From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Campagnolo Record crank fatigue prevention/cure?
Date: 22 Mar 2000 17:15:34 GMT

James Thomson writes:

> I have two pairs of original Campagnolo Record cranks which I would
> like to use on two vintage bicycles I'm restoring. One pair appears
> sound, while the right hand crank of the other pair has the
> beginnings of the classic fatigue cracks between the crank and
> the spider, extending about 1mm into the crank.

I have broken more than two dozen cranks, mostly Campagnolo Record,
over the years, most of which broke in the pedal eye, some at the
neck below the eye and one at midspan and a couple at the place you
mention...  BUT these did not break at the crack of which you speak.
A new crack developed a few millimeters away and propagated straight
across the crank.  These did not go to failure but were obviously
beyond safe use, having separated more than 1/3 the cross section.

The web crack that your crank has would best be removed by using a
round file and polishing it with a wooden dowel with fine sand paper.
I always threatened to do that but the cranks broke before that crack
ever got to a worrisome depth.  My C-Record cranks, in contrast did
not have this web crack because they were properly designed with
respect to this problem.  However, their pedal eyes lasted slightly
more than 2000 miles, dumping me on the road long before I even
considered inspecting for cracks.  I had just finished 2200 miles in
the alps having just purchased them a few weeks before they both broke
after the trip, one breaking off, the other having a crack all the way
through one side of the pedal eye.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Campagnolo Record crank fatigue prevention/cure?
Date: 22 Mar 2000 22:38:20 GMT

Russell Seaton writes:

>> My C-Record cranks, in contrast did not have this web crack because
>> they were properly designed with respect to this problem. However,
>> their pedal eyes lasted slightly more than 2000 miles, dumping me
>> on the road long before I even considered inspecting for cracks. I
>> had just finished 2200 miles in the alps having just purchased them
>> a few weeks before they both broke after the trip, one breaking
>> off, the other having a crack all the way through one side of the
>> pedal eye.

> You rode Campagnolo Record cranks 2200 miles in the Alps?  Not
> loaded touring?  Record uses a 135mm bcd so the smallest ring is a
> 39.  Coupled wth Campagnolo's biggest rear cog, a 26, you have a 40
> inch low gear.  I've ridden in the Alps, Dolomites, and Rockies.  40
> inches is not low enough for me.

> I'm about 190 pounds.  I have ridden 1998 Chorus cranks for about
> 4-5,000 miles.  No broken pedal eyes or spiders.  Rode/ride the
> 1991 Shimano Deore DX cranks for several tens of thousands of miles.  No
> broken crank.  I had to pedal a pretty slow cadence up some of those
> mountains.  Didn't have any lower gears.

What gears you use is up to you, I am more aerobically limited than
strength and use a 46-50 with 13-15-17-19-21-24.  When I was "young
and beautiful" I used a 47-50 because I started on 5-speed half step
and never changed, not using the small chainwheel but rarely.

the bike and rider are at:

http://www-math.science.unitn.it/Bike/Countries/Europe/Tour_Reports/Tour_of_the_Al

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Crank Life?
Date: 14 Dec 2000 21:18:19 GMT

Shawn Amir writes:

> What is the consensus for the life span of a crank--lets say a DA?
> I would like to avoid being neutered by my top tube when I stand.

Having broken many cranks, I can safely say that they do not break
suddenly but develop cracks slowly enough that visually checking them
at 200 mile intervals is adequate to prevent crank separation on a
ride.  Most of my cranks were detected that way.

The place that requires careful inspection is around the pedal eye
where a crack can be detected under bright light.  Remember, all
cracks are "hair line " cracks until they separate or are ridden n the
rain so that grey juice is generated.  In fact, when water gets into
such a crack it sounds like chewing on gristle as the fissure is
pressed closed.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 4 Jan 2001 17:57:32 GMT

Sue Rogers writes:

>> What alloys are you interested in.

