A Non-friction bicycle lights generator (dynamo)

Barf. No drag at all means no power transferred... there has to be SOME drag.

...Jim Thompson

They admit to a very small drag. But the flipping-magnet scheme is very clever, and as they point out there's very little mechanical power required, and no friction like wheel-contact generators have.

I like it.

John

When i were a lad i had a bike with a dyno-hub and hub brake. No back torque from the dyno-hub unless the lights were switched in and both generator and brake were pretty imune to rain. IIRC there was no limiter on the dyno and would blow bulbs if i went down hill too fast..

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I'll stick with my 6v halogen lamp and 4 NIMH batteries. Lasts 4 hours and no drag.

Cheers

| I'll stick with my 6v halogen lamp and 4 NIMH batteries. Lasts 4 hours | and no drag.

... and I'll stick with my light with 3 really bright LEDs. Runs about 15-20 hours on four AA NiMH cells before it gets dim enough that it doesn't help me see (but it will help me be seen for perhaps 60 hours of use) and again, no drag. (Though my goal is mostly fitness, not transportation, so drag isn't such a problem, but even so, it's nice that it's not there.)

The lights with LEDs are really nice. They're really bright -- some being as bright as your halogen lamp -- and last a very long time. And vibrations won't break the filament.

Mine last so long that the self discharge rate of the NiMH cells would be a larger factor than the current drain of the lights themselves for a normal person -- except that I do about an hour of riding each night :)

(So yes, I only have to charge my batteries every two weeks or so.)

They admit in the small print that "technically there is some resistance" and I think the word "technically" is redundant. If there is some, they cannot say there is none.

In practice I suspect there is no noticeable resistance because it takes out so little power.

I prefer the national grid providing the energy for my batteries for my lights, rather than me.

It doesn't look a very efficient way of converting mechanical energy.

Their animation looks very vague indeed. Perhaps deliberately so.

I got the impression that LEDs do appear very bright light sources when you look at them directly, but they don't seem as good at illuminating the path ahead due to their lower light output. I think the human eye can't perceive a great difference between two point sources near the upper end of perceived brightness very well.

I heard it is also a myth that LEDs are more efficient than filaments. Efficiency of the latter varies with voltage and current. Low voltage bulbs (e.g. 2.5V) have to pass the most current, so the filament has to be thicker, hence there is more heat conducted along and out of the wire. And also more resistive losses from wiring and internal resistance of the batteries. On the other hand they can't make the filament too thin otherwise it will break too easily. One can buy bike light bulbs designed for 6V batteries, but I have not seen any for 12V.

Filament efficiency also drops as the battery voltage drops below the bulb's rated voltage: the filament does not get hot enough to radiate visible light very well, but still manages to radiate energy in infra red - depleting batteries for less light output. Nickel cell voltage droops worse than alkalines or zinc-carbon.

From the website:- "No Friction! No Resistance!"-- That statement looks like false advertising to me, I'm surprised the UK consumer laws do not apply. Or have they cracked the laws of Thermodynamics?

I was looking on their website for perpetual motion machines and water-powered cars, but I guess they are still under development.

Barry Lennox

For a moment I thought it might use Wiegand wire. And I can't believe I DL'ed a 6 meg video to see a magnet flip around. Googling for that posting address shows this poster doing a lot of low-grade spamming to only "relevant" groups, apparently trying to stay under the oh-its-spam-lets-nuke-em radar. Looking a little more, not everything he's posted is spam, in this post he's actually asking for some help in getting this thing manufactured:

I would actually have some respect for the guy if he didn't use Usenet newsgroups for his free advertising.

Hmm, I just read his post on alt.cad.autocad, and the "appropriate responses" he got to his question, it's fairly amusing.

Okay well it is _mechanically_ frictionless but it will have the same retarding effect. Only very little because it is so weedy. I expect someone else can see a small white LED but they are not enough to illuminate a path ahead.

I think the main reason the guy wants help promoting it is because it isn't sufficiently better than existing products.

Now if someone made a system that used the energy wasted while braking, that would be a good idea. Not only do you need the normally undesirable friction, you need a lot of it. Going up a hill, you turn it off. Going down a steep hill heading toward a red light, you turn on your high-geared dynamo to top up your batteries.

Obviously this is no substitute for real brakes, but a lot of times you can see you need to slow down way in advance. Maybe you could have a two-stage brake: grip lightly to engage the dynamo, grip hard to apply brake pads.

This technique is used in some electric vehicles, and known as regenerative braking. there it puts energy back into the batteries that drive it.

I'd have respect if it was a really hot product. As it is, it is really lukewarm.

Does it have a big fat cap to store a decent charge? Does it trickle charge a battery?