Despite the continuous advances being made in lithium-ion battery technology, many cyclists still prefer to use dynamo-powered lights on their bikes - there's no having to remember to recharge the batteries, no subsequent forgetting to put the light back on the bike, and no worrying about the batteries unexpectedly giving out mid-ride. Dynamos, however, have their own drawbacks. Friction-powered sidewall units slow the bike down and wear out the tire, while dynamo hubs must be built into the wheel, and add to the bike's revolving weight. Now, however, German inventor Dirk Strothmann has created what he claims is a better alternative - a small, no-contact, self-contained dynamo bike light.

According to Strothmann, his fork- or brake caliper-mounted Magnic Light works with any type of metallic wheel rims. While other contactless dynamos do exist, those incorporate wheel-mounted magnets. Dirk's product, however, has the magnets in the dynamo, and utilizes eddy currents. In a nutshell, these are electrical currents that are induced in a conductor, when that conductor is exposed to a changing magnetic field.

"Relative movements of magnets and neighbored conductive material induce eddy currents in the conductive material - in our case the metallic rim," Dirk explains on his Kickstarter fund-raising site. "These eddy currents have their own magnetic fields which are absorbed by the Magnic Light generator kernel and by this way produce electric energy."

This phenomenon apparently even works with aluminum and magnesium rims, as the rim material only needs to be conductive, not magnetic. He states that there is a slight braking effect on the wheel, but that it is less pronounced than that caused by traditional sidewall dynamos. As can be seen in his pitch video below, the light output does appear to warble slightly, in time with the spinning of the wheel.

The light itself is produced by dual CREE LEDs, which at approximately 16 mph (26 km/h) are said to kick out a respectable 150 lumens. In its present prototype state, the Magnic Light simply turns off when the wheel stops turning. If there's sufficient consumer interest, however, a future version might include a capacitor to keep the bulbs burning while the bicycle is stopped.

It all perhaps sounds a little fishy, but Strothmann says that the public can come check the system out for themselves, when his light is on display at the FAHRRAD bicycle trade show in Essen, Germany, from February 24th to 26th - potential investors might want to wait until after then before sending in their money!

For people who are interested in funding the project, a pledge of US$199 will get them a front and rear light, when and if the funding goal is reached, and the light goes into production. A pledge of $130 will get them a front light only.

Source: Kickstarter

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    About the Author

    Ben Coxworth

    An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.

    All articles by Ben Coxworth



    • re; Anders

      No it not. The Reelight requires you to mount the magnets onto the spokes, this creates a weak magnetic field in your rim. I think I prefer the Reelight.

    • Isn\'t that quite similar to the Reelights which we\'ve had for years?

      Anders Nissen
    • The problem this unit shares with older dynamo designs is that when the bike slows down and or stops the light output is weak to negligible. Many if not most accidents occur at intersections where the bike is just picking up speed from a dead stop while an errant motorist may try unsuccessfuly to beat a stale traffic light and not see the dim dynamo output leaving the cyclist vulnerable at a most critical time. Needs capacitor!

    • It would seem to me they could wire in a capacitor to even-out that flickering and also provide enough capacity to maintain the light for a short period of time after stopping.

      Charles Gage
    • If this conversation were regarding lights for an automobile that were illuminated only when the car was moving, it would be absolutely laughable. Get a grip! Or at least a capacitor.

      Bruce H. Anderson
    • I\'ll believe it when I see it in the stores. It looks like a fake system using batteries

      Stewart Mitchell
    • Is there magnets inside the tire?

      Stewart Mitchell
    • I really took offense at the tone the author took at the end that this might not be a really possible. Anyone who knows anything about magnets and motors knows that this is not only possible, but is the principle on which many AC motors operate. However, I completely agree with the comments that it needs a capacitor to keep the light burning for a few minutes (at a lower brightness), after the bike comes to a stop. Watching the video should help answer questions about how well it works. If I rode a bike, I might consider this.

    • I don\'t get it either, the created opposing eddy current would be static relative to the magnet creating it. Wouldn\'t it ? Otherwise, why not make your own generator for your own lights ? I cant find anything on the net to support this principal yet, please somebody prove me wrong !!

      Steve Rock
    • WHY do those who comment not read the full text of the article?

      Posts repeatedly comment on the Items failure to remain lit with a stationary bicycle. Plainly shown in the article is the following text: \"In its present prototype state, the Magnic Light simply turns off when the wheel stops turning. If there\'s sufficient consumer interest, however, a future version might include a capacitor to keep the bulbs burning while the bicycle is stopped.\"

      Another case of \'Foot-in-mouth\' for Posters?


    • Does this device have moving parts? Appeances are no moving parts.

      Is the wheel rim a constant distance from the device? There is mentioned flicker in the produced light; that may be rim warble. Breaking increases light output by decreasing the rim to device gap. Don\'t lock the wheel!

      As you pass the devices magnet over the wheel rim surface your doing work: 1) metal of the rotating rim experience an increasing magnetic field on the forward side of the device\'s magnet. The field induces eddy current to oppose the advancing magnet. 2) metal of the rotating rim experience a decreasing magnetic field on the rear side of the device\'s magnet. The field induces eddy current to attract the retreating magnet.

