TiHabanero

I have always struggled with brazing dropouts to the stays. I use slotted stays with traditional dropouts. Yesterday I brazed in a dropout and upon cleaning the joint a crack at the end of the slot revealed itself. It was not there before brazing, and it leaves me wondering how this happened. Is it possible I severely over-heated the joint?

unterhausen

how hard was it to get the dropout into the slot? Even severely overheated tubing takes a certain amount of force to crack. I can imagine a couple of ways for that to happen

TiHabanero

The dropout is a snug fit in the stay, however it was not excessive. Next question: Can the crack be successfully fixed by simply brazing it or do I need to start out with a new tube?

unterhausen

does the dropout extend past the crack inside? Which direction does the crack go, perpendicular to the length of the stay?

The trick to brazing dropouts is to heat the dropout first, and be patient. When the dropout is hot inside the tube, then you can start heating the tube.

dsaul

Steel expands when you heat it. If the dropout fit tight in the slot, heating the dropout could cause it to expand enough to crack the tube. This would be more likely to occur if the slot has sharp inside corners.

unterhausen

A picture would help. I feel like expansion doesn't really explain this. The tube should expand too. Seems to me that there would have had to have been a lot of deflection in the tube at the corner of the slot to get a crack. The only time I have cracked a stay was trying to get a dropout out. You can't put any force on the dropout or the stay will crack.

The best answer is to replace the tube. Some would insist that's the only answer. But the main thing is to practice. Some 3/16" steel plate from the hardware store and some 1/2" tubing would be an inexpensive way to get experience with this. Then just stuff as much filler in as you can. It's not an easy operation to learn given the difference in thickness. Even with the number of dropouts I have brazed, I still have to take a deep breath before I start on one because it just seems to take forever before the joint is hot enough.

TiHabanero

The crack starts at the middle of the slot and travels for 5mm the length of the tube. Would have expected the crack to form at the corner of the slot, not in the middle and now wondering if there was a crack there all along and I never noticed it. Looks as though a new stay will be slotted and fitted this weekend. Nuts.
The other dropout brazed up beautifully, and I do know I used a "cooler" flame so as to not heat things up as quickly.

unterhausen

you are right, that crack isn't the right direction. What brand stay?

TiHabanero

True Temper R2 stays. Not terribly thin at all. Just curious as to what I did to cause the split where it is. Makes no sense as it should have been in the corner. Needless to say, I am really bad at brazing drop outs!