Published in September 2009 Australian Longwall Magazine

Longwall mines have three tyre options for equipment – pneumatic, solid or foam-filled – all with their own advantages and disadvantages.

Having seen the longwall industry swing back and forth with the three choices for many years, Louden was driving back to Toowoomba from a Queensland Mining and Engineering Exhibition in Mackay when he came up with the idea for a new wheel design.

With an international patent filed back in 2006, he was free to talk with Australian Longwall Magazine about the design.

He said the wheel used a series of leaf springs that untypically have a bolt-like connection on either end allowing them to be easily replaced if damaged.

“If you look at the side of the wheel it will look like a fan,” he said.

“You have got all these leaf-springs stacked in like blades going all the way round running close to each other.”

While people think this may lead the wheel to wind up like a clock spring, Louden said this was impossible as the design had the leaf springs going in both directions by using numerous layers.

Louden applied to ACARP with his design and was awarded $296,000 in funding to help develop and test wheel prototypes underground over 2.5 years.

In the past six months Louden has been working with ACARP developing the design and investigating materials suitable for a robust version of the wheel for underground.

Louden said he was looking for strength, impact resistance and the ability of the components to do millions of cycles without getting stressed.

He already has an early prototype which is being tested at close to 70 kilometres per hour on a go-kart he bought off a friend.

Louden said he was getting a comparable ride on the 100m-long concrete driveway at Big Tyre’s factory to what you would get using pneumatic tyres.

With the driver close to the ground and the wheel, Louden said the go-kart made an ideal test vehicle given its good acceleration and braking. He added a few people from the mining industry had taken the kart for a spin as well.

Louden expects numerous benefits from the new wheel design.

“Our design is definitely a lot more heat-resistant than pneumatic, solid and foam-filled tyres,” he said. “It can breathe better and it doesn’t have the same considerations that produce heat, so we expect not only safety but productivity improvements as well.”

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.

While the underground market is a more obvious choice for the wheel, Louden made some queries when ACARP dedicated a man from its open cut division to help monitor the project.

Louden said if the wheel worked underground it would certainly work above ground where the environment was less rigorous.

“But if we can produce a wheel that is bigger than the largest pneumatic then it has the potential to usher in a whole new range of mining trucks that can carry much greater loads, and consequently involve less manpower and a smaller fleet to worry about.”

Louden said Big Tyre’s wheel design would not be limited by load as the design took the load directly down from the hub into the tread area. Through ACARP, Louden’s design can be fast-tracked and he can work directly with the industry on a product it is looking and waiting for.

In feedback during the proposal stage for ACARP funding, Louden discovered the industry’s concern for improved lateral stability of tyres on slopes. This was a point he had not previously considered, but is in fact one of the new wheel’s strengths.

“When a machine with pneumatic tyres is operating transversely on a significant slope, the tyres are in danger of being pushed off the rim because you have a large sideways load on them that pneumatic tyres are not really designed to handle,” he said.

Big Tyre currently supplies solid rubber-tyred wheels to longwall mines and is the preferred supplier for Bucyrus and Sandvik.