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  1. #1
    Nighttime Rider
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    Generator (dynamo?) newb. A few questions.

    For a commuting bike.

    I was thinking about getting a dynamo hub for my Speed P8 with 20" wheels
    with the idea of having backup power for my CygoLite Dual Cross head light.
    The battery supplied is 4.8V.

    Is a dynamo voltage specific?
    Does the higher rpm with a 20" wheel a problem?

    I really am not sure of all of the considerations of having a dynamo for a
    specific light, so any info would help.

    Thx

    CE

  2. #2
    Year-round cyclist
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    I would suggest you read Peter White's excellent lighting pages. I know he sells them, but the technical information you have there would answer most of your questions.

    Now, to get more specific:

    1. Dynamos (whichever you select) produce alternating current. Moreover, the Shimano DH-3N70 and SON produce 0.5 A at all times, with voltage increasing with your speed.

    2. The good headlights made for generators have these characteristics:
    – Only 3 W (or 2.4 W front, 0.6 W rear).
    – Well focused beam, so you get the light only where you need it; more efficient use of the light beam and less blinding of others; a 3 W Lumotec is about as bright/effective on axis than a typical 10 W MR-11 spot light, and a 3 W E-6 is even better.
    – Some kind of voltage control to keep the lightbulb from burning at high speed.

    Basically, forget using the generator for "backup power" unless you want to design your own electronic controller. However, you could use a SON or Shimano dynohub with an E-6 or Lumotec headlight for most of your ride and use your CygoLite headlight for tricky passages.
    Michel Gagnon
    Montréal (Québec, Canada)

  3. #3
    GATC
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    Hearing that a 3W dynamo lamp (in the right location?) is roughly equivalent to 10W halo just makes my day, thanks for that specific comparison. With 1 or 2 dynamo-powered headlights down around the fork blades, would you need a head-mounted light to emphasize your visibility to other vehicles?

  4. #4
    Year-round cyclist
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    I currently use a small light, the Planet Bike Beamer 5, to supplement the lighting output of the Schmidt E-6. It sounds strange, since the E-6 is much more powerful than the Beamer 5, but the latter has three uses:
    – it has a small spot in the centre and 5 "satellite spots", so the two bottom spots go squarely in potholes;
    – it works even if I'm stopped at a street corner;
    – when riding in a brightly lit business district, the flashing mode is interesting, especially for pedestrians.


    Because the Lumotec and E-6 are large headlights, I think they are more easily seen by other vehicles than the typical MR-11 headlight.There is a bit of theory behind my assertion, because I'm aware that target size is more important than target brightness to make it detected. But it's also based on my experience in traffic as I had much more close calls when I used a 10 W or 15 W MR-11 headlight then when I switched to a Lumotec (the E-6 came a few years later and I don't have the MR-11 headlight anymore to compare). The only deficient aspect of my lighting is, I think, visibility from around 45° off axis, front left and front right quadrants.

    Would a head-mounted headlight help? It might, especially in the latter situations, but it adds weight to the helmet and I tend to move my head a lot when riding, so such a light would, at best, be distracting. However, I have used a head-mounted headlight a few times off road to supplement the E-6. It's not the ideal setup for off road riding (see below), but it's OK since it might happen once or twice a year.


    One or two dynamo-powered headlights? It depends jhow fast you ride. With a DLumotec primary, I'm told the E-6 secondary provides good lighting at 12-14 km/h. But with a Lumotec or E-6 primary, the E-6 secondary starts to provide useful lighting at 15-18 km/h (i.e. both headlights better than one) and both reach full power at around 22 km/h. I don't find the secondary that useful in the city; it's a bit more useful in suburban territory and quite useful on dark roads, especially if going downhill.




    One last word: I used the Lumotec Oval Plus previously (before the E-6 was available). It's also a very good light, but the standlight function is almost useless. Right now, I have an old commuter bike with a round Lumotec, I have an E-6 on the tandem and the single touring bike, and my daugther's bike has the Lumotec Oval that I had for 4 years on my tourer. No experience with the DLumotec (the LED-based one) though; I read that it's slightly less focused than the standard Lumotec (but still great); it's most important advantage is that you can leave it on all the time.

    The Lumotec is probably as good/efficient for city use – if you have street illumination, that is, and it includes a white reflector. It also spills a bit more light sideways, so it might be better than the E-6 on slightly winding multi-use trails. But the E-6 is superb if you ride on unlit roads in a new moon... even on wet asphalt. And in the city, the E-6 is good enough to clearly see cracks and potholes even when wet.
    Finally, none of these lights work well on singletrack. Even if you were to ride at more than 12 km/h to bring the light at full power, you are very likely to light a perfectly bright path directly in front of you... and have no light when your trail turns right or left. In a nutshell, the Lumotec and E-6 headlights are so effective on the road precisely because they don't shed light left and right or to the birds.
    Michel Gagnon
    Montréal (Québec, Canada)

  5. #5
    GATC
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    One or two dynamo-powered headlights? It depends jhow fast you ride. With a DLumotec primary, I'm told the E-6 secondary provides good lighting at 12-14 km/h. But with a Lumotec or E-6 primary, the E-6 secondary starts to provide useful lighting at 15-18 km/h (i.e. both headlights better than one) and both reach full power at around 22 km/h. I don't find the secondary that useful in the city; it's a bit more useful in suburban territory and quite useful on dark roads, especially if going downhill.
    I have one particular long unlit downhill where I have to work to stay under 30mph, and work *hard* to stay under 20mph, so I don't doubt I would get full power from 2 headlights.

    It's good to hear that you think the dynamo lights do give you sufficient vis to other traffic. I was wondering about a helmet lamp more because I'm putting a handlebar bag on that will block a lot of easy mounting points for a bar lamp than because I want to weigh my head down. Maybe I just need to work on some more options for that.

    I think I am going one more winter w/ my 15W halo regardless but it's good to formulate ideas of what to save for hopefully for next winter.

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