Originally Posted by
Andrew R Stewart
Wow, lots of stuff flying out in the wind of this thread.
You're right, but unfortunately none is necessarily germane. Before debating what is the best way to fix it, it's worthwhile to consider why it cracked in the first place.
The OP says the crack is at the top of the top tube/seat tube joint. When all is good, this is possibly the least stressed joint on a frame, and if the crack is in the seat tube itself, it's a good clue as to the cause.
The typical steel seat tube is not strong enough to support the post or rider in cantilever. It requires that the post pass beyond the top tube joing carrying it's torque into the triangle. When that's the case, the seat post buttresses the seat tube through and beyond the top tube joint, and a failure of this kind could only occur if the welded area was over hardened and brittle, and couldn't flex with the post within (IMO, not likely).
In an earlier post, I mentioned this, and suggested that a properly sized (fit and length) seatpost would adequately support the joint, and just about any repair option would do. However, an improper seat post will lead to a repeat performance no matter how it's fixed,
because regardless of how the joint is made the seat tube above still won't be strong enough.
We can debate filet braze, vs. weld till the cows come home, but unless the cause of the failure is addressed, repairing it is an exercise in futility.