dropout chain tensioner

Discussion in 'Motorized Bicycle General Discussion' started by oldsurfer, Aug 11, 2010.

  1. oldsurfer

    oldsurfer New Member

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    i have the 45degree front to back drop outs ..the torque from the drive pulls the hub loose ...any one know how to set up a device to prevent this from happening.wee.
     
  2. KCvale

    KCvale Well-Known Member

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    Yes. I think they are called 'Skewres', in short little off-set eye bolts you put on both sides hub bolts before the hub nuts, and a stay that cups around the end of the frame chainstay like this.

    [​IMG]

    In short very cool cheap little helpers, especially when chain matching with no tensioner.
    Your local bike shop should have them.
    That bike by the way is a Grubee GT1, it comes with them as well as a hub mounted drive sprocket.
     
    #2 KCvale, Aug 11, 2010
    Last edited: Aug 11, 2010
  3. oldsurfer

    oldsurfer New Member

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    i have the opposite front to back
     
  4. Chalo

    Chalo New Member

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    You don't need a device; you need a proper installation. Grease the axle threads before replacing the nuts and tighten them firmly (with a box end wrench or socket, not an adjustable wrench). If you have a quick-release axle, use a steel enclosed cam type QR lever, oil its mechanism with chain lube, and tighten it through 90 degrees of cam clamping.

    If that does not work, take your bike to a shop and have them check the rear dropout alignment (there is a tool for this). Also have them replace smooth hub locknuts with serrated ones if possible. You'll need to match the thread diameter and pitch exactly, and there are a lot of varieties to choose from. If you have other issues I have not guessed at, a qualified bike mechanic will probably be able to identify them.

    (There are some unpretentious shops out there that will work on your MB-- it helps to find one that is open-air so that the smell of your bike engine does not linger and annoy the mechanics.)

    You can use chain tugs as shown in the earlier picture, but they are always a poor substitute for good careful installation. Since your dropouts are front opening, you'll have to loosen and remove the tugs entirely before being able to remove the wheel. And you'll have to use the kind that have an overhanging lip with bolts through it, like this:

    [​IMG]

    In this particular case, you would have to file away the raised area that's intended to ride in the rear-opening dropout slot.

    Chalo
     
  5. oldsurfer

    oldsurfer New Member

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    i am not sure i'm following you on the grease issue? what does that have to do with a tight fit? i have replaced the smooth nuts with serrated one from a bike shop...and used a correct size wrenches to tighten ..still i am going to fabricate some chain tugs....thanks for your advice...i really appreciate the help!!!!!!
     
  6. Chalo

    Chalo New Member

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    Here's the deal: When you tighten a nut, you apply a certain amount of torque, and you get a certain amount of tension on the fastener. Friction takes the torque and wastes it, without using it to tension the fastener. The more you can reduce friction, the more tension (clamping) you get for a given torque on your wrench. So if you are savvy, you grease the treads so that a reasonable amount of wrench torque results in a decent amount of clamping. Good bike mechanics all do this.

    Serrated axle nuts are good for preventing loosening, but serrated locknuts-- the ones facing the insides of the dropouts-- are more significant to preventing axle slippage.

    Chalo
     

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