Underground coal mines must weigh up the pros and cons of the three existing tyre options for equipment – pneumatic, solid or foam-filled.

But over the past few years Queensland-based Big Tyre has been designing a new wheel to better meet underground coal mining conditions.

The patent-pending design is based on layers of bolted leaf springs, which give a fan-like appearance to the wheel when there are no side skirts fitted.

The wheel is claimed to be safer and more heat resistant than pneumatic, solid and foam-filled tyres and is also expected to have superior lateral stability on slopes.

The absence of compressed air is a safety benefit.

Heat generated in a tyre comes from waste energy when the tyre flexes and depends on the load and speed it is managing, so an increased capacity to handle heat in the design concept means tyres can be built to handle greater loads and/or greater speeds.

After successfully trialling a small version of the wheel on a go kart in 2006, Big Tyre has now developed the LHD-sized wheel with the assistance of ACARP funding.

To test the prototypes the company acquired a large tyre tester from Goodyear’s tyre manufacturing facility in Melbourne, which closed two years ago. Using this tester the first full-size prototype has been spun at 20 kilometres an hour with a 3 tonne load, and was statically tested to 7t.

However there is considerably more development ahead as the larger prototype did not satisfy all requirements.

Big Tyre managing director Bruce Louden told International Longwall News that preliminary tests demonstrated that although the wheel concept worked well, stronger springs were required to meet his targeted load and suspension characteristics to compensate for the outer wheel structure and tread being more flexible than anticipated.

“It’s fairly unrealistic to expect the first prototype to be the one that’s ready for commercialisation,” Louden said.

“You do your best on engineering and design but you expect to discover a few things to improve once you have made your full-size prototype.”

Further components are being manufactured while the wheel undergoes anti-static tests.

Despite some keen industry interest in the wheel, Louden is aiming to increase the capacity of the prototype to handle working loads of 10-15t before trialling it on an LHD and demonstrating it to the wider underground coal mining sector.

“Having built and tested the first prototype we are optimistic of it having a successful outcome,” Louden said.

“Developing a new wheel is not a short-term objective.”

He said ACARP has remained very supportive of the project, with this important source of funding fast-tracking the R&D which previously relied on Big Tyre’s profit streams.

“We’re extremely grateful to have ACARP support – without them the significant progress we have made in the last couple of years just wouldn’t have happened.”

While the wheel is first targeting the underground mining market, ACARP has appointed an engineer working in the open cut realm to help monitor the project alongside underground engineers.

If the wheel can successfully meet underground conditions there is the potential that much larger versions could be produced to usher in a bigger range of mining trucks capable of greater loads.

Big Tyre is Queensland’s largest retreader of mining tyres and is the preferred supplier of solid rubber-tyred wheels for Bucyrus (now Caterpillar) and Sandvik.