Cracks in my cranks
Abram Dancy
crack goes left to right, from the inside edge of the crank maybe halfway
across the width of the crank. Upon closer inspection, I found a total of
three cracks on the non-drive side, evenly spaced around the crank, and one
or two similar cracks on the drive side. For what it's worth, they don't
look particularly deep.
The cranks have about 10K miles on them, and bear a Specialized logo.
How serious is this? Should I replace them tomorrow, or wait for bigger
signs?
Abram Dancy
S. Anderson
some type of finish material ( like clearcoat or something..). This is an
early-warning that everyone wishes they noticed before breaking a part. At
the VERY least, take it to a shop tomorrow and have them assess exactly what
those cracks are. Crank breakage, while rarely fatal, is extremely
uncomfortable!! ;-)
Cheers!!
Scott..
--
Scott Anderson
Remove the z's for e-mail..
"Abram Dancy" <abram...@verizon.net> wrote in message
news:ptWJ8.4737$b73...@nwrddc01.gnilink.net...
Ken
accidents occur when a crank breaks. It's about the next worse thing to
having your stem break. Your life or good health are not worth the price of
a crank set
Ken@Kauai
Abram Dancy <abram...@verizon.net> wrote in message
news:ptWJ8.4737$b73...@nwrddc01.gnilink.net...
VA guy
crankset. You don't need a crash or broken bones, especially as the best
part of warm weather cycling season begins!
"Abram Dancy" <abram...@verizon.net> wrote in message
news:ptWJ8.4737$b73...@nwrddc01.gnilink.net...
Abram Dancy
said it was unrideable. He's going to replace the cranks under warrantee,
which surprised me, given that I didn't buy the bike there, and it's a
couple years old, too. Assuming I get the bike back before too long, he's
won my business for a bit.
Thanks for the input, everyone.
Abram
"VA guy" <do...@mailme.net> wrote in message
news:PW5K8.686$NG1...@newsread2.prod.itd.earthlink.net...
Matt Temple
>
> The mechanic at the bike shop concurred with the advice proffered here. He
> said it was unrideable. He's going to replace the cranks under warrantee,
> which surprised me, given that I didn't buy the bike there, and it's a
> couple years old, too. Assuming I get the bike back before too long, he's
> won my business for a bit.
>
> Thanks for the input, everyone.
>
but I have a question, and its this: Will Specialized, the producer/
marketer of the crank reimburse the bike shop? I assume so,
but I don't think I've seen it stated, or I forgot. If you
bought a car in NY, you wouldn't be surprised if a dealier in
CA did warrantee repair should your car break down.
It seems that these cranks are inherantly defective, unless it
sould be demonstrated that they were over-torqued, etc., no?
Matt Temple
--
=============================================================
Matthew Temple Tel: 617/632-2597
Director, Research Computing Fax: 617/632-4012
Dana-Farber Cancer Institute m...@research.dfci.harvard.edu
44 Binney Street, JF 314 http://research.dfci.harvard.edu
Boston, MA 02115 Choice is the Choice!
jobst....@stanfordalumni.org
> It seems that these cranks are inherently defective, unless it should
> be demonstrated that they were over-torqued, etc., no?
This is the age old story in bicycle failures, the customer misused
the equipment. That was given when a spoke broke as well as a Sturmey
Archer hub threw the rider over the bars when he tried to accelerate in
top gear. Unless the crank shows impact dents or is bent, there is no
misuse possible. That is, if the failure was no consciously generated
with suitable tooling for some misguided reason.
I am especially aware of this with cranks, of which I have probably
broken about 30 since Campagnolo introduced aluminum cranks in its
product line in the early 1960's. I discovered the main cause of
failure and gotten rid of it on my current Shimano DA cranks but crank
manufacturers are not interested in the solution. It's been done this
way for 100 years, don't bother us.
As I have reported, most crank failures occur at the pedal eye and the
reason is that there is morion there, no matter how tight it is made.
