Is my Fissure dangerous??
 

Hi Folks,

I just noticed this small fissure on my aluminium heat treated light frame by Bianchi.

Anyone else suffer this & recommendations?

Thanks

http://i116.photobucket.com/albums/o...pss2s9bw9c.jpg

IMHO yes to the dangerous question. Stop riding it and bring it to your LBS for a frame repair (if possible) or replacement frame.

Oh boy! Thanks.

Probably not but it might get worse over time i suggest that you put a hose clamp around it. https://www.springmasters.com/sp/ima...h-standard.jpg

Not good. I would mark it with a Sharpe and see if it gets bigger, it might be just a surface "split", but it looks cracked.

Get a reinforcing ring made up and fitted. Can be shrunk onto the frame. Paint is cleaned off, ring is machined to an interference fit, end of frame is cooled, ring is heated and dropped on with a tiny bit of retaining compound.
Unless, of course the frame still has warranty....

Oh, BTW when you wrote fissure I thought you meant on your ass!

If that crack were on the bottom of the head tube I would say dangerous. If the frame were under warranty I would take it back regardless. If it were me, and I'm known for taking unnecessary risk, I would monitor. The clamp idea seems reasonable. If that crack moved even a little while riding I would carry it home.

Probably not, but why take a chance on something like this? Front end failures always end in catastrophe. Repair it properly...or scrap it.

Take the headset out and look to see if the crack is also inside the head tube. If it is, don't put it back together

^^^This. It's aluminum. The crack will spread and eventually it will fail catastrophically. It cannot easily be repaired; and by that I mean an affordable, permanent fix.

I thought that too....That's why I read this thread lol. Disappointed now................:cry:

Haaaa, that's the first thing I thought of when I saw the picture. Probably a somewhat reasonable last-ditch-effort fix, provided you can get it to stay in place. If that were the case, I'd also pour epoxy in there and make sure to not ride hard.

With that said, a replacement, or even a repair by a qualified machinist is a much better option.

Weird that it's at the top.

I wonder if the headset was replaced and whoever did it bunged up the job.

First of all, it's not dangerous yet, and may never be. Though it will spread eventually, eventually can be a very long time.

The head tube gets much thicker below that crack, so it will may not spread much, and if it does it'll probably be slow. Meanwhile, you have the fork well trapped in the head tube, so it's not going to fall off suddenly.

As pointed out, there's not much you can do at a reasonable price, though I'd certainly try my luck pursuing a warranty claim.

FWIW, the likeliest cause is galvanic corrosion or simple rust on the bearing, caused by the steel bearing pressed dry into the aluminum frame, combined with a design that allows water entry. I'm seeing much more of these failures with aluminum frames, including two of mine in Cozumel that are cracked top and bottom. On the bright side, they've been that way for a few years, and the cracks aren't growing.

Yeah. Back in '01 my new Colnago Dream Plus (also aluminum) cracked at the top of the head tube right at the six o'clock position after only a few months. The crack was obscured by the headset overhang. I finally noticed it when I was sitting on the ground cleaning the bike and looked up. Always wondered is someone botched the build. At least Colnago warrantied the frame.

I can't see how though. That's why I think it's weird. When pressing in a cup, it only goes so far and then bottoms out. If you keep pressing, I don't think the cup would apply any outward pressure to the inside diameter of the head tube. Seems more likely that the cup would begin distorting. Not positive though.

I'm thinking there was a defect there right from the start. It was hidden from sight inside the tube and under the paint on the outside.

Nope. All clean on inside and greased properly.

One guy mentioned it could be from the build, similar to what you mentioned. I looked inside & found no corrosion. It's quite clean. I am monitoring it.

My solution is actually quite simple:-

https://www.gripsport.com.au/photo-a...irs-head-tubes

I have access to a brilliant buddy who is an engineer, has access to high temp alumnium forming equipment to lay a collar.

noun
1.
a long, narrow opening or line of breakage made by cracking or splitting, especially in rock or earth.
"the bacteria survive around vents or fissures in the deep ocean floor"
synonyms: opening, crevice, crack, cleft, cranny, *****, slit, groove, gap, hole, breach, aperture, vent, interstice; More
2.
a state of incompatibility or disagreement.
"a fissure between philosophy and reality"
verb
1.
split or crack (something) to form a long, narrow opening.
"low cliffs of fissured Silurian rock"

Sorry to disappoint you boys! Lol

http://i116.photobucket.com/albums/o...pssckh4pbl.jpg

The bike in question FYI.

I am not a heavy rider: 73kg

Riding smooth surfaces generally.

I don't think I'd ride it like that: the crack will propagate. If you insist on riding it cracked, check out point 3 below, and drill a hole to stop the stress concentrator.

Trevtassie's idea is a good one. I'm not as concise as he is, so...

