Today I had a bit of spare time so I did some more experiments with the robinson couplings. I think I have finally found the solution.
Using the rockets my Scouts started work on a few months ago, I tried placing some metal washers either side of the joint, to allow me to compress the inner tube without tearing it when tightened. I have managed to tighten the nuts quite a bit now, enough that now the limitation is my grip on the bottle….so very tight!!!
Here’s a picture of the two completed pressure chambers.
I have decided to name these two rockets Dewey and Huey, for the upcoming competition I will rename Weston Wocket to Louie, these are the names of the 3 robots from the film “silent running”.
I pressure tested both to 100psi. They both passed so it looks like I have finally have a working design for Robinson Couplings.