I heard a rather surprising anecdote from a riding buddy today. He has a road bike with a carbon seatpost (unknown make, I didn't ask) with a plastic blinky light mount wrapped around it. He was JRA, hit a pothole, and the post snapped completely off right above the plastic mount, roughly in the middle of the exposed post.
Clearly, the light mount must have been too tight and created a stress riser. But I'm really surprised that an all-plastic band could exert enough clamping force to create a problem, given that the post was presumably designed to withstand a seat collar anywhere along its length.
Anyone ever encountered this? You think this was a defective post or are carbon posts really so temperamental?
I heard a rather surprising anecdote from a riding buddy today. He has a road bike with a carbon seatpost (unknown make, I didn't ask) with a plastic blinky light mount wrapped around it. He was JRA, hit a pothole, and the post snapped completely off right above the plastic mount, roughly in the middle of the exposed post.
Clearly, the light mount must have been too tight and created a stress riser. But I'm really surprised that an all-plastic band could exert enough clamping force to create a problem, given that the post was presumably designed to withstand a seat collar anywhere along its length.
Anyone ever encountered this? You think this was a defective post or are carbon posts really so temperamental?
I wonder if the failure mode was abrasion?
-- Ryan Cousineau [email hidden] http://www.wiredcola.com/ "I don't want kids who are thinking about going into mathematics to think that they have to take drugs to succeed." -Paul Erdos
"Dave" wrote: (clip) Clearly, the light mount must have been too tight and created a stress riser. > ^^^^^^^^^^^^^^^ I am more inclined to think the plastic exuded some residual solvent or other chemical which weakened the resin in the carbon-fiber post.
I heard a rather surprising anecdote from a riding buddy today. He has a road bike with a carbon seatpost (unknown make, I didn't ask) with a plastic blinky light mount wrapped around it. He was JRA, hit a pothole, and the post snapped completely off right above the plastic mount, roughly in the middle of the exposed post.
Clearly, the light mount must have been too tight and created a stress riser.
"Clearly'? Howdoyafigure? I doubt the blinky had anything to do with the breakage.
But I'm really surprised that an all-plastic band could exert
Quoted message said:
enough clamping force to create a problem, given that the post was presumably designed to withstand a seat collar anywhere along its length.
Still think the blinky had an effect?
Quoted message said:
Anyone ever encountered this? You think this was a defective post or are carbon posts really so temperamental?
On Jan 26, 5:38 am, "Qui si parla Campagnolo" <[email hidden]>
Quoted message said:
Quoted message said:
Clearly, the light mount must have been too tight and created a stress riser. "Clearly'? Howdoyafigure? I doubt the blinky had anything to do with
the breakage.
I dunno, every busted carbon seatpost I've seen or heard about broke at the clamp or the collar, not that this is a huge sample size. I found it quite a coincidence that this post broke off right above the blinky...the way my friend described it, the break was flush with the top of the mount.
On Jan 26, 5:38 am, "Qui si parla Campagnolo" <[email hidden]>
Quoted message said:
Quoted message said:
Clearly, the light mount must have been too tight and created a stress riser. "Clearly'? Howdoyafigure? I doubt the blinky had anything to do with
the breakage.I dunno, every busted carbon seatpost I've seen or heard about broke at
the clamp or the collar, not that this is a huge sample size. I found it quite a coincidence that this post broke off right above the blinky...the way my friend described it, the break was flush with the top of the mount.
I think the plastic strap would have broken way before damaging the carbon seatpost.
