infamous campy SR crank spider web hairline crack: real question
 

yes. that. the notorious crack, more like hairline prediction of a crack in the back of the spider junction. i've read/searched tons of articles/posts inc. the ones on C&V here yet with some real curiosity.

will it really break under 'ordinary' riding? non-criterium, non-compete, less than a few miles daily city riding, i mean. i've read horrors breaking at pedal eyes, but didn't really see the cases spider arm really "broken"? i understand no one can guarantee it, just asking 'in general', common sense. should a less-than-a-millimeter hairline be really a panicking thing or like hey, it's common just ride with a caution?

i do have round files, am capable of filing/sanding things, and it doesn't seem to be too hard to file a couple mils away. should i just do it and forget about it?

got one pair that had looked totally fine in the pics, then i see it in person. less than a millimeter, obvious initiation that i can also see from the outside flat too. (and trust me, not the first time i see this). yes i'd easily return 'em unless it's from South Africa—and the one i had to wait nearly two months to arrive... under current situation, it'll most likely take another two months to sort it out—return, refund etc etc.

i mean, the problem is always, that SR/NR crank arms are too pretty to give up...

https://cimg6.ibsrv.net/gimg/bikefor...d326290f0d.jpg

Yes, they can. Get the file out.

What's scary about those cracks is it can literally be just the tip 9f the iceberg, where there's actually a lot more damage within the crank, under the surface, not visible from the outside......pretty much a potential "silent killer".
Easing it out with a file can give you an idea on how deep it really goes into the crank.

Yes, easily. That crack is a serious stress riser. Even at fairly modest pedal forces, it'll gradually propagate itself and eventually break.

FWIW I rode a campy crank with a small starter crack like that in the web for years, before I finally chickened out and replaced it. I think I've seen a picture once of someone who let it go until it actually failed. That would take a while. Keep a careful eye on it and if it starts to get substantially bigger, stop riding it. I'm not sure if filing the web now that a crack has started will be any help.

This isn't like cracks that begin at the pedal eye or across the main body of the crank arm. Those fail relatively quickly and often dangerously, and any crank with that type of crack should be retired immediately. I broke a crank completely through without warning once, at it was both disconcerting and potentially dangerous. From then on I learned my lesson and watched carefully for cracks.

done. luckily the surface was all, no internal fatigue/cracks. did moderate filing & polishing on both sides. i can sleep now.

https://cimg5.ibsrv.net/gimg/bikefor...7bc62ecd29.jpg

That's a nice, clean job of it :thumb:

DD

thank you. means a lot, especially from you, sir!
:)

Funny how threads about the same topic sometimes pop up at the same time:

https://groups.google.com/forum/#!to...es/b3DsZL4XQiU

and a link from Jim Merz's reply:
https://forum.cyclinguk.org/viewtopic.php?f=5&t=121671

https://cimg7.ibsrv.net/gimg/bikefor...1d842e15d3.png

https://cimg8.ibsrv.net/gimg/bikefor...c848a7bb47.jpg
Note how the crack starts on the high side of the crank downstroke where all the force would be down and out due to the pedal and crank arm acting as a lever. Also, in this picture, does it look a little like the web was filed a bit?

https://cimg9.ibsrv.net/gimg/bikefor...ae2bac5340.jpg
https://cimg3.ibsrv.net/gimg/bikefor...45b53e1f82.jpg

Pretty sobering!

It looks like you've resolved your issue; however double check for micro-cracks by stressing the crank while examining under bright light and magnification.

I was rudely introduced to the road a few years back when I broke a crank so I routinely check my vintage cranks using this method. If there are cracks, you'll see them.

Note that the beach marks show that the crack had extended approximately 40% of the way across the crank shaft, and yet someone continued to ride it. It would have been easily visible, yet it was ignored. +1 Inspect cranks regularly with light and magnification.Not unusual for used campy record cranks from BITD to have really big miles on them.

