Four Months Outdoors

After four months outside and the first cold spells, here’s a status update on the mechanical side.
I dropped the LoRaTube and broke the part at the end of the tube (the piece that’s glued to the PVC pipe).

In addition, the end piece of the assembly,  the one bearing the weight of the whole battery stack and the contact pressure from the springs, had been printed too “light” and had slowly deformed under load. I redesigned it as a beefier part, matching the diameter of the new glued sleeves, and printed it with higher density (40% infill + gyroid pattern).

New Design

In hindsight, I had printed it too thin and not dense enough. I reworked the cap as well as the glued end-piece of the PVC tube, increasing the wall thicknesses and printing at 40% infill with a gyroid pattern.

I should also mention that I changed printers, moving from my old Ender 3 V2 to a Bambu Lab machine (huge upgrade). The part, even though it is still PLA, comes out noticeably denser. Under-extrusion on the Ender? Slicer differences? Whatever the cause, the whole assembly feels much more solid now.

Here is the new end piece of the assembly, which both closes the tube and holds the batteries in place.

Here are the new end caps for the PVC tube.


And here is the new mounting bracket that holds the 50 mm PVC tube (the tube that carries the electronics).

And the end part of the tube : 


I also changed the part that holds the 50 mm tube. It’s thicker, I increased its diameter, and I printed it with 40% gyroid infill as well. It’s the green part in the photos below.

Resilience

In any case, it’s by iterating that I’ll converge towards a system that’s robust in all conditions (Soyuz technique!).
The length of the 40 mm-diameter PVC tube to cut is 115.8 mm. By cutting it to the correct length, I was able to remove the crescent-shaped spacer I had added earlier.

In the last photo, you can see the device responsible for making contact with the positive terminal of the last cell.
It consists of two parts that can move relative to each other. Contact pressure is provided by three compression springs. The travel is about 15 mm. The system looks robust and works well so far…

I’ll leave the device assembled over the coming months. I’ll only bring it back into the lab when I receive the V4 PCB, if it looks OK for an outdoor test.