Originally Posted by
3dvvitch
That all makes sense! I guess the thing that really stands out to me about the welds is less the filing and more the size or volume of the weld joint itself. Maybe it's just an optical illusion (they are skinny tubes), but it looks to me like the material deposition at the weld on those old frames is WAY greater than on virtually all modern stuff. I don't know if that would be the result of a greater number of passes or if you can just create a very large puddle on a single pass? And then, theoretically, what would be the mechanical consequences of doing it that way?
Yes agree they look like they must have started our pretty chunky! The initial size of the bead is related to the thickness of the metal quite a bit and Ti tubes will be thicker than steel ones. But modern Ti bikes usually have smaller welds than those look like they were I agree. Perhaps on these older frames the Ti was thicker wall than what we use now.
You can shove a bit more material in on the first pass but only up to a point. I reckon they probably did a second pass with lots of buildup with the intention of filing it down. Idk what that does on Ti but on steel you would be worried about distortion and weakening the metal from overheating.
On Ti it's quite common (nowadays) for some reason to do a first "fusion" pass (which means not using any filler rod) and then a second pass with filler over the top.