I don't know the details any more than you do, and this was my first thought also. But then, why really care? The eddy currents will generate heat and we'll ultimately feel that as a drag, as in magnetic brakes - given that the lights have an acceptable brightness, the drag is the only real issue. I could be wrong but I don't see leakage inductance as looming very large in this application.

There is no noticeable drag when using a single rear light. In fact, when I lost the light I didn't notice that it was no longer operating. Before I lost it when I lifted the bike off the ground and gave the wheel a spin it kept going as if nothing were there. Multiply that by three (2 front, one rear) and maybe, just maybe, the cumulative effect will be perceptible. More likely though is you'll feel the effect of your slightly unzipped jacket catching the wind before you'd feel that.

People say the same things about dynamo hubs, and I don't believe them either. I'm going to find out on my own. Lights on vs. off, dynamo wheel vs. no dynamo. The only dynamo hub I've ever used was on a Citibike and they are so loaded down anyway they don't count.

There will always be drag, starting with the power output to the light and increased by the inefficiencies. Dynamo hubs can have 3 to 9 watts worth roughly speaking, which can be noticeable (moreso at lower speeds). I suspect that there is less drag with this technology than for dynamos with equivalent power outputs.

Yes, there has to be drag. As far as I can tell, the big advantage of this approach is that it's easy to install. I suspect there might be a low limit to how much power is available from the eddy currents (lower than what is possible for a dynamo).

That's my guess. It just stands to reason that the magnetic fields from induced eddy currents cannot be as strong as the fields from the original magnets. And they're also going to be further away from induction coils. So the power generated would be lower. They compensate by using high quality magnets. Whether that can fully compensate for the weaker magnetic fields, I don't know.

Another advantage over bottle generators is no roller surface, and no bearings and seals. That's really what attracts me to it.

One might suspect that they would have made it brighter if it was possible (being bright appears to make things easier to sell). That it isn't brighter suggests that there's limited power available.

It's interesting.

I'd be surprised if it's less for the same power output. The best dynamo hubs have been measured to have efficiency of up to 65% and I'd think that would be hard to achieve with this approach. OTOH, the power output from this device is much lower (according to the maker it has an output of under a Watt at 30 km/h) and partially makes up for that with very high efficiency LEDs - so it might still have less drag than the higher power output hubs.

How much higher efficiency are the LEDs than what other dynamo lights are using?

I'll say it again, there is no discernable drag from this light. You out it on and you forget that it's there.

There will always be drag, but will it always be perceptible? Hub dynamos and bottles have cogging as the poles interact with the permanent magnets. This causes noticeable vibration that is mistaken for drag but really doesn't add to drag, since it is an energy storage effect. The Magnic (I assume) has no vibration, so the drag should feel smooth, like very gentle braking.

I don't really see why the efficiency in this system will be a lot better, if at all, than that of a recent SON or SP. Slowing down the rider is slowing down the rider, whether or not the rider can perceive it. If into the bargain it puts out half the light or half the illumination (this group still hasn't grasped which of these performance metrics is actually important), then it is not a step forward despite the novel technology. Not even when version 2 brings its functional spec close to the level where Germany could consider certifying it. The performance target is still to match a SON/Edelux 2, SON/Luxos, or a SON with one of the other top-level B&M lights. If we want to argue about price/performance, just substitute the Shutter Precision PV-8 for the SON, at $130 each versus $200+ each, with a Lyt or other mid price but high-end B&M. I still think "efficiency" is a case that must be proven: Lumens per mechanical watt or illuminance per mechanical watt.

Not even like very gentle braking. Maybe if you are coasting you'll stop about a foot short.

How well is the Magnic sealed? It contains an electronic circuit board, so water ingress could damage circuit boards unless they are waterproofed. And in mass production it's difficult to conformal coat all surfaces except the ones that provide electrical contact and maintain optical integrity. Or does it have a good drip control system?

The LED lighting revolution has come upon us pretty quickly, and aplications are still being sorted out. Everybody seems to be all over Magnic's eddy current thing, but IMO the true evolutionary step is a new design paired dynamo and headlamp with power and regulation optimized to work as a single, cohesive unit.