This is shown by the need for left hand threads on left pedals and the
wear erosion on the face of the crank. A simple modification to a
tapered face on the pedal shaft similar to those on automotive lug nuts
gets rid of the failure and the need for left hand threads. I recall
cars that had left hand lug nuts on the right side of the car left
over like tying and soldering from an era just as before tapered-face
lug nuts.
Jobst Brandt <jobst....@stanfordalumni.org> Palo Alto CA
Benjamin Lewis
> As I have reported, most crank failures occur at the pedal eye and the
> reason is that there is morion there, no matter how tight it is made.
What is "morion"? My dictionary says either a kind of helmet, or a dark
variety of smoky quartz; neither of these seems to apply here.
--
Benjamin Lewis
On a paper submitted by a physicist colleague:
"This isn't right. This isn't even wrong." -- Wolfgang Pauli
Toby Hamilton
> > As I have reported, most crank failures occur at the pedal eye and the
> > reason is that there is morion there, no matter how tight it is made.
>
> What is "morion"? My dictionary says either a kind of helmet, or a dark
> variety of smoky quartz; neither of these seems to apply here.
Really? My dictionary says it means "motion". But then it's a Typo to
English dictionary. Comes in very handy, mostly for making sense of my own
typing. ;)
--
Toby Hamilton (th-...@rogers.com)
Benjamin Lewis
Ah, thanks. Normally I can figure out typos from context, but for some
reason missed that one.
Doug Taylor
>Ah, thanks. Normally I can figure out typos from context, but for some
>reason missed that one.
It could be that you assumed it was a real word because Mr. Jobst
typically expresses himself in abstruse engineer-speak laden with
technical language, which makes it difficult for lay people, liberal
arts majors, and other non-geeks to understand what he is trying to
say. It is unclear whether he is showing off or simply never learned
how to write. In any case, you are excused :-)
--dt
Tim McNamara
Doug Taylor <tayl...@choiceonemail.com> wrote:
> It could be that you assumed it was a real word because Mr. Jobst
> typically expresses himself in abstruse engineer-speak laden with
> technical language, which makes it difficult for lay people, liberal
> arts majors, and other non-geeks to understand what he is trying to
> say. It is unclear whether he is showing off or simply never learned
> how to write.
Is there something worng with learning proper terms and proper concepts
for a specialized subject like, say, bicycles? While Jobst's comments
are sometimes challenging to follow (ditto for the rest of the
engineering types, especially when they are talking to each other) I
appreciate the chance to learn something in an idiom much removed from
my own expertise. The posts of Jobst and the other engineers have been
genuinely helpful to me many times in the past 10-12 years.
IMHO the people who accuse their more learned peers of "showing off"
generally are those who resent having a light shone on their ignorance.
Unfortunate and self-damning, because that is precisely what dispels
ignorance and myth, replacing it with knowledge.
Benjamin Lewis
> Is there something worng with learning proper terms and proper concepts
> for a specialized subject like, say, bicycles? While Jobst's comments
> are sometimes challenging to follow
Funny, I've never found that to be the case at all; they seem to be very
clearly worded and reasoned to me. I agree with you otherwise, though.
Matt O'Toole
<jobst....@stanfordalumni.org> wrote in message
news:pGSK8.7445$3w2....@typhoon.sonic.net...
> This is the age old story in bicycle failures, the customer misused
> the equipment. That was given when a spoke broke as well as a Sturmey
> Archer hub threw the rider over the bars when he tried to accelerate in
> top gear. Unless the crank shows impact dents or is bent, there is no
> misuse possible. That is, if the failure was no consciously generated
> with suitable tooling for some misguided reason.
>
> I am especially aware of this with cranks, of which I have probably
> broken about 30 since Campagnolo introduced aluminum cranks in its
> product line in the early 1960's. I discovered the main cause of
> failure and gotten rid of it on my current Shimano DA cranks but crank
> manufacturers are not interested in the solution. It's been done this
> way for 100 years, don't bother us.
>
> As I have reported, most crank failures occur at the pedal eye and the
> reason is that there is morion there, no matter how tight it is made.
