Electronics tube depth test II


#1

I finally got my Endcap laser cutting done! Thanks to fellow OpenROV builder Tyson Haverkort who sorted me and my files and my acrylic out good