(The Velogical rim dynamo is another, different step in this direction: optimized to work with a short list of modern LED headlamps.)

Most other tire and hub dynamos are legacy designs expected to power anything from modern LED headlamps to old 3W filament bulbs, and modern LED headlamps are designed to be powered by anything from a Shutter Precision PD-7 to a 60 year old Soubietz bottle dynamo.

With a hand-in-glove matched optics, LED, electronics and purpose designed, dedicated dynamo, I think there even might be some life left in the all-in-one headlamp and tire driven dynamo design, well under the price point of Magnic. Or maybe not! :)

One thing Magnic could learn from the past: redesign the heads to place the lamps above or below the dynamo, rather than out to the side. Magnic's current layout with the lamps on the same horizontal plane as the tire/rim maximizes shadowing.

Because a bottle generator will have bearing friction, the magnets or coil spinning on an axis. It will also have some loss in the rolling surface interfacing with the tire. In this kickstarter generator it's the magnetic eddies that are moving, the flux lines cutting across fixed coils, so there is no mechanical friction. When I visualize this, all of the drag is directly related to the power generated, so I expect it to be more efficient in that sense than bottle generators. A hub generator, maybe not much difference but depending on the engineering.

We already know that the drag is greater than the ultimate power consumed by the light and we've got some pretty good data, here and there, on drag from various dynamos so that side doesn't really need any proving. The actual drag from this tech, yes I agree that we need some measurements to put the question to rest. That may be a little tricky for DIY tests though, since a coast-down doesn't get precise enough for that small amount of rolling drag and simply spinning the wheel unloaded doesn't actually translate to the drag on a loaded wheel. So we may have to wait for someone with more sophisticated equipment and a little time on their hands.

I see they have a mount for V-brakes. I wonder if it'd work for cantilevers too.

I don't know any more about it than anyone else. Since there are no serviceable parts I assume that it's sealed up pretty well. There are no seals around moving parts, obviously.

Now on sale http://clevercycles.com/magnic-light-complete-set,, buy and try..

http://clevercycles.com/blog/2013/08...-magnic-light/

While bottle generators are another thing entirely, and have lots of drag due to friction, hub dynamos may or may not perform better than the Magnic. I don't really know myself yet. I don't have any capability to perform the measurements either. I will have both a Magnic light and a dynamo light available to me in April so I'll at least be able to do a test of perceived drag, if I can feel either.

As for weather sealing, the Magnic is completely sealed as there are no external moving parts or switches. Whether it is entirely waterproofed down to 50 feet is something else.

I have Canti's on my bike and it worked using their simple bracket that attaches to the brake pad holder. I think the bigger problem is disk brakes as there is nothing at the rim.

I agree that the position of the iight is a bit awkward. I mounted my taillight on the right side as you ride on the left on NYC's one-way streets. It is the accepted practice here even if it isn't a universal one. Buses are on the right. If you were close enough behind me on my left you may not see it, but by then its already too late!

Well, in one sense of 'better', the answer is clear: A SON or similar hub dynamo will drive a 90 lux (no expert here! but if I'm reading the numbers right, @15kph) Edelux II. The Magnic folks have claimed 16 lux* (@20kph).


*'Very bright' - Clever Cycles blog.

The new kickstarter version (rather than the retail version) has a standlight, though. That's why this has bubbled back up.

I wish the full set on the new kickstarter was 1 front 2 rear, but I went in on it and added a 2nd rear -- I was tempted by the old version, but the lack of a standlight was a deal-killer. I'm tired of batteries running out on my beater bike, but am not ready to go dynamo on a very old bike with a wheel size that doesn't match any of my others -- this way, if I upgrade the bike I can just move the lights.

Blog says they sold the 1st batch, maybe the next one has been upgraded

Yea Calhoun bike in MN sent me a B&M Lyt it had no standlighjt either
sadly this will be the stock Brompton thing..


they burned me bad when I returned it , and stuff like gouging me $20 for a short piece of wire to hook up the taillight .. that they omitted even sending in the 1st place..



a place to avoid ..

Yep:
http://www.kickstarter.com/projects/...ess-bicycle-dy

This is the new one we've been talking about. Adds a standlight and is aiming to hit the German StVZO standard, which the first one didn't.

