Reinventing the cog

Engineers from Germany’s Fraunhofer Institute have looked to the past to develop cogs that are lighter, quieter and cheaper to manufacture than the conventional alternative.

Inspired by the cogwheels in 150-year old Dutch windmills, where metal teeth were individually mounted on wooden hubs, the team from the institute’s Technology Development Group (TEG) in Stuttgart has developed composite cogwheels with metal teeth and separate plastic or metal foam bodies.

These composite wheels are manufactured by attaching individual metal teeth to a flexible steel rolled strip, which is bent and joined at the ends and then filled with plastic or foamed metal.

The project’s deputy manager Dr Christian Feddern explained that the chief advantage of the new cogs is their relatively low weight, making them particularly suitable for use in the aerospace industry. ‘If you replace metal with plastic or metal foam, you can get a very high weight reduction,’ he said.