This has happened before. It was a fairly common problem on early bikes. You can get this sort of damaged welded and repaired, I've seen it done. Personally, I don't think I'd ever quite have 100% faith in a weld though. Certainly if going down this route don't try it at home! Find someone who knows exactly what they're doing with cast aluminium alloys. Probably best to source a second hand leg?

Read this thread. It covers both welding and second hand options.

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