Dynamo hub arrived: notchy rotation - normal?

Discussion in 'Technical Chat' started by nafuk, Nov 5, 2010.

  1. nafuk

    nafuk Guest

    Hello,

    My Mavic A319 rimmed, double butted, Shimano DH-3N30 dynamo hub has
    arrived from Fatbirds.co.uk - £73 (includes postage, over-voltage
    protection unit for rear light, quick release skewer and connector for
    the dynamo terminals).

    When spinning the wheel (not on bike yet) and holding the axle the
    rotation feels notchy.

    Is this the bearings being overtight or just a dynamo hub effect?

    Cheers,
     
    nafuk, Nov 5, 2010
    #1
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  2. It's the magnets in the dynamo hub, giving the rotating bits some
    angles they prefer to be at relative to each other.
    In use, you won't notice it, or certainly not above walking speed
    (once you are moving fast enough for the light to not flicker).
     
    Alan Braggins, Nov 5, 2010
    #2
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  3. nafuk

    Mike Guest

    Recently got one of those myself from the same place. As Alan says,
    it's fine once you're riding.

    The wheel seems quite a bargain. I'm using mine with a B&M Lumotec IQ
    Cyo and getting an impressive amount of light.

    Cheers,
    Mike
     
    Mike, Nov 5, 2010
    #3
  4. nafuk

    Marc Guest

    OOH Ohh OOOH I know this one! I asked the same question last month.
    It's normal and you won't notice it when it's on the bike and moving.
     
    Marc, Nov 5, 2010
    #4
  5. nafuk

    nafuk Guest

    Thank you for all the replies.
    Now waiting for Santa to bring me some pedal powered search lights
    from B&M.
     
    nafuk, Nov 7, 2010
    #5
  6. nafuk

    Marc Guest

    I got one of them as well! You won't regret it!
     
    Marc, Nov 7, 2010
    #6
  7. nafuk

    Tosspot Guest

    Standlight has just packed up on my Toplight Line Plus, which is only
    two months old, so B+M can stick that one where the sun don't shine. I
    shall be going back to the trusty B+M D-Toplight, or maybe a Toplight
    Flat, because I did like the low profile of the Line Plus if nothing else.
     
    Tosspot, Nov 7, 2010
    #7
  8. nafuk

    Marc Guest

    I;ve just has the second Brompton rear standlight pack up in less than a
    year, both of them within weeks of being new. Anyone got an suggestions
    for an Dynamo LED standlight that will fit on a L Brompton?
     
    Marc, Nov 7, 2010
    #8
  9. nafuk

    Phil Cook Guest

    Replace the capacitor?
     
    Phil Cook, Nov 7, 2010
    #9
  10. nafuk

    Tosspot Guest

    I might give this a go, as, TBH, the light does work. Is it really a
    capacitor? It must be a fair few uFarrads if it is.
     
    Tosspot, Nov 8, 2010
    #10
  11. nafuk

    Marc Guest

    a) my soldering id not that great
    b) I would imagine the problem is vibration/shock , so it's the
    board/mouting that is probably the problem
     
    Marc, Nov 8, 2010
    #11
  12. nafuk

    nmm1 Guest

    Yes. I believe that they are typically about 1 Farad, which shows
    how much capacitor technology has improved in the last 40 years!


    Regards,
    Nick Maclaren.
     
    nmm1, Nov 8, 2010
    #12
  13. nafuk

    Marc Guest

    Cheers! Where do I send it? ;-)
     
    Marc, Nov 8, 2010
    #13
  14. nafuk

    Tony Raven Guest

     
    Tony Raven, Nov 8, 2010
    #14
  15. nafuk

    Phil Cook Guest

    Fronts will be that big but rears may well be smaller. There are two
    capacitors in a B+M Cyo front light. I think the standlight one is 1F
    5.5V and there is another of 1000 microF 16V.
     
    Phil Cook, Nov 8, 2010
    #15
  16. I've just had a second one go, but they last much longer for me. If you
    find out what's loose, I'd be fascinated to know.
     
    David Damerell, Nov 8, 2010
    #16
  17. nafuk

    Tosspot Guest

    <boggle> Are we talking about amps/second? FFS, My flabber is ghasted,
    cos in my book it was called a battery!
     
    Tosspot, Nov 8, 2010
    #17
  18. No, we're not talking about amps/second. We're talking about
    amp·second/volt.
    (If 1 F capacitor delivers 1 A, its voltage will drop by 1 V/s.)
    But it's still pretty flabbergasting, when in my youth a 0.5 F
    capacitor was something the size of tin of treacle.
    Nowadays you can get 4 kF capacitors smaller than that.
     
    Julian Bradfield, Nov 8, 2010
    #18
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