nlerner

So you went with a known failure-prone replacement?

daka

That was my first reaction too, but the truth is that similar breakages occurs in other brands of crankset. If it's aluminum, the fatigue curve is ugly. Replacing with a used part is a crapshoot, since the amount of existing fatigue cycles on it is unknown, but an NO$ Campy crankarm could last another 40 years.

Bad Lag

Yes. Yes I did. I think that choice is about nostalgia as much as anything. I will check it over carefully before accepting it from the seller.

I could leave the Mighty Comp on, as it is the first cotterless crank I ever had (fall 1973) and was the first crank installed on my Bob Jackson frame after I acquired it (ca. 1974).

I may even work my way back to using NR high flange hubs, despite their needing periodic maintenance. I have the hubs and rims, all I need is spokes.

ThermionicScott 

This quote from Ric Hjertberg on the topic always comes to mind:


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

Bad Lag

That's not my mind set but I get the point.

For me, it is the nostalgia. If I break another, I will be very unhappy and will re-mount my trustworthy Sugino Mighty Comp.

repechage

the Phil provides significant adjustment, one can easily move it 2mm in most circumstances. The unfortunate part was Phil made way back 4 different road spindles, none of them catalog number marked.

Bad Lag

Ah!, you are correct and thanks for the reminder. In fact, I had to move the bottom bracket to the right to allow the Campagnolo to fit the bike.

When installing the Mighty Comp, instead of adjusting the front derailleur (no big deal, really), I could have moved the bottom bracket back to the left.

When I get my hands on the new crank, I need to check the chain line and the frame spacing. If there is room, I would like to move the bottom bracket back to the left a bit. That would be a good thing.

Atlanta

Thank you for the heads up! I hadn’t heard about these specific failures on these cranks before.

mpetry912 

it's fairly common for Campy cranks to fail at the spider / arm join or at the pedal eye.

The IRD Defender crankset is a nice alternative and offers a 110 BCD so you can run 50/34 chainrings.

this one, custom milled and anodized by the late John "drillium" Williams, looks just about like the campy.

/markp

Bad Lag

If this replacement crank fails, I may take your idea and run with it.

I haven't yet fitted it to the spindle, however, everything else about it looks almost new.

The one that broke went from no defects, to cracked and then to broken in half in a span of ~6 months. It all happened after the last inspection.

Bad Lag

The new crank is installed.

It looks really nice - almost new. I'll give it the inaugural ride tomorrow.

Bad Lag

New crank is just fine.

It located itself on the spindle exactly where the previous one went.

It did not loosen at all during the ride.

I am happy with the purchase. It was expensive but it was a complete crank and had both chain rings installed, the outer of which look unused. The chain ring bolts look new, too.

steelbikeguy

Is this another Campy Record crank?
If so, did you file the web that is prone to developing cracks?
I'm assuming that you closely inspected the web for any signs of existing cracks too.

Steve in Peoria

Bad Lag

Yes, it's another Campagnolo Record crank. The thing is just this side of brand new. If there's an existing crack, I could not see it.

Here's an image of the crack across the old one. Although you cannot see it in the image, because of the direction I shot it from, the crack is pretty far away from the actual web (transition region). Perhaps note that it cut across the bottom of the deeply engraved Campagnolo badge as an indicator of where it cracked.

repechage

Appears to me that it propagated from two directions - the “web” crotch and the shield stamping.
note the dark oxide witness near the web acute corner- it was on its way for a long while. Finally let go.
not shown is the face of the crank at the shield logo stamping.
my hunch it would show polishing from ankle and or shoe through the anodizing there on the face.

when these cranks let go near the pedal eye- toe strap/ shoe rub through the anno was almost always present.

one racer we convinced to retire his cranks had rubbed 2mm into the surface ! Aaack!

late in the Record crank production life, besides adding beef, Campagnolo dropped the machining decoration, and moved the shield logo to a laser etching about mid arm.

the forging “grain” appears far from uniform -
it is what it is.

mpetry912 

Bad Lag I respectfully suggest that you at least "kiss" that new crank arm with a file or (even) a piece of rolled up emory paper

"Look almost new" can fool you. Those parts are approaching 50 years old now and you have no idea what indignities they've been subjected to.

you want to break and rouind the sharp edge at the web - even if there's no visible crack - rounding off the sharp edge will prevent a crack from forming and (worse) propagating.

