A custom bag cap was necessary to function as a sealed connection between the aluminum foil bag and the fitting on the copper tube that attaches to the checkvalve. The dimensions of the bag’s mouth were measured with calipers and a first prototype was designed based on two pieces: an inner piece that presses against the end of the mouth with an o-ring and that can be tapped to fit to a 1/8 NPT fitting, and an outer piece that screws onto the mouth and forces the inner piece to seal (see picture 2).
The first prototype worked well and was lightly modified over time. Most of the caps were printed in HIPS as we were out of ABS at the time, but both ABS and HIPS print well.
Finished and printed the first design of the rain collector pouch cap. It’s two parts: one that presses against the top of the opening with an o-ring and another that screws onto the pouch’s threaded mouth, which presses onto the first part as it is tightened.
This assembly was designed in Fusion 360 rather than OpenSCAD so I could design it quickly. Designing multiple parts that are dependent on each other can be significantly easier using Fusion360 than it is with OpenSCAD, though OpenSCAD has its advantages.
The threads were made by creating a helix and then sweeping an area through the path of the helix. It added some twisting but prints and fits just fine in both ABS and HIPS.