Dynamo or generator lights offer riders an alternative to battery lights, but at a lower power level. Modern LED lamps make the dynamo approach more practical, giving out more light per watt than older incandescent bulbs. Light output still won't match the intensity of the best battery-powered systems. If you're satisfied with less candlepower and don't mind the feeling that you're pedaling with the brake on, dynamo lights keep shining as long as you keep moving.
Operating Theory
Dynamo lights work like the alternator on a car engine, using the rotational force of the wheel to turn the shaft of a small generator. The bottle dynamo looks like a small metal bottle. A small drive wheel at the "mouth" of the bottle contacts the rim or sidewall of the bike tire, turning the generator in the bottle. Roller dynamos mount on the bike frame and roll on the rear tire tread when in working position. Hub dynamos -- the best approach -- build the generator system into a bicycle wheel hub. Power output ranges from three to six watts. The maximum output of a cyclist approaches 125 watts at full power, so even that three watts produces an obvious drag, according to Bicycle Lighting Systems.
Best Hub Dynamo
Fully contained within the wheel hub, the hub dynamo operates regardless of weather conditions. For a hub dynamo system with a barely noticeable drag and good output even at low speeds, Seattle Bicycle Supply chose the Shimano DH3D30 in 2007. Shimano now offers the updated DH-3D71, also compatible with disc brake systems and the best choice for inclement weather. The 6 Volt 3 Watt output mates to many popular headlamps.
Best Halogen Light
The LT145 Schmidt E6 Headlight connects to Shimano dynamo hubs, accepting the standard 6V 3W output. The waterproof headlamp mounts to readily available brackets and includes a magnetic on/off switch in the lamp body. The high-intensity halogen bulbs replace easily. This light's focusing system illuminates a rectangular area in front of the bike, with enough power to shine through the glare of approaching headlights, says Sheldon Brown.
Best LED Light
The LT132B Lumotec IQ Fly Plus connects to Shimano dynamo hubs easily and provides a graduated-intensity beam like those installed on European sports cars. The reversed LED's focus light on the lamp's reflector, which controls shape and intensity. The resulting beam puts more power into the upper edge where the light covers the most distance, and less power into the lower part of the beam that shines upon the near part of the roadway. Running the headlight without a taillight on the same system might shorten the life of the replaceable LED's. All Busch & Muller Lumotec Plus lights include "standlights," says Peter White of Peter White Cycles. A storage capacitor in the light holds a charge for several minutes after the bike stops, keeping the headlight on at a lower intensity level during short roadside breaks.
Member Comments