2 hours before this posted I bought a really clean Super Record crankset off Ebay. After reading this I went back and took a REALLY close look at the pictures and there appears to be a small crack. 😮😕 Has anyone tried drilling a hole at the end of the crack then grinding it out to a V shape and TIG welding it? I have done this with great success on other aluminum items. It would only take a "tack" weld to fill the V so the heat affected zone would be quite small. I would leave the TIG weld to a friend, he has a custom metal fabrication shop and does this type of repair on auto and motorcycle components often. He's a much better welder than me.

Here's a picture from the auction, it's not the best. The area in question is circled in red, I can't tell if it's just a line, a crack or dirt. I guess I'll know for sure when it gets here.

https://cimg0.ibsrv.net/gimg/bikefor...a920ad7467.jpg

double checked it with a loupe under a blinding light. currently no more visible crack or sign. and will check often to see if there's any.
excited to see if the filing really has done any 'practical' effect. :)

for whom might have wondered, i've used:
1. gentle hand-filing with a hobby size round file, about 1/16 ⌀
2. finishing with 3M320F block. peel-off-cut a small piece like a blanket, taped to a small rod. applied with the hand drill with low-speed. very meditating it was.

wanted to do it delicate way, have seen horrendous jobs on the web, that actually ruined the nice connecting outline from the arm the the spider.
happy with the output, for now.

thanks for all the insights & advice.

Would like to see more pics of filed / fixed cranks...

It's not just vintage cranks. I've broken two 'modern' (2010-ish) drive side cranks. The first was an FSA Gossamer that I could feel had some lateral movement, sure enough, a crack had developed on the crank arm. The second was a Sugino RD2 that broke clean off while riding, luckily I managed to keep it upright.

https://i.postimg.cc/zvhg4RLf/17-B87...7-FE5-AC97.jpg

here you have them. quick iphone shots with desk light.

https://cimg6.ibsrv.net/gimg/bikefor...0c76d5c8bf.jpg
https://cimg7.ibsrv.net/gimg/bikefor...5030318d93.jpg
https://cimg8.ibsrv.net/gimg/bikefor...610d16dbab.jpg
https://cimg9.ibsrv.net/gimg/bikefor...b1b2f83bc8.jpg
https://cimg0.ibsrv.net/gimg/bikefor...bb908222f0.jpg

Nice to see how far up the arm you went, helpful!
Will try to post pics of mine tomorrow.

Yep, I had a bounty last year with a beautiful frame and components, including an SR Royal super light crank. Sure enough, there was a hairline, and when I started filing, I couldn't find the end of the crack. Though I may re-purpose the chainrings at some point, the drive side crank is wall art.

The cranks in my photos were part of a University Engineering school's materials study to see failure modes in bicycle components - once identified, the parts were continually stressed until failure. Not my pics nor my university but very practical in scope.

Oh, thanks for that info. That makes more sense. I had never seen a campy crank with one of those spider starter cracks that had completely failed in real life.

Here's a campy triple currently on my Mclean, that I filed a year or so ago.
https://cimg0.ibsrv.net/gimg/bikefor...441d9ba402.jpg

https://cimg0.ibsrv.net/gimg/bikefor...9efb07c597.jpg

and here is a pista crank on my raleigh track that I filed a few years ago. It has held up fine but I don't ride the bike that much.
https://cimg5.ibsrv.net/gimg/bikefor...ca34ef1fa5.jpg
https://cimg7.ibsrv.net/gimg/bikefor...5e794189b0.jpg

Nice job of polishing out the hairline orangeology . I worked in failure analysis of steel, in the construction industry (quality engineer,) for 30+ years, you might want to do a "poor man's" Magnaflux test to the spider, for peace of mind. Soak the spider liberally with WD-40, or even some thin spray lubricant, then wipe it dry after letting it sit for a bit. Once cleaned off, apply some baby powder to the entire piece, then blow it clean. If there is a crack anywhere you'll see it where the soaked in liquid has absorbed the powder.

Bill

I appreciate this tip. Thank you for sharing.:thumb:

My Super Record crankset arrived, no cracks, it was just a shadow in the photo. It's a beautiful thing! :love: