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Date: 27 Jun 2007 17:51:09
From: Ben Pfaff
Subject: today must be Massive Bike Failure Day
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On my way home, a few hundred yards from the office, I managed to
get my shoelace stuck in the chain. Somehow it managed to rip
the front derailer out of position. I was able to limp to the
side of the road and cut my shoelace off, then lift up the chain
and get the remaining piece out of the chain, then bend the
derailer by hand until it was functional again.
Then, a mile or two from home, I lost a pedal. I coasted to the
side of the road, waited for the line of cars to go by, and
retrieved the pedal. At this point I realized that the pedal
hadn't fallen off; rather, the threaded part of the crank had
split. I had to make it the rest of the way home pedaling with
my left foot and using the right foot to kick the remaining part
of the crank over to start the next stroke. Challenging, but not
exactly fun.
I'm glad that I have a new bike on order. I'm expecting it to be
delivered tomorrow.
--
"If a person keeps faithfully busy each hour of the working day, he
can count on waking up some morning to find himself one of the
competent ones of his generation."
--William James
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Date: 28 Jun 2007 04:22:12
From:
Subject: Re: today must be Massive Bike Failure Day
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Ben Pfaff writes:
> On my way home, a few hundred yards from the office, I managed to
> get my shoelace stuck in the chain. Somehow it managed to rip the
> front derailer out of position. I was able to limp to the side of
> the road and cut my shoelace off, then lift up the chain and get the
> remaining piece out of the chain, then bend the derailer by hand
> until it was functional again.
> Then, a mile or two from home, I lost a pedal. I coasted to the
> side of the road, waited for the line of cars to go by, and
> retrieved the pedal. At this point I realized that the pedal hadn't
> fallen off; rather, the threaded part of the crank had split. I had
> to make it the rest of the way home pedaling with my left foot and
> using the right foot to kick the remaining part of the crank over to
> start the next stroke. Challenging, but not exactly fun.
> I'm glad that I have a new bike on order. I'm expecting it to be
> delivered tomorrow.
You are not safe from another crank failure, but it is good to hear
others admitting that this occurs. Most people are intimidated into
silence by accusations that the bicycle was improperly used. I heard
lots of that over those years that I had at least one crank failure
per year. I broke more than two dozen cranks that way before I said
ENOUGH!
Consider that left cranks have left hand threads so they won't unscrew
and fall off. Consider that tightened as tight as practical, tandems
that do not use tandem cranks (threading on the left front and rear
cranks (that carry the transfer chain [on right hand cranks]) unscrew.
Somehow this interface that violates a basic mechanical design rule is
not recognized in the bicycle industry for what it is, a joint asking
to fail. Cars used to have left hand threads on left wheels for the
same reason. "Do not center loads on threads!" Today lug nuts have
conical faces and lock into place securely. No more left hand threads
on passenger cars.
I modified my cranks to have a conical seat for a conical shoulder on
the pedal shaft. Because I must use existing pedals, I emulated the
conical shoulder with a split conical adapter that is pressed securely
into the thread relief of the pedal shaft by the taper. Formerly I
inspected both cranks with a loupe under bright light before every
longer ride (finding cracks on occasion). Today I no longer do that
and have not had a failure since I modified the cranks more than ten
years ago.
If you don't believe your pedals are moving, just look at the face of
the crank when the pedal is removed. The erosion you see is fretting
damage caused by movement and this movement generates crack both on
the crank face and in the threads.
I cannot interest anyone in the bicycle component business with this
modification, because as Carl Fogel says, "just because Jobst said so
is not proof that it occurs".
http://www.chiark.greenend.org.uk/~damerell/bikes/brandt-cranks.jpg
http://pardo.net/bike/pic/fail-001/FAIL-016.html
Others have had their cranks modified after such a failure, but what
do they know.
Jobst Brandt
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Date: 27 Jun 2007 20:50:35
From: Brian
Subject: Re: today must be Massive Bike Failure Day
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"Ben Pfaff" <blp@cs.stanford.edu > wrote in message
news:871wfwrjeq.fsf@blp.benpfaff.org...
> On my way home, a few hundred yards from the office, I managed to
> get my shoelace stuck in the chain. Somehow it managed to rip
> the front derailer out of position. I was able to limp to the
> side of the road and cut my shoelace off, then lift up the chain
> and get the remaining piece out of the chain, then bend the
> derailer by hand until it was functional again.
>
> Then, a mile or two from home, I lost a pedal. I coasted to the
> side of the road, waited for the line of cars to go by, and
> retrieved the pedal. At this point I realized that the pedal
> hadn't fallen off; rather, the threaded part of the crank had
> split. I had to make it the rest of the way home pedaling with
> my left foot and using the right foot to kick the remaining part
> of the crank over to start the next stroke. Challenging, but not
> exactly fun.
>
> I'm glad that I have a new bike on order. I'm expecting it to be
> delivered tomorrow.
>
> --
> "If a person keeps faithfully busy each hour of the working day, he
> can count on waking up some morning to find himself one of the
> competent ones of his generation."
> --William James
Ha! I'm ahead of the curve...my #3 chainring tore apart *two* days ago!
Happened just as I was beginning the daily grind up the Alex Fraser bridge.
I hate that.
B.
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Date: 28 Jun 2007 17:34:25
From: Marlene Blanshay
Subject: Re: today must be Massive Bike Failure Day
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it's mercury.... the planet that governs transportation is now in
retrograde...beware!!!!
Brian wrote:
> "Ben Pfaff" <blp@cs.stanford.edu> wrote in message
> news:871wfwrjeq.fsf@blp.benpfaff.org...
>> On my way home, a few hundred yards from the office, I managed to
>> get my shoelace stuck in the chain. Somehow it managed to rip
>> the front derailer out of position. I was able to limp to the
>> side of the road and cut my shoelace off, then lift up the chain
>> and get the remaining piece out of the chain, then bend the
>> derailer by hand until it was functional again.
>>
>> Then, a mile or two from home, I lost a pedal. I coasted to the
>> side of the road, waited for the line of cars to go by, and
>> retrieved the pedal. At this point I realized that the pedal
>> hadn't fallen off; rather, the threaded part of the crank had
>> split. I had to make it the rest of the way home pedaling with
>> my left foot and using the right foot to kick the remaining part
>> of the crank over to start the next stroke. Challenging, but not
>> exactly fun.
>>
>> I'm glad that I have a new bike on order. I'm expecting it to be
>> delivered tomorrow.
>>
>> --
>> "If a person keeps faithfully busy each hour of the working day, he
>> can count on waking up some morning to find himself one of the
>> competent ones of his generation."
>> --William James
>
> Ha! I'm ahead of the curve...my #3 chainring tore apart *two* days ago!
>
> Happened just as I was beginning the daily grind up the Alex Fraser bridge.
> I hate that.
>
> B.
>
>
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