Are You in the Dark About Dynamo Lighting?

What is a dynamo?

Though their design has changed, dynamos, devices that convert mechanical energy into electrical energy, have been available on bicycles for over a century. Early dynamos were tire-driven, resembling small “bottles” that rubbed against a tire or rim.  Between World Wars I and II, English bicycle component manufacturer, Sturmey Archer (SA), first popularized their “Dynohub,” placing the power generator within a bicycle hub. By turning a wheel into a dynamo, durability was improved and the problems of rim or tire-driven systems, such as drag and tire wear, are mostly eliminated. Tire-driven dynamos are still manufactured today though most common modern models are hubs.

What makes a good dynamo light?

While bicycle lights come in a variety of sizes and brightness, most dynamo lighting equipment is designed to comply with German road-use regulations. These stringent and specific regulations are in place to ensure that cyclists are well lit from all directions and that the lights don’t interfere with other traffic.

According to the German rulebook for vehicles (StVZO/TA), a bicycle headlamp should have a horizon, meaning that to not blind oncoming traffic the light’s beam is limited by a hood at the top and aimed so that the center of the beam hits the ground 10 m from the front of the bicycle. Lights that adhere to these guidelines are beneficial for city riding due to a fairly concentrated headlight beam that can illuminate potholes and other hazards on darkened streets.

In most places around the world cyclists are required to have a white light up front and a red light in rear. A single dynamo can power both front and rear lights.

Lights that include the standlight feature will stay on for at least 4 minutes after you’ve come to a stop, as required German law.  Some will stay on longer, but manufacturers do not often advertise this.

Is dynamo lighting bright enough?

It is important consider brightness and how this translates to beam pattern when choosing a dynamo lighting system.

Brightness is often described by different units of measure called lux or lumens.

Where lumens are a measure of the visible light emitted from a source, lux is a measure of the concentration of a beam of light. Two lights with identical luminosity could have very different lux measurements depending on how the light is focused by lenses and reflectors.

Almost all of the city lights designed for the European market are rated in lux. Manufacturers like to use lumens to promote their lights because the numbers sound larger. However, since lux is a measured value and is much more standardized, this measurement better reflects the brightness of a light.

Why dynamo lighting is rare in North America

In many European countries, including Germany and the Netherlands, most bicycles designed for everyday use come equipped with some kind of dynamo light.  Bicycles there often have tabs for attaching tire-driven dynamos or come with hub dynamos right from the factory.