Killed a Spider out on the trail tonight- Mtbr.com
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  1. #1
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    Upset Killed a Spider out on the trail tonight


    Does anybody have an extra set of 180's gathering dust they want to part with?

  2. #2
    blame me for missed rides
    Reputation: weather's Avatar
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    ouch! i bet you were JRA.

    edit: i think you didn't screw in the inner chainring bolts, that's why it failed. those bolts are structural.
    Last edited by weather; 05-06-2004 at 05:15 PM.

  3. #3
    The name's Norm...
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    Oh, man!!! Were you okay? That's mean lookin'! Besides the bike, were you damaged?

  4. #4
    "Mr. Britannica"
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    Quote Originally Posted by weather
    you didn't screw in the inner chainring bolts, that's why it failed. those bolts are structural.

    Really? didn't know that........

  5. #5
    Cracker-magnon
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    Quote Originally Posted by roadiegonebad
    Really? didn't know that........
    Yup, they help transfer the stress accross the arms of the spider, otherwise you got 3 big stress risers right there.
    "Life is a [email protected]#^ing story problem, get used to it - my son.

  6. #6
    horizontally compliant
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    owww

    hope you didn't kill any body parts as well!

  7. #7
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    Idea! Live and Learn

    These cranks lasted 3 years without those bolts in the granny holes. I bet the fact that I was riding without them in place voids the lifetime warranty. I literally was just riding along when they broke.......riding along through a muddy creekbed and when I started to power out of the stinky muck, my ride ended and I walked back to the car. I think White Industries will sell a set of cranks today.

  8. #8
    Dain Bramaged
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    I'm betting there's a whole buncha bolts being installed tonight

    I know I will be. I never thought of that before but you can sure bet there's some shortened inner bolts gonna go on my RF cranks ASAP. Sheesh!

  9. #9
    Whiskey Tango Foxtrot
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    New question here. are you serious?

    you sound serious.... but neither my crappy stylos on my DiSS nor the nice RF's on my chameleon have those bolts in place. both were OEM SS cranksets.

  10. #10
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    Wow...

    I now slowly creep away from the computer to go put the inner ring bolts on my Turbines...

    --Billy


    A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.
    - Douglas Adams

  11. #11
    Retro Grouch
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    Cool-blue Rhythm Looks like a defect to me..

    Quote Originally Posted by weather
    ouch! i bet you were JRA.

    edit: i think you didn't screw in the inner chainring bolts, that's why it failed. those bolts are structural.
    From what little I know of structural engineering I disagree with your theory (and I'm sure Race Face will also). When you drill a hole in a structural member you weaken the member. The mere threading and inserting a bolt into the hole should not add any more strength and may actually increase the internal stresses. Of course one should remember that science is a process and not the accumulation knowledge; as all scientific theories are eventually proven wrong

    I would call Race Face before I sign off on a warranty.

    1G1G, Brad
    Last edited by aka brad; 05-08-2004 at 10:37 AM.

  12. #12
    blame me for missed rides
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    this is a high-cycle fatigue problem. with a hole in the middle of the spider arms, effectively with each revolution the force that used to distribute across the spider arm cross-section is now carried by the two much smaller cross-sections alongside the hole--the stress is simply multiplied, and the lifespan/# of cycles before failure of the spider arm decreases exponentially. you notice that the cranks failed exactly at where the cross-sectional area across the spider arm is the smallest. with the bolt in place, the force is carried by both bolt and those two cross-sections. that's a much bigger cross-sectional area, similar to the situation where the hole was not there.
    Last edited by weather; 05-08-2004 at 01:13 PM.

  13. #13
    "Mr. Britannica"
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    3/5 right

    but 3 of the breaks were across the inner bolt holes, and the other 2 look to be at the "step" where the chainring sits.

  14. #14
    blame me for missed rides
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    Quote Originally Posted by roadiegonebad
    but 3 of the breaks were across the inner bolt holes, and the other 2 look to be at the "step" where the chainring sits.
    it's because the other two spider arms are attached to the crank arm and thus the force has a LOT of cross-sectional area. my guess is that when the other 3 spider arms fail, these two arms are simply sheared off at the tab.

  15. #15
    "Mr. Britannica"
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    you've assume that the 3 "loose" granny holes broke first... that may be true, but who really knows for sure?

  16. #16
    blame me for missed rides
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    if the tabs are the problem, then they could've broken off from all our cranks by now.

  17. #17
    blame me for missed rides
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    realized my last post was wrong (hey, i'm not an engineering student), as the tabs have no more cross-sectional area than the arm alongside the hole. the force on the spider arms are not along the center line either, but rather a "sideways" bending force.

    revised theory here:

    w/o the hole, stress gradually changes (from tension to compression) across the cross-section of the arm; when there's a hole in the spider arm, the stress (instead of being gradual) is concentrated at two hot spots (one tension, one compression) alongside the hole. the effect is the same: the spider arm fails early at these two spots due to increased stress. the two spider arms that connect to the crank arm are saved because the crank arm took up the bending force.

    damn hope i have a finite element software handy.

  18. #18
    "Mr. Britannica"
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    I asked Raceface about the inner bolts and sent them the link to the picture above. Here is their reply in total, verbatim:

    We feel that installing a reinforcement ring or granny ring will increase the strength of the spider. Installing granny bolts alone most likely will not have a large impact. Having granny ring bolts installed is not a requirement of warranty on Turbine LP cranks. Our old Turbine DH cranks came with an aluminum reinforcement ring, it would most likely help in this situation. Unfortunately we no-longer manufacture or stock the reinforcement rings, they may be available in a secondary marketplace.

    Also please note that bicycle components should be visually inspected on a regular basis for any cracks or fractures. There's a chance that the Turbine LP cranks pictured may have been cracked before the product failed. Sometimes these hairline cracks can be very difficult to detect, however for your own personal safety and well being we recommend carefully inspecting your components. Thanks for your email.

  19. #19
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    Race Face

    The race face warranty feller told me that the fact that I didn't have bolts in the granny holes wouldn't preclude them from warrantying the crank after I made my last post. I bet they want to replce it with an ISIS model, because they have phased out all their square taper cranks. The broken crank is on its way back to them for them to look at. I've broken a lot of parts recently........I blame those god forsaken Gnome bastages.

  20. #20
    WAWE
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    Quote Originally Posted by weather
    i think you didn't screw in the inner chainring bolts, that's why it failed. those bolts are structural.
    From what I understand, the inner bolts are only required on the Next LP and North Shore models because of their removable chainring spider tabs.

  21. #21
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    Here's that DH stiffner they were talking about

    <center><img src="https://gallery.consumerreview.com/webcrossing/images/Bike211.jpg"></center>

  22. #22
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    looks like the granny gear is a reinforcing piece of the spider

    Sounds like the stress of the gears is distributed across all of the granny gear bolt-hole walls as well as preventing the holes from being ovalized as us super-strong-single-speeders (S.S.S.S.) hammer cranks. So installing the granny bolts would be better than nothing at all. Installing the granny gear or a reinforcing ring (granny minus teeth) would be the best. Don't like it cuz it's more weight and that's why we got rid of the granny to begin with!

    Excuse my crude diagram, but these are the newer Turbines that have the front of the granny bolt-holes filled (stronger?) The older ones were just drilled all the way through. Maybe that's why the Turbines were redesigned?


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