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  1. #76
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    Quote Originally Posted by crashtestdummy
    Thomson setback posts are machined and then bent to the setback position. You would think if there were any fatigue points they would be caused by this. This doesn't appear to be the case in apacherider's situation though.
    I'm not talking about "induced" fatigue points caused by the actual bending/manufacturing process. I'm talking about the funky forces caused by the saddle not being in the same relative position as on a straight post (maybe even exacerbated by the saddle being back on the rails).

    Again, I'm no engineer but it seems clear to me that it just isn't the same situation all around, setback vs straight. Doesn't it seem odd that the OP has a history of Thomson seatposts and the only one he's broken was a setback?

    We all know Thomson makes the best seatposts but I wonder if their parameters for a setback are as stringent as on their straight ones? You know, like they might be saying "setbacks aren't the best way to re-position a rider (due to long thighs or too-short a top tube or whatever) but if the rider really wants one we'll give him one, even though it's not going to be as strong as our straight seatposts". Maybe. Kind of like doing curls with your elbows out in front of you and not at your sides.
    A blind man searches in a dark room for a black hat that isn't there. Dashiell Hammett

  2. #77
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    Setback seatposts used to be used much, much more than inline posts, so I don't really think so.

  3. #78
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    Quote Originally Posted by xcguy
    I'm not talking about "induced" fatigue points caused by the actual bending/manufacturing process. I'm talking about the funky forces caused by the saddle not being in the same relative position as on a straight post (maybe even exacerbated by the saddle being back on the rails).

    Again, I'm no engineer but it seems clear to me that it just isn't the same situation all around, setback vs straight. Doesn't it seem odd that the OP has a history of Thomson seatposts and the only one he's broken was a setback?

    We all know Thomson makes the best seatposts but I wonder if their parameters for a setback are as stringent as on their straight ones? You know, like they might be saying "setbacks aren't the best way to re-position a rider (due to long thighs or too-short a top tube or whatever) but if the rider really wants one we'll give him one, even though it's not going to be as strong as our straight seatposts". Maybe. Kind of like doing curls with your elbows out in front of you and not at your sides.
    The seat on that particular seatpost was pretty far back on the rails. Meaning in addition to having the setback post, I had the seat moved back a little further back beyond the neutral position on the rails. If that makes sense. The result was that the post was clamped on the forward 1/3 of the usable rail area. Not sure if that made a difference or not but it would have given a little bit more leverage on the top end of the post. Although I bet my saddle rails would have bent before the seatpost did.

  4. #79
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    Quote Originally Posted by steadite
    But doesn't include the radius where the fatigue occurred....

    Your analysis of the fracture (post #14) is correct...only thing I would add is that I see multiple fatigue origins on the tensile side of the post (there are "ratchet" marks along about a 5 mm length) rather than just one initiation site. This argues against the discreet material defect theory and for the theory of "just plain exceeded the fatigue strength of the material".
    This is correct - there is a large process zone there where the material fatigued. Only thing wrong in that post is the assertion that there was subritical crack growth through 1/2 of the circumference - you can see the crack origin pretty clearly and the crack would have gone to a critical flaw size well before that. T6 aluminum is a 40ksi material and pretty much linear to very close to failure. The rider must have been putting some serious weight down on the nose of his saddle (many times).

    I'm surprised to see such a process zone in T6.

  5. #80
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    Quote Originally Posted by apacherider
    Nope. No wrecks. No falling down. Nearly all my riding with that seatpost was on pavement. Some fireroads, some singletrack. I spend more than half my time in Dallas, the balance in Taos, NM. The Cannondales that I ride with this particular seatpost have spent over 90% of it's time in Dallas rather than Taos.

