Joined: Jun 2010
Posts: 2,132
Likes: 1,522
From: Medford MA
Bikes: Ron Cooper touring, 1959 Jack Taylor 650b ladyback touring tandem, Vitus 979, Joe Bell painted Claud Butler Dalesman, Colin Laing curved tube tandem, heavily-Dilberted 1982 Trek 6xx, René Herse tandem
Can you measure the inner diameter of the bottom bracket as it is now?
philpeugeot is right, it looks like it has some sort of lining or shell that might be able to be pushed out. Telling us the diameter will give us a clue as to whether that's a good or bad thing to do. For reference, the inner diameter of a BSA bottom bracket is 33.6mm or so.
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.