The Magnic cannot compete with a hub dynamo in terms of efficiency, because all it does is to replace the action of friction for a bottle dynamo, with Eddy current action, in transferring the rotation of the wheel to the rotation of the rotor in a dynamo. That transfer, necessarily lossy, is absent in a hub dynamo, since its rotor is rigidly attached to the wheel. The Magnic can have an advantage over a hub dynamo in terms of movability of the dynamo from one bike to another. However, wheels build over a reasonable dynohub can be had for about 60 euro in Germany - I am not sure about the US market. The price and the practical need to keep a dedicated Magnic mount on a bike really tame the incentive to use one. Still, I think it may be fun to employ a new technology just for the sake of it.

Added my Magnic review
 

Um, no. In actual real life usage, I can tell you unequivocally that the Magnic light is far more efficient than my Schmidt SON/IQ Cyo setup.

In any case, I wrote up a review of the Magnics that will hopefully answer provide some useful information as there seem to be plenty of questions and misinformation about them: http://www.bikeforums.net/showthread...-Magnic-Lights

I don't see how you can say that "X is far more efficient than Y" if you haven't 1) measured the electricity produced by X and Y and 2) measured the drag produced by X and Y. Since we're talking about lights, we probably should also 3) calculate the lumens/watt for their emitters as well.

Ultimately, you could compare watts to drag or lumens to drag -- take your pick, but you're going to have to get quantitative data on at least two variables here.

You've given some quantitative data for the two lights in your other thread (i.e. you can feel the drag from one but not the other), but you haven't actually measured it that I can tell. And while you've talked about how bright they are -- 30 lux vs 60 lux -- note that lux doesn't tell how much light the light emits, only how much light reaches one particular point (the brightest area) or the average over an area that they consider to be "the" important area -- "lux" is quite vague and not suited to comparisons regarding efficiency.

Comparing average lumens (average, because many dynamo lights have a visible flicker) would be ideal, and if you want to compare beam patterns you could count only the lumens that go where you want them, but then it becomes subjective.

As for typical values, I've heard that hub dynamos are around 50% efficient (so a hub generating 3 watts of power would generate about 6 watts of drag if it was 50% efficient), and modern LEDs tend to put out about 100 lumens/watt. I don't really have any idea how efficient the magnic light's electrical generation would be, but I wouldn't expect their LEDs to be particularly unusual.

How did you do that? Most kickstarters I've been involved in only let you support at one level.

From what I gather people have been "overpledging" somehow and having it noted that they want a second rear light, to be followed up on upon delivery. There are more than a few messages about it on the Kickstarter project.

OK, I'll admit it was a mistake to say "unequivocally". The overall drag of the Magnics compared to the Cyo/SON is significantly lower.. a simple wheelspin test confirms that easily enough. Of course, the light output is a fair bit lower as well, so it gets a lot murkier in terms of overall system efficiency. Personally I haven't performed any tests that are anywhere close to scientific, so I can only tell you my conclusions based on my observations, namely that (and yes, I understand Lux is highly dependent on beam pattern) in my estimation the Magnics are roughly 1/2 as bright as the dyno setup but have far less than 1/2 the drag.

AFAIK Dirk has investigated the actual system efficiencies. IANA electrical engineer so I can't pretend to follow it in great detail. There is some info here: http://www.kickstarter.com/projects/...ess-bicycle-dy (under What's new in Magnic Light iC?) regarding the LED efficienty but I'd love to hear him explain it in greater detail. I can ping him and see if he can provide something more substantial if you're interested.

Look at the comments/Q&A -- they're allowing people to overpledge and then in your "shipping info" ask for the other rear light. Not sure they'll allow an infinite number of different overpledge options, but this was a request of a lot of people. (I mostly want 1 front and 2 rear -- the bike I'm planning to put them on is a city commuter, and these will be additional visibility/running lights to the battery ones it already has.)

Based on the location of the light you'd probably want to run two fronts anyways, since the wheel will obscure the side view of one light or the other. One thing I didn't mention but really like about them is that they illuminate the wheel, enhancing side visibility, especially if you have reflective tire sidewalls (like many Schwalbes have).