Jonny69
Senior Retro Guru
So those alloy Meca Dural frames are not bonded or welded, they have expanders in the ends of the tubes like a quill stem to make them friction fit. Access to the expanders is through holes in the tubes and by taking the head badge off. Completely crackers!
https://www.pedalpedlar.co.uk/blogs/thejournal/vintage-bike-of-the-week-meca-dural
https://www.pedalpedlar.co.uk/blogs/thejournal/vintage-bike-of-the-week-meca-dural