Round Up: Dynamo Lights

Cyclescheme, 25.09.2012

Round Up: Dynamo Lights

Dynamo systems convert pedal power into electricity, giving fit-and-forget lighting in exchange for a little extra effort

Dynamo lighting is green energy. A generator in or on the wheel siphons off a little pedalling energy to power your bike lamps. It's the predominant system in countries where transport cycling is popular, such as Germany and the Netherlands, because it's so convenient. Your lights are bolted to your bike and are always ready to shine; there's no recharging routine to remember or disposable batteries to buy, and no faffing with fixture or removal each ride.

The only real downside is a small amount of drag. And it is small. At typical commuting speeds, and depending on its efficiency, a dynamo might require 5-15 Watts of your energy. That will slow you down by less than 1mph, or less than 0.5mph for more efficient systems. That's assuming you don't just pedal a bit harder.

There are two popular types of dynamo: ones shaped like a bottle that press a little roller agains the sidewall of the tyre; and ones where the generator is built into the hub. There's also the Reelight system (see below), which works by magnetic induction.

Bottle or sidewall dyanmos are the cheapest. They used to be the most common, although they are being overtaken by hub dynamos these days. They work better if the tyre has a file-pattern dynamo track on the sidewall. Some slip badly in the rain, which means you lose power – and light! The better ones (Axa, Basta, Busch und Müller, Nordlicht) cope well enough with most conditions short of snow, sleet or mud. You can improve performance and reliability by taking care to orient the roller on the tyre just right, and by making sure the roller is pressing on the tyre properly, not just skimming it.

Hub dynamos are, as a rule, more efficient and reliable than bottle dynamos. The drag is lower and they don’t slip. They tend to cost more, however, and you can't just bolt them onto your bike: you need a new wheel, with the new hub at its centre. Your local bike shop can build this for you.

As well as the generator, you'll need lamps. Almost all dynamos are 6 Volt systems with a 3 Watt output, powering a 2.4 Watt front lamp and 0.6 Watt rear. If you run a battery-powered LED rear light, you can fit a 3 Watt bulb up front for extra brightness. Lacking raw power, a lot of work has gone into designing dynamo lamps to make best use of the power they have, and even a 2.4W front lamp will provide enough light for unlit lanes.

Many dynamo lamps incorporate a reflector and some have a stand-light, which comes on when you stop. This is a secondary LED in the lamp, or just the main LED if it’s an LED lamp. The dynamo charges a capacitor, which powers the LED. It’s seldom bright enough to see by but it’s enough to get you seen.

The suggestions here are not exhaustive. They are intended to give an idea of the range available.

Generators


Nordlicht 2000 

Nordlicht 2000

A sturdy, metal-bodied sidewall dynamo that's available for left or right side (of the wheel) operation. It turns smoothly and reliably, although if you have trouble with the rubber roller slipping, an optional steel dynamo wheel is available (£2.99).

£31.99 

www.fisheroutdoor.co.uk


Shimano Nexus DH-3N30

Shimano Nexus DH-3N30

This is the cheapest in Shimano's range of hub dynamos, a nutted hub designed for rim braked wheels. Other models are available with quick release fittings, and for disc or roller brakes. For fast road riding you might want something lighter or more efficient, but for commuting this does everything you need.

£34.99

www.madison.co.uk


SP SV8

 SP SV8

At 360g, this is very light for a dynamo hub. It's efficient too: SP claim 72%, which means minimal drag relative to the light output. SP also offer a similar hub for disc brakes, and another for small wheel bikes. Even better (and more expensive) is the SP switchable hub dynamo, which offers drag-free operation when the lights are off.

£89.99+

www.ison-distribution.com

 

Lamps

 

Reelight SL100 set

 Reelight SL100 Set

Reelights are powered by wheel magnets (provided). When these pass by the lamps as the wheels rotate, magnetic induction makes the lamps flash. There's virtually no drag and no batteries are needed. This set is designed to flash whenever the wheels rotate, day or night. Other versions keep flashing for a while after you stop, or provide constant light.

£35.99

www.raleigh.co.uk


Busch und Müller Lumotec Plus

 Busch und Müller Lumotec Plus

Designed for use with sidewall dynamos, since it doesn't have an off switch, this German headlight has a reflector and a stand-light that shines for up to four minutes. You can swap the 2.4W bulb (e.g. for a 3W bulb) easily and without tools. Busch und Müller have a vast range of dynamo lamps, front and rear; this is one of their most basic.

£20

www.amba-marketing.com


Exposure Revo

 Exposure Revo

The 800-lumen Revo is intended for mountain biking in the dark, although it's also suitable for riding at speed on unlit roads. The multiple-LED lamp incorporates a powerful stand-light, which stays lit for 10 minutes. To power the Revo, you will need a good quality dynamo hub (such as the SP SV8). While it's an expensive light to buy, running costs are essentially zero – as with any dynamo setup.

£199.95

www.exposurelights.com

 

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