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hole in chain stay



 
 
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  #1  
Old January 16th 18, 12:52 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
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Posts: 1,015
Default hole in chain stay

Today there was a guy with a MTB and on the
chain stay there was a small drilled hole,
maybe 5mm in diameter. The hole didn't go out
on the other side so it was just one entry
point. It looked completely undramatic to me
but he insisted it reduced strength. Well, of
course, but not to a degree where the tube
would fail, right? I'd estimate the tube
diameter to 2cm plus change. It was an old MTB,
90s or the Millenium, so does that mean most
likely steel and possibly aluminium? BTW, are
carbon frames like horror story glass-fiber
boats in the sense that a crack thru
micro-vibrations can make steady but all but
undetectable progressions before the whole
thing come crashing down?

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  #2  
Old January 16th 18, 05:41 AM posted to rec.bicycles.tech
Tim McNamara
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Posts: 6,827
Default hole in chain stay

On Tue, 16 Jan 2018 01:52:09 +0100, Emanuel Berg
wrote:
Today there was a guy with a MTB and on the chain stay there was a
small drilled hole, maybe 5mm in diameter. The hole didn't go out on
the other side so it was just one entry point. It looked completely
undramatic to me but he insisted it reduced strength. Well, of course,
but not to a degree where the tube would fail, right? I'd estimate the
tube diameter to 2cm plus change. It was an old MTB, 90s or the
Millenium, so does that mean most likely steel and possibly aluminium?
BTW, are carbon frames like horror story glass-fiber boats in the
sense that a crack thru micro-vibrations can make steady but all but
undetectable progressions before the whole thing come crashing down?


Metal bikes joined by welding, brazing, lugs, etc., often have vent
holes drilled into the tubes near the heating site. The reason for this
is that the heat expands the air inside the tube and the vent hole gives
it a controlled place to go- instead of, say, sputtering out through the
molten brass at the joint. Usually this hole is about 1-2 mm, but some
are larger.
  #3  
Old January 16th 18, 06:08 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
external usenet poster
 
Posts: 1,015
Default hole in chain stay

Tim McNamara wrote:

Today there was a guy with a MTB and on the
chain stay there was a small drilled hole,
maybe 5mm in diameter. The hole didn't go
out on the other side so it was just one
entry point. It looked completely undramatic
to me but he said it reduced strength. Well,
of course, but not to a degree where the
tube would fail, right? I'd estimate the
tube diameter to 2cm plus change. It was an
old MTB, 90s or the Millenium, so does that
mean most likely steel and
possibly aluminium?


Metal bikes joined by welding, brazing, lugs,
etc., often have vent holes drilled into the
tubes near the heating site. The reason for
this is that the heat expands the air inside
the tube and the vent hole gives it
a controlled place to go- instead of, say,
sputtering out through the molten brass at
the joint. Usually this hole is about 1-2 mm,
but some are larger.


Thanks a lot, I CC this reply to him
right away

--
underground experts united
http://user.it.uu.se/~embe8573
 




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