Crack on headtube alu frame

[swizzly]

Hi!
Last year on my 2007'-er Canyon Nerve EX 8.0 I noticed a crack on the head tube (see attached image):

Unfortunately, the bike was over the guarantee period, thus it can't be sent back to the manufacturer. Since I really love this bike, I am trying to find a fix to save it, it would be a pity to toss it in the garbage.
I was thinking about to use a spanner ring to avoid the increase of the crack. The first "prototype" looks ugly, and I don't really know whether I could trust:

I mainly use the bike to get to work (50% asphalt and 50% dirt road in the woods) no heavy terrain or jumps whatsoever. I would like to know whether someone has some better idea how to fix the crack, and whether what do you think, can I trust such a fix.
Thanks!

[JanJ]

I've seen something like that on motorcycles, and it was repaired by a welder that had custom Aluminum welding systems..    I think it is heat source that is surrounded by an inert gas....

This was for a repair for a old scrambler frame that was aluminum....  The fix was successful.
Since it was a off road motorcycle, He did not re-paint the frame.   If I remember, the frame was charred for a couple of inches around the repair...

[Painkiller]

"I mainly use the bike to get to work (50% asphalt and 50% dirt road in the woods) no heavy terrain or jumps whatsoever"
In your quote above, Is this something new you do with the bike or the way you have always been riding it? This style headtube seems to be more prone to cracks like this. I have seen more and more alloy frames do this. For the average person it would not really be worth the effort. The main reason is it now has only scrap value fixed (poorly) or not. I had a similar one a couple years ago and conducted a 'What if" evaluation to repair. it went something like this. It involved welding the crack but first boring a hole at the end of the fissure. Then machining a ring to be bonded to the outside top of the tube. Then machining a sleeve to be bonded to the inside of the head tube. We concluded that with this process it would be stronger than before. (some disagree). This was never done to my frame in the end. I bought it broke just for parts. However, merely having welded is not the answer. The frame has served its life. I highly recommend you replace it

[GeorgeET]

First thing to do is drill a small hole ( 1/8") at the end of the crack to keep it from spreading. Kind of like a lollipop. This works on plastic too BTW like windshields.

You can than remove the fork and bearings and take it to a welder. Not sure what the frame material is but for aluminum TIG welding is good, for steel MIG welding. It wont be pretty but will work.

You may consider checking at Nashbar site they have some nice frames that go on sale at a good price.

[nfmisso]

Any sort of effective repair is going to cost a great deal more than a replacement frame.

Any idea what caused the crack in the first place?

The strap you put around it is not strong enough to make a significant difference.

[swizzly]

Hi guys!
Thanks for the replies for everyone. As of the possible cause of the crack: I didn't do any extreme ride, really only "bike to work". I am not sure, but as far as I can remember once I crossed a small rainwater "channel" (a small <3-5cm high, slant walled < 30° that crossed the road, really not a big obstacle) which hit the front wheel and the fork absorbed the hit, and I wasn't particularly fast (maybe 20kmh). I only notice the crack several weeks later. Maybe this hit and the age of the frame together caused the crack.
Someone told me that the location of the crack indicates, that the headset was pushed falsely (maybe with too much force, maybe the tube was slighly too small or the headset was not fully in the right angle) into the tube, which caused tension and after the years the material just gave in.
Anyways, I am disappointed, that the frame which is not particularly a cheap one just cracks after 6 years of really easy use. I have an older alu bike 10+ years and it had never had a crack.

[nfmisso]

Another reason I don't have aluminum framed bikes.  As a Mechanical Design Engineer, I have to have a great deal of materials knowledge.  Aluminum has its place, just not for my bike frames.  My bicycle acquisitions going forward are double butted chrome-moly steel (cro-mo) and manganese-moly steel (Reynolds 531).

[elmore leonard]

(02-16-2015, 05:39 PM)nfmisso Wrote:  Another reason I don't have aluminum framed bikes.  As a Mechanical Design Engineer, I have to have a great deal of materials knowledge.  Aluminum has its place, just not for my bike frames.  My bicycle acquisitions going forward are double butted chrome-moly steel (cro-mo) and manganese-moly steel (Reynolds 531).

I agree with Nigel. Steel frames hardened with moly are the way to go. These moly steel hardened frames can use lighter stock for the frames then straight carbon steel frames.