Tuesday, October 9, 2012

Dynamo-powered lights, part 1

Considering that Europeans commute by bike a lot more than North Americans do, I thought using their collective wisdom on bike lights could help. Generally, North Americans prefer battery-powered lights, whereas Europeans prefer dynamos (aka generators). Someone whose word I trust tells me that Germany requires fender-mounted lights to be dynamo-powered. In other words, battery-powered lights are illegal.

Also, Germany has many regulations about what bike lights must do and must not do. They specify the shape that the light beam must have, and they specify minimum and maximum brightness. Since bike lights are required for a great many bike commuters in Europe, and since most bike commuters take the requirements seriously, high quality lights are mass produced and widely available in Europe.

Long ago, I took a bike tour in Europe which lasted for three months. Before I left, I equipped my bike with a dynamo and lights. The system worked reliably, without my ever having to make changes, adjustments, or repairs. This memory, combined with the points in my preceding paragraphs, made me realize that dynamo powered lights would be good for me. The purchase price can be high, but it might end up being a better value than batteries.

A generous friend gave me a Sanyo H27 dynamo hub as a gift. Building wheels is something I enjoy a great deal, so the chance to build a wheel out of this was a plus, not a burden.

I bought my lights on http://www.xxcycle.com, which is a French web site. They offer an English version of their site, and you can have the prices displayed in US dollars and other currencies. Their prices are low enough that, even with the shipping cost, I saved money, compared with buying the lights from one of the few sources in the US. The headlight is a Busch & Müller IQ Fly R Senso + (174SNDI). The output is rated at 40 Lux, which is a different scale than lumens. The beam pattern is odd. The lens creates two beams. One is very short and very wide. The other reaches and spreads ahead, illuminating the road. This latter beam is oddly rectangular-shaped. I'm sure there's a rationale for the German regulation requiring this, but it doesn't bother me nearly as much as it amuses me.

I haven't installed the tail light yet.

Europeans do not use flashing headlights or tail lights, and I don't feel the need for one.

The lights have a "standlight" (aka standlicht) feature whereby they stay on even after the bike stops moving. They accomplish this by putting a capacitor in each light. I'm grateful for this. The headlight also has an "auto" mode where it lights up when it is sufficiently dark outside but not when it's light. I haven't tested this. I have decided that a "daytime running light" might prove to be useful, and the cost of running it is negligible.

Speaking of cost, I should talk about the energy required to light my lights. As I've said, I haven't installed the tail light. The headlight's electrical causes the dynamo hub to increase the drag that it creates, however, I can't perceive this load while riding. In other words, the energy requirement from my body is low enough that it's nearly free. That may change when I add the tail light, but I doubt it. At high speeds, I can feel a vibration in the handlebars, but it doesn't bother me.

I've felt comfortable traveling on very dark roads at speeds of up to 25 mph. This is quite fast on a bicycle. I can accomplish this speed only going downhill. I can go faster than that in the day, but it's a generous enough speed that I don't feel very restricted. In other words, the light makes me feel quite secure in traffic.

This post is part one. Part two will feature more pictures, a description and report of the tail light, plus mention of my other approaches to safety at night.


  1. Nice article Tom. I've looked into dynamo lighting but didn't think I needed it. I don't ride long distances in the dark. My 10 mile commute is about the longest I'd be out there and a rechargeable battery light can cover that easily.

  2. Its not so much about whether your batteries will last 10 minutes (if they don't you've got bigger problems). Its about knowing that your lights just work. You don't need to think about it at all, just ride and lights happen.