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Here's a kit (and how to make) a no-friction bike light dynamo. Learn about electromagnetic induction and make a bike light! - Thanks Hone Link.
No-friction bicycle dynamo light kit
Posted by Phillip Torrone |
Mar 26, 2007 04:53 AM
Bicycles, DIY Projects, Kits |
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So this light would be of the flashing type and it would not provide enough power to light the path ahead? Over here flashing lights are reserved for emergency vehicles and turn signals making this type of light illegal.
A great concept, though. It just needs to be made smaller and produce continuous light. Even better if it can share the magnet with my speedometer.
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I've got one of them; yes, it's flashing, which is legal in the UK anyway.
It's not really designed for lighting the path ahead, I've got a halogen light for that. What it is designed for (and indeed, what this kit is old as) is a safety light, to make the cycle, and cyclist more visible at night.
I bought mine because my rechargeable halogen front light regularly went flat and stopped working half way through my journeys, and I needed something to make my cycling legal if that happened.
They also do a "standby lights" version, which has an ultracapacitor that gets charged, and when you apply your rear brakes, the rear lights are lit - which is important if you're stopped at a junction, since otherwise, you would not have any lights.
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They're legal in the UK since October 2005 it seems.
from the link above:
"To be legally approved a light may flash at least once and not more than four times per second with a brilliance of at least four candle-power"
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A much more elegant version of theese is the Reelight (a Danish invention) I've installed the first version on my sisters bike, very easy, as the light is right there by the magnet no wires.
The new version has a capacitor that charges so it flashes when you're standing still too, first time I saw one of those I thought the light was haunted!
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Actually, this is *not* a no friction light. It is a no-contact light. There is still a magnetic force applying friction to the wheel in the form of resistance. Induction is by its very nature a resistive force. For this reason, we can't launch copper wire bundles into orbit to make energy from the Earth's magnetic field... they would slow and eventually stop, plummeting back to the surface.
Yikes... if you want to split hairs... Friction:
...
3. Physics A force that resists the relative motion or tendency to such motion of two bodies in contact.
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Yes, there is obviously a loss of rotational energy in the wheel caused by the induced current in the coil. In my experience of riding with one of these, you don't notice it apart from the quiet 'tick tick' sound as the magnet inside gets flipped. It's certainly considerably easier on the legs than the traditional dynamo rubbing against the sidewall of the tyres.
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A new designs of this dynamo (already made version) is ready from now.
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a good site which give information
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