      If you have a good bike with no rim warble then your device magnet always produces the same magnetic field strength in the rim. At any constant velocity wheel rotation the device will induce a static field in the rim surface about the device. At any non-zero constant velocity wheel rotation there will be constant eddy currents in the rim\'s metal surfce, about the device, that will produce a constant magnetic field.

      If your going to generate electricity for the LED lamp then you\'ve got to have a changing magnetic field for a conductor to exprience. The only conductor that gets to experience a changing magnetic field is the wheel rim. Any conductor connected to the illuminating LED\'s does not get to experience a changing field as field in the rim appears constant from the perspective of the device.

      For this device to work, there must be some moving part.

      I propose that the primary magnet of the device is rotated by the moving rim\'s induced field. The induced eddy currents in the moving rim persist with sufficient intensity for a long enough duration to force a rotation of the devices spindel mounted permanent magnet. The device\'s permanent magnet is likely an armature with many poles. Think of it as a paddle wheel and the rim is water. Possibly the side of the armature opposite of the wheel rim is mounted a coil that experiences the rotating armature\'s many poles to produce power to light the LED lamp.

    • DOH>>>> I don\'t know, but any gizmo gimmic that could ever fall into my a wheel let alone my front wheel would not be on my... gosh golly gee gotta have one of those list. Looks like an accident waiting to happen to me.

    • I don't understand how this can work. The eddy currents are generated in the rim. How can they power the LED's?

    • Hey, this is an excellent idea, completely sound physics, why did the writer make it sound incredulous. Why didn\'t I think about it myself. It\'s just that the power output becomes very small. The inventor himself said that capacitors will smoothen out the output. Fixed magnets are inducing eddy currents in the moving spokes, which in turn move forming a changing magnetic field which has a power penalty compared to magnets on the rim. Amazing idea, why the criticism?

      Dawar Saify
    • Why not use the spoke (nipples? the little nuts that that tighten the spokes) they could easily be made from a ferro-magnetic material, no change in weight.

    • The device\'s permanent magnet experiences force exerted on it by the opposing magnetic force produced by the rim\'s eddy currents. The faster the rim moves past the device\'s permanent magnet, the stronger the eddy current and its magnetic force.

      The magnetic force produced by the rim\'s eddy current opposes the magnetic force exerted by the device\'s dynamo\'s permanent magnet armature.

      Think about those magnets shown floating above the icy cold super conductor. The super conductor is producing an opposing magnetic field via eddy currents.

      The device does use a dynamo. The mechanical coupling between the rim and the dynamo armature is replace by the repulsive magnetic force realized between the armature and the rim.

      The moving rim spins the devices dynamo via an invisible magnetic coupling. Spinning the wheel faster or decreasing the gap between the device and rim will improve the magnetic coupling.

    • Not even the best rims are one hundred percent uniform and eddy currents are by their nature unstable so the device itself having No moving parts is entirely reasonable.

    • I just use a windup just 5 dollars and it never turns off.

      Joe Tomicki
    • make one that will charge a electric bike.

      Joe Tomicki
    • Joe, please pass by Perpetua Mobilia 101, you don't get something for nothing and charging a battery will take a lot out of Eddy. note comment in video - bike slowed down, but not as much as mechanical dynamos (no mechanical energy loss) Reviewer, cyclist don't necessarily prefer dynamos, in sensible countries its a legal requirement!

    • Spaghetti, this bike light has a dynamo in it. Instead of turning the dynamo's armature's spindle by mechanically coupling to the moving rim, it is magnetic coupling that spins the armatue. The rim's eddy currents produce a magnetic force pushing against the armature causing it to spin...

      Slowburn, your right about the unstable (uneven) eddy currents, that's why this bike light flickers.

      Ridelo, the eddy currents produce a magnetic field that pushes against the bike lights magneto armature. The push against the armature spins the armature.

    • @rustybee

      There is no 'spinning' involved! No moving parts in the guts of this thing only magnets and coils arranged in a certain way.

    • so... if you're stopped at a traffic light, and your wheel is turned a bit to the right, you're virtually invisible to oncoming traffic. great idea!

    • @smartygirl, easy fix. mount two, one to either side, and a capacitor or a simple rechargeable battery would carry the load while it is sitting still, and even out the light. movement will recharge it.

      @mgb, Two types of magnets were shown in the video, flat plates, and cylinders. The plates will be spaced about the rim, and the cylinders will be used (I think) buried in the end they never show us. (the one against the rim) I think they are using the proximity effect where a moving magnetic field close to another magnetic field causes current to move.

      I like the idea, but the cost is pretty steep.

    • My 1955 Rudge three-speed came with an auxiliary battery pack to keep the lights lit up while at a standstill when the dynamo wasn't putting out. I found screw-base LED lamps to give me more light output.

      Charlie Greenwood
    • Magnic Light is now available for sale:

      Dirk Strothmann

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