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Thread: Magnic Light: contactless bicycle dynamo light

  1. #61

    Default Re: Magnic Light: contactless bicycle dynamo light

    you know... I just reviewed the video from the kick-starter site again...
    I reallllllly hope there is some outstanding innovation here...

    yet, at the very beginning of the video - right after the shot of Mr. Strothmann at his desk introducing there is a second shot.
    In this shot, he is standing next to the fork and mounting the unit on the right brake arm. (watch mounting 0:19-0:22 onto the brake arm)
    -the unit quickly snaps from his hand to the rim. Suggesting a strong magnetic attraction.

    ...maybe the inner-tube valve?
    ...maybe he has a steel front rim?

    what do you cats see?

    Im quite excited about this once the patent goes through and these are availbe at a slightly lower price (hopefully).
    I wonder if you could retrofit a bracket with a shallow arch matching the wheel.
    Thus allowing maybe a daisy chain of 2 or more units for stacking the watts or raising the voltage?
    Last edited by krienert; 03-01-2012 at 04:10 PM.

  2. #62
    Flashaholic* Steve K's Avatar
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    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by krienert View Post
    -the unit quickly snaps from his hand to the rim. Suggesting a strong magnetic attraction.

    what do you cats see?
    I see his left hand wrapped around the wheel and the dynamo bracket, pulling it into place.


    Steve K.

  3. #63

    Default Re: Magnic Light: contactless bicycle dynamo light

    glad to stand corrected.
    Maybe im to analytic...
    Good things in time i suppose.

  4. #64

    Default Re: Magnic Light: contactless bicycle dynamo light

    Just had an email from the inventor. I asked him specifically about current output and he confirmed that the device puts out less than 500mA, more likely around 300ish. So not surprisingly, it has a lower power output than a conventional dynamo.

    In the video the output appears to be brighter and last longer than a Schmidt hub powering what looks like an Edelux. It's not an especially fair comparison (even assuming the wheels were given exactly the same amount of push) because the Edelux has a shaped beam and doesn't use the brightest and most efficient LED on the market, whereas the magnic light is using a pair of Cree XM-L's running somewhere around 0.3A with radially symmetrical optics.

    Still, quite impressive. I look forward to learning the secret of its operation...

  5. #65
    Flashaholic* Steve K's Avatar
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    Default Re: Magnic Light: contactless bicycle dynamo light

    The Kickstarter site is intended to get people interested, so it's a bit light on technical details. They do mention "150 lumens", which I interpret as roughly 1.5 watts (assuming a typical LED efficacy of 100 lumens/watt), so the light is clearly not going to produce as much light as the current LED dynamo lights from B&M. Add in the optimized beams of the B&M lights, and the Magnic is at a disadvantage.

    I suspect that the lower power output of the Magnic is part of why it spins longer than the hub dynamo.

    I don't think that the Magnic will replace any hub dynamo applications, but it certainly would be handy for those currently using bottle dynamos. I think it would also be great for those who just need lights now and then. I used to use a "dynamo-block" light this way. It was a bottle dynamo with a bulb/reflector mounted on the dynamo. It just took one bolt to put it on the fork bracket, so it was easy to remove for times when it wasn't needed.

    If they do get this into production, I'd be interested in hearing stories about the technical challenges that they ran into and how they solved them.

    Steve K.

  6. #66

    Default Re: Magnic Light: contactless bicycle dynamo light

    I shouldn't kid myself. I am to analytically minded.
    The notoriety these brothers are getting is substantial, yet they seem modest - and only concerned with sharing their product/concept.
    Seems like a pretty clear indicator of their legitimacy.

    Although the electrical ratings might be lower than a hub dynamo (as listed at this point), I will be hard pressed not support these cats down the way if things become affordable, just to open the can'o'worms to see the physics behind it.


    As previously mentioned by others - It will be nice to hear about the trials and tribulations in the prototyping process once all their patent work goes through.

    Random thought... concerning the longevity of the eddy currents induced into the rim - would it be possible to array a couple of these devices around a quarter of the circumference of the wheel, to stack voltage/current - or would the eddy's of each unit conflict with one another in some way? (probably too early for this question... oh well)

    Warm regards.
    j

  7. #67
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    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by Steve K View Post
    If they do get this into production, I'd be interested in hearing stories about the technical challenges that they ran into and how they solved them.
    They might see problems with water ingress and humidity. By the way, I wish them success, but can't they use a 3d-printer as the next step?

