Steering Tube Failure - Fetish Bike
10-09-07, 02:27 PM
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Steering Tube Failure - Fetish Bike
Has anyone seen or heard of a Fetish Steering Tube Fail? I was involved in an accident with one, which I've attached pics. This looks like a complete failure of the carbon steering tube, but I would like to know if anyone has seen something like this before, and if you have heard if Fetish has had this problem in the past?
Revised PICs in JPG format below
Revised PICs in JPG format below
Last edited by wgfletcher; 10-09-07 at 06:25 PM.
10-09-07, 02:51 PM
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10-09-07, 02:56 PM
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What is this demonry?!
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honestly who saves pictures as .bmp....Can't tell what the hell happened from the pics, save them as jpeg in at least 800x600 then post them again.
Last edited by Szczuldo; 10-09-07 at 03:02 PM.
10-09-07, 03:31 PM
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that sucks. i almost bought a fetish too.
10-09-07, 03:34 PM
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Were your injuries/crash a result of the steer tube breaking, or was the steer tube breaking just another result of your crash? If so, then you can't blame a bike company/part for breaking in a crash especially if its a serious crash, which it sounds like in your case. If the steer tube just randomly broke, and your injuries were a result, its time to call Johnny Cokrine.
Last edited by asmallsol; 10-09-07 at 03:49 PM.
10-09-07, 04:19 PM
#11
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What's in the baggie in the second pic? Is that where you stash your... stash? 
Be careful when you reuse that front brake caliper. It looks like the cable tension bolt is broken.
Be careful when you reuse that front brake caliper. It looks like the cable tension bolt is broken.
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"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
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"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
10-09-07, 04:27 PM
#13
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The breakage looks a lot like a failure in torsion. It is not at a stress riser where cracks from fatigue will develop, and it isn't a crush failure from overtightening a clamp. If I were just looking at this from the pictures, knowing nothing of the situation, I'd say that the crash happened first and the handlebars were torqued around during the fall, breaking the steering tube.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
10-09-07, 06:03 PM
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The crash occured because the steering tube failed. Actully, this is the bike from the person in front of me. We were sprinting - about 30mph, when he started to wobble and then all of the sudden he was holding the handlebars. He rode the bike into the ground face first and I went right over him.
I don't know what spacers he had on the bike at the time, but this bike was 2-3 months old when it happened. The other weird thing is that bag in the tube, it was there, so I'm wondering if that was left from the molding processes. Not knowing how carbon is put together, I wouldn't know if that is standard or not?
I don't know what spacers he had on the bike at the time, but this bike was 2-3 months old when it happened. The other weird thing is that bag in the tube, it was there, so I'm wondering if that was left from the molding processes. Not knowing how carbon is put together, I wouldn't know if that is standard or not?
10-09-07, 06:07 PM
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Catastrophic.
10-09-07, 06:22 PM
#18
nom nom nom
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Lots of carbon forks/frames have that plastic bag type thing in them. Leftovers from molding. Sucks that you/the other guy crashed though.
10-09-07, 07:20 PM
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In alot of carbon things like forks where your molding around a solid piece of foam, the foam is there just for support during manufacturing. After the part is finished, the solid piece has no purpose, however because of the shape it can not be removed. In cross country skiing (another sport were weight weenies run rampid) skiers will trim the tail of the ski to expose the interior foam, and will pour an acid solution that dissolves the foam, all to save like 10 grams.
10-09-07, 07:49 PM
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It appears from your photo that the tube de-laminated on the inside,but I,m not a polymer carbon fiber expert.How does one know what grade CF tube you purchase,its not graded like steel with a label?We do however have many self ordained experts on anything from CF to sex here at BF, at no charge to you.
10-09-07, 08:36 PM
#22
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The breakage looks a lot like a failure in torsion. It is not at a stress riser where cracks from fatigue will develop, and it isn't a crush failure from overtightening a clamp. If I were just looking at this from the pictures, knowing nothing of the situation, I'd say that the crash happened first and the handlebars were torqued around during the fall, breaking the steering tube.
Generally, CF is not prone to fatigue; giving it one of its redeeming characteristics.
Torsional fracture of brittle materials follow a spiral path around most of the circumference, then closed off with a longitudinal break. Shows clearly in these pictures. But something would have to have applied the breaking torque; something would need to restrain the wheel from being turned at the road surface, while the rider is hammering away on both peddles and handlebars.
Could the rider have locked the front wheel in some type of trap (drainage grating or edge of curb) while hammering away in the sprint? If that were so, I would expect some twisting in the wheel rim, or at least abrasion on the side wall of the rim.
... Nice catch, Brian.
Last edited by Skeleton; 10-12-07 at 06:15 PM.