> This is shown by the need for left hand threads on left pedals and the
> wear erosion on the face of the crank. A simple modification to a
> tapered face on the pedal shaft similar to those on automotive lug nuts
> gets rid of the failure and the need for left hand threads. I recall
> cars that had left hand lug nuts on the right side of the car left
> over like tying and soldering from an era just as before tapered-face
> lug nuts.
My neighbor recently broke the crank on her exercycle the very same way, at
the pedal eye. It was a steel crank, Ashtabula-style, and maybe low
strength; but this was not a cheap piece of machinery.
I've broken three or four cranks myself, all this way too, except for a
Mavic that cracked between the spider arms.
Matt O.
Alex Rodriguez
>
>On Monday, June 03 at 16:09 jobst....@stanfordalumni.org wrote:
>
>> As I have reported, most crank failures occur at the pedal eye and the
>> reason is that there is morion there, no matter how tight it is made.
>
>What is "morion"? My dictionary says either a kind of helmet, or a dark
>variety of smoky quartz; neither of these seems to apply here.
Typo. He meant motion.
-----------------
Alex __O
_-\<,_
(_)/ (_)
Doug Taylor
I do not dispute Jobst's expertise, experience and knowledge about
bicycles and bicycle engineering. Few people in this n.g or anywhere
can hold a candle to his background, and I admit that freely.
However, I think it clear to anyone who passed english composition in
high school that he can't express himself for shit and that his holier
than thou attitude can be off-putting. Put it this way: if the same
technical question were posed to Sheldon Brown and Jobst, whose answer
would be clearer and whom would you feel better about trusting
(leaving, of course, politics aside ;-) ?
--dt
jobst....@stanfordalumni.org
>> As I have reported, most crank failures occur at the pedal eye and
>> the reason is that there is morion there, no matter how tight it is
>> made.
> What is "morion"? My dictionary says either a kind of helmet, or a
> dark variety of smoky quartz; neither of these seems to apply here.
How about "motion"?
Benjamin Lewis
> Benjamin Lewis writes:
>
> >> As I have reported, most crank failures occur at the pedal eye and
> >> the reason is that there is morion there, no matter how tight it is
> >> made.
>
> > What is "morion"? My dictionary says either a kind of helmet, or a
> > dark variety of smoky quartz; neither of these seems to apply here.
>
> How about "motion"?
Yes, that makes much more sense. I actually didn't realize that this was a
typo until after I posted.
--
Benjamin Lewis
"Love is a snowmobile racing across the tundra and then suddenly it flips
over, pinning you underneath. At night, the ice weasels come."
--Matt Groening
Stella Hackell
> Tim McNamara <tim...@mac.com> wrote:
> >
> >> It could be that you assumed it was a real word because Mr. Jobst
> >> typically expresses himself in abstruse engineer-speak laden with
> >> technical language, which makes it difficult for lay people, liberal
> >> arts majors, and other non-geeks to understand what he is trying to
> >> say. It is unclear whether he is showing off or simply never learned
> >> how to write.
> >
> >Is there something worng with learning proper terms and proper concepts
> >for a specialized subject like, say, bicycles? While Jobst's comments
> >are sometimes challenging to follow (ditto for the rest of the
> >engineering types, especially when they are talking to each other) I
> >appreciate the chance to learn something in an idiom much removed from
> >my own expertise. The posts of Jobst and the other engineers have been
> >genuinely helpful to me many times in the past 10-12 years.
> >
> >IMHO the people who accuse their more learned peers of "showing off"
> >generally are those who resent having a light shone on their ignorance.
> >Unfortunate and self-damning, because that is precisely what dispels
> >ignorance and myth, replacing it with knowledge.
>
> I do not dispute Jobst's expertise, experience and knowledge about
> bicycles and bicycle engineering. Few people in this n.g or anywhere
> can hold a candle to his background, and I admit that freely.
> However, I think it clear to anyone who passed english composition in
> high school that he can't express himself for shit
You're way off base. Jobst expresses his ideas clearly and well, using
the vocabulary appropriate to his subject. He doesn't always define
his terms for the lay reader, but you can look them up, and he (or another
poster) will usually explain them if asked politely. Jobst's writing
is concise and efficient, and he obviously takes trouble to get
it right.
