Steve, Thank you for your reply. I had wondered about using a heatsink of some sort. I have an update for you, I have had some practice attempts this morning, I started out welding the thinner tube to some section that is actually slightly thinner than the bottom bracket shell but still much thicker...

Thank you for your reply, I shall let you know how I get on tomorrow!

I am pulling my hair out here! I have a cycle bottom bracket shell which has a thickness of 3mm. I am trying to weld the rear chain stays to it and they have a thickness of .9mm. I can't get a puddle going without blowing through the chain stays. If I wait until there is just enough heat to start th...