Wednesday, November 17, 2010

Dynamo (generator) lighting primer

I like modern generator lights better than the stick-on blinky lights most people use, especially for riding in the city and especially for riding with kids. They are a lot brighter than they used to be and let you be seen in traffic even during the day. They always are there, ready to go, and you don't have to change the batteries or charge them or think about them. Some you don't even have to turn on. The new LED ones have a "standlight" that keeps them bright for a few minutes after stopping, like at a stoplight. In general, a generator light is a great idea and really worth it for any bike you plan to ride for a long time in traffic, like your regular commuting bike. By the way, there's a technical difference between a generator and a dynamo but it doesn't matter to this application much, and the definition varies by the country you're in.

Let's say you live in Chicago and want to put these things on your bike.

The Generator or Dynamo (Power Supply)
The cheap pretty good way to do this is get a standard bottle dynamo from the olden days at Working Bikes or old stock somewhere. Union, Soubitez, Sanyo are all good, but anything will work. They are all 
6 volt 3 watt units (with very few exceptions: one rare 12 volt version exists). Make sure the brackets will fit together and fit on your bike and that the old wheel spins OK. In general it's recommended that you put on a bottle generator with the tire moving away from the mounting part, toward the spinny thing part, so the generator can't get caught in your spokes or something and become an emergency brake instead. Many old bikes don't do this though. You can put these things on the front wheel or the rear, and they come in both right and left versions if you have a specific mounting location in mind. The axis of the spinner has to be exactly in line with the radius of the wheel to keep noise down. Use a string from the middle of the spinner to the axle to verify the angle. The spinner itself should be right on the dynamo track molded into most tire sidewalls. If the dynamo is designed for the rim, which is unusual but much quieter, make sure it isn't rubbing the tire at all. A thin rubber spinner is needed for rim mounting.
A dynamo hub is always there and you don't even notice it.
If you want to go fancy instead get a new Busch & Müller or Axa/Basta bottle generator - efficient, black plastic, less noisy - for about $50, or use an old quiet Sanyo under-the-bottom-bracket generator if your tires are smooth. For very fancy, next time you need a new front wheel get a dynamo hub for it. They start at about $45 for Sanyo, $65 for Sturmey-Archer or Shimano and go up toward astronomical (ca. $300) for hand-carved aluminum hub jewelry from Germany, they don't make noise and they don't cause noticeable drag, even the crummy ones, whatever you might read online. There are various qualities of prebuilt dynamo wheels to fit most bikes, available on order from most bike shop wholesalers.

If you look around and you're lucky you might find an old 1960s Sturmey-Archer Dynohub. They last forever if you don't take them apart (! there is a special tool and way to do it or the magnets lose their oomph) and they work fine with modern LED lights. They produce slightly less power (1.7 to 2 volts) than modern generators so if you use old fashioned incandescent bulbs you need special low-voltage ones. Dynohubs can unscrew themselves if you put them on backwards - wide part on right is correct, for most models. Some have integrated brakes or even hub gears in them.

There is a recent product that calls itself a contact-free dynamo where you put little magnets on your spokes and the light generates power from them; neat, but inefficient (and that's how the others work, too, only with many more magnet points). These lights are dim, in my experience, but better than nothing since you don't have to think about turning them on.

The Lamp Options

Then, once you have a generator, you can get old used lights with bulbs in them. Total cost for the system with an old generator: $15 or less. But you'll be happier with LED lights. And it's getting very hard to find replacement bulbs in Chicago, though you can look online. Boulevard Bikes, JC Lind and a guy in New Hampshire named Peter White are the go-to people I know about for LEDs, though many shops in town can order these things. Read the Peter White Cycles website if you want details, then buy it locally. He is the distributor, so he'll still get his cut even if you don't order from him. Or go talk to the people at any local place that has some in stock.

The cheapest Busch & Müller LED front light with a standlight and reflector that I've bought new recently was $28 on special, but the really bright ones go up to over $100. The $28 one (a Lumotec Oval Plus) is still quite bright, and it blows the doors off one of those blinky things. You can ride down a dark forest path with it. It has a reflector integrated into it too. The bright ones like the Cyo N Plus are even better for that kind of thing but may be overkill in the city. I like the Cyo without a built in reflector myself, though both are good. In fact, no model I know of is particularly bad. The Lyt is a recent one that seems OK - we have one on one of our kids' bikes. Get a standlight if you can, especially in the city where you will be easier to see at an intersection. We also have had good luck with Basta front LED lights, but they didn't have a standlight so we swapped them out. I think the quality has been better on the B&M. Surely, there are excellent Japanese lamps available — many dynamos are from Japan — but I haven't seen them in the US yet. Comment if you find a source.

The back light with a standlight (!) will also be about $20 to $40. I like the Busch & Müller Top Line Plus, or Seculite Plus for fenders, but any of them are OK. There's one that has a brake light function if you slow down suddenly - neat idea, almost works. Get one that mounts well on your bike - fender, rack, or cantilever brake nubbin with an adaptor. Other brands of these things include Spanninga, Basta, and I'm sure plenty of others. The back light connects to the generator just like the front one does (especially if the generator is on the back wheel), or it can connect to the front light itself if you want to turn the whole system on and off with a switch on the headlight. I just leave mine burning all the time and it doesn't ever need me to think about it.

