Dynolights and hills
 

Peter White or Sheldon may have covered this already, but I'm not sure.

From doing some research on Peter's site on the various light patterns of dynolights that he carries, I understand that fast riders and those who have a lot of downhill sections need to have something with a fair amount of throw.

Since the dyno generates power from the front wheel's RPM- Is the light any dimmer going uphill due to the slower RPM's?

Yes, the light output ramps up from zero when standing still. Once you get up to about 6mph there's a reasonable light output to see by, but it does still increase as you go faster.

My understanding is that modern quality lights have a voltage limiter, so that they don't get destroyed from too much current. There's a certain speed at which a particular light attains its full brightness: above that speed, there's no change, below it, the light's dimmer. LED headlights seem to reach full brightness at lower speeds, so if you're worried about being able to see going uphill, you might consider an LED. I've never used a dynohub, but I've had bottle generators, which work similarly, and while the light is somewhat dimmer if you go very slow, I don' think it's ever been a problem with my LED fly IQ. I don't think it was much of a problem with the Lumotech either, but it's been about a year since that bike was stolen.

For one thing, since you're going slowly, you don't need as much light. Also, I get the impression that the hub generators are more efficient, which would seem to make this less of a problem. Finally, some lights (including the fly) let you adjust them as you ride (provided you mount them in easy reach). This is quite handy.

Regards,
Mike

My understanding is that modern quality lights have a voltage limiter, so that they don't get destroyed from too much current. There's a certain speed at which a particular light attains its full brightness: above that speed, there's no change, below it, the light's dimmer. LED headlights seem to reach full brightness at lower speeds, so if you're worried about being able to see going uphill, you might consider an LED. I've never used a dynohub, but I've had bottle generators, which work similarly, and while the light is somewhat dimmer if you go very slow, I don' think it's ever been a problem with my LED fly IQ. I don't think it was much of a problem with the Lumotech either, but it's been about a year since that bike was stolen.

For one thing, since you're going slowly, you don't need as much light. Also, I get the impression that the hub generators are more efficient, which would seem to make this less of a problem. Finally, some lights (including the fly) let you adjust them as you ride (provided you mount them in easy reach). This is quite handy.

Regards,
Mike

I'm aware of the voltage regulation that prevents the light from being destroyed- older systems probably had issues with over charging.

I'm more concerned with the slower speed of going uphill. If I knew of a way to pull up some sort of topographical function on Google Maps or Earth (or anything that showed elevation change) I'd post a pic or link.

Downhill I'd imagine I could brake if I felt like I was out riding the light.

In a lamp such as BM IQ Cyo there is a standlight function that kicks in when you are very slow. There is some reduction in brightness but there is still plenty of light. In my own DIY system the battery and dynamo power are smoothly blended together. The power delivered to the lights is steady, practically independent of the speed, no matter whether LED or incandescent lights are connected.

I have a B&M LUMOTEC IQ Cyo headlight running on a Shimano 3N80 dynamo. I have ridden plenty of times at night up some long 5km + climbs at about 7km/h average

Firstly the standlight function only outputs a small portion of the full light for a fairly short amount of time. You will only get about 5mins of light at 30% brightness (my estimate). After 5 minutes the light will start to fade to a point where it's quite useless if your still climbing a hill. (unless you can keep your pace above 10km/h, that'll give you more then half brightness... plenty of light for that speed)

The way i get around it is to wear my Petzl head torch on my helmet and use that when the dynamo light isn't enough.

I have yet to find a DIY system i can build that has auto battery cut in when the dynamo isn't producing enough current. Everyone that i've found on the internet requires you to make/fabricate your own PCB. Which i am not skilled enough to do. Wish someone would put a DIY kit together that included a printed PCB.

2_i you smarty pants

pawnii, here and the other thread. Sure, I've been thinking about putting out a kit. However, things do not just end up with the PCB. There are issues of housing, mounting, cabling, switch, indicator lamps and housing for the latter. E.g. with my own board I found that issues of protection against water are very serious. With 5+ layers of coating for the PCB, I might still get a short, disabling the circuit, after a year+ of the bike with circuit outside. Either I would need to solve these problems or the recipient of the kit would need to solve them himself.

Some LED headlights do continue to get brighter at higher speeds, at least up to 20 mph or so. At higher speeds the extra heat generated may limit brightness, except on lights designed for high speeds like the Supernova E3 Triple. Here's a chart for the Edelux, which compares the brightness at each speed for that light, versus their halogen bulb (E6) (yellow line), and I believe the Lumotec LED light (gray line), and a competing 1 or 2 watt LED headlight (blue line):

http://www.starbike.com/images/SON/e...ngsstaerke.png

http://www.starbike.com/images/SON/e...ngsstaerke.png

The brightness reaches 15 lux (as bright as a halogen light or an older LED) at only 3 mph / 5 kph, and levels off near max brightness by 12 mph / 20 kph. But the brightness increases a little bit more up to 18 mph / 30 kph, at least. I doubt you would see a difference.

Anyway, back to your question about hill-climbing, as long as you can keep the bike moving as fast as a brisk walking pace (3 mph), there should be enough light to see the road in front of you, but the light will not be as visible to oncoming traffic (as usual).

I think the B&M IQ Cyo and the Supernova E3 Pro would have similar lines and similar brightness.

2_1 i don't mind working out the case myself. I quite like the idea of making my own housing, mounting, cabling, switch and indicator lamps. All i would like is a pre-made PCB and components in the kit.