Non-contact generators

[bazmond]

Hello,
I’m on the final year of my degree and i’m currently researching into generators and dynamos for bicycles. I already have an awareness of sidewall dynamos and hub generators but I’d like to find more data regarding non-contact systems such as the reelight product. As you may already be aware the reelight system uses magnets that are connected to the wheel spokes to induct electricity. So far the reelight system is the only non-contact generator i could find. I’v done a patent search and there are at least half a dozen patents for this technology, some of which are quite old. Having said that, there seems to be very few products on the market of that type and its made me think why?
I was wondering if you guys could give me some info regarding this type of generator?
Has there ever been any high output, non-contact generators that you know of, or have you ever experimented with this type of technology before? Any links, product names etc are most appreciated.
Thanks for your time.

[dabac]

It's probably down to sheer, unforgiving physics.
The magnetic field decays rather quickly, which lessens the available power significantly as soon as you have a bit of clearance - like what you need in a flexible set-up like a bicycle wheel.
So, barring some amazing break through this leaves us with either fairly small lights(to be seen with rather than to see with) powered by magnets in the spokes, or one of the traditional solutions.
Of course you can attempt to counter for the poor power transfer characteristics by adding more and bigger magnets, but not many riders would appreciate heavier wheels.
Another option would be to use a storage system, much like some of the reelights do today but taken further. It might not do a commuter much good, as it would need a bigger portion of daylight riding in order to support a smaller portion of night time riding.

Any other solution I can think of are just other means of integrating the generator into other rotational parts of the bike, which functionally isn't much different from the hub generator and would require quite a lot of custom work.

[frenchyge]

there seems to be very few products on the market of that type and its made me think why?

I would guess it's because bicycle generators are a very niche product and that niche is already filled quite well with the hub and bottle dynamos you mentioned as prevalent. There just aren't a lot of customers in that market to be putting a lot of effort ($$) into designing new generator technologies.

[lostinsk]

Hello,
I’m on the final year of my degree and i’m currently researching into generators and dynamos for bicycles. I already have an awareness of sidewall dynamos and hub generators but I’d like to find more data regarding non-contact systems such as the reelight product. As you may already be aware the reelight system uses magnets that are connected to the wheel spokes to induct electricity. So far the reelight system is the only non-contact generator i could find. I’v done a patent search and there are at least half a dozen patents for this technology, some of which are quite old. Having said that, there seems to be very few products on the market of that type and its made me think why?
I was wondering if you guys could give me some info regarding this type of generator?
Has there ever been any high output, non-contact generators that you know of, or have you ever experimented with this type of technology before? Any links, product names etc are most appreciated.
Thanks for your time.
I can answer probably why there aren't more of these systems out there.

With the magnet on the spokes, and the coil on the frame, the system actually makes a thump every time the magnet passes the coil (something that you can hear and feel in your hiney), at least with the one system on the market that produced enough light to be worth carrying around. I suppose anything without a powerful enough magnet to go 'thump' wouldn't produce the requisite power.

[frenchyge]

Having more magnet poles smoothes it out some. The Shimano hub uses 8 poles, which can be felt while turning the axle by hand, but not while riding.

But yeah... strong magnets are required because of the clearances involved, as mentioned above.

[bazmond]

Thanks to everyone who responded to my original message, your input is most appreciated! I'll have to come back on here later in the year and report on how things went on my degree and possibly get some feedback reguarding any designs.

[dabac]

One thing that I'm curious about is if the seat post possibly could be put to some use. As long as you're in the saddle the seat post will see some bumps and varying degrees of compression. It'd be neat if the seat post could be equipped with some piezo crystals, or an extremely short stroke suspension coupled to a linear generator. Have that piezo/genny powering a rear light high up under the saddle and you'd be set for rear light for the lifetime of the system. Then maybe a similar thing could be integrated into the stem as well.

[Peter@vecchios]

Hello,
I’m on the final year of my degree and i’m currently researching into generators and dynamos for bicycles. I already have an awareness of sidewall dynamos and hub generators but I’d like to find more data regarding non-contact systems such as the reelight product. As you may already be aware the reelight system uses magnets that are connected to the wheel spokes to induct electricity. So far the reelight system is the only non-contact generator i could find. I’v done a patent search and there are at least half a dozen patents for this technology, some of which are quite old. Having said that, there seems to be very few products on the market of that type and its made me think why?
I was wondering if you guys could give me some info regarding this type of generator?
Has there ever been any high output, non-contact generators that you know of, or have you ever experimented with this type of technology before? Any links, product names etc are most appreciated.
Thanks for your time.

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