A new spin on gears

Did people who drove the first cars look back at the horse-drawn carriage and wonder why something as obvious as a self-propelled vehicle took so long to invent? Some advances just make perfect sense. Drew Turney reports.

Gears are greasy, dirty, hot and sharp as teeth grip cogwheels to transmit torque. They cost a lot, wear out quickly and often need decidedly un-environmental inputs like petroleum or other fossil fuels. So it's been up to Victoria-based inventor Andrew French to change all that, upending the field from work begun in the late 80s on a Hunter Valley farm with colleagues to replace the metal teeth of traditional gears with contactless magnetic wheels.

New mechanics

The gear wheels are turned using magnetic repulsion, and so far the only point of contact is a single bearing, though French is in the midst of perfecting magnetic bearings as well, which will render the entire system entirely without wear and tear as no two components touch.

The technology suits meshed gears sitting side by side as well as driving parallel drive shafts. There's no vibration destabilising the whole assembly or restricting energy efficiency, because there's no contact it's all-but silent and the magnetic wheels – covered with a coating of zinc – are stackable so as to ultimately transmit as much torque as needed.

And by adding different diameter wheels to the same output shaft system, different RPMs can be applied for shafts driven by the same drive wheel, with built-in slip for every shaft.

That means if any of the devices in the system seize up, the rest will keep going and there'll be no damage to the assembly overall. Just power it down, swap out the wheel and get it back to work.

Energy inputs can be traditional, but the system is particularly suited to sustainable energy like solar or wind, and energy generated can be stored in a levitating flywheel that has a similar minimum of friction. Because there's no contact between wheels they’ll even work through walls and can operate with nothing more than a quick glance to make sure they're aligned, without the need for quantitative gauge measurements.

MGT's magnetic wheels can also be arranged in a standard power coupling. In one example, two 240mm discs generated almost 90Nm of torque, and French and his team are currently developing couplers capable of up to 600Nm.

Just as in the gear wheels setup, when overloaded the wheels simply slip – with no contact there's no catastrophic vibration or impact. In fact they don't even have to be properly aligned to generate spin.

A better choice

Even if you're not an engineer the advantages seem obvious. With no heavy metals pulling each others’ masses there’s little to no wear and tear. There's no heat generated from friction. The life cycle of the product is cheaper overall, and when asked how to make it a compelling buy compared to the long-entrenched manufacturing of traditional gear systems, French says it's cheaper up front as well. The company formed to commercialise the magnetic gears – MGT Magnetics, Generation & Transmissions Pty Ltd – has seen interest from customers all over. Groups and communities in the developing world with no access to power grids is a particularly active market, and NASA fitted two small MGT gears to the first Mars Rover. And it's easy to see why. French and his partners have done most of their real-world development and sales in agriculture, but when the potential market is anything that needs a drive shaft, the possibilities seem limitless.

Whether it's aviation, marine, manufacturing, mining or beyond, there probably isn't an industry around that wouldn't be interested in a cheaper, cleaner, more efficient torque transmission system. When you consider the number of gearboxes in the automotive industry alone it seems like a revolution in the making.

All in the numbers

In a test carried out by Queensland after-market automotive supercharger manufacturer Raptor Superchargers, one of MGT's magnetic gearboxes was spun to around 17,000rpm and held up. It was then installed in a Holden ute and operated to the vehicle’s maximum rpm count of 5,900 with no loss of integrity. When compared to a pulley-driven belt drive, French says the transmission is far more efficient, exceeding 22% (ie: it needs 22% less energy input).

A lot of MGT's activity has been in pumps for the agricultural sector, and after a recent Mono Pumping conversion, the system needed only eight solar panels rather than 12 and produced 50KPa more pressure than before.

But the biggest tick came back in 2007 when Dutch machine testing assessor Torquetest evaluated efficiency of MGT's products and found they had an astounding 99-100% mechanical efficiency. mgt.com.au