Snapped Rear Mounting Studs (3rd time!)

Discussion in 'Motorized Bicycle General Discussion' started by motorizedmatt, Sep 13, 2010.

  1. Chalo

    Chalo New Member

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    The amount of eccentricity that causes tight and loose spots on a fixed gear or single speed bike is usually not even visible. You'd express it in tenths of a millimeter at most. But if the tight spots are too tight, they can cause noticeable resistance in the pedals, break axles, wreck freewheel bearings, etc.

    If you must have runout in your drive sprocket, bias the chain tension towards looseness, so that it does not tighten excessively at any point in the wheel's rotation.

    Chalo
     
  2. kipharley

    kipharley New Member

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    I use nyloc nut's where ever there isn't a heat source,Also try green lock-tite on all assembled threaded connections.chain guard,fender braces,crank arm nuts,ect ect.Kip.
     
  3. mapbike

    mapbike Active Member

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    Yes Kip thats a good idea with the nyloc nuts, I also use them and as the jam nut, I put a standard nut on first and then I put the nyloc but behind it and jam it tight against the other, these never come lose on mr ever, and I also put loctite on both as well but I use the blue.
     
  4. DudeZXT

    DudeZXT New Member

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    I had the exact same thing happen with 3 bolts and ended up having to drill & tap new holes into my engine.

    I put the bolts in with no other mounting hardware and matched everything up, on the side, and realized that my bolts were a few threads too long to pull everything together tight. I also realized that a torque wrench set to 50~75 in/lbs. is tighter than I had done with my hand (I had been afraid to tighten them too much for fear of stripping/breaking things with my gorilla grip).

    Make sure your bolts are the right length (won't bottom-out without pulling everything tightly enough) and a torque wrench is highly recommended!
     
  5. kipharley

    kipharley New Member

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    Blue locktite will work just as well as the green.The green is for already assembled parts.It penitrates
    like WD-40.Kip.
     
  6. mapbike

    mapbike Active Member

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    Thats cool, never used that before, but sounds like it could come in handy for some situations. there ya go you just learned me something I was not aware of....! LOL

    Shan

    dnut
     
  7. kipharley

    kipharley New Member

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    "OH BOY" Do I get a Gold Star? Glad to learn ya sompin! Kip.
     
  8. Nougat

    Nougat New Member

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    No, no - green Loctite is for "I never ever want this to come apart ever again." There is no place for green Loctite on these machines, let alone red. If you're going to use any at all, blue is all you should use.
     
  9. Al.Fisherman

    Al.Fisherman New Member

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    Most common reasons for studs to break are..

    Cheap Chinese studs... I change out ALL to grade 8.8 About the same as US grade 5.
    Incorrect mounting...mounts to both seat tube and down tube. Need as close to perfect fit.
    I use RED locktite on all studs (if removal is desired heat is needed).
    Proper torque 6mm 50-70 INCH pounds... 8mm 150-204 INCH pounds (I use 50 and 150)
    I double nut with a nylock nut as the second one.
    Here are some pictures of my mountings, I have never had a nut or stud, come loose, break or strip out.

    Proper mounting...
    [​IMG]

    I make these shims in order to get the proper torque. The nuts are too close to the clamp for a proper socket fit. I don't have a nylock nut on this illustration.
    [​IMG]

    I make this "L" bracket to eliminate engine twist due to engine torque. This way I don't have to over tighten mount nuts.
    [​IMG]

    Almost every bike frame needs a custom made front mount. The proper angle for the optimum mounting is 75 degrees.
    [​IMG]...[​IMG].......A bought mount can be had
     
    #29 Al.Fisherman, Sep 15, 2010
    Last edited: Sep 15, 2010
  10. Al.Fisherman

    Al.Fisherman New Member

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    [​IMG]

    Shims can be used between the rear mount and engine case.
    [​IMG]..[​IMG]
     
    #30 Al.Fisherman, Sep 15, 2010
    Last edited: Sep 15, 2010
  11. kipharley

    kipharley New Member

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    Green loctite works just fine.It certainly doesn't "weld" the two parts together.Kip.
     
  12. donutguy

    donutguy New Member

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    Try grade 8 bolts, but I bet your frame will break before the grade 8 bolts do...especially since you drilled a hole through the frame.....not good-keep an eye on that area. I'm sorry that ain't more helpful but that hole would scare the heck out of me.
     
  13. kicking

    kicking New Member

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  14. kipharley

    kipharley New Member

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  15. kipharley

    kipharley New Member

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    You may also try peddling more at start-up before you engage the clutch,when you do release the clutch slowly.That's where most of your torque is coming from.Kip.
     
  16. kicking

    kicking New Member

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    I could not find the thread on boring out an hole to an little larger bolt size ; then filling the hole with hard material such as marine tex which I have used or . I may try the alumaweld stuff too. here is one good thread and I am sure there are more . http://motorbicycling.com/f3/no-more-broken-studs-bolts-me-11691.html
    I am having the same problem , I have my motor on the bench right now and "will fix it :
     
  17. kipharley

    kipharley New Member

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    I might try running a 6mm tap into the mount and access the threads to determin whether or not they need messing with.If you think they're sloppy enough maybe you should look into heli-coils.
    If my advice makes sense use it,if not use your best judgement.Kip.
     
  18. mapbike

    mapbike Active Member

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    Go and buy you a 1/4 - 20TPI Bottoming Tap and a stick of 1/4"X20 all Thread rod or just get some grade #5 or #8 Bolts that are the correct length and run the 1/4"-20 Tap into the existing 6mm holes after putting some thin oil like 3 in one oil or something simular so that the tap will not seize while retapping the hole out from the 6mm to the 1/4, just remember to run it in (the tap) 2-3 threads in depth at a time and then back out and then back in again repeating this proccess until the tap bottoms out in the hole, unscrew tap out of hole and then spray the hole out with either brake cleaner or carb. cleaner to get the alum. shavings out and then you are ready for your new 1/4" studs or bolt which ever you choose. very simple proccess use a small cresent wrench to turn tap if you dont have a tap wrench and make sure it is running straight into the hole.
     
    #38 mapbike, Sep 22, 2010
    Last edited: Sep 22, 2010
  19. kicking

    kicking New Member

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    I have the short cut to this thread bike ,, in case im online ,,, i will paste it on my reply to the next person ,, snaped studs ,,, happens an lot !!! and i have learned ... do not use stainless steel too .... thanks ,,, P.S I wanted to send my motor back after the stud broke .... but this site tells me it happens a lot
     
    #39 kicking, Sep 22, 2010
    Last edited: Sep 22, 2010
  20. Kinskeys

    Kinskeys New Member

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    I broke mine too and I retapped it to 8mm, so far so good.
     

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