Installation Tips
Deciding where to mount the lights is a big decision. Generally I attach the front light to the brake mounting bolt in the front fork, though there are lots of options. This is good unless you need the space for a big basket or rack. If you turn the bracket over 180 degrees you can bolt it onto a fender, too. I don't often mount the headlight on the handlebars but some people do, and the suppliers above carry adapters to make it simple. The taillight works best on the fender, I think, but my bikes have steel or SKS fenders that are sturdy. The rear rack is also a good place; you can use a strip of vinyl coated stainless steel with bolt holes at each end to attach it. They sell these in bike stores to mount racks. There are also good adapters at the light supply stores. If you don't have fenders or a rack, and you aren't planning any (why not?) you can often mount these lights on the seat post or on a reflector type hanger coming from the rear brake bolt or frame cross between the seat stays. 

If you are going to drill a hole in a fender to mount it, remember that the drill bit will go right through your tire, too, and either remove the wheel or put a drill-proof board under your drilling site. Otherwise you'll be patching the tube, too. Not that I ever made that mistake, of course. Make sure you are drilling low enough and straight enough to have your lamp even and vertical when you are done.

I prefer to hook them all together with double stranded cable (two wires) which is more reliable than the old single wire. One of the wires, sometimes marked with a lightning bolt symbol, goes to the bottom of the bottle generator (or the lightning bolt side of the hub connector). The other wire, often with a ground/earth symbol that looks like a T with 3 top lines or with a white stripe, connects to any screw or other part of the bottle generator mounting bracket. I usually put a couple of centimeters of bare wire around the bolt at the mounting bracket's elbow, between the two arms of the bracket. At the lamp end, if there is no terminal for the ground wire, it connects to the metal arm or screw that holds the lamp onto the bike. If you connect everything and it doesn't work, reverse the wire connections first - LEDs, unlike light bulbs, can be particular about which wire connects to which side. (with AC power sources like generators it shouldn't matter but sometimes the system converts to DC and then it does.) The lights can flicker a little at low speeds, more with hub than tire generators.

There are lots of ways to route the wireI sometimes run the electrical wire along an existing brake or gear cable, sometimes run it in a plastic pipe which looks less fiddly than the thin wire, sometimes I zip tie it to the frame. Be careful not to make it hard to take the bike apart if something like a tire needs repair. Leave enough slack in front that the wheel can turn fully or you'll rip out your new lighting system all the time. 
I prefer stainless steel zip ties that look better on your bike and last longer than the black plastic ones. Harder to get off but you can crush the connector with a pliers. I got mine at a giant orange home supply store. I prefer the look of zip ties to the old method of winding the wire around and around the frame.

Total cost: $15 (for old style) to $75-90 (new lights, old bottle dynamo) to $150-200 (new hub and lights) to $$ for a SON hub with Schmidt EdeLUX lighting. There's a guy in Boston at a place called City Bikes who builds his own US made metal and glass retro styled LED standlight system - toward the high end of the scale.

There are a few how to articles and videos 
I've seen about making your own standlight headlight. It's a good way to save money since the electronics cost much less than the finished lights, but I think it's a little too involved to get into here and I just buy the finished lights myself. But there is a do-it-yourself option if you want. 
The bluish colored dynamo light (Cyo N Plus) on our bike, left,
is pretty visible even compared to car headlights
It's a pain and it costs some money to plan a generator lighting system out, and it takes an hour and some zip ties to connect it, but then you never have to think about it again, and it always works well. We use them on all our regular bikes, including the kids' bikes.

We just added a post about lighting children's bikes.

last edit 3/27/12


  1. I agree that dynamos are a worthwhile investment. I've been pleased with the Shimano dynamo on my bakfiets as well as the Schmidt Nabendynamo on a recumbent. They both work well. I love that I can just "get on and go" and not worry about whether this is the trip where my batteries will run out.

  2. Need a new front hub? Tired of that old useless roller brake? Sturmey-Archer has a couple of drum brake dynamo hubs for the front that should (I think) fit a lot of cargo bikes. There are also a few that will take a disc brake. The length of the cable run makes it a good idea to choose a hydraulic disc brake rather than a standard cable one, probably.

  3. Nearly New bikes on Broadway also has a box of old generators and lighting parts.

    1. ...except that Nearly New seems to have gone out of business...

  4. A few people have asked me how to use an old dynamo with new dual wire lights. It's simple - hook the wire with the ground symbol (3 lines on a T) molded near it (or just choose one - if it doesn't work you can swap the two wires) onto the metal part of the dynamo clamp (or onto anything metal on the bike, if the dynamo is properly installed with the sharp clamp screw that cuts through the paint). The other wire, the lightning bolt one, goes to the power output of the dynamo. Usually the rear lamp hooks into the back of the headlight then. See Peter White's site for more and more and more info.

    Clever Cycles in Seattle was selling cheap prebuilt $99 front dynamo hub wheels in 700c and 26 in sizes recently. Have a look - cheaper than many other hub options.

  5. Thanks for the tip on the 26" wheels with hub generator at clever cycle! I came across your page after looking all over the web today and that fits the need for the bike I'm working on upgrading (to useful!).

  6. Very helpful post covering all the basic options well. All of my regularly used bikes have generator setups, it's just so convenient, and the LED lights are much better than the old incandescent ones.

    1. They are getting easier to find, too. I think generator LED lights should be on most people's bikes all the time - it makes bikes so much easier to see in traffic. If you ride a lot in the city in the dark and have the basic non-standlight on your Bakfiets maybe consider a replacement one of these years with a standlight version - ours came with a nice but non-standlight Basta and it's much more visible at a stop light now with the B&M.

  7. They need to bring back the bottle generator with updated technology.


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