> and that his holier
> than thou attitude can be off-putting.
Well, that's a matter of taste.
>Put it this way: if the same
> technical question were posed to Sheldon Brown and Jobst, whose answer
> would be clearer and whom would you feel better about trusting
> (leaving, of course, politics aside ;-) ?
I would trust them both. I would read both their answers and learn
what I could from each.
When I built my first wheels, I used Jobst's book as my main guide,
because I happened to have it already. I used Sheldon's directions,
which are written very differently, for reference and to check my
own understanding. I could have done it the opposite way with
equally good results.
Stella Hackell
(English major and editor)
Tim McNamara
Doug Taylor <tayl...@choiceonemail.com> wrote:
> I do not dispute Jobst's expertise, experience and knowledge about
> bicycles and bicycle engineering. Few people in this n.g or anywhere
> can hold a candle to his background, and I admit that freely.
> However, I think it clear to anyone who passed english composition in
> high school that he can't express himself for shit and that his
> holier than thou attitude can be off-putting. Put it this way: if
> the same technical question were posed to Sheldon Brown and Jobst,
> whose answer would be clearer and whom would you feel better about
> trusting (leaving, of course, politics aside ;-) ?
I have some idea of Sheldon's politics, since he has mentioned them in
various contexts; I have no idea what Jobst's politics are, since he
never mentiones them.
Some of Jobst's posts do suffer from mangled syntax and typos, it is
true, and some of them take some puzzling to sort out because of this.
He can be a little edgy at times. However, I'm not sure that I'd trust
anyone's expert opinion less because they don't write in a Strunk and
White style and aren't bland and opinionless. Nor would I necessarily
trust someone's opinion more because they write immaculately.
Good information is good information and I am prepared to cut people a
little slack in how it's expressed (although I don't find myself doing
that with the occasional idiot. Sheldon's mellowness has not exactly
rubbed off on me; I tend more towards the tetchy end of the spectrum).
Sheldon's posts are usually quite clear, and he usually seems to say
the same things that Jobst does... although he is more
welcoming/tolerant of new technology than is Jobst. My impression is
that Jobst views bikes as a tool to be used for riding, whereas Sheldon
seems to take a more eclectic stance.
Both of them- along with several others in this newsgroup- have greatly
enhanced my understanding of bikes and bike riding. They've also saved
me money and grief regarding equipment purchases.
johan_bornman
wrote:
>A simple modification to a
>tapered face on the pedal shaft similar to those on automotive lug nuts
>gets rid of the failure and the need for left hand threads. I recall
>cars that had left hand lug nuts on the right side of the car left
>over like tying and soldering from an era just as before tapered-face
>lug nuts.
Jobst, I'm glad this topic came up again. Last time it was under
discussion I couldn't figure out what your modification looks like.
This time you mention lug nuts. What are these and how do you mimic
them on the pedal/crank interface?
Johan Bornman
jobst....@stanfordalumni.org
>> A simple modification to a tapered face on the pedal shaft similar
>> to those on automotive lug nuts gets rid of the failure and the
>> need for left hand threads. I recall cars that had left hand lug
>> nuts on the right side of the car left over like tying and
>> soldering from an era just as before tapered-face lug nuts.
> Jobst, I'm glad this topic came up again. Last time it was under
> discussion I couldn't figure out what your modification looks like.
> This time you mention lug nuts. What are these and how do you mimic
> them on the pedal/crank interface?
"Lug nut" is automotive jargon for (typically four or five) nuts that
hold car wheels in place. These were originally common flat faced
nuts that held the steel rim on the brake drum, or before that, the
rim/tire to the periphery of a wooden spoked wheel. The need for left
hand threads on the wheels on the right side became apparent. At
about the same time someone realized that fretting motions between
nut, bolt and rim, could be arrested by the conical faced nuts all
cars, trucks and buses use today. I suspect this was not the first
application of such nuts because they are used on other machinery.
