can it be done? if its paperthin tripple butted then probably no, but frames that arnt top,top of the range superlight could be doable perhaps?
any one achived it?

Yep – my Hustler cracked at the top tube as a result of using a shim and a long seat post :roll:6 months ago. Got it welded by someone who fabricates aerospace parts and it's been sold since.

My Intense Uzzi SL cracked after about 4 years. IUntense repaired it for me and it ran for another 4 before failing in the same spot.

I bought a Kona from 1111 off here that has a welded head tube. My son's been riding it for 6 months and it's been fine.

An ultra thin Cannondale – fixed by an aircraft welder. Barely coke can thickness.

any contact info for your alu welding friends?

As far as I understand it, Aluminium can be welded successfully BUT it has to be heat treated afterwards otherwise it may fracture later. Exactly how it's treated depends on the type of alloy.

You will need to know what the parent metal alloy is, probably either :

The digit "6" as in 6xxx designates magnesium and silicon as the major alloys
The digit "7" as in 7xxx designates zinc as the major alloy.

Then have the right filler alloy to match.

http://reynoldstechnology.biz/our_materials_7005.php
http://reynoldstechnology.biz/our_materials_6061.php

7000 series alloy will age harden naturally without any need to heat treat.
6000 series alloy can be heat treated to age harden. Local heat treat can be used on a repair.

Just look in yellow pages for someone that welds aluminium, and ask to see some of their work.

I had my road bike smuggled into Sellafield and welded when a bonded joint failed. It has been perfect for 6 years now, apart from a faint green glow…..