> The alloy used to make Shimano 600 cranks.  I had a cycling accident
> recently where my front wheel slid away at very low speed. I came
> down very heavily on mine and the bike's right hand side, thereby
> giving the end of the pedal a good whack on the tarmac cycle path.

> Having had two alloy cranks (one a Shimano, the other probably a
> Campag) break on me back in the 1980s when I did a lot of cycle
> racing (and crashing), I know how sudden the fall from a broken
> crank while pedalling is and there's no way I want to risk that
> happening.

I think your fear is unwarranted because cranks do not break suddenly
and without "warning", the warning being that a crack has developed
through more than half the cross section.  I have broken more than two
dozen Campagnolo and Shimano cranks of which a couple broke suddenly.
On inspection it was apparent from the face of the crack that it had
been there for a long time judging from oxidation.  Subsequently I
inspected for cracks at reasonable intervals and detected cranks that
were no longer safe.

If you cannot see a crack under bright light, and the crank is not
bent, there is no reason for replacing it.  Cranks break from metal
fatigue and a crash (single load cycle) does not affect fatigue if it
does not bend the crank.

> Therefore I am replacing the cranks on this bike before using it
> again.  (I no longer cycle race, just commute).  As the accident
> wasn't my fault, I'm looking to claim damages off the other party
> involved and need to prove that it's not a good idea to whack the
> end of alloy cranks onto concrete with 11.5 stone of rider on top.

That may be your perception but it is not the way metallurgy works.

> Hence my request for any official literature on alloy crank failure.
> I have the 1985 Cycling Weekly article on crank failure, written by
> a metallurgy lecturer at Derby University, but if there's anything
> more up to date, I'd appreciate it.

I don't think you'll find support for your contention and for the sake
of those who pay insurance premiums, I hope you don't press this case
further.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 5 Jan 2001 18:06:07 GMT

Jay Beattie writes:

>> I think your fear is unwarranted because cranks do not break
>> suddenly and without "warning", the warning being that a crack has
>> developed through more than half the cross section.  I have broken
>> more than two dozen Campagnolo and Shimano cranks of which a couple
>> broke suddenly.  On inspection it was apparent from the face of the
>> crack that it had been there for a long time judging from
>> oxidation.  Subsequently I inspected for cracks at reasonable
>> intervals and detected cranks that were no longer safe.

> To Sue and Jobst: which Shimano cranks and where did they break? I
> have never broken a Japanese crank and always thought the Shimano
> were bullet proof.  I am crestfallen.

At the pedal eye and at the web between crank and spider finger as
well as at the corner of the square hole where the Dura Ace crank
presses onto the spindle.  Most failures (Campagnolo & Shimano) were
at the pedal eye, something that I fixed a few years ago by counter
sinking the thread 90 deg and installing a split collet to immobilize
the pedal spindle that otherwise frets (the reason we need left hand
thread on left pedals) and initiates cracks.  I don't look for cracks
once a week anymore.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 8 Jan 2001 18:35:59 GMT

Bill Putnam writes:

>> Most failures (Campagnolo & Shimano) were at the pedal eye,
>> something that I fixed a few years ago by counter sinking the
>> thread 90 deg and installing a split collet to immobilize the pedal
>> spindle that otherwise frets (the reason we need left hand thread
>> on left pedals) and initiates cracks.  I don't look for cracks once
>> a week anymore.

> Do you have a drawing of this you could post?

The problem is that it differs for each pedal spindle and may not even
fit without modifying some spindles, depending how the thread relief
is formed.  For my SH-SPD pedals, the thread relief is cylindrical and
12.45mm in diameter with an OD of 18mm.  The collet ring has a half mm
cylindrical edge at 18mm diameter, is 2.3mm thick and tapers at 45
degrees.  The ID has a half mm chamfer where it butts against the
spindle (for the spindle fillet).  The collet is split in two using
the thinnest reasonable saw.