    Plus, much of last year (spring and summer) I was recovering from a monster huge car accident I was in, that occured in October 2007. Car drivers fault, ruined a road bike, I got a nice check. Broken ribs, messed up tailbone, shoulder etc. So....all last spring and summer I would ride everyday, but just on pavement. Falling and wreckin' was verboten! Pretty incredible how careful you can be while riding if you are scared of re-breaking a rib.
    Apache,

    This is interesting because if this is true, you're essentially telling us that you didn't abuse it. However, what I was interested in knowing was whether you used a torque wrench to tighten the bolts. According to Thomson, a majority of failures like these happen due to over torquing. You're really lucky to escape without injury. Let us know your thoughts on this.



    -Ron

  6. #81
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    Quote Originally Posted by Cozy.Beehive
    Apache,

    This is interesting because if this is true, you're essentially telling us that you didn't abuse it. However, what I was interested in knowing was whether you used a torque wrench to tighten the bolts. According to Thomson, a majority of failures like these happen due to over torquing. You're really lucky to escape without injury. Let us know your thoughts on this.



    -Ron
    Yes. I used a torque wrench. I use a torque wrench on virtually all my bike parts. In the past, back when I used square taper bottom brackets, using a torque wrench was essential. I have kept that practice up over the years. I'm 100% positive a torque wrench was used on this particular seatpost. Matter of fact, if you look at one of the bolts, you can see where I kind of buggered up the head of one of them with the torque wrench as it slipped off.

    Besides, where the seatpost broke is far removed from the area where the bolts affix to the seatpost itself. I do not see how there could be any correlation.

    Like I have said before, I'm a big fan of Thomson seatposts. I have them on many of my bikes. I would never consider using anything but them. I have gone through and carefully looked at all my other Thomsons, checked for cracks and also checked the torque on the bolts. Each were crack free and right on the money.

  7. #82
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    I wouldn't worry about it Apache. Manufacturers buy metal in bulk, and then process it into a final product. Sometimes the metal has defects. Thompson is pretty good at detecting flawed material, and their machining techniques are top-notch. I'm no expert metalurgist, but I've got a little experience from the machinists end. Looks like there was a flaw that slowly expanded to failure. It happens. See if Thompson is willing to warranty the post, and call it a day.

  8. #83
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    Quote Originally Posted by Barkleyfan
    I wouldn't worry about it Apache. Manufacturers buy metal in bulk, and then process it into a final product. Sometimes the metal has defects. Thompson is pretty good at detecting flawed material, and their machining techniques are top-notch. I'm no expert metalurgist, but I've got a little experience from the machinists end. Looks like there was a flaw that slowly expanded to failure. It happens. See if Thompson is willing to warranty the post, and call it a day.

    You seem to be inventing your own little story here. I have been in talks with Thomson and so far, no mention was made of defective material. They absolutely stand by their products. It seems you know more about their material than they do.

  9. #84
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    Quote Originally Posted by Cozy.Beehive
    You seem to be inventing your own little story here. I have been in talks with Thomson and so far, no mention was made of defective material. They absolutely stand by their products. It seems you know more about their material than they do.
    I think you meant to say you work for Thomson. Why on earth would any manufacturer mention to a customer that there was a flaw in their product materials? You do not need to admit fault to stand by your product. You just send out a replacement item or fix it if possible.

  10. #85
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    Quote Originally Posted by wormvine
    I think you meant to say you work for Thomson. Why on earth would any manufacturer mention to a customer that there was a flaw in their product materials? You do not need to admit fault to stand by your product. You just send out a replacement item or fix it if possible.
    You bring together some of your "little" machinist experience working for some company in the past to make generalizations about Thomson and their QC. How come you know that their material is defective for certain? Can you spell F-L-U-F-F?

  11. #86
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    Quote Originally Posted by Cozy.Beehive
    You seem to be inventing your own little story here. I have been in talks with Thomson and so far, no mention was made of defective material. They absolutely stand by their products. It seems you know more about their material than they do.
    LMFAO Vested interest? Seriously, WTF do you care about Apaches resolution? If you wanna pretend Thompson does UT testing on every inch of every peice they put out, pretend away. Having done production level QA, I know it's highly unlikely. Especially for the price. Sometimes flaws get through.It's not the end of the world.

