benkp

Hi all,
How fast does one need to cycle to produce light with a dynamo hub?
I'm thinking about a sturmey archer dynamo/drum brake or a nexus dynamo with a roller brake.
Could i dawdle along at, say, 8 m.p.h. and still have light?
The wheel would be 26", and i'd want a reasonably bright light - light enough to see where i'm going on dark streets, not just a light so drivers can see me.
Thanks

Sci-Fi

The Shimano Dynohub (6v 3watt) will deliver that output around 5.9 mph.

As far as lights, the.minimum, imho, should be around 60 lux for enough light to see the road and distance. B&M Cyo Premium 80 lux is what I'm using on 2 of my bikes and a Philips Saferide 60 lux (no longer made) on my cruiser bike.

desconhecido 

In my experience, even an old SA Dynohub will provide good light at low speeds (5 mph or more) when paired with a good quality modern LED headlight like the better Busch and Muller lights. The Germans, apparently, take their dynamo powered headlights seriously and if you order from a European retailer a really nice one can be surprisingly inexpensive, depending on the current value of the variable "inexpensive." LED headlights are so good that I think they might be magic.

I don't think that better quality hubs buy you much more light. What they do is give you less drag (particularly when the light is turned off) and lighter weight.

alo

I use solar lights. They stay on even when you go slow or stop riding. Maybe some of you have some bright dynamo lights which I have not seen. But these solar headlights are much brighter than any dynamo light I have seen. I would encourage people to try them, then let us know what you think.

https://www.bikeforums.net/electroni...le-lights.html

desconhecido 

A bit more about the LED lights. The total light output is important and your're not going to get enough light if the LEDs don't produce enough. Then there is how the light reflector and lens is designed to spread the light out in front of you. If you look at Peter White's site he has some good inrformation about a couple of good lights that will show what I'm getting at. Then there is a Finnish company, Herrmans, that claims to have a high output light with innovative reflector and lens technology the H Black Pro. There are some youtube videos touting the extraordinary excellence of their technology. I don't have enough knowledge to critique their claims, but the videos are entertaining. The lights were'nt very expensive a couple years ago so I bought one but haven't tried it out yet.

GamblerGORD53

Forget the goofball roller brakes needing special greasing. Probably doubles the drag anyway. I'm pretty sure you can do 10 mph without sweating anyway.
My SA XL-FDD has 24,000 trouble free miles. The lights fire up just pushing it, even backwards. It has done 2 tours on a 120 lb bike, the first one was with a POOR rear caliper. A strong fork is needed. It is VERY unlikely you could wear out a SA hub, that needs NO adjustments. Maybe the cable once a year or 2. I have strong 2.3/ 2.0 spokes and SA long pull levers. I had to make a rivet, they come short pull.
You could likely do with the smaller 70 mm hub. I have the first Edelux headlight with only 50 or 60 lux. The new ones have 90.

benkp

true, 8 m.p.h. would be pretty slow for me, though it happens sometimes when it's windy. At any rate, sounds like the consensus is I don't need to worry about it so long as i select a good headlight. I actually would like to have a 24" wheel in front regardless, if I can figure out a way for it to work i might try it just for the hell of it.

Moe Zhoost

I had a Sturmey dyno drum hub on my commuter bike and had plenty of light from 3 mph on. Like GamblerGORD53, I have tens of thousands of miles on the hub with few problems, although I did have to replace the cartridge bearing on one side. I'm currently using a Shutter Precision hub, which I really, really like.

pdlamb

IIRC, the Shimano and Son dynos will develop full power (3W) at 6 mph. Mine (one of each) stop flickering a bit below that, maybe 4 mph.