10-09-07, 08:53 PM
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The road was smooth and clear. The only thing that the person mentioned was touching wheels with another rider a couple of weeks earlier, but didn't go down.
When he went down, the handle bar didn't come out (ala George Hincapie), but the front wheel/fork collapsed under him and he rode the frame holding the handlebars into the pavement.
When he went down, the handle bar didn't come out (ala George Hincapie), but the front wheel/fork collapsed under him and he rode the frame holding the handlebars into the pavement.
Last edited by wgfletcher; 10-09-07 at 08:59 PM.
10-09-07, 09:28 PM
#24
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It is possible that there was a void in the carbon fiber. Did you preserve the pieces of the fork, and most importantly, did you NOT try to press the broken pieces together?
If the fork broke without any help from an obstacle or crash, then it was definitely defective, with the most probable failure being a void in the CF layup. During a sprint there is definitely plenty of torque put on the steering tube. If there was a void, and just looking from the picture, the void would likely be at the back of the fork, on the side of the tube opposite of the brake caliper. This is where the break is lateral across tube, as opposed to spiraling as the rest of the break was.
If the fork broke without any help from an obstacle or crash, then it was definitely defective, with the most probable failure being a void in the CF layup. During a sprint there is definitely plenty of torque put on the steering tube. If there was a void, and just looking from the picture, the void would likely be at the back of the fork, on the side of the tube opposite of the brake caliper. This is where the break is lateral across tube, as opposed to spiraling as the rest of the break was.
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Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
Cat 2 Track, Cat 3 Road.
"If you’re new enough [to racing] that you would ask such question, then i would hazard a guess that if you just made up a workout that sounded hard to do, and did it, you’d probably get faster." --the tiniest sprinter
10-09-07, 10:06 PM
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OK, so I did a quick calculation on the torsional stress. This is based on some standard values for shear strength of carbon fibre, and common dimensions for headset and handlebars. I "eye-balled" a nominal thickness for the wall of the headset.
Roughly, 300 lbs of force applied against the drops of the handlebars could cause torsional fracture of the CF tube. As an "impulse" force, this is not hard to attain for an average weight/strength rider - but it would need to be applied under severe loading conditions. How so? As Brian suggested, on impact following a crash, or as I suggested when the wheel is restrained by a road trap. In both cases, I would expect the rim of the wheel to be twisted.
I don't think this high level of force (torque) could be achieved from previously engaging against the rear wheel of a lead bike. Nor could this level of torque ever be achieved by sprinting with an unrestrained wheel and handlebar.
1) It won't prove my point, but what was the condition of the wheel rim? (Keep that wheel rim - it'll be very relevant.)
2) Further to Brian's comment: The attached pic shows what might be a delamination on the inside wall as indicated (circled in red). Am I reading the picture correctly? If so, I would imagine that delamination could not arise during the crash, but at the moment of internal failure.
Some post failure abrasion happened on the handlebar end of the stem as the rider drove the handlebar into the ground (as seen by the transparent resin remaining after some of the CF fibers are ground down.)
Also on my markup pic (circled in green) there is a conspicuous "thumbnail" crack. If I read it right, it could suggest pre-existing delamination, since its position is beyond but connected to the torsional crack ring.
Interesting ... (but sorry for your troubles and injuries).
Roughly, 300 lbs of force applied against the drops of the handlebars could cause torsional fracture of the CF tube. As an "impulse" force, this is not hard to attain for an average weight/strength rider - but it would need to be applied under severe loading conditions. How so? As Brian suggested, on impact following a crash, or as I suggested when the wheel is restrained by a road trap. In both cases, I would expect the rim of the wheel to be twisted.
I don't think this high level of force (torque) could be achieved from previously engaging against the rear wheel of a lead bike. Nor could this level of torque ever be achieved by sprinting with an unrestrained wheel and handlebar.
1) It won't prove my point, but what was the condition of the wheel rim? (Keep that wheel rim - it'll be very relevant.)
2) Further to Brian's comment: The attached pic shows what might be a delamination on the inside wall as indicated (circled in red). Am I reading the picture correctly? If so, I would imagine that delamination could not arise during the crash, but at the moment of internal failure.
Some post failure abrasion happened on the handlebar end of the stem as the rider drove the handlebar into the ground (as seen by the transparent resin remaining after some of the CF fibers are ground down.)
Also on my markup pic (circled in green) there is a conspicuous "thumbnail" crack. If I read it right, it could suggest pre-existing delamination, since its position is beyond but connected to the torsional crack ring.
Interesting ... (but sorry for your troubles and injuries).
Last edited by Skeleton; 10-09-07 at 10:42 PM.