  12. #87
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    Sorry, you lose. Your attitude is the traditional way of thinking and it doesn't help. All to often its easy to say 'things break, let's move on'. If this was someone in your family getting hurt, you would probably change your outlook. Your claims about Thomson's QC is some conjecture at best. I'm also not sure what caused you to "LMFAO". All this is a circus act to you.

  13. #88
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    Cozy.Beehive has at last exposed the truth, 2 Thomson seatposts, of the thousands upon thousands of posts sold, have broke. The sky is officially falling. Thomson is not perfect, the Apocalypse has begun.

    PS anyone wanna trade their Sette for my 30.9x367 Thomson? I no longer feel safe.

  14. #89
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    Quote Originally Posted by Cozy.Beehive
    Sorry, you lose. Your attitude is the traditional way of thinking and it doesn't help. All to often its easy to say 'things break, let's move on'. If this was someone in your family getting hurt, you would probably change your outlook. Your claims about Thomson's QC is some conjecture at best. I'm also not sure what caused you to "LMFAO". All this is a circus act to you.
    If we are allowed a 0% failure rate then every manufacturer in the world would shut their doors. No product is perfect, and no amount of testing is going to ensure that it is. The idea is to design it right, build it right, and have enough QC checks in place to try and get as close to that 100% perfect as you possibly can.

    You want a product with a 0% chance for failure? Go pick up rocks and sell them as paper weights. Of course, then someone will drop one on a family member's toe and sue you anyway.

  15. #90
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    To the op, glad you are okay. I consider Thomson posts and stems to be the best in the industry, and it sounds like you would agree. I would let them have it for testing, but request it back, because you will need proof that you broke one.

  16. #91
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    Quote Originally Posted by adam728
    If we are allowed a 0% failure rate then every manufacturer in the world would shut their doors. No product is perfect, and no amount of testing is going to ensure that it is. The idea is to design it right, build it right, and have enough QC checks in place to try and get as close to that 100% perfect as you possibly can.

    You want a product with a 0% chance for failure? Go pick up rocks and sell them as paper weights. Of course, then someone will drop one on a family member's toe and sue you anyway.

    I didn't propose anywhere that the manufacturer in question has 0% failure rate.

  17. #92
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    Quote Originally Posted by Cozy.Beehive
    I didn't propose anywhere that the manufacturer in question has 0% failure rate.
    No, but you're pushing an issue, that not only isn't yours, but one that is one of the least to be concerned with in the whole of the mountain bike component world...you have more of the flavor of a lawyer looking for that very small exception on which to base a rule...
    "...the people get the government they deserve..."
    suum quique

  18. #93
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    Quote Originally Posted by MarcusSommers
    To the op, glad you are okay. I consider Thomson posts and stems to be the best in the industry, and it sounds like you would agree. I would let them have it for testing, but request it back, because you will need proof that you broke one.
    It hit their mailbox in Georgia, last friday. Should be getting a new one back any day now. No problems! Only reason I started the thread was due to the rarity of a failure. Had it been some other random part I would not even have mentioned it, much less started a thread. I hope you guys now include periodic checks of all your parts for cracks. I personally don't know when this crack formed or how long I'd been riding with it this way. Think I mentioned before, that I'm rather anal about bike maintenance, so this crack was a complete shock to me.

  19. #94
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    Please read on the engineering issues and analysis of the broken seatpost in question. Here's the results of my latest interview with a Thomson insider. http://cozybeehive.blogspot.com/2009...ightening.html


    Apache, you're copied to this as well. Thomson says there is no doubt in their minds that you overtightened this seat post, as much as 2.5 to 3 times the recommended values (read link above). Again, that's not me saying it. I also have a vested interest in this matter only so far as to get objective information.

  20. #95
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    What a fukin joke?

