6 bolt freewheel adapter

Discussion in 'General Questions' started by Mainer, May 11, 2012.

  1. Mainer

    Mainer New Member

    Hi All,

    I'm new here. I hope this is the right forum to ask this question.

    Has anyone out there heard of this? A adapter that would allow mounting a reverse BMX freewheel (also called Lefty or Southpaw) to an ISO 6 bolt hub? I'm trying to drive the left side of a Nuvinci hub with a geared motor. No need to run a disc brake in conjunction with the freewheel. Just to be clear, the threading would be standard 1.37 x 24 (or the smaller metric 30.0 x 1.0) but left hand threaded...

    Any help would be appreciated.



  2. pbeggs

    pbeggs Member

    ive seen one ,.. it was made by a guy with his own machine shop,...

    what are you useing for an engine and the rest of the drive train?

    engine type 2 stroke 4 stroke happytime?(chinese 2 stroke)

    reduction gearing?

    for most of the setups we run need a 36-44 tooth sproket when driving that side of the hub,.. (when running a happytime)

    we are very willing to help find a solution to any problem but we need info.
  3. Cavi Mike

    Cavi Mike Member

  4. pbeggs

    pbeggs Member

    he has the 6 holes,.. needs to screw on the freewheel the opposite of that part:(
  5. Cavi Mike

    Cavi Mike Member

    Ahh, I read it wrong. That would stick out so far it would hit the fork ends so obviously this isn't something that would ever go into mass-production. There are only a few options here, the best of which are:

    #1) Thread the hub. Obviously you'll need access to a lathe.

    #2) Buy a hub with threads on both sides. Staton makes them:
  6. BigBlue

    BigBlue Active Member


    I believe you would run into space issues with a 135mm chainstay clearance in the back end with the Nuvinci and a freewheel.

    Here's a link on endless-sphere.com that deals with that specific issue. One recommendation would be attach a fixed sprocket to the ISO 6 hole disc hub and run a freewheel on a jackshaft or the engine, depending upon the setup you have. Ooops - see that you originally stated a geared motor. I assume an electric motor.


    Another issue would be how are you going to power the Nuvinci?

    Good Luck,

    AKA: BigBlue
    Last edited: May 13, 2012
  7. loquin

    loquin Active Member

    I posted a sketch of this some time ago, here. Don't know if anyone has ever built one.

    For ease of manufacturing, you could probably thread a tube, then weld the threaded tube to a flat ring (which has the 6 disk brake holes drilled)
  8. BigBlue

    BigBlue Active Member


    I don't think an adapter would work with a chainstay width of 135mm. Per the endless-spere.com post, only 13mm is available between the Duvinci disc hub and the left chainstay. My Dicta freewheel body is 15.60mm in width. I am sure other Southpaw freewheels are similar in width. Even if you could get it to fit, remember chainstays are tapered and I am sure the sprocket would rub on the left chainstay. Most outer sprockets on 9 and 10 speed cassettes are usually 11 or 13 toothed. A 18 or 22 toothed sprocket is more than likey to rub on the chainstay. A possibility would be a tandem with a 140mm or 145mm chainstay width.

    The Tophat would be a good alternative to mount a fixed sprocket to the Duvinci disc hub. You might still be able to have a disc brake. Again, if using a 135mm width chainstay, mount a frewheel to the motor or jackshaft.

    On another note, I like your adapter. Might use it some time down the road. A possibility is to weld a bottom bracket cup to the adapter.


    AKA: BigBlue
    Last edited: May 14, 2012
  9. loquin

    loquin Active Member

    I thought of that, Chris. I bought one (as the left cup has the 1-3/8-24 left-hand threads, I believe,) a while back.

    I've ground off the bottom of the cup, and am about ready to weld it to a 'donut.' (in this case, I'm making a LH Freewheel adapter for a creative engineering sprocket mount.) But, that cup is HARD! With a CAPITAL 'H' !!! I ruined a bi-metal 1-1/8" hole saw on it already! And, after I couldn't drill it out, it made sense - it's a bearing cup, after all... I'm bright that way - AFTER I bang my head against the wall, I generally figure out that the wall is hard, too, LOL

    Anyway, I've heated the cup up to a dull red, and let it cool. Hopefully, that, and the heat from the welding will soften it enough that I can drill out the center!
    Last edited: May 15, 2012