pressed seat lug help...

[NBC]

hi all

I've got an older mercian vincitore, with a pressed seat lug that by the hands of a previous owner has come to be crushed, and will not hold the seat post up,

I'm planning to replace the rear end of the frame, as the tubes aren't in the greatest of condition from being spread apart to accommodate 130mm spacing, and the seat tube will be replaced as well, because i am not sure if the issue has been compounded by an over reamed seat tube,

so the question i really have is how to repair the seat lug ?

i was thinking after removing the seat tube from the lug, but leaving the lug brazed to the top tube, to cut out the binder section and weld in a new piece of metal, then braze an allen key binder boss on afterwards ?

also i looked at mr sachs' oops atmo folder on flickr, i presume the technique used to remove the down tube from the bottom bracket shell could be applied in the same way to a seat tube ?

this will be my first foray into actually repairing a frame, rather than starting from scratch, so i feel as though i'll need some sound advice on this, or experience of a similar repair

if anyone had any method photos or an order of attack, that'd be brilliant too

feel free to comment, and thanks in advance

nathan colman

thanks in advance

nathan colman

[Andrew R Stewart]

First thing is to establish the current geometry. Placing the frame in a jig is a good way to maintain the geometry during the repair process. Next i would determine the reason of the seat post slipping. The lug binder ears being crushed is a common cause, many pressed seat lugs never had any inside reinforcement added. I would ascertain the seat tube's condition. Your speculation of over reaming might be the case but you should confirm this as best you can. Then with this assessment decide whether you're comfy keeping the seat tube, or not. Replacing a seat tube is not a small repair. Then i would consider how to deal with the seat lug and it's binder. If you're keeping the ST I would consider just replacing the binder ears with a full barrel. If the lug was brazed with brass this is a far easier repair to do then replacing the lug. If you decide to replace the ST but keep the lug I'd do the binder repair first then pull/grind out the ST. Whether you are trying to maintain the style of the bike or not is another factor in how far you go in repairing the minimum or replacing as much as you can (with the same shapes and binder style).

I would favor replacing as little as possible. Sight unseeI'd'd tentowardds replacing/repairing the binder and only replacing the seat stays/bridge. But this is a complex situation with go/no gos at a few steps. Andy.

[e-RICHIE]

Pry the ears apart until the area looks like a facsimile of its former self.
Drill the hole (if needed) and insert some scrap tubing to be brazed in.
Afterwards, drill through the scrap, and file it all up atmo.