The conical seat performs two functions; that of preventing relative
motion between nut and rim, and increasing friction by its 60 degree
(120 deg cone) pressure angle to prevent unscrewing.
http://www.tirerack.com/wheels/tech/nutsandbolts.htm
Both of these features are also essential to good pedal to crank
attachment, both because pedals have radial load precession that
causes rotation in the thread, and a cantilevered load.
Main Entry: cantilever
Function: noun
Etymology: perhaps from cant + -i- + lever
Date: 1667
: a projecting beam or member supported at only one end: as a : a
bracket-shaped member supporting a balcony or a cornice b : either of
the two beams or trusses that project from piers toward each other and
that when joined directly or by a suspended connecting member form a
span of a cantilever bridge -- see BRIDGE illustration
For bicycles the proper modification would be to a tapered shoulder on
the pedal spindle instead of a flat one, and of course a matching
taper in the face of the crank. I have by installing a split conical
faced washer between the pedal shoulder and the crank in such a way
that it securely clamps the spindle on the inside as it is tightened
into the taper faced crank bore. This reduces the probability of
crank failure at the pedal eye as well as getting rid of left hand
threads on left pedals.
This is not something that can be done at home. It takes a lathe and
milling machine. I chose stainless steel for the washers because it
is not a high stress application where currently aluminum is the
contact and I didn't want these to rust.
Tim McNamara
jobst....@stanfordalumni.org wrote:
> For bicycles the proper modification would be to a tapered shoulder
> on the pedal spindle instead of a flat one, and of course a matching
> taper in the face of the crank. I have by installing a split conical
> faced washer between the pedal shoulder and the crank in such a way
> that it securely clamps the spindle on the inside as it is tightened
> into the taper faced crank bore. This reduces the probability of
> crank failure at the pedal eye as well as getting rid of left hand
> threads on left pedals.
>
> This is not something that can be done at home. It takes a lathe and
> milling machine. I chose stainless steel for the washers because it
> is not a high stress application where currently aluminum is the
> contact and I didn't want these to rust.
Has this eliminated your crank breakage problems?
jobst....@stanfordalumni.org
Yes. The cranks I modified were nearly 20000 miles old so I decided
to try the modification because it would be no loss if it didn't help.
I have brand new cranks on the shelf, also modified now and am sure
that the pedal eye failures are resolved.
Considering that cranks break there (in fatigue) and that at times, I
climb some steep places, that require great torque, without crank
failure, it occurs to me that this is truly a long term fatigue
problem. The cracks initiate from the eroded face of the crank caused
by pedal shaft fretting there and in the threads.
To me this is much like the spoke failure problem that went on for
ages under the belief that someone temporarily overloaded a wheel.
The difference here is that we have a much more apparent model from
the automotive wheel nut as an example how it should be done.
Don't hold your breath. "Who knows more about crank failures, this
non-bicycle mechanic or Campagnolo/Shimano?" As you see, this
assessment recurs all the time in defense of the status quo.
Benjamin Lewis
> Don't hold your breath. "Who knows more about crank failures, this
> non-bicycle mechanic or Campagnolo/Shimano?" As you see, this
> assessment recurs all the time in defense of the status quo.
Have you tried suggesting this to Shimano? It seems to me that they could
not only put a great marketing spin on it, but it would be in their
interest to sell high-end pedals/crank combinations that are incompatible
with anything else.
There's even the minor advantage that it really *is* better.
Robert Haston
"Tim McNamara" <tim...@mac.com> wrote in message
news:timmcn-BBA0A5....@gemini.visi.com...
Karl Nelson
> For bicycles the proper modification would be to a tapered shoulder on
> the pedal spindle instead of a flat one, and of course a matching
> taper in the face of the crank. I have by installing a split conical
> faced washer between the pedal shoulder and the crank in such a way
> that it securely clamps the spindle on the inside as it is tightened
> into the taper faced crank bore. This reduces the probability of
> crank failure at the pedal eye as well as getting rid of left hand
> threads on left pedals.
