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Thread: Fatboy 2007 lower fork pinch bolt snapped

  1. #11
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Internet science at its best.
    I agree that it pays to be careful but in this case it would be easy to check. The company is based in Chorley - they cite NASA, Ford, ALSTOM, Triumph and Harley among others as clients - give them a bell.
    It seems the effect they reported above was based on research done at the Jost Institute of Tribotechnology at the University of Central Lancashire.

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  2. #12
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Quote Originally Posted by Four Speed View Post
    I agree that it pays to be careful but in this case it would be easy to check. The company is based in Chorley - they cite NASA, Ford, ALSTOM, Triumph and Harley among others as clients - give them a bell.
    It seems the effect they reported above was based on research done at the Jost Institute of Tribotechnology at the University of Central Lancashire.
    Step away from Google!

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  3. #13
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    I already have, I use DUCKDUCKgo. :wink:

    If you fancy some interesting bedtime reading, here is the engineering PhD on bolt loosening that identified the 'Jost' effect above:
    http://clok.uclan.ac.uk/6649/2/Eccle...er%20Copy).pdf

    The research was done in 2010, so it's pretty recent. Hope it helps towards resolving the stanchion pinch bolt loosening issues.

    Safe riding.
    Last edited by Four Speed; 07-09-2017 at 04:45 PM.

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  4. #14
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Quote Originally Posted by Four Speed View Post
    I already have, I use DUCKDUCKgo. :wink:

    If you fancy some interesting bedtime reading, here is the engineering PhD on bolt loosening that identified the 'Jost' effect above:
    http://clok.uclan.ac.uk/6649/2/Eccle...er%20Copy).pdf

    The research was done in 2010, so it's pretty recent. Hope it helps towards resolving the stanchion pinch bolt loosening issues.

    Safe riding.
    Non of which applies to this application. Please stop posting random stuff you have found on the internet to try and add content to something you know nothing about. Its misleadind and has no relevance to this important subject. If you are a qualified engineer and have experience of fastner applications thats great but anyone can search the internet and find stuff which is not relevant or even misleading.

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  5. #15
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Quote Originally Posted by Four Speed View Post
    here is the engineering PhD on bolt loosening that identified the 'Jost' effect above:
    http://clok.uclan.ac.uk/6649/2/Eccle...er%20Copy).pdf
    Very interesting ...

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  6. #16
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Thanks Alex. Glad someone actually read it. It is interesting isn't it. Loctite found the same. It seems to be rather more than a coincidence.

    Phil, if I may. The research I highlighted shows that fasteners with spring washers are more likely
    to loosen with transverse vibration. The stanchion pinch
    bolts had spring washers, the bolts loosened.
    Personally I use Loctite. Loctite also supply test data on spring washers loosening. I have a research
    background and
    would welcome (no sarcasm intended) your lines of thought on the matter and why this research is not relevant?

    At the end of the day, I am not the one with loosened and broken stanchion pinch bolts. It's not something any of us want to happen. The prospect is frightening.
    Most important is finding a solution.
    Last edited by Four Speed; 08-09-2017 at 02:00 PM.

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  7. #17
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Quote Originally Posted by Four Speed View Post
    The research I highlighted shows that fasteners with spring washers are more likely to loosen with transverse vibration. The stanchion pinch
    bolts had spring washers, the bolts loosened.
    .
    So where is the transverse vibration/shear loading on a pinch bolt. The two surfaces are part of the same piece, there is no relative shear loading or shear vibration. Its purely a tensile force. It may have a cyclic element but its still tensile. It is also not a nut and bolt, it is a bolt into a threaded hole.

    No research needed.

    End.

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  8. #18
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    Thanks Phil that's helpful. Would the split surfaces not be subject to transverse movement under conditions of cycling?

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  9. #19
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    The pinch bolt pinches. it does not take side loads, as it does not actually clamp surfaces together as there is residual a gap usually.



    In the original post the pinch bolt had snapped (not worked lose)

    IMHO... the reasons are

    1) bolt over/under tightened at the factory (possible)
    2) bolt faulty manufacture (possible)
    3) bolt of the incorrect grade (improbable)
    4) bolt overloaded through accident damage (improbable)
    5) bolt incorrectly refitted at some stage during a service operation (possible)

    Its a small bolt, and the tightening torque is quite low. Its easy to get it wrong if you do not use the correct specification. Very easy to over tighten.

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  10. #20
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    Re: Fatboy 2007 lower fork pinch bolt snapped

    After reading the post by Four Speed I have looked up some of the findings of the people who have run tests. I have decided that in some applications it is wise to use Locktite . So...job done, new bolts, oil and seals. Back on the road,now I am going to check my fault codes....

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