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  1. #76
    rugged individualist wphamilton's Avatar
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    Quote Originally Posted by Road Fan View Post
    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?
    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.

  2. #77
    coprolite fietsbob's Avatar
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  3. #78
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    Quote Originally Posted by wphamilton View Post
    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.
    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!

  4. #79
    tcs
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    Quote Originally Posted by zacster View Post
    ...hub dynamos may or may not perform better than the Magnic.
    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.
    "When man first set woman on two wheels with a pair of pedals, did he know, I wonder, that he had rent the veil of the harem in twain? A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Typewriter Girl, 1899.

    "Every so often a bird gets up and flies some place it's drawn to. I don't suppose it could tell you why, but it does it anyway." Ian Hibell, 1934-2008

  5. #80
    Senior Member antimonysarah's Avatar
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    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.

  6. #81
    coprolite fietsbob's Avatar
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    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 ..

  7. #82
    Senior Member antimonysarah's Avatar
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    Quote Originally Posted by fietsbob View Post
    Blog says they sold the 1st batch, maybe the next one has been upgraded
    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.

  8. #83
    2_i
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    Quote Originally Posted by zacster View Post
    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.
    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.

  9. #84
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    Added my Magnic review

    Quote Originally Posted by 2_i View Post
    The Magnic cannot compete with a hub dynamo in terms of efficiency...
    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

  10. #85
    Senior Member dougmc's Avatar
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    Quote Originally Posted by dhalbrook View Post
    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.
    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.
    Last edited by dougmc; 01-15-14 at 06:58 PM.

  11. #86
    Senior Member himespau's Avatar
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    Quote Originally Posted by antimonysarah View Post
    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.
    How did you do that? Most kickstarters I've been involved in only let you support at one level.
    Punctuation is important. It's the difference between "I helped my uncle, Jack, off a horse" and "I helped my uncle Jack off a horse"


  12. #87
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    Quote Originally Posted by himespau View Post
    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.

  13. #88
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    Quote Originally Posted by dougmc View Post
    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. ...
    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.

  14. #89
    Senior Member antimonysarah's Avatar
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    Quote Originally Posted by himespau View Post
    How did you do that? Most kickstarters I've been involved in only let you support at one level.
    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.)

  15. #90
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    Quote Originally Posted by antimonysarah View Post
    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).

  16. #91
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by dhalbrook View Post
    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.
    @dhalbrook: Ok, I haven't yet taken a good look at Dirk's new Kickstarter page, but I am an EE and I'll try to assess what he says from that point of view. If you also gain some more insight from him, that would be great.
    @dougmc: I applaud your rigor. I also support seeing some measurements. But on the optical side I think the ideal is to measure the ability to illuminate that which is useful to see, not to measure total light output, or electrical to optical energy conversion (lumens/watt). Depending on lumens to characterize optical output gives a product positive marks for spraying light where it isn't needed or might not be wanted.

    A focus on lumens rather than illumination means that the best light is one with no light distribution control system - no light guides, lenses, reflectors, Fresnels, blackouts, et cetera. LEDs without lenses do not radiate full intensity into a 2pi space and the distribution is predictable, but it places a lot of its light where it might not be wanted or needed. Clearly one can use 10 degree (or narrower) factory-lensed LEDs to approximate spotlight functions. But that isn't what some of the better generator lights are doing (i.e. Lumos and Edelux 2), they are using sophisticated light distribution controls to approach the behavior of European automotive lights. For those of us who think that's the best model for bicycle light performance, illumination needs to be the target metric.

  17. #92
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    Quote Originally Posted by dhalbrook View Post
    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.
    As far as I know, wheelspin tests are not really indicative of drag with a load on the hub.

  18. #93
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    Quote Originally Posted by njkayaker View Post
    As far as I know, wheelspin tests are not really indicative of drag with a load on the hub.
    Yes, spin down tests probably aren't a great way to compare but the difference there is pretty striking. That said, I'm convinced that that all things being equal, the Magnics have a lot less drag (not that either has all that much drag to begin with). My guess is that if you rode both you'd come to the same conclusion.

    FWIW, I'm a huge supporter of dyno light systems in general so I'm not trying to denigrate them at all. Just trying to convey my observations about the Magnics to an obviously skeptical crowd. I'd love to see an independent reviewer (Peter White or Jan Heine perhaps) do more rigorous testing when the iC lights are ready so we can get some true apples to apples results.

  19. #94
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by wphamilton View Post
    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.
    Excellent point, that the lack of mechanical friction sources should have a pretty big effect on efficiency, comparing to dynes in tests like the one Heine printed relatively recently. If the drag on a loaded wheel is about the same magnitude as the air drag of the spokes (and I'm not saying that I think it is or it isn't), it will be hard to see the effect of the Magnic in a spin-down test.

    I can easily agree with Zacster that the drag is imperceptible.

