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Thread: Dye Penetrant Testing

  1. #1
    bleep bloop bleep AL9000's Avatar
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    Dye Penetrant Testing

    Guys,

    I've recently acquired some Suntour Superbe cranks (Record copies), and also run some Sugino Super Mighty's (also Record copies).

    I was having a close look at the Superbes to check for fatigue cracking at the arm-spider interface, as it's a known problem on this style of crank, and saw what looks like a couple of crack initiations.

    Given that many of us use vintage parts with unknown histories under heavy loads, in the interests of not 'becoming unseated' (also known as binning it), I plan to grab some ink & lacquer from work and test all my cranks/stems/bars. Depending on how much I can get, I'll offer to test anyone else's parts, as long as you can get them to me (cleaned!).

    If you catch the crack early, you can either destroy the part, or remove it with a burr grinder to prevent further growth and subsequent failure. I'd bin handlebars, but probably try and save cranks with small crack-like indications.

    Lots of bike failures, many crank failures:
    http://pardo.net/pardo/bike/pic/fail/000.html

    Another reason not to ride large OD, thin walled frames, buckling instability:
    http://pardo.net/pardo/bike/pic/fail/FAIL-017.html

    Doubly unfortunate, crank fails, rider maintains poise, then seatpost fails (I've had the seatpost bolt fatigue before, saddlebag kept it in place):
    http://pardo.net/pardo/bike/pic/fail/FAIL-035.html

    Dye-Penetrant:
    http://materials.open.ac.uk/mem/mem_dye3.htm

  2. #2
    mj
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    Re: Dye Penetrant Testing

    Sounds good Blakey, I'll put my hand up for that!

    (and I'm hoping that you don't find anything wrong...)

  3. #3
    bleep bloop bleep AL9000's Avatar
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    Re: Dye Penetrant Testing

    From little cracks, big cracks grow...

    Visual only for now. Dye pen to come.


  4. #4
    NJS Certified PiledHigher's Avatar
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    Re: Dye Penetrant Testing

    Arrrgh, you are bring back memories of materials lectures, scary stuff for a chem eng.

    Damn stress risers, personally never broken a crank and in no rush to find out. Pedal eyes are another well reported failure point, not good when foot and pedal drop off the end of your crank!
    Quote Originally Posted by heavymetal View Post
    The furries probably think us bike people are a bunch of freaks.
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    Whatever! Next month I'm gonna ride a uni cycle with a paddle tyre accross Bass Straight with Afgan midget siamese twin strippers on my shoulders to raise awearness for migrant exploitation. Amature...
    Quote Originally Posted by justdave View Post
    That's sig worthy, some one jump on it!
    Quote Originally Posted by Charlie View Post
    Slightly confused as to what a town bike was (is it fixed, where can I find one, how much does it cost, how long must I wait for shipping?) I googled "town bike".

    Well I feel silly now

  5. #5
    CraigC
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    Re: Dye Penetrant Testing

    If you're worried about this concept, stay away from conversions and track bkes. Buy something new?!?!?!?!?!?!?!? If you don't have the money, welll............................................. ..............

  6. #6
    NJS Certified PiledHigher's Avatar
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    Re: Dye Penetrant Testing

    Quote Originally Posted by CraigC
    It's called buiying new cranks, you Fucktsick!!!!!!!!!!!!!!!!!!!!!!!

    Seriously, If you're worried about this concept, stay away from conversions and track bkes. Buy something new?!?!?!?!?!?!?!? If you don't have the money, welll............................................. ..............
    Well not sure who you are having a go at, but Blakey is offering to help people and I'm just ssaying that not every thing old was well designed, take the attitude that they have with planes and inspect stuff that is known to break.

    New stuff is not infalible, there is a reason that there was two redisgns of the Isis crank followed by a new style of crank coinnections, as engineer I can say that engineers stuff shit up (and lots of it is bigger than a crank) google: tacoma narrows bridge!
    Quote Originally Posted by heavymetal View Post
    The furries probably think us bike people are a bunch of freaks.
    Quote Originally Posted by lokione View Post
    Whatever! Next month I'm gonna ride a uni cycle with a paddle tyre accross Bass Straight with Afgan midget siamese twin strippers on my shoulders to raise awearness for migrant exploitation. Amature...
    Quote Originally Posted by justdave View Post
    That's sig worthy, some one jump on it!
    Quote Originally Posted by Charlie View Post
    Slightly confused as to what a town bike was (is it fixed, where can I find one, how much does it cost, how long must I wait for shipping?) I googled "town bike".

    Well I feel silly now

  7. #7
    CraigC
    Guest

    Re: Dye Penetrant Testing

    Quote Originally Posted by PiledHigher
    Quote Originally Posted by CraigC
    It's called buiying new cranks, you Fucktsick!!!!!!!!!!!!!!!!!!!!!!!

    Seriously, If you're worried about this concept, stay away from conversions and track bkes. Buy something new?!?!?!?!?!?!?!? If you don't have the money, welll............................................. ..............
    Well not sure who you are having a go at, but Blakey is offering to help people and I'm just ssaying that not every thing old was well designed, take the attitude that they have with planes and inspect stuff that is known to break.

    New stuff is not infalible, there is a reason that there was two redisgns of the Isis crank followed by a new style of crank coinnections, as engineer I can say that engineers stuff shit up (and lots of it is bigger than a crank) google: tacoma narrows bridge!
    I completely agree, Engineers have no fucking idea (never trust a professional with a Uni degree,,,,,,,,, useless/unless), My experience has been, either use "used' parts and expect failure or use new parts and have a piece of mind that 'stuff could happen'.

  8. #8
    NJS Certified
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    Re: Dye Penetrant Testing

    Quote Originally Posted by CraigC
    I completely agree, Engineers have no fucking idea (never trust a professional with a Uni degree,,,,,,,,, useless/unless), My experience has been, either use "used' parts and expect failure or use new parts and have a piece of mind that 'stuff could happen'.
    Glass half empty much? :roll:

  9. #9
    CraigC
    Guest

    Re: Dye Penetrant Testing

    My point was:
    Ride it until it breaks, then replace! (I am so, Zen)

  10. #10
    bleep bloop bleep AL9000's Avatar
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    Re: Dye Penetrant Testing

    Quote Originally Posted by CraigC
    I completely agree, Engineers have no fucking idea (never trust a professional with a Uni degree,,,,,,,,, useless/unless), My experience has been, either use "used' parts and expect failure or use new parts and have a piece of mind that 'stuff could happen'.
    Well, you could also use used parts that are tested and known to be good, or known to have flaws but are still fit for service (AS3788/API579 for the enginerds) with an acceptable safety margin at original stresses or at reduced stresses.

    Which is more reliable, a 20 year old part that is put into service and then inspected every 12 months with a method that has a 95% probability of detection of >0.5mm cracks [1], or a new part put into service and never inspected?

    There are a lot of old parts with unknown history (For Sale: Record Pista cranks, only ridden to church on Sundays) out there, and I'd wager that the majority of us here are using old bits too. It doesn't hurt to have a look occasionally and lower your probability of failure.

    Edit: 'Ride it until it breaks' is all well and good, but sudden crank/bars/stem failure is probably going to experience final fracture under a heavy load, which generally means high speed/acceleration, so the consequences are likely to be nasty.

    PS: Engineers are useless, they don't understand how things are really done, I know. But we're the ones that have to put our signature on paper and take responsibility if it doesn't work. :roll:

    Is it time for engineers to bitch about managers now? You know, not giving us enough funding or expecting unrealistic outcomes? :-D

    All in fun!

    [1] Numbers vary. Go ask an NDT tech

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