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Belly Tank Lakester project Ep35. Attempting to make a nosecone by hydroforming welded aluminium barrel shape (see previous episode).
Previous episode, welding up the approximate shape needed:
• Hydroforming a nosecon...
Outcome:
It partly worked. It is a little bit more rounded off than before. First 2 attempts limited by leaks and on the 3rd attempt we just went for it and the metal in the centre eventually ruptured next to my seam weld.
Materials:
If you want to see the parts and fittings I used to make this all go together I have discussed these from 08:00 onwards.
Analysis:
The way steel stretches versus aluminium is discussed in the video. Steel stretches until it reaches a limit point above which a lot more force has to be applied to stretch it further (until it eventually breaks). This limit point is not there for aluminium, once it starts to stretch it will continue to until it eventually breaks. In practice this means the weakest area, in my case next to the weld, perhaps due to it being heat annealed by nearby welding, will stretch first while other areas have not started to stretch yet, and then fail at that point.
My options now - comments invited.
1) It is slightly more rounded off than it was originally so now I cut it into upper and lower nosecone sections, smooth down the welds and English wheel it to finish off the shaping.
2) I patch the ruptured area, anneal the whole thing using a blowtorch to make the metal softer and have one more try at hydroforming it. It may still just blow at the point wherever the metal is softest but may be worth trying even so.
It was an interesting experiment anyway!