Rear Hub too large for Sproket adapter..PLEASE HELP!

Discussion in 'Motorized Bicycle General Discussion' started by Motion70, Mar 28, 2014.

  1. Motion70

    Motion70 New Member

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    Hi, I have a vintage one speed coaster brake Rollfast bicycle that I am motorizing. Being that the spokes are old I wanted to use a sprocket adapter to keep the tension off of them. However, all of the sprocket adapters I find require a 1.5" diameter rear hub while my rear hub is a 2" diameter. I know this sounds like a large rear hub, but I double checked against other bikes and it is 2". Am I stuck with having to use the ragjoint or do I have other options. Any help is greatly appreciated!! Thank you.
     
  2. mapbike

    mapbike Active Member

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    http://www.mmbikeparts.com/sprocket_adapter.htm

    Go here and give them a call, ill bet he can bore one of the standard Shimano 110 adapters to work on your coaster hub, you'll need to hwve an exact measurement by using calipers, but I'd say thos would be a good option.

    Best wishes.
    Map
    .wee.
     
  3. Motion70

    Motion70 New Member

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    Thanks for the reply! I called him and he said he would be unable to bore it out enough to fit the 2" rear hub. I really want to avoid using the ragjoint but I am not sure I am going to find another solution. Thanks!
     
  4. mapbike

    mapbike Active Member

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    Myself and man others here have many thousands of miles on the stock coupler/rag joint without a single issue, with any adapter or setup it is very important that the spokes be tight and in good condition for the wheel to be safe, the rag joint works just fine when done right, just be sure to get it secured good and straight, you'll have good service with it if you do.

    Map
     
  5. 2door

    2door Moderator
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    Back to your original post, you said "the spokes are old". Are they rusty, bent? If the spokes are in bad shape you really should consider re-lacing the rims no matter how you mount the sprocket.

    I concur that installed correctly, the rag joint will give you many many troublefree miles.The key words here are, 'installed correctly'

    Tom
     
  6. mapbike

    mapbike Active Member

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    Ditto.......... Tom
     
  7. rangefinder

    rangefinder New Member

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    I would avoid all the hassle of rebuilding an old wheel.
    Is your wheel perfectly true, and in "round"?
    Is the coaster brake hub on it serviceable, and parts available?

    You already know the spokes are gone.

    I would just head to a local bike shop and order a new wheel.
    The vendors who advertise here have good quality wheels too.

    Get a good wheel. If you can get one with 11g spokes and drum brake!
     
  8. Motion70

    Motion70 New Member

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    The wheel I have is true and the hub and coaster brake are in good working order. A few of the spokes are a little loose but I believe they will tighten up no problem (I am currently out of town so I cannot be sure). The main reason for the sprocket adapter was just the fact that the spokes are from the 30's and I didn't want to put unnecessary stress on them. I want to shy away from a new wheel as I am trying to keep the patina/look that the bike has. Here is a link to my photobucket page if you would like to see the bike I am beginning with. Is there a way to modify the available adapters or possibly make my own? Thanks for the replies!

    http://s1173.photobucket.com/user/classiccamaros/library/Motorized Bicycle?sort=3&page=1
     
  9. 2door

    2door Moderator
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    It is somewhat or a myth or misconception that a sprocket adapter prevents stress on the spokes. The spokes are attached to the hub and the rim. They transmit the rotating force from the hub to the rim/tire. Therefore whatever rotates the hub, engine or pedals, that force is then applied to the spokes that in turn apply it to the rim. So your theory that a sprocket adapter will not stress the spokes is 50% incorrect. It will spread the force to all of the spokes as opposed to only one side as a 'rag joint' does, but again I'll submit that once properly installed on a known true wheel with tight spokes that 'rag joint' will perform just fine.

    Of course if you are an accomplished machinist and/or have access to a machine shop you can build a sprocket adapter. There have been several seen here made in a home shop/garage.

    Tom
     

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