On 01/24/2015 09:04 AM, Ron Mc wrote:
I analyze fractures as a professional. The photos clearly show that
the thick part of the fracture and progressively cracked from both
sides before the area was reduced enough to let it pop - it's a
fatigue failure, and it's been going on a long time. TX PE No, 75665
Two questions: 1) what do those alpha-numerics mean? 2) can we surmise
the fatigue failure is the result of poor design?
On Friday, January 23, 2015 at 4:28:56 PM UTC-6, Bill Lindsay wrote:
A completely not-bent derailer tab would definitely suggest that
the derailer just decided to explode itself into bits on its own,
which is indeed WEIRD. JRADSA = Just Riding Along Derailer Self
Immolation
On Friday, January 23, 2015 at 1:20:15 PM UTC-8, John wrote:
Since I didn't see it happen, I have to do my best to
understand based on the after-effects. I was riding in some
sticky mud at the time, but there was no mud on my chain or on
the derailer. I took the photo without cleaning the RD. It's
a bit greasy, but no mud or rocks or sticks were involved as
far as I can tell. I was JRA (love that acronym) and it
appears as if the derailer broke in two, flopped around the
chainstay still attached to the cable, and jammed the wheel to
a stop. I'll be checking the wheel for damage, but the
derailer hanger is definitely not bent or damaged. The small
half of the derailer was still securely bolted in place. It's
weird, I tell you. Just WEIRD!
I bought a better Shimano RD at Harris Cyclery during
a business trip to MA this week. I'm hoping it fails in a
more graceful manner after a long life.
On Thursday, January 22, 2015 at 1:56:10 PM UTC-6, Bill
Lindsay wrote:
I'm curious about the CAUSE and the EFFECT. Which was it:
A. Did the derailer just separate into two parts on its
own? Then the broken off part got caught in the spokes,
causing you to lurch to a stop?
Cause: Derailer fell apart on its own Effect: Broken
bits fell into the wheel
B. Did your derailer get caught in the spokes while you
were riding? Your wheel ripped the derailer in two and
you lurched to a stop
Cause: Spokes grabbed derailer Effect: Bike lurched to
a stop and the wheel broke the derailer
C. Could something else have gotten into your rear wheel,
like a stick?
Cause: Stick in the spokes grabbed the derailer. Effect:
Bike lurched to a stop and the stick broke the derailer
Getting the rear der caught in the spokes is not uncommon.
The result is usually a busted derailer and often a badly
bent derailer tab. Derailers randomly commiting suicide
by exlpoding themselves into two parts while JRA (just
riding along) is not common.
On Sunday, January 18, 2015 at 2:56:14 PM UTC-8, John wrote:
Towards the end of my ride today, I heard a loud
crunch and my Ram lurched to a stop. Didn't take long
to figure out the cause. My Shimano Tiagra RD had
separated into two pieces. The larger chunk with
cable attached wrapped around the right chainstay and
lodged in my spokes. The other piece remained bolted
to the dropout. Fortunately, I was going very slowly
at the time, so no damage was done to my wheel. I
wasn't shifting at the time, just pedaling along. I
was able to break the chain and remove the cable so I
could at least roll my bike to where my wonderful wife
rescued me. Surprising because the RD is only a couple
of years old and has not suffered any tip-overs that
might have damaged it. I took a couple of pictures of
the fracture:
https://www.flickr.com/photos/53546004@N07/16312803255/
<https://www.flickr.com/photos/53546004@N07/16312803255/>
https://www.flickr.com/photos/53546004@N07/16125257318/
<https://www.flickr.com/photos/53546004@N07/16125257318/>
Is it just me, or is this not uncommon?
Off to shop for a new RD.
John
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