Check the pedal eye too

/markp

Bad Lag

I'll post some side view photos so you guys can take a look at this failure from other perspectives.

My guess is it got started about 6 months ago, after the last inspection. The black area is probably corrosion and oil from riding all winter. Once it cracked, that last bit went all at once. The light grey section was bright, shiny aluminum when it forst broke but it has gone to grey as it oxidized over the last few weeks.

I've been thinking about how to reshape the edges. Some attempts others have made did not seem quite right. I was thinking about polishing all the sharp edges off, hopefully removing any microcracks in the process.

Thanks for the reminder about the pedal holes. I'd forgotten about those.

79pmooney

1977 and 78 I went around riders whose wheels I'd been on as they broke their NR crank at the pedal threads when they stood. First at the bottom of a hill, the second coming out of a criterium corner. I've heard of many more of those crashes since, both at the pedal spindle and the spider base. Now, granted, NRs went forever as the choice gear of funds limited racers. "$25 for NRs with no scratches, just 8 seasons of racing under a very strong rider? I'm in!"

repechage

cranks don’t talk, but they do leave witness. Toe strap rub or shoe rub, depends on the rider’s feet is bad news for 7000 series aluminum, Campagnolo in an advert once noted that was the alloy family they used.
the cranks were made for decades, unsure if the same alloy used throughout the production life.
I have always been shy of cranks with rider “polished” arms, the cranks that failed always had some localized anodizing removal.

Also, a pedal strike in a turn can put quite a load on the arm, especially if the rider skips his rear wheel into the air. We saw bent pedal shafts from time to time, often enough to stock replacements.
With bigger, stronger riders, definitely the guys who were stronger than smart, we almost always were able to sell them a replacement crank arm along with the pedal axle, spindle, the term your choice.
spending their money to keep them safe.

Bad Lag

Are you implying I NOT attempt to reshape the edges to remove microcracks and remove stress risers?

repechage

I did not write that- was commenting on used cranks or cranks in service that show rubbing wear from shoes or straps that breached the anodizing.

as to filing away acute edges- I radius the semicircle around the two adjoining surfaces.
scratch removal is a good thing.

if you are extremely worried and wary, aircraft Spruce and specialty sells a crack check dye kit for aluminum.

mpetry912 

what I'd suggest is - get some emery cloth - 400 grit or finer and cut a narrow strip

lay it in the "web" between the crank arm and spider arm. just do a coujple pulls to round off the sharp edge.

all you really need to do is round off the sharp edge on the forging

Really extreme filing is only required when a crack has developed and propagated far into the "web"

after that it's hard to undo.

Your cranks may be "just the other side of new" or whatever you are telling yourself, so if you want to ride them for years without worry - do this now.

Back in the days when I was doing a lot of work on cars, I had a buddy who did not want to replace the rod bolts with the (very high quality) ARP rod bolts

"the old bolts look new".

dude, you ALWAYS use new rod bolts on a 911 (930) engine rebuild. How many load cycles have those old bolts seen? Millions !

So for want of a $120 set of rod bolts he put it back together.

when the rod let go after about 500 miles it was spectacular. Looked like somebody had dropped a grenade in there. Ruined everything - Case, crank, rods, everything.

suggest you take care of that crank. it's a known failure item. re-assurances of "just like new" will not defeat fracture mechanics.

speaking of which, see pic. I will buy lunch for the 1st person who can identify this part ! Hint: it is a titanium forging.

/markp

steelbikeguy

It's a disc from a turbine engine... but no idea whether it is a turbine stage or a compressor stage. Probably a compressor stage, based solely on the removable blades?
I don't suppose it's an infamous failed disc, such as from engine #2 of the DC-10 that crashed at Sioux City, Iowa?

Steve in Peoria
(I've spent too much time watching AgentJayZ's youtube channel on overhauling jet engines)

mpetry912 

yes, steelbikeguy that's exactly what it is, the turbine disk from United Flight 232, its the fan disk from the #2 GE CF-6 jet engine

I'll email you a gift card !

the point being that even very high quality, inspected and "certified" parts can fail in service

as discussed in this thread

/markp

steelbikeguy

I have an unfair advantage, because I was an employee of McDonnell Douglas (in St. Louis) when the crash occurred in 1989.
I even clipped an editorial cartoon... although I'm not certain if this was in reference to UAL 232 or the crash in Chicago when an engine pylon failed. It was not a great era for the DC-10.



Steve in Peoria