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  1. #1
    Guy on a Bike TreeUnit's Avatar
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    BB Lockring as Fixed Gear Lockring

    Several weeks ago, a visitor to the local bike co-op described to me a sort of suicide hub he was riding on. The hub consisted of a standard screw-on freewheel hub with a track cog screwed onto it, and a bottom bracket lockring screwed on the outside of the cog to hold it in place.

    I decided to give it a try. After two weeks, I am happy to report that this variety of suicide hub has worked well for me. The cog is still securely in place, and I have not experienced any "slipping cog".

    So what does the FG community think? If this setup proves to be effective on a widespread scale, any screw-on freewheel hub could become a fixed-gear hub, no need for a track hub or rear wheel.

  2. #2
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    Where you went wrong was getting ideas at a bike co-op.

  3. #3
    surly old man jgedwa's Avatar
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    I think there was a mis-communication somewhere in the description here. A track lockring has a significantly smaller diameter than a BB lockring, and so it is impossible to screw them both on the same threads. Plus, the track lockring threads are reverse.

    I am pretty sure that what it was was a normal road hub (that had been redished and respaced probably) with a cog screwed on and then a BB ring screwed on after it. The BB ring will not be an actual lockring in this application since it threads in the same direction (and do not "lock together"). THe BB ring really only adds a few more threads of friction to resist it and the cog coming loose. It probably does add a bit, but not much.

    Nothing necessarily wrong with this set-up, but it is probably not a good idea to try to skid stop with this set up.

    jim
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  4. #4
    niteridar
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    i have a mavic wheel on an old maillard hub. both sides are fixed/fixed. and they both use bottom bracket lockrings. ive tried to screw on a track lockring, but the lockring was too small.

  5. #5
    Guy on a Bike TreeUnit's Avatar
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    Quote Originally Posted by jgedwa View Post

    I am pretty sure that what it was was a normal road hub (that had been redished and respaced probably) with a cog screwed on and then a BB ring screwed on after it. The BB ring will not be an actual lockring in this application since it threads in the same direction (and do not "lock together"). THe BB ring really only adds a few more threads of friction to resist it and the cog coming loose. It probably does add a bit, but not much.

    Nothing necessarily wrong with this set-up, but it is probably not a good idea to try to skid stop with this set up.

    jim
    That's exactly what I described. I have encountered no difficulties with skidding and stopping so far.

  6. #6
    surly old man jgedwa's Avatar
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    Whoops. So, you did. Somehow I read an extra "track lockring" into your original question. Sorry.

    jim
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  7. #7
    surly old man jgedwa's Avatar
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    Quote Originally Posted by soul05 View Post
    i have a mavic wheel on an old maillard hub. both sides are fixed/fixed. and they both use bottom bracket lockrings. ive tried to screw on a track lockring, but the lockring was too small.
    At the risk of looking like a fool twice in the same thread: is this possible?

    Is the cog not the normal size? Seems like the cog would have to have larger thread diameter to fit over the lockring threads.

    Did the BB lockrings thread on the normal way, or reversed? If they go on the normal way (and the cog HAS to go on the normal way), then it is not really functioning as a lockring.

    jim
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  8. #8
    yo yo yo yo yo
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    Quote Originally Posted by soul05 View Post
    i have a mavic wheel on an old maillard hub. both sides are fixed/fixed. and they both use bottom bracket lockrings. ive tried to screw on a track lockring, but the lockring was too small.
    that means the hub is free/free
    Quote Originally Posted by tx_what_it_do View Post
    machined are for brakes. non-machined are more for brakeless.

  9. #9
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    "THe BB ring really only adds a few more threads of friction to resist it and the cog coming loose. It probably does add a bit, but not much."

    It's a little different, right? It's like how a hub works- the nut that goes outside the cone nut doesn't just add more threads, it sort of fuses together with the cone nut. In terms of the physics I suppose it's the difference between static and kinetic friction. The static friction is higher and having the extra lock ring (though threaded in the same direction) adds an area of static friction, so that if the inner cog unscrews it becomes more difficult to continue unthreading once it hits the lock ring.

  10. #10
    Guy on a Bike TreeUnit's Avatar
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    As near as I can tell, the cog and lockrign are held solidly in place because they push off of each other. This outward pushing in turn pushes their threads against the threads of the hub very, very hard. The cog thread/hub thread friction is so great, it can hold up even against skids.

  11. #11
    surly old man jgedwa's Avatar
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    Quote Originally Posted by samwell View Post
    "THe BB ring really only adds a few more threads of friction to resist it and the cog coming loose. It probably does add a bit, but not much."

    It's a little different, right? It's like how a hub works- the nut that goes outside the cone nut doesn't just add more threads, it sort of fuses together with the cone nut. In terms of the physics I suppose it's the difference between static and kinetic friction. The static friction is higher and having the extra lock ring (though threaded in the same direction) adds an area of static friction, so that if the inner cog unscrews it becomes more difficult to continue unthreading once it hits the lock ring.
    But, consider that one does not generally tighten the cog and BB ring AGAINST each other. The cog is tightened against the shoulder of the hub and the ring is tightened against that. As I understand it, this just extends the thread area.

    Don't get me wrong, I am not saying it is not a useful cobble. Nor am I saying that a BB ring does nothing. But it does not "lock" anything in place. I run a couple of bikes this way myself.

    jim
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  12. #12
    Perineal Pressurized dobber's Avatar
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    Quote Originally Posted by jgedwa View Post
    THe BB ring really only adds a few more threads of friction to resist it and the cog coming loose. It probably does add a bit, but not much.
    It's acting in a manner similar to a jam nut, quite common and functional if done properly.
    This is Africa, 1943. War spits out its violence overhead and the sandy graveyard swallows it up. Her name is King Nine, B-25, medium bomber, Twelfth Air Force. On a hot, still morning she took off from Tunisia to bomb the southern tip of Italy. An errant piece of flak tore a hole in a wing tank and, like a wounded bird, this is where she landed, not to return on this day, or any other day.

  13. #13
    surly old man jgedwa's Avatar
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    Quote Originally Posted by dobber View Post
    It's acting in a manner similar to a jam nut, quite common and functional if done properly.

    In order to actually jam them together, one would have to tighten down the cog, tighten down the ring, and then put counterclockwise force on the cog and clockwise force on the ring. You sure you want to put any loosening force on that cog?

    In any case, I think the "jamming" you are talking about is really not all that relevant in this high-torque application. The forces involved in a headset, and even in loose-ball axles are not like what we have here. And notice how poorly those hold there.

    I think that tightening down the cog as tightly against the hub shoulder is the best bet. then maybe throw on the BB ring for good measure if you feel like it.

    jim
    Cross Check Nexus7, IRO Mark V, Trek 620 Nexus7, Karate Monkey half fat, IRO Model 19 fixed, Amp Research B3, Surly 1x1 half fat fixed, and more...
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