  8. #68

    Default Re: Magnic Light: contactless bicycle dynamo light

    3d printer! brilliant!
    You could send him a message with such a recommendation!
    Would certainly help with future pro-tying and retrofitting of their design.

  9. #69

    Default Re: Magnic Light: contactless bicycle dynamo light

    OK, I may have a prototype working, but it has little to do with the Eddy currents but rather with the steel insert into the rim at the joint where the rim's circle is closed. I mounted a small but strong magnet, with its poles horizontal, on a vertical axle through a bearing. When approaching the axle (just a bolt) with the magnet to the top of a spinning alu rim, and the magnet pole never getting closer than 0.5 cm to the rim, the magnet begins to swing and/or rotate around its axle. However, the pull producing the motion is not from Eddy currents, that would be here negligible, but from the image of the magnet in the steel insert. I think this could be an explanation for the operation of their dynamo in spite of the absurd verbal claims.

    Regarding the Eddy currents, I tried an AC magnetic field from a demagnetizer approached to a spinning rim and, at 0.5 cm from the pole of the demagnetizer (one that has been used for heads of tape recorders), the rim could not care less, apart from some effect at the steel insert.

  10. #70

    Default Re: Magnic Light: contactless bicycle dynamo light

    2_i,
    That experimentation sounds close to what I was tinkering with a few days ago.
    The only verifiable returns i got from the rim were the inner-tube valve causing the two opposite poled horizontal mag's to spin on a small bearing hanging from an old spoke close as .2 and as far away as 2cm from the rim surface.
    Not really eddy currents as the significant power provider in my test though...

    Wonder if it will work with tube-less wheels...

    I hope something interesting is reviled when these do-hickeys ship.

    cheers-

  11. #71

    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by krienert View Post
    Not really eddy currents as the significant power provider in my test though...

    Wonder if it will work with tube-less wheels...
    I was wondering about the steel rims they discuss. To make the magnet swing, there needs to be a variable field on that magnet. For fixed magnet orientation, a steel rim at a constant distance would not provide such variation. However, as a rule the rim would never maintain a constant distance when spinning, so the field would vary and the magnet move.

  12. #72

    Default Re: Magnic Light: contactless bicycle dynamo light

    about this the device, i noticed this post on
    http://www.bikerumor.com/2012/02/24/magnic-light-a-dynamo-that-functions-free-of-components/
    ...near the bottom there is a post by -when-
    "
    Rim-driven eddy current lights have been tried before.They only work for very very very true wheels, like +/- thousandths of an inch as the field diminishes as e^x from the surface."

    Anyone know which trials this is referencing to? Its new to me, so It would be cool to hear of others in the past - even if they disappeared.

    cheers
    Last edited by krienert; 03-05-2012 at 06:14 PM.

  13. #73

    Default Re: Magnic Light: contactless bicycle dynamo light

    They are doing something right - The just reached their $50 G goal yesterday. And by the looks of how many trade shows are contacting him to come and show his product, these brothers must really be onto something.
    Looking forward to future news on this.

    I wonder how/what is the means for fitting 20 Neo magnets in such a small container...

  14. #74

    Default Re: Magnic Light: contactless bicycle dynamo light

    Look, as far as I can tell it is just a poor man's standard dynamo. Is it likely to be useful - sure from time to time you need to attach quickly something dirty to a bike without lighting provisions. However, people are enticed because they think of something mystic and special - not there though, and in Germany bikes sold these days without hub dynamos represent a true margin. The very fact that you can come up with something so primitive owes to the fact that LEDs got to be so efficient. Incidentally I think it would be time to come with something involving just a magnet on a spring and getting energy from the fact that the bike undergoes constant acceleration - just a version of old wristwatches getting wound up due to your hands moving.

  15. #75

    Default Re: Magnic Light: contactless bicycle dynamo light

    a poor mans standard hub dynamo it might be - but its a eloquent evolution of concepts from dynamo theory none the less.
    Comparing my 'poor mans' experimenting in like ideas (A diametrically magnetized torus on the shaft of an old printers stepper motor
    spinning near the rim results in similar output values) resonates me to give credit in seeing someone make it availbe to other people.

    aka - I spent some time dabbling with this kinda thing a while ago, and its nice to see it produced.
    Although... personal opinion here - ...what their asking is way to expensive for my taste.
    Seems like a poor mans dynamo at a rich mans ticket.

    cheers.

