Have just tried doing it, Dead impressed it was so easy
What did you use that alutight stuff seen it on youtube and looks impressive.
Cheers,
Bob
Is it suitable for oil sump or alu fuel tank ?
It's not really welding. It's friction brazing. Being around for donkeys years. I like the bit on the Alutight youtube video where they
recommend using a screwdriver to scratch through underneath the molten metal 
At least my technoweld stuff came with a poxy bit of stainless wire to
do this.
It's very effective and the bond is strong. The main issue is that you need to hold the parts in place (I tend to use some lightweight brackets
rivetted in place) otherwise when you're making one joint the heat from the blowtorch melts all the other joints and the whole thing falls apart.
Pre-heating in the oven helps for large pieces.
But it ain't welding.
Whatever you decide it 'is' - it works very well.
I used Technoweld for some large'ish pieces on my car; inlet tubing and an adaptor from my Airflow Meter to a Conical air filter. There are some
pictures of the engine installed in the bare chassis, in my photo archive, that show these bits.
There are two issues;
1) heating large objects to make a joint can be difficult. Large in this context means anything over 250 grams. Aluminium conducts and cools very
quickly. Hence Ben's comment about pre-heating in an oven. I built a stand that sat over a 2nd blowtorch to provide heat fast enough on some of
the bigger parts I've made.
2) the filler material is harder than the parent metal. This can lead to cracking at the joint between the filler and parent meal if the part is
subject to vibration etc...
Otherwise it works well and is a really practical way of joining Aluminium (and it's alloys!).
quote:
Originally posted by BenB
It's not really welding. It's friction brazing.
You are not actually melting the 2 joining parts, only the low temp filler rod
More like glueing realy
If you believe the Technoweld information then the parent metal does melt.
Right after you've melted the filler rod on to the parent material you are supposed to use the Stainless Steel Abrader (a piece of Stainless
Steel wire) to scratch the oxide layer from the parent Aluminium. When you do this within the puddle of filler material a chemical reaction occurs
which locally melts the Aluminium allowing the filler material to alloy with the parent material.
I've never managed to get it to work very well. Whether it is me or whether something else is going on it just hasn't worked.
e.g. tried to weld a bracket onto the ally fuel tank and the filler rod material just falls off.
You're not doing it right - check out the video's on the Technoweld site 
quote:
Originally posted by Trollyjack
You are not actually melting the 2 joining parts, only the low temp filler rod
More like glueing realy