To repair or not repair cracked head tube

[mk one]

My normal procedure for a small crack is to remove the clear lacquer from the tube and take the polished finish down, as this often has loads of contaminants in it. Degrease the whole area, chamfer out the crack to allow full weld penetration from both sides, re-clean.
Starting at the outside edge, weld down the crack on the inside of the tube. Re-melt the start position and repeat down the outside of the tube. I use 100A peak/65A base AC pulsed at 150/sec, +65% balance.

File or grind weldment in and out back to original surface and polish a bit.
Ream out the head cup seat, face the tube and chamfer the inside edge of the tube face to reduce future stresses.

I use 5183 filler to get a good post-weld strength without heat treatment. The normal 5356 used on 7005 alloys needs time to age or a heat treat. It will work OK unheated, but is more prone to fatigue cracking.
Also use Tempguard gel to prevent the re-heat from getting near the old welds which could be over aged by it, and also makes for a quicker heat/weld/cool cycle, which is also better for the final strength.

All the best,

Right, i think ive got all that :shock:

Amazing finish on that Manitou repair

 

[themountie]

Re:

Well guys mines gone off to my dad's engineering works so hopefully they can get it sorted

 

[AntoineV]

Need you to repair my bikes !!! Why are you so far from here ?...

 

[ibbz]

Sorry to resurrect this
There’s a Scapin Columbus steel frame on sale on eBay which has cracks in the head tube
Is this weld fixable ?
Or a lost cause ?
I think lost but thought I’d just ask

 

[basketcase]

Other side cracked too?
Wouldn't be surprised to see that lower arm of the crack go right around.

 

[ibbz]

Other side cracked too?
Wouldn't be surprised to see that lower arm of the crack go right around.

Yes I think so
https://ebay.us/m/mBofoe

How’d anyone manage to crack a steel frame like that ? Must’ve done an Evil Knievel type jump

 

[basketcase]

The guy is actually selling it ?
He ought to be giving it away, for someone to experiment with ........

 

[danson67]

That's a new head and downtube needed...so Yes, repairable, but probably not worth the effort.
That seller should be giving it away

All the best,

 

[joglo]

Hi, I just wanted to share my two cents about fixing cracked head tubes too.
Brilliant work from @danson67!
Just it may not work for all cracked head tubes, as very often it's not a single crack, but often more, or at least from both sides. I have bought once KTM Ultra (the blue one with AMP fork) for the parts, the head tube looked almost like parchment paper with many small cracks. No way to fix permanently something like this with welding.
Moreover pure from a financial standpoint are many old frames less worth as the costs for a solid welding work (and shipping etc.).

Therefore I want to share some additional ideas to fix it, at least in a way that the frame can still be used to some extent:

- Use an ring at the outside to reinforce the cracked head tube
Someone has done this very nicely in combination with an own produced extra long head set cup to fix a RM Edge: https://www.mtb-news.de/forum/t/rocky-mountain-alu-edge-mit-riss.969784/
I have done it a bit similar and from both ends for an kids bike with 24" wheels, turned than into an fake Yeti or better Yeti homage

https://www.mtb-news.de/forum/t/cla...94-moechtegern-mini-yeti.988068/post-19484651
First of all those rings have to sit very tight, but I have glued them to the head tube in addition, so also the cups of the headset than from the inside. The result looks good to me and seem to be robust.

- Cheap&dirty, use a hose clamp
https://www.mtb-news.de/forum/t/m45...e-lackierung-look-a-like.903489/post-19857104
Not looking good and nothing for the long run and heavily used bikes, but good enough to keep a pup bike running.

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