Welding.

flickerx

Here's the road bike frame that rob1891 gave me



As you can see there was a large crack in the down tube:



I think I mentioned it earlier in this thread that when I brought it into the shop, they wouldnt take out the b/b for me on safety grounds. They were afraid that if I put a new b/b in, that I might actually use the frame to build a bike, and they thought doing that would be lethal...

So I ploughed on anyway and got ready to prep the frame for a rebuild. But as mentioned on the bottom bracket thread I just couldnt get the b/b out. I still wanted to have a go at welding the down tube back together anyway, so I jammed the frame in a vice, and tried to line up the crack as best I could. You can see as well that I burned all the paint off with the oxy acetylene torch and then cleaned the surface down with steel wool and cloths to try to make sure the surfaces were clean for a weld.



So generously using a brazing rod and a load of flux, I stuck it back together. Bearing in mind my welding technique was still in its infancy, I managed to tack it down and then build up a mass around where the crack was. It looks pretty bad but the weld is fairly solid - I put a lot of pressure on the frame once the weld had cooled to check if it was reasonably solid. My girlfriend who is a sculptor said that I could easily file down the weld to make it smoother, without necessarily damaging the bond where the crack was - but I didnt do this, because the frame wasnt completely aligned properly when I welded it - the frame kept on popping out of the vice and it was driving me insane, so once I had it steady I just tacked it down and got to work. It wasnt perfect.

Anyway here's the results. Looks a bit like someone's got some gold coloured chewing gum and stuck the frame back together! If anyone feels like taking it and having a go at removing the b/b let me know, its yours to collect at any time of day or night (its outside my house at the moment). Someone out there might even want it for an art project. I painted it a small bit but it looked awful, but I cant find the photo of that though.

Thanks to rob1891 for the frame to have a practise on anyway (and sorry for the delay in putting these pix up, been mad busy with finishing off the self build fixies lately), it was much appreciated.

rob1891

Hey great job, has anyone said to you that it is unsafe other than the bike shop?

I think the traditional fix is to insert a tightly fitting tube inside the frame across the crack and then braze it in like you would a lug (at least that was a fix done on the seat tube of a bike of my dad's many years ago ... it cracked at the same spot in the end). I would wonder if the fillet style braze you have is strong enough by itself at that point on the bike ... but I know nothing about frame building so I only have questions :-)

Would you chance riding it yourself? I hear the best way to test head tube strenght is to stick the wheels either side of a ^ shaped thing and jump up and down on the thing :-)