You'd probably get a steel ring made up (this is aesthetic: more strength in less volume, not as bulky as Al). A machine shop, or a machine savvy friend with a lathe will be needed. Steps would be

1) Remove fork and top bearing cup.
2) Inspect to see where the crack has propagated to.
3) If it's a through crack that's propagated through the thick flange (where the bearing cup is inserted) to the head tube, drill a small (~1.5mm) hole at the very end of the crack. In other words, the crack should lead right into the hole. This is really important: the end of the crack acts as a "stress concentrator". The same as the little slit in the soy sauce packet: it's easy to open the packet at that little cut. Much harder if there's no cut. The drilled hole removes the stress concentrator. You can fill the hole with bondo or whatever.
4) Remove the paint around the rim of the flange, using stripper and BRASS wool, You want the paint removed, but not any metal.
5) Measure the flange diameter with a micrometer. A ruler's not going to cut it for this work. Make sure you measure several places that are not near the crack. If you happen to know what a "pi tape" is, you can measure circumference, but you'd have to allow for the influence of the crack. From the circumference, you'd back out a diameter (D = C/pi).
6) Make or have made a steel collar (possibly with a shoulder to allow for precise positioning). The collar should have an ID of 0.9990 to 0.9988 x the diameter of the flange. Note that 1) this is SMALLER than the flange, and 2) the precision is as stated. Your collar ID should be plus or minus a few "tenths". That is tenths of a thousandth of an inch, or +/- 0.0002". Steel is a few times stronger than Al, so you'd probably be ok using a collar about 60-70% as thick (OD-ID) as the Al flange. You should chamfer the inside edge of the collar to allow for easier assembly. If you truly want the strongest, most fatigue-resistant collar with minimal thickness, have the collar heat treated and tempered. I'd use chrome-moly: good strength and pretty widely available. 4340 is a very strong steel and would be good for this application. They make bikes out of this stuff, so...
7) To install, you want a manual arbor press of about 12 tons (you don't need that much force - you need an arbor press big enough to fit the frame) and a sensible guy/gal with experience and a deft "touch". Get a big bowl or tray (big enough to allow you to submerge the flange and some of the head tube), and fill it half-full with isopropanol. Add crushed dry ice for the other half. Stir (with a spoon! not your finger!), and put the frame headstock in the mix. Leave it there for ten minutes or more. In the meantime, put your collar in the oven at about 150° for ten minutes or more.
8) You need a friend here. Pull the frame from the dry ice bath and place it in the arbor press, flange up. Pull the collar from the oven with tongs and put it on the top of the flange. Use the arbor press to push the collar on until its even with the top of the flange (or, if you had shoulders machined onto the thing, until its bottomed out). A reasonably sized arbor press can squash your head tube like a beer can: this is why you want the experienced, sensitive guy to limit how much force you are applying. The heat and cold may have changed dimensions enough so that the collar slides on easily. Be careful to ensure that it ends up with it's end co-planar with the flange. After a few minutes, the frame heats up, the collar cools down, and you have what is known as a "shrink fit". It's not going anywhere.

I went through this to let you know what's involved in adding a collar. A machine shop will be able to help you. A friend who's a machinist might be able to you less expensively. Hint: A box of donuts for the shop and a box of coffee may be very effective in getting this done. Especially if you selectively make appreciative comments like "This is cool! I had no idea of what you did in the shop!"

Don't know if this was mentioned but I thought most FRAMES had a life time warranty

I read this after my long post. Your approach is good, but as an engineer I would humbly suggest that a machinist might be of more help. No offense to your buddy - maybe he has a machine shop in his basement.

You don't "lay" a collar with high-temperature forming, this is call forging. You don't want a forged collar. You want to machine one and shrink fit it. This is because to forge something this precise, you'd first have to machine the forming dies anyway. Male AND female. For a one off, its not necessary, but you might want to heat treat and temper those dies after machining. Machining the collar directly cuts the machining in half, and eliminates the forming step.

You could use aluminum, but you'd want the collar at least as thick as the original flange. I think steel would be less bulky, about the same weight (maybe less), and more attractive.

Many approaches shown in the Australian link you posted involved welding. You can weld your frame, but you'd then have to post-weld heat treat the whole frame which would require a new paint job. And that Bianchi pale green is sweet.

Whatever you do, if that crack has propagated to the head tube, get someone who knows what they're doing drill a hole to eliminate the stress concentrator (that is, the end of of the crack). The picture below shows the idea: drill at the end of the crack. If you want to get really nutso about it, you'd ream the hole (to get a smooth ID) and then peen the edges. This can be done by putting a ball bearing about 2x the hole size on each side of the hole, backing one bearing up with a rigid support, and whacking the other bearing with a hammer. This removes the sharp edge (which is also a stress concentrator), and cold forges the edge (strengthening it).

Good luck!

https://qph.ec.quoracdn.net/main-qim...42a55f1d380e5d