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  1. #1
    Senior Member coldfeet's Avatar
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    Bottle Generator on the Rim?

    Hey y'all, I'd like a generator system for lighting, but am also planning on a front hub motor. Rear hub motor isn't an option, because a Rohloff is also planned. Stokemonkey would be nice, but the price of this build is already getting bit high.

    Anyway, had dismissed bottle generators, because I like using Big Apple balloon tires, and the sidewalls don't seem strong enough. Then I thought, hey! if I'm not using the rim for braking, ( disc brakes ) how about running the generator on the rim?
    b&M dymotec uses a rubber roller, and you could rough up the rim to give traction.....

    What do you think? Should i just go back to taking the tablets?

  2. #2
    just pokin' along desertdork's Avatar
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    Have you considered a bottom bracket dynamo?

  3. #3
    Senior Member coldfeet's Avatar
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    Quote Originally Posted by desertdork View Post
    Have you considered a bottom bracket dynamo?
    No, I haven't. Wouldn't the same problem with thin tires be a concern?

  4. #4
    Senior Member canopus's Avatar
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    No, the BB dyno would have the tire contact on the crown of the tire, not the sidewall. A dyno can't be any harder on the tire than the ground contact is.
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  5. #5
    Senior Member coldfeet's Avatar
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    Quote Originally Posted by canopus View Post
    No, the BB dyno would have the tire contact on the crown of the tire, not the sidewall. A dyno can't be any harder on the tire than the ground contact is.
    I knew that, and granted, the ground is wearing away the tire as well, but the contact area of a dynamo has to be narrower than the contact patch the tire has on the ground. Big Apples are nice tires, but there isn't a lot of meat on them, probably something to do with how well they roll. Anyway, I have a Big Dummy, the BB isn't anywhere near the rear tire. Thanks for the suggestion though.

  6. #6
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    I've used both bottle and BB generators but have never let the roller run on the tire sidewall. The BB ones run right on the center part of the tread (i.e. same place that the road touches), and I adjust the bottle style to run on the side of the normal tread area - but not on the sidewall. Both generally work fine. The BB style requires less careful placement and adjustment, but the location tends to be dirtier in inclement weather conditions and I've had more problems with the roller slipping when there's any snow on the road. I've also sometimes had an issue with the BB type disengaging from hitting a big pothole - just when you don't want the light to go out. Placing the bottle style so it contacts on the tread does pose a problem when using fenders - I've had to carve away a little part of the fender to avoid interference.

  7. #7
    xtrajack xtrajack's Avatar
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    I went through similar issues my self, with my Xtracycle build. I used a front hub motor, because someday I think I would like to install a NuVinci hub on the rear. I am going to go with a front mounted bottle generator, however, I am not using Big Apples. I use Schwalbe Marathon Plus tires.

    I had thought about using a Magten Lightset that I first heard here on BF. The problem is that the magnet ring is about 185mm and my X has a 203mm rotor on the back. I am not sure that putting a magnet ring on the front wheel would be a good idea, because of the magnets in the motor.
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  8. #8
    `````````````` CaptainCool's Avatar
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    Are the batteries in the hub, or on the bike? If they're on the bike, could you tap into those instead?

  9. #9
    Senior Member coldfeet's Avatar
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    Quote Originally Posted by CaptainCool View Post
    Are the batteries in the hub, or on the bike? If they're on the bike, could you tap into those instead?
    I certainly could, and am planning on that for primary lighting, I'm just wondering about a generator light for the backup. I guess AA is the way to go.

  10. #10
    coprolite fietsbob's Avatar
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    There was a bottle generator made to run off the rim, in the Past ,
    maybe
    seek those out on the auction site.


    but if you have an Electric motor assist planned ,
    just power the light from the same or another 6v battery.

    stoke monkey is a Big Dummy/Xtracycle option,
    more torque than hub motors, but wont go on standard single bikes

    B&M wire brush roller bottle generators are OK , I have set up bottle dynamos , higher on the tire , then they run off the tire tread edge rather than the Dynamo track on the sidewall..
    Last edited by fietsbob; 12-06-10 at 01:03 PM.

  11. #11
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    I would say a dynamo of any kind would be a waste on a electric bike. Your going to be putting the main battery power into making light ... and due to frictional losses Etc your going to be losing energy .... if it's just for a back up I would personally recommend a battery set.

    If your planning on a back-up for when the main battery is dead carry a smaller battery of the same voltage which you can switch to just for the light's. That way you still have your main lighting.

    If your planning a "complete system's failure" back-up lighting then a complete set of spare light's would be my choice as it's just as likely to be a blown bulb or wiring issue ... meaning a alternative way to supply power would still leave you without a light.

    What makes you want a dynamo as a back-up?

  12. #12
    Randomhead
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    they used to sell rubber hoods for bottle dynos. Have no idea if you can still get them, but they cut down on the wear quite a bit.

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