Okay then, **** off you **** its Mr Gaylord to you! -- Martin: "For a minute there, you bored me to death." VTR1000 Firestorm TDR250 http://ukrm.net/BIKES/Yamaha/tdr250.html martin dot smith nine zero three at ntlworld dot com
I thought mass produced frames would be welded by machine not by hand to try to avoid human error. -- Martin: "For a minute there, you bored me to death." VTR1000 Firestorm TDR250 http://ukrm.net/BIKES/Yamaha/tdr250.html martin dot smith nine zero three at ntlworld dot com
No, a butt joint doesn't *have* to be 100% penetrated. It depends on the spec you're working to. No porosity in an aluminium weld? Almost unheard of. The main cause of porosity is absorption of hydrogen in the weld pool - very hard to avoid. The most common defect in an aluminium weld is porosity/gas. Even very strict specifications, eg ASME IX (welder qualification, pressure vessels), allow some porosity. I can't remember offhand, but individual gas pores a quarter or third of the wall thickness is usual. In fact, I can't recall ever seeing any spec where some porosity was not allowed, even BNFL. Maybe this guy can tell me which one it is and I'll see if I can get hold of a copy? I don't know about "general" stuff for aluminium, but a weld width of 3T for a normal butt weld is *very wide*. If you're not going to do a full penetration butt weld then the actual throat thickness of the weld is important. It may just be welded on the surface but that can be enough (as long as it's fused...). Obviously a nice butt welded joint is preferable. Bevelling both surfaces would call for more careful welding. Does this guy not realise that bike frames are welded by robot? Preheat aluminium? Hmm, usually there is only one reason to preheat and I don't think this guy knows what it is. 150-175 amps for TIG welding 5-7mm aluminium? I don't think so. That's too much for MIG and not enough for TIG Are you sure he's a certified welder? He keeps talking about preheat for some reason. As far as I know, the *only* reason for preheat is to control the cooling (will cool slower), for prevention of H2 cracking and better HAZ properties.
mb wrote: Aircraft certified, yes - & recently retired after a lifetime in aerospace. I have no idea how much he knows about aluminium bike frame welding though. He's a Ducati & MV guy so probably more up on hand-welded tubular steel when it comes to bikes. He's built some race cars too for some bonkers race in Alaska - V8 engineed Beetle was the latest iirc.
