Lighting up the road

Using a bicycle to get around has become hugely popular in the UK, both in the city and the suburbs. And while UK Councils and the Highways Agency are drawing up plans and policies to improve the safety of cyclists on public roads, riders themselves must ensure they are taking the necessary precautions, notably that they are seen. Using lights is essential, and strobing bright flashes have become synonymous with cyclists. However, as these are mostly battery powered, they can dim and stop working without warning. If the rider is a long way from home this potentially opens them up to a dangerous ride back in the dark. The classic solution of dynamo power offers a solution here, and with sufficient pedal power the lights will remain on. However, there are significant drawbacks with the original design. Pull up at the traffic-lights and the lights that were shining away dim and disappear in seconds. They also add a significant amount of friction to the wheel, meaning the rider often has to pedal twice as hard. The challenge The challenge this month is therefore to come up with bike lights that do not require disposable batteries, by addressing the two major drawbacks of dynamo power. Making the dynamo itself near frictionless would be a good start. While there have been great improvements in bearings, turning the magnets of a dynamo needed to generate the alternating current, still requires significant exertion by the cyclist. Perhaps mounting the dynamo in a different position, in the bike hub or on the chain, would prove more efficient? However, fundamentally, the generation of power by mechanical means needs to be re-thought. Energy to power the lights will obviously need to come from somewhere, so perhaps vibration might be the answer? In addition, the lights need to be able to store some energy to prevent the classic dimming of dynamo powered lights when riding slowly or at a standstill. This should be pretty easy for most to figure out, and remember it must be battery-free. Of course, as this is for a bicycle it should be relatively lightweight. And making it quiet and doing away with the whirring sounds of the old systems would round off the design perfectly. The idea we have in mind answers these problems elegantly and addresses all of the issues mentioned above. The solution to this challenge will appear in the May issue of Eureka. In the meantime, see what you can come up with. -Solution- Solution to the April 2014 Coffee Time Challenge The solution to last month's Coffee Time Challenge, to re-design dynamo powered bike lights, comes from Kickstarter start-up company, Magnic Light iC. The key to its bike lights are in its exploitation of the physical phenomenon of eddy currents. It's able to generate electricity by using magnets in the dynamo that generate eddy currents as the metallic rim spins. An internal conductor in the dynamo induces an electrical current as the wheel rotates and changes its magnetic field. And since it is non-contacting, this method of power generation is friction-less and causes no noticeable additional resistance to the wheel. The energy produced is sufficient to power LEDs, is silent and also lightweight. Though the output wavers with the spinning speed of the wheel, this has been address by an onboard microprocessor that is able to adapt with wheel speed and maintain peak efficiency. A built-in capacitor also allows the lights to stay illuminated when the bike comes to a standstill. Though the voltage and current generated is relatively small, the Magnic Light iC is optimised for the LEDs used, allowing for more light to be generated per unit of power and about 160 lumens per watt. The Magnic iC is soon to be fully commercialised and widely available, but if you can't wait, the lights are available from its website. www.magniclight.com