>
> This is not something that can be done at home. It takes a lathe and
> milling machine. I chose stainless steel for the washers because it
> is not a high stress application where currently aluminum is the
> contact and I didn't want these to rust.
>
I am curious why you didn't simply use the lathe to machine a taper
into the pedal spindle itself. I have your design for the collar but
keep putting off making it because I keep wondering why that wouldn't
be better.
I also wonder about letting the steel taper (whether collar or
spindle) mash its own taper into the softer aluminum of the crank.
What would happen then? As you have said, centering that taper in the
hole is a problem, and it's the other thing holding me up.
Karl Nelson.
jobst....@stanfordalumni.org
>> Don't hold your breath. "Who knows more about crank failures, this
>> non-bicycle mechanic or Campagnolo/Shimano?" As you see, this
>> assessment recurs all the time in defense of the status quo.
> Have you tried suggesting this to Shimano? It seems to me that they
> could not only put a great marketing spin on it, but it would be in
> their interest to sell high-end pedals/crank combinations that are
> incompatible with anything else.
I showed a typical DA crank to to a Shimano engineer at InterBike who
knew exactly what I was talking about and understood the solution. I
had crank with an almost cracked of pedal eye, the crank that I am
riding now with its modification and a new crank and pedal that was
hand tight so that the assembly could be inspected.
It was difficult to make this approach because Shimano does not want
to talk abut designs without a disclosure agreement. To bridge that
chasm, I first showed him the broken crank and asked if he recognized
the condition. The conversation got underway so I could tell him that
I had lots of these and discovered a solution for the problem which I
showed in a neutral manner, not asking for any agreement or
disagreement. Just the facts as I have presented them here. The man
was visibly interested and we parted without any resolving comment
other than "g'day".
> There's even the minor advantage that it really *is* better.
As I said, don't hold your breath. Neither Race Face nor Truvativ,
with whom I talked, have taken the subject any farther, even though
they have such crank failures often.
jobst....@stanfordalumni.org
>> For bicycles the proper modification would be to a tapered shoulder
>> on the pedal spindle instead of a flat one, and of course a
>> matching taper in the face of the crank. I have by installing a
>> split conical faced washer between the pedal shoulder and the crank
>> in such a way that it securely clamps the spindle on the inside as
>> it is tightened into the taper faced crank bore. This reduces the
>> probability of crank failure at the pedal eye as well as getting
>> rid of left hand threads on left pedals.
>> This is not something that can be done at home. It takes a lathe
>> and milling machine. I chose stainless steel for the washers
>> because it is not a high stress application where currently
>> aluminum is the contact and I didn't want these to rust.
> I am curious why you didn't simply use the lathe to machine a taper
> into the pedal spindle itself. I have your design for the collar
> but keep putting off making it because I keep wondering why that
> wouldn't be better.
Obviously, that is the manufacturing solution but if you look at it
you'll see there isn't enough "meat" on an existing pedal to do it.
The taper would run into the wrench-flats and leave these two flanks
unsupported, besides not leaving enough space for a good wrench. It
also reduces foot-to-crank clearance, that for my size is close
anyway.
> I also wonder about letting the steel taper (whether collar or
> spindle) mash its own taper into the softer aluminum of the crank.
Why not just drive the pedal in with a hammer! Aluminum is not
modeling clay and would not deform more than a fraction of the contact
face needed to restrain the loads in question.
> What would happen then? As you have said, centering that taper in
> the hole is a problem, and it's the other thing holding me up.
Put a dummy spindle in the bore, uses a center finder on the milling
machine and you have the setup.
Bluto
> I am curious why you didn't simply use the lathe to machine a taper
> into the pedal spindle itself.
I can't speculate as to Mr. Brandt's reasoning, but my own reason for
not doing that would be that the hardened steel which composes most
pedal spindles is difficult to cut, yields a poor finish, and might
well be more susceptible to failure at the cut area because of
localized annealing, galling, or residual surface stresses.
Such parts are machined in an annealed or normalized condition, then
heat treated afterward for hardness and strength. Subsequently they
are best worked by wet grinding.
Chalo Colina