When we admire great machines, we too often overlook the contribution of the gears. These hardy wheels are unsung heroes of machinery — so undervalued by popular imagination that they inspired the woeful saying: “I’m just a cog in the machine”.
But a well-designed gear system can make a huge difference. Take the recent advance in wave energy farming technology, for example.
One way to capture the energy of an ocean wave is by using a buoy. This approach is known in the wave industry as a “point absorber”. The buoy bobs up and down (see video at the bottom) with the movement of the waves and the motion propels gears down below that drive a generator.
In one of the most cost-effective wave farming systems yet introduced, a rack and pinion gear is taking on this task and helping increase energy output by a factor of 5. The CorPower wave energy converter’s “cascade gear” was designed with the help of researchers at KTH. And the system recently won an innovation award from MIT.
The idea of a rack and pinion gear is that it can convert rotational motion into linear motion, and vice versa.
Think of a rack and pinion steering system. You rotate the steering wheel and at the end of the steering column is a pinion, or cogwheel, which meshes with a rack aligned with the axle. Turning the wheel then moves the axle in a horizontal motion, from side to side.
In the CorPower wave conversion system, the rack is pushed up and down by the buoy bobbing on the waves. This action then moves eight small gear wheels. The secret to the cascade gear design is how the pinions and the gears work together along with flexing units. Eight pinions share the force from the rack, which is evenly distributed. The system then can handle high forces and high velocities at the same time. The high velocity is transferred to high rotational speeds of the pinions. It’s also highly efficient.
Here’s a nice animation that shows how a point absorber captures wave motion (shared with permission of Niels Christian Buhl)