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  1. #1
    shaken, not stirred. gnome's Avatar
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    Computers & Hub Dynamos?

    I am building up a Raleigh twenty as a fixed gear commuting bike for winter. As it is going to be for winter I am putting a hub dynamo on the front. The dynamo will either be a S-A Dynohub or a Shimano DH3N20 dynamo hub. I want to run a basic computer so that I can accurately log my distance and speed. Will the magnets in the hubs interfere with the computer sensor?
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    Plays in Traffic 1ply's Avatar
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    Not being familiar with the product here's my question - does the dynamo go only on the front wheel? If so can you place your sensor for the computer on the rear?
    2006 VFRfive less than 5000k for sale. 2011 MB FantomCross 105
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  3. #3
    rhm
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    multimodal commuter rhm's Avatar
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    Quote Originally Posted by gnome
    I am building up a Raleigh twenty as a fixed gear commuting bike for winter. As it is going to be for winter I am putting a hub dynamo on the front. The dynamo will either be a S-A Dynohub or a Shimano DH3N20 dynamo hub. I want to run a basic computer so that I can accurately log my distance and speed. Will the magnets in the hubs interfere with the computer sensor?
    No, there should be no problem with that. If you're worried, put the computer sensor as far from the hub as possible. If you don't already have the computer, you might consider one that puts the sensor on the rear wheel. I have one with two sensors, for example, one for speed and one for cadence; and to combine the wires as much as possible, they put the wheel sensor on the rear wheel.

    Changing the subject slightly.... I built up a Raleigh Twenty using the new Sturmey Archer dynamo hub / drum brake combination, which is nice because it's hard to put decent caliper brakes on the R20's fork. If you don't already have the hub you're going to use, check it out:
    http://aebike.com/page.cfm?PageID=30...ils&sku=HU2200

  4. #4
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    Quote Originally Posted by gnome
    I am building up a Raleigh twenty as a fixed gear commuting bike for winter. As it is going to be for winter I am putting a hub dynamo on the front. The dynamo will either be a S-A Dynohub or a Shimano DH3N20 dynamo hub. I want to run a basic computer so that I can accurately log my distance and speed. Will the magnets in the hubs interfere with the computer sensor?
    if it's a wired connection, it won't. I have a Schmidt dynamo hub with a Cateye Mity 8 computer and the two play together just fine. The Mity's sensor is on the front wheel.

    I've heard of flakiness with wireless computers as interference can cause the computer to either stop registering your speed or tell you that you're going 50 mph while stopped at a red light; but that can occur even if you don't have a dynamo. I don't know if adding a dynamo will increase the likelihood of that, but I've never had a problem with a wired bike computer.

  5. #5
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    Peter White's web site claims that you can use the hub dynamo in place of the wheel magnet to provide data to your computer, which seems like a pretty elegant solution to the problem.

    Considering how close I have to keep the wheel magnet to the sensor to get my bike computer to work, it should be pretty easy to mount the computer pieces far enough away from the hub generator to eliminate interference. I have a Schmidt hub generator on one bike and a Shimano 3N-71 hub generator on another bike, with computer sensors on the back wheels of each bike, and there's never been a problem.

  6. #6
    Back after a long absence joelpalmer's Avatar
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    Quote Originally Posted by markf
    Peter White's web site claims that you can use the hub dynamo in place of the wheel magnet to provide data to your computer, which seems like a pretty elegant solution to the problem.

    Considering how close I have to keep the wheel magnet to the sensor to get my bike computer to work, it should be pretty easy to mount the computer pieces far enough away from the hub generator to eliminate interference. I have a Schmidt hub generator on one bike and a Shimano 3N-71 hub generator on another bike, with computer sensors on the back wheels of each bike, and there's never been a problem.
    I haven't looked at that page for a bit, but I think that he was referring to a specific computer that has the magnet for the computer actually on the hub. Mine goes out near the wheel so that wouldn't work for me. Like I said, I think be depends on what kind of a computer. This is something I'm researching as well though since I want to get a dynamo hub on my commuter eventually.
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  7. #7
    Super Moderator Allen's Avatar
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    I have three bikes with Shimano dynamo hubs and computers, never had any issue.

    Unrelated to the dynamo hub, one of my computers is very picky about the alignment between the magnet and pickup. If either gets knocked out of place much the computer will not receive data. I happened to have some quite strong, small rare earth magnets; placing one on the wheel magnet effectively boosted its signal and the pickup's reception is much better.

  8. #8
    Senior Member ollo_ollo's Avatar
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    Also no problems with a Sturmey Archer DynoHub & front wheel magnet/sensor setup on a wired computer
    visit my homebuilding blog: www.monoplanar.blogspot.com

  9. #9
    shaken, not stirred. gnome's Avatar
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    Thanks for the help

    Thanks for the help. Now I just have to build the bike before winter is over.
    Does anyone have any recomendations on what light I should get to go with the dynamo hub? I have settled on using my Shimano hub.
    Get a bicycle. You will not regret it if you live. ~Mark Twain, "Taming the Bicycle"
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  10. #10
    tired donnamb's Avatar
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    I like my B&M Lumotec Senso Plus. I have the oval one. It will stay lit for about 2 minutes after you stop pedaling.
    "Real wars of words are harder to win. They require thought, insight, precision, articulation, knowledge, and experience. They require the humility to admit when you are wrong. They recognize that the dialectic is not about making us look at you, but about us all looking together for the truth."

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