The crank must be carefully countersunk to 18mm diameter exactly
concentric to the thread.  When the pedal is screwed in firmly, only
the half mm of cylindrical portion of the collar is visible along with
its split.  Ideally all pedals would have tapered faces on the spindle
to fit into tapered crank faces and we wouldn't hear much about pedals
coming loose anymore, right or left and crank failures at this place
would most likely vanish entirely.

The bicycle industry can't be bothered.  Their opinion is that there
is no problem.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 8 Jan 2001 23:53:14 GMT

Karl Nelson writes:

> Despite the problem of pedal differences you mention, I would like to
> also request a drawing.  I think if I could see a drawing, I could see
> what modifications are needed for my pedals.  It would also be helpful
> to see a picture of the spindles that it works on and and example of one
> which would have to be modified so I could verify that as well.

> Did you design the collet on a computer (and have a CAD file you could
> post) or did you work from a hand drawing?  If you don't have any
> drawing you could post, even a close-up digital photograph would be
> better than nothing.

The drawing exists in ME-10 2D Mi file and in DXF (AutoCAD drawing
transfer format).  If you like I could send you the file in either
format and as I said the inside diameter is specifically for my
pedals.  You would need to measure yours and make sure that the thread
relief is already cylindrical or you must machine it to be so.

> Even if the industry doesn't listen, it would be a great service to
> the individuals who do.

Bicycle science isn't high tech, the most important part of it being
marketing, as we see by the colored tires and rims on the road today.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: alloy failure
Date: 9 Jan 2001 00:04:47 GMT

Bill Putnam writes:

> Thanks for the explanation.  This is a straightforward modification.
> It's hard to believe that the manufacturers don't include this in
> their designs.  It could even be backward compatible if the spindle were
> tapered and a collet and keeper were used in the opposite direction to
> present a flat face to the "old" style crank arm.  I've attempted an
> ASCII design to verify your description-if you have Microstation
> handy I could attach a Microstation file to an e mail for a better
> drawing. The collet chamfer is omitted.

> ______________________
>   | |        | |      |
>   | |        | |      |     Crank cross section
>   | |________| |      |
>   |/          \|      |
> ----------------------
>   |    18mm    |

Yes.

>     __________    _
>    /|        |\     1.8 mm
>    ------------   -             Collet
>                   _ 0.5 mm
>   |    18mm    |


>     __________
>     |        |
>     |        |             pedal threads
>     |        |
>     |        |
>     |        |
>  ----------------
>  ||  | 12.54|   ||
>  |---------------|
>  |               |           pedal flats for wrench
>  |               |
>  |               |

Yes.

> Did you use a steel collet?  Did you turn this out of bar stock or
> purchase it off the shelf?

I used stainless steel and had it made to my drawing.  The friend who
built my bicycle also bored the cranks, something that is not just
countersinking but must be accurately concentric with the thread.

Your suggestion of backward compatibility doesn't work because there
are no extra threads to accommodate the missing length when the washer
is inverted.  Besides the overhang that would produce with so little
bearing area would be an invitation to failure.  My suggestion is to
offer new cranks with the countersink and the collet as well as new
pedals with a conical face to go with the cranks.  Old pedals of this
brand would need the collet new ones would fit and soon there would be
no old style pedals to bother with.  If Shimano can come up with their
aero pedals with a unique thread a few years ago, this one is easy.

> This modification would have prolonged the life of one of my cranks-
> a Sugino Mighty Tour that cracked at the pedal eye.  The Nervar Star,
> and two Campy Nuovo Record cranks would still be where they
> are (my bin of failed bicycle and car components) due to cracks at
> the spider, however.  And there's still the fretting occurring between
> the spindle and crank taper.  Maybe the cotterless steel cranks are
> the most durable cranks so far (aside from potentially Ashtabula).

All the bicycle folks I talked to say there is no problem so why mess
with it.

Jobst Brandt      <jbrandt@hpl.hp.com>