Mitigating crank failure

Russell Seaton writes:

Phil Lee used the term "invariably". The online dictionary says
invariably means "Not changing or subject to change; constant".
From the pictures above you can easily deduce that shoe rubbing is
not a constant/invariable beginning of cranks cracking. I think a
reading of the FAQ and Brandt's postings about cranks cracking would
provide a better cause and understanding than shoe rubbing. These
pictures are the ones found posted on this forum. I am sure there
are other pictures on the web showing all manner of crank failures.

There are more at:

http://pardo.net/bike/pic/fail-001/

Jobst Brandt

In article R0jcf.1635$Xj5.831@dukeread02,
says...


With another customer's broken crank coming in this week for replacement,
I've been thinking... is there a better solution to all these broken cranks?

Crack propagation on cranks breaking at midsection is invariably started
with shoe rub. Since nobody would pay for cranks with a "shoe rub shim" on
it, why not sell shoes that have felt/terrycloth/foam bits that cover the
inside of the ankle? This would be unobtrusive, could be dyed the color of
the shoe, and cut down on deeper cuts in the metal that would start cracks.

These shoes could be sold to the radonneur/brevet/messenger/commuter/old
fart group of riders that would appreciate such a feature.

Thoughts?

Set the cleats up so that there is no rub. Unless my pedalling style gets
really sloppy, trying to hard when I am tired, my shoes don't touch the cranks.
--------------
Alex

wrote:
Phil, Squid-in-Training wrote:
Crack propagation on cranks breaking at midsection is invariably started
with shoe rub.

Is it?

http://pardo.net/pardo/bike/pic/fail/crank-fail-002.jpg

http://www.atmosp.physics.utoronto.c...amit/crank.htm

http://pardo.net/bike/pic/fail-001/CrankmodXthree.jpg

http://www.yellowjersey.org/jayscranks.html

http://www.yellowjersey.org/photosfr...t/yesdeydo.jpg

http://pardo.net/pardo/bike/pic/fail/FAIL-001.html



http://www.yellowjersey.org/jayscranks.html

I'm surprised at how little hollow there is in the "Hollow Tech". That
crank is 10% hollow and 90% crank. Hardly worth the effort, or expense.

Is this typical?

John

john wrote:

I'm surprised at how little hollow there is in the "Hollow Tech". That
crank is 10% hollow and 90% crank. Hardly worth the effort, or expense.

Is this typical?

I think just at that location of the arm it essentally solid. It is
much more hollow in the middle.

wrote:
Moving feet out - i.e. increasing Q factor - is a bad idea.

Possibly so, but if the rider's ankles are contacting the crank arm
their legs are actually quite close together... so they could probably
stand to move them out a bit.

The other thought I had was simply poor cleat setup... or are there
some pedals that have huge float and don't restrict inward heel
movement at all? If so, that would be the solution... the cleats need
to be set up so that ankle rub doesn't happen... and if the rider likes
to have their toes pointed out a lot, then pedal axle extensions make
sense.

On Wed, 09 Nov 2005 12:04:01 -0500, dvt wrote:

Adding thickness to either side (shoe or crank) will just make shoe rub
more annoying. The only solution I'd consider is an increase in the
spacing. But many don't like a wider Q factor, so I guess we'd be stuck
with the lowest profile cranks available. Maybe the angle of the arm
could be adjusted, too.

The shape of different crankarms will make a difference in shoe
contacting the crank. Placement of the cleat in the shoe and type of
shoe can change distance between shoe and crankarm. Type of pedal
makes a difference. Shimano MTB pedals position the shoe a bit
further from the crankarm than road pedals. Washers between pedal and
crankarm move shoe away from arm. Wider Q doesn't necessarily put
shoe or ankle away from arm. Plastic laminating tape on the crankarm
protects it.

I've got big feet and don't like my cranks getting cosmetically
marked. I haven't had a crankarm fail because of rub...yet.

wrote in message
...
Russell Seaton writes:

Phil Lee used the term "invariably". The online dictionary
says
invariably means "Not changing or subject to change;
constant".
From the pictures above you can easily deduce that shoe
rubbing is
not a constant/invariable beginning of cranks cracking. I
think a
reading of the FAQ and Brandt's postings about cranks
cracking would
provide a better cause and understanding than shoe rubbing.
These
pictures are the ones found posted on this forum. I am sure
there
are other pictures on the web showing all manner of crank
failures.

There are more at:

http://pardo.net/bike/pic/fail-001/

So, is shoe rub (which causes polishing rather than scratches)
capable of causing or accelerating crank failure? -- Jay Beattie.

On 9 Nov 2005 10:17:26 -0800, wrote:

dvt wrote:
wrote:
Phil, Squid-in-Training wrote:

Crack propagation on cranks breaking at midsection is invariably started
with shoe rub.

Phil Squid used the term "invariably". The online dictionary says
invariably means "Not changing or subject to change; constant". From
the pictures above you can easily deduce that shoe rubbing is not a
constant/invariable beginning of crankset cracking. I think a reading

No, you really can't. On all the cranks *breaking at the midsection* you
found, visible shoe rubbing was present around the crack.


Jasper

after the last crank failure i rotored over to the LBS and asked for
the crank box
paleontology-worth the study-crank design!!!
picked out 4 and threw em in the bottom of toolbox 3
now i pray the CR stays
also see Crank saver in archives

jbuch wrote:
Phil, Squid-in-Training wrote:

With another customer's broken crank coming in this week for
replacement, I've been thinking... is there a better solution to all
these broken cranks?

Crack propagation on cranks breaking at midsection is invariably
started with shoe rub. Since nobody would pay for cranks with a "shoe
rub shim" on it, why not sell shoes that have felt/terrycloth/foam
bits that cover the inside of the ankle? This would be unobtrusive,
could be dyed the color of the shoe, and cut down on deeper cuts in
the metal that would start cracks.

These shoes could be sold to the
radonneur/brevet/messenger/commuter/old fart group of riders that
would appreciate such a feature.

Thoughts?



If you are really into "high performaqnce components", I would suggest
that you remove the cranks and have them coated with synthetic diamond
or "diamond-like carbon" to increase wear resistance.

There are other hard wear resistant coatings that could be applied for
the lower cost or second quality level biking components.

you'd better not mention wear resistant anodizing on this group....