  16. #76

    Default Re: Magnic Light: contactless bicycle dynamo light

    There is a video at http://www.youtube.com/watch?v=ScrU0YErT7k I assume is the one mentioned earlier. Another poster says if there is significant energy being draw, the wheel should not spin for long. The video is 8 seconds and you can hear the freewheel ratchet slow significantly during that time. Also, the light starts to flicker significantly at the end, although that might be a video frame rate artifact.

    There is a newer vide at http://www.youtube.com/watch?v=aCpA2yHE1Iw showing a magnetic sphere rolling down a U-shaped aluminum channel. The channel is almost vertical, but because the moving ball sets up a current in the channel, the ball (magnet) rolls slowly. The Magnic Light Kickstarter page says "I didn't count but it felt like it was several hundred times I let a ball magnet run down an alumnium rack with slow speed to explain the physics behind Magnic Light." I'm not sure how it explains the physics, but maybe somebody here understasnds more?
    Last edited by EnabLED; 03-13-2012 at 11:54 AM.

  17. #77
    Flashaholic* AnAppleSnail's Avatar
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    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by EnabLED View Post
    There is a newer vide at http://www.youtube.com/watch?v=aCpA2yHE1Iw showing a magnetic sphere rolling down a U-shaped aluminum channel. The channel is almost vertical, but because the moving ball sets up a current in the channel, the ball (magnet) rolls slowly. The Magnic Light Kickstarter page says "I didn't count but it felt like it was several hundred times I let a ball magnet run down an alumnium rack with slow speed to explain the physics behind Magnic Light." I'm not sure how it explains the physics, but maybe somebody here understasnds more?
    That's a common physics demo. A moving magnet sets up a current in the aluminum, (Moving electrons) and these moving electrons have a magnetic field that slows the magnet. This is magnetic braking, but we have spent the thread trying to see how to turn magnetic braking into generative force. My guess is that they have a dynamo inside the housing that induces eddy currents in the rim, turning the dynamo. But I haven't built one to see if that makes any sense.
    My biggest light-hog is my camera.

  18. #78

    Default Re: Magnic Light: contactless bicycle dynamo light

    Kinda reminds me of the 'non-friction bicycle dynamo' light at www.freelights.co.uk which ISTR being discussed here four or five years back (they used to have a d-i-y kit that is no longer listed but using the archive.org 'wayback machine' I found instructions at: http://www.freelights.co.uk/howmake.html) - nowhere as efficient as a hub dynamo or as bright as even department-store battery-powered led lights...

  19. #79
    Flashaholic* Steve K's Avatar
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    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by Dr Tszap View Post
    Kinda reminds me of the 'non-friction bicycle dynamo' light at www.freelights.co.uk which ISTR being discussed here four or five years back (they used to have a d-i-y kit that is no longer listed but using the archive.org 'wayback machine' I found instructions at: http://www.freelights.co.uk/howmake.html) - nowhere as efficient as a hub dynamo or as bright as even department-store battery-powered led lights...
    I had the same thought, but didn't remember what it was called. I didn't realize it was in production... has anyone ever seen one in use?

    Steve K.

  20. #80

    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by Steve K View Post
    I had the same thought, but didn't remember what it was called. I didn't realize it was in production... has anyone ever seen one in use?
    I used a "Red Alert" by "Leader Sports" for several years. I still have the magnet on the wheel but removed the light because (a) the unit would shift (just general bike getting knocked about) and start rubbing on the magnet; and (b) the light has to be mounted below the level of the tire, so there is a "dark zone" when you are behind and a little to one side, the light is hidden behind the tire and rim.

    Overall it seemed to work well, and while it would sometimes get knocked in and start to rub, I rarely had it get pushed out and stop working. It is pretty picky about clearance, with a working range of a few mm, but I do not have a precise number. "Super close" does not seem to make it brighter, but "not very far away" is enough it stops working entirely. This makes sense in that what the wheel magnet does is flip an "armature" in the main housing, and either it flips or it doesn't. Overall brightness may have been comparable to an early Vista Light, but was dim compared to modern LED blinkies. Newer LEDs might fix some of that. The flash rate was slower than a regular blinky, but still fast enough. Mine stopped when stationary, but I read someplace there was a model with stand light functionality.

    I quite like the "never needs batteries" attribute, but for my needs I prefer a brighter and less finicky battery blinky mounted where it is never shadowed by the tire. Better yet for my use is probably a hub generator, ideally with wiring tucked out of the way somehow, but I have not gotten A Round Tuit.

    I suspect a good product for my needs would be a generator "can" like the Red Alert, but tucked directly behind the seatstay where it is hard to knock accidentally, plus a wire running to an LED mounted so it never gets shadowed by the rim and tire. The all-in-one concept is cute, but having gone to the trouble of installing a light, I'd like people to be able to see it.