  20. #95
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by 2_i View Post
    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.
    This was one of my thoughts, too, earlier in this discussion. But while that loss of energy transfer is a down check to efficiency, it might be compensated by high intensity magnetic fields, lack of mechanical drag, possibly more efficient LEDs and possibly better LED drive strategy (i.e. lower current, more advantageous operating point). I still think it needs a test. I can't do it, however.

  21. #96
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by dhalbrook View Post
    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
    You can say unequivocally that it is more effective (a subjective user-centered assessment) than your SON/Cyo, and you made that case very clearly in your excellent review. You can't say it's more efficient (an objective data-driven assessment) without actual testing or good test data obtained from somebody else's test.
    Last edited by Road Fan; 01-17-14 at 10:39 AM.

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    Quote Originally Posted by dhalbrook View Post
    Yes, spin down tests probably aren't a great way to compare but the difference there is pretty striking.
    No, it's pretty meaningless.

    Quote Originally Posted by dhalbrook View Post
    That said, I'm convinced that that all things being equal, the Magnics have a lot less drag (not that either has all that much drag to begin with).
    You really need numbers not guesses. The Magnics produces less power it seems too..

    Quote Originally Posted by dhalbrook View Post
    My guess is that if you rode both you'd come to the same conclusion.
    It seems that people have a hard time detecting the drag of a (good) generator while riding. So this doesn't seem right either.
    Last edited by njkayaker; 01-17-14 at 11:06 AM.

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    Quote Originally Posted by Road Fan View Post
    This was one of my thoughts, too, earlier in this discussion. But while that loss of energy transfer is a down check to efficiency, it might be compensated by high intensity magnetic fields, lack of mechanical drag, possibly more efficient LEDs and possibly better LED drive strategy (i.e. lower current, more advantageous operating point). I still think it needs a test. I can't do it, however.
    You don't need the Magnic to take advantage of these. I'm skeptical that the LED's being used in the Magnic are any more efficient than what are being used in good generator lights.

    I suspect that the energy obtainable from the eddy currents is very limited (much lower than what is available from a generator hub). One issue is whether you can get enough light from the energy that can be produced.

    We don't have any idea whether ratio of usable energy to drag is better than a hub generator. (Ideally, we'd want 100% usable energy to drag.)
    Last edited by njkayaker; 01-17-14 at 11:17 AM.

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    Quote Originally Posted by njkayaker View Post
    You don't need the Magnic to take advantage of these. I'm skeptical that the LED's being used in the Magnic are any more efficient than what are being used in good generator lights.

    I suspect that the energy obtainable from the eddy currents is very limited (much lower than what is available from a generator hub). One issue is whether you can get enough light from the energy that can be produced.

    We don't have any idea whether ratio of usable energy to drag is better than a hub generator. (Ideally, we'd want 100% usable energy to drag.)
    You don't need to suspect anything. Dirk has stated as much, which is why he puts such an emphasis on the efficiency of the LEDs he's using. That isn't to say another manufacturer can't (or isn't) using equally efficient LEDs, but that the Magnic Light is working with much lower wattage produced than a typical dynohub.

    Here is some detail on the magnets and LEDs he's using: http://www.magniclight.com/magniclig...rtseite/techno

    Apparently something in the Cree Xb-D family.

    Here is a chart about the LED efficiency, with accompanying text. Take from it what you will: https://s3.amazonaws.com/ksr/assets/...jpg?1387147866

    2.Leds with 160 lumen per watt
    The Magnic Light generator is tailored to the LEDs used, which reach almost 50% of the theoretically possible values- while good old standard systems barely attain 10-25 %:

    Theoretically, the maximum white light you can obtain from 1 watt is appr. 350 lumen.However, good-quality LEDs only deliver about 40 lumen per watt (as used in many bicycle lights), which represents only 11% of the maximum. Light bulbs, on the other hand, only put out 10-15 lumen per watt, while theoretical maximum light possible is 685 lumen per watt (for green light). .
    With high power LEDs one can reach appr. 80 lm/W, while the Cree LEDs used in Magnic Light deliver ~160 lumen per watt. This is possible because we feed each LED with less than 1 watt, which results in the ability to operate at temperatures below 35 C. This way, we harvest roughly 46% of the theoretical maximum white light, and hence 4 times more than standard LEDs.
    Last edited by dhalbrook; 01-17-14 at 02:13 PM.

  25. #100
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    Quote Originally Posted by njkayaker View Post
    No, it's pretty meaningless.


    You really need numbers not guesses. The Magnics produces less power it seems too..


    It seems that people have a hard time detecting the drag of a (good) generator while riding. So this doesn't seem right either.
    First of all, I've stated more than once that I too would love to see numbers. And second of all, it's no secret that the Magnics produce less power. I clearly stated that in my review, and nobody's claiming otherwise. Maybe it's me but it seems you're being deliberately obstinate.

    As for whether or not other people could feel the difference, you're right, it's hard to say. The difference is pretty clear to me, but maybe others wouldn't notice it as much. That's why it was only a guess.
    Last edited by dhalbrook; 01-17-14 at 02:14 PM.

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