Dynamo – Lighting while biking is possible!

Cycling. Has it ever been more popular in the UK? With success after success this year on the saddle, more and more of us will be taking to our bikes for the commute to work or for leisure; inspired by our champions like Sir Chris Hoy, Bradley Wiggins, Lizzie Armitstead or Victoria Pendleton. We’ll all have thighs like tree trunks before the end of the year…

Getting back on track though, the night’s are fair drawin’ in, so cyclists will soon be turning to their dynamos to ensure they keep safe on the road and can see where all those pesky potholes are!

Dynamos take some of the mechanical energy from the turning of your wheels and convert it to electrical energy, producing a current to power your lights. No need for batteries or impossible magicians!

There are 3 common types of dynamos: direct contact; hub; and those that use electromagnetic induction. Oooh… fancy!

In direct contact dynamos, a roller lying against the outer surface of the tyre turns as the wheel spins, which in turn, turns the generator (a magnet inside a wire coil) and produces a current. Although the light from this method is constant (as long as the wheel is moving), the increased friction leads to increased wear and slows the rider down.

A picture of a hub dynamo

A picture of a hub dynamo

Hub dynamos tend to be built into the axel of the wheel and require specialised installation; which makes them correspondingly more expensive than their direct contact cousins; but the resistance is greatly reduced and they have the added benefit of being waterproof (being wet causes the direct contact ones to slip occasionally)!

The (relatively) young whippersnapper on the scene is electromagnetic induction. In this setup, powerful magnets are attached to the spokes of the wheel and another to the bicycle frame. As the wheel turns, these magnetics briefly pass one another causing the one in the frame to spin within its coiled wire sheath. The beauty of this is that there’s no friction – as in contact or hub dynamos – and as a result much less wear and tear. However, the light beam isn’t constant – it flashes periodically as the magnets pass one-another.

But, what you get out is always down to the rider – the faster you cycle the brighter the lights will be or more frequently they’ll flash!

About Derek Shirlaw

I'm passionate about science communication, social media, and my home country, Scotland. In particular, I have a real interest in astronomy, digital marketing, and the great outdoors.
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