This is one of those neat ideas that’s been tried before, but somehow the technology was never quite up to the job.This time, with a few caveats, it works rather well. So, how do lights function without any power? Energy has to come from somewhere, of course, and as so often in cycling, the engine is your legs.The principal is similar to most bicycle computer wheel sensors. A magnet is fixed to the wheel spokes (a pair in this case), and as the wheel turns, the magnets whizz past a stationary electrical coil in the back of the lights, producing a pulse of electrical energy. In the old filament lamp days, this would not have produced a tiny glimmer, but with modern ultra-bright LEDs, the output is good, and the extra rolling resistance negligible. Oddly, considering that red LEDs are better understood than white, the front white light is stronger than the rear red.
Front and rear Reelights. Both lights incorporate reflectors and twin LEDs. Note the large magnet fixed to the spokes
A set of two lamps plus four magnets weighs 240g, which compares well to battery lights, or a dynamo or dynohub system. Is the output comparable? Not as bright, obviously, but very eye-catching, because the lamps flash as the wheel revolves.The magnets should be mounted opposite each other, giving two flashes per wheel revolution – actually, it’s more complicated than this because each light contains two LEDs, and when the magnets pass, these each flash back and forth twice, producing four very quick pulses of light, but it looks like one.
The magnets can be fitted to most spoke layouts.We tried them on Alexander’s 14inch Triang Moulton, which has 20 spokes, and an uneven five pairs per side, so the magnets produce a slightly off-beat flash: light, space, space, light, space. Groovy.
So what are the disadvantages? Obviously at low speed with a big wheeled bike the lights flash rather slowly, and at high speed on a small-wheeler they flash in a frenzied blur. Flashing bicycle lights are now legal in the UK, but only if they flash at 60 – 240 flashes per minute. At 12mph, a 26-inch wheel revolves at about 130rpm, which comes in at just over four flashes per second, so if you go any faster you’re in illegal territory. On a 16-inch folder, you’d reach top flash at a mere 7mph.To make matters worse, the legislative meanies have ordained that a rear light should be at least 350mm above the ground (there’s no minimum front lamp height). As the Reelights fit on the axle, this technically makes the rear light illegal on any bike with sub 26-inch wheels.
Should we worry about all this nonsense? Not really.Think of the Reelight as a back-up system and it’s excellent. On Alexander’s bike they function as Volvo-style ‘day running lights’, particularly useful in the mad people-mover throng outside Manor Park Primary on a foggy winter morning. At 12mph, the little Triang Moulton emits a healthy eight flashes a second, which should wake even the dopiest school-run mum. Rolling resistance is too small to measure, and the only real disadvantage is that the powerful magnets cause the lights to vibrate on their brackets in a rhythmic (or in this case, off-beat) manner.This might annoy, but it might help you to hum a little tune as you bowl merrily along.
Legal things apart, Reelights are ideal for small-wheeled bikes. They fit a Brompton and fold away without any issues, and the high flash rate kicks in at walking pace, and becomes almost steady at speed – there’s certainly enough light to get you home in an emergency. If you want more, you only need to fit more magnets… Reelight also produces the SL120, which emits a steady 120 flashes per minute while in motion, plus a full five minutes standlight capability when you stop.
Reelight SL100 front & rear £28 . SL120 £36 . Derailleur bracket £2 . Spare magnets £7 Danish Manufacturer www.reelight.com . UK Distributor 2pure tel 0131 448 2884 mail info@2pure.co.uk
A to B 57 – Dec 2006