    I looked online briefly and found this (fuzzy) picture of the Red Alert: http://www.est.hi-ho.ne.jp/~newj/_ _/+/_/Goods/_RedAlert.html -- what this picture does not show is there is a "lump" on the backside that you can twist and it moves the generating stuff towards or away from the tire -- so you can aim the light separately from adjusting the generator/magnet clearance.

  21. #81

    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by fyrstormer View Post
    Even good riders can only output 250-300 watts in a sprint.
    Your figures are out by nearly a factor of 10.

    I'm an unathletic person and I can sustain over 200W for hours on end.

    High-end racers can sustain double that, 1000W in a sprint. Elite world-class sprinters can output nearly 2000W

  22. #82
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    Default eddy current decay

    This might be relying on eddy current decay. It is widely used for crack detection (cracks in metals!) There are scientific papers from the 1960's that describe eddy current decay so I won't go into it. (it is a sum of exponentials) I think that they are inducing eddy currents in the rim, which decay slowly enough for the pick-up coil to capture enough magnetic flux as the rim moves past, carrying the decaying eddy current.
    Nothing new, but still clever.

  23. #83
    Flashaholic* Steve K's Avatar
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    Default Re: eddy current decay

    Interesting concept... I hadn't considered the decay time for the eddy currents before, and that there would be currents flowing in the portion of the rim that had gone past a magnet. The only issue I can think of regarding this concept is that the eddy currents would always be flowing in the same direction, so this wouldn't produce an AC magnetic field that could induce current in a coil in the dynamo.

    I'm a little disappointed that there hasn't been any news in regards to the mysterious workings of the Magnic. After all of the debate on the web, I'm still dying to know what's inside that little gadget!

    Steve K.

  24. #84
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    Default Re: Magnic Light: contactless bicycle dynamo light

    In a program usually devoted to presenting fringe inventors with their fringe mechanical contraptions in bland surroundings, a regional German TV station reported on the Magnic Light, last scheduled airing of this episode seems to be on 21-MAY-2012, 0525-0550 CEST.

    http://www.mdr.de/einfach-genial/eg_fahrrad108.html

    streamed:
    http://www.mdr.de/mediathek/fernsehe...-dea15b49.html
    (minutes 02:30-06:35)

  25. #85
    Flashaholic* Steve K's Avatar
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    Default Re: Magnic Light: contactless bicycle dynamo light

    nice video, and it looks like they have a newer version that what the Kickstarter video showed. Now if I could just get Google Translate to convert the audio to English....

    Steve K.

  26. #86
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    Default Re: Magnic Light: contactless bicycle dynamo light

    The video made me wonder what the effect would be of closing the permissable 5 mm gap to 1 at the front wheel. The brake light's increase in brightness seemed impressive when the brake moved closer to the rim.

    It seems to take a bit more than two seconds after the pedaling starts until the light brightens. Not much action when walking the bike....

  27. #87

    Default Re: Magnic Light: contactless bicycle dynamo light

    My guess is the eddy currents in the rim are magnetically gripping a strong internal magnet and spinning it. I took a small RADIALLY polarized ring magnet and held it very close to my rapidly rotating wheel and it spun like crazy. It won't transmit a lot of torque to the magnet but it was enought to convince me this could be a legit product.

  28. #88

    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by mrcharly View Post
    Your figures are out by nearly a factor of 10.

    I'm an unathletic person and I can sustain over 200W for hours on end.

    High-end racers can sustain double that, 1000W in a sprint. Elite world-class sprinters can output nearly 2000W
    I'd have to agree. I'm far from a competition level cyclist and I can do 1200+ watts for a short burst.

  29. #89

    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by Steamdonkey View Post
    My guess is the eddy currents in the rim are magnetically gripping a strong internal magnet and spinning it. I took a small RADIALLY polarized ring magnet and held it very close to my rapidly rotating wheel and it spun like crazy. It won't transmit a lot of torque to the magnet but it was enought to convince me this could be a legit product.
    What spun it was the steel insert joining the rim, not the eddy-current nonsense .

  30. #90
    Flashaholic* Steve K's Avatar
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    Default Re: Magnic Light: contactless bicycle dynamo light

    Quote Originally Posted by 2_i View Post
    What spun it was the steel insert joining the rim, not the eddy-current nonsense .
    That sounds like an assertion of fact, and not merely an opinion. What's the source of your information?

    Steve K.

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