, out on the side of the road, it’s even hotter. So much so, I needed gloves to prevent burning my hands on the hot metal arms of the camera tripod. It’s undoubtedly a good testament to the durability of components in this road-train combination hauling such enormous loads in this intense heat.

Tri-drive, double-reduction, singularly cool.

C509 – a brutish machine.    

An hour or so later, the familiar deep reverberation of a Cummins engine brake signalled the arrival of Greg Loughlin. He was taking me for a run to collect a load of gold ore and see how the Sisu rear axles performed firsthand.

Greg was heading for the Fairylands ore pit, part of the Lawlers mine project, which also comprises the sites of Great Eastern, Hidden Secret, Golden Swan and New Holland. The Lawlers mine is an underground mining operation located on the Norseman/Wiluna Greenstone Belt, approximately 900km northeast of Perth. Today, Lawlers is a ghost town with little left to mark its existence. It got its name from Patrick Lawler, who first discovered gold there in 1892. At one stage, the town’s population was more than 8000, and it was the third-largest in the state. But more on that another time.

In more recent history, the Lawlers mine operation has made the most of its abundant mineral reserves, with an annual average production of 234,000 ounces of gold. To put that into a dollar value, at the time of writing, the price of gold was about AU$2300 (about $2500) per ounce, which loosely translates to an annual average turnover of AU$538 million (about $581 million).

115 tonnes of gold ore takes some moving.

Greg swung the C509 around in a wide arc to get his three trailers arranged in a straight line, ready to load at the mine site. A sudden gust of wind swirled a thick blanket of dust over the truck. “Those wind gusts are common out here,” he pointed out.

Dust is arguably the worst enemy of internal combustion engines and truck drivers alike. The fine dust particles quickly find their way into air cleaners, and in these conditions over a short period, drastically reduce the efficiency and economy of the engines.

When these big 625hp engines work hard, they can gobble up more than 45,000 litres of air per minute. That’s as much air as a human breathes in four days.

Dust suppression around the mine site and on haul roads is vital for the health and safety of the workers and equipment. However, sourcing the crucial water required for dust suppression can often be as hard as extracting the precious gold ore.

The Lawlers mine, like many Western Australian mining operations, is located in an arid area where the water is limited, and the local supply may be of poor quality. Consequently, the mining companies build storage and treatment plants to conserve local water supplies. In addition, at most sites, approximately 17% of the water is recycled. However, Greg explained that they recycle as much as 70% of the water at some mine sites.

Nevertheless, my assignment was to investigate the rear axles on this C509. As stated, they are heavy- duty Sisu FR3P-48 hub- reduction tridem. The main advantage of this type of planetary drive axle in heavy- haulage operations is its ability to reduce the burden on driveshafts under extreme loads. Sometimes, this style of rear axle is referred to as a double-reduction final drive because it has one reduction in the differential centre and a second reduction out on the wheel hub; consequently, they’re also known as hub- reduction axles.


Inside the Sisu hub-reduction axles.

Double-reduction axles certainly have superior strength and durability because the gear down occurs in two stages, a tremendous asset when loads are 200 tonnes or more. Consequently, with extreme loads, during lift-off, as the truck works up through the gear changes, there is a wide fluctuation in torque through the driveline as the engine revs rise and fall. Torque is spread across a greater gear area in double-reduction rear axles, significantly reducing the risk of sudden axle failure due to massive reverse torque.

There are three separate oil reservoirs, one around the crown and pinion and one in each wheel-hub end. Accordingly, this means that on steep gradients, especially if the vehicle is facing the slope, the oil level remains at a level where it will continue to cool and lubricate bearings and meshing gears.

If there is a downside to hub reduction rear axles, they are not as fuel-friendly as single-reduction rear axles.

The Neway AD369/10 Tridem rear suspension is a good marriage with the Sisu FR3P-48 rear axles and incorporates a non- torque reactive parallelogram suspension geometry.

Driver Greg Loughlin.

The design of the Neway AD359/10 reduces driveline noise and vibration by maintaining a more constant driveline working angle during axle articulation and high torque input.

Furthermore, it minimises the effects of pinion angle change caused by high torque input that can exceed the maximum recommended driveline working angles, including acceleration with heavy loads and climbing steep grades.

Likewise, the parallelogram geometry reduces chassis frame rise due to suspension wind-up. The suspension assists the driveline in maintaining proper cancellation angles, which promotes extended universal joint life. It is crucial with short inter-axle shafts, such as with tandem and tridem drive-axle configurations.

With the C509 now loaded, Greg climbed back into the air-conditioned cabin, turned off the fast idle and began to fill out his paperwork. Then it was down to the business side of the job. With a 155.2- tonne payload, the 625hp Cummins under the hood was undoubtedly going to get a workout as it sent its tenacious torque down the driveline to the Sisu hub reduction axles. The cabin shuddered as the road train lifted off, and 155 tonnes of gold ore rolled out of the mine site.