  21. #96
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    That was quick. Turns out you didn't even read the link I posted.

  22. #97
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    Quote Originally Posted by Cozy.Beehive
    Please read on the engineering issues and analysis of the broken seatpost in question. Here's the results of my latest interview with a Thomson insider. http://cozybeehive.blogspot.com/2009...ightening.html


    Apache, you're copied to this as well. Thomson says there is no doubt in their minds that you overtightened this seat post, as much as 2.5 to 3 times the recommended values (read link above). Again, that's not me saying it. I also have a vested interest in this matter only so far as to get objective information.
    Did you even ask anyone's permission to do such a thing?

  23. #98
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    Quote Originally Posted by Cozy.Beehive
    Please read on the engineering issues and analysis of the broken seatpost in question. Here's the results of my latest interview with a Thomson insider. http://cozybeehive.blogspot.com/2009...ightening.html


    Apache, you're copied to this as well. Thomson says there is no doubt in their minds that you overtightened this seat post, as much as 2.5 to 3 times the recommended values (read link above). Again, that's not me saying it. I also have a vested interest in this matter only so far as to get objective information.
    What else was said? We only have limited quotes and nothing you have put up there is "proof" of the claims being made. Having looked at the pics I have a hard time believing that line blaming the customer. A REALLY hard time thinking anyone with any training would see that failure and fall for that line. Your own "information" even points to holes in the lines you were fed blaming the customer.

    "Dave : "I also observed that the bolt heads are distorted. The bolts are grade 12.8. We know how much torque it requires to distort the bolt heads, and it is in excess of 125 inch pounds. ....."

    THAT is ABSOLUTELY idiotic. You are a fool for putting such a stupid comment online and thinking it supports your "case".

    In my opinion, I wouldn't "trust" any "engineer" who acted like you have been.
    No supporting evidence of your claims, reproducing claims made by others (who may or may not be qualified and ARE not independent) and misrepresenting this as being an open minded and valid investigation of an issue.


    Do you have permission to use the photos?

  24. #99
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    Smile

    Quote Originally Posted by ash240
    What else was said? We only have limited quotes and nothing you have put up there is "proof" of the claims being made. Having looked at the pics I have a hard time believing that line blaming the customer. A REALLY hard time thinking anyone with any training would see that failure and fall for that line. Your own "information" even points to holes in the lines you were fed blaming the customer.

    "Dave : "I also observed that the bolt heads are distorted. The bolts are grade 12.8. We know how much torque it requires to distort the bolt heads, and it is in excess of 125 inch pounds. ....."

    THAT is ABSOLUTELY idiotic. You are a fool for putting such a stupid comment online and thinking it supports your "case".

    In my opinion, I wouldn't "trust" any "engineer" who acted like you have been.
    No supporting evidence of your claims, reproducing claims made by others (who may or may not be qualified and ARE not independent) and misrepresenting this as being an open minded and valid investigation of an issue.


    Do you have permission to use the photos?


    Sorry that you didn't like the outcome of this case. I'm not supporting either one, just informing people of what the user did, and what Thomson says. Be known, that if you live in Georgia, and contact Dave Parett, he'll be more than happy to lead to on a factory tour to show you how everything is done. Maybe you can argue with him there? In the end, I obviously see contradications. Apache says he used a torque wrench, like he always did...Thomson claims he didn't and that their observation of the broken specimen shows there's only limited number of ways that seatpost could break. My job is to inform people that eitherway, you cannot afford to overlook the tightening values of nuts on bolts on your bike. That's some sound advice that many people in the bike industry has been giving over the years. Not many riders keep a tool like a torque wrench at home nor know how to use it. Meanwhile, you're most welcome to do a rebuttal of Dave's comments on my blog. I value the discussion. If you think something was stated wrong, come and talk about it.

  25. #100
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    Weird thing is, I use a Park Tool Torque Wrench and it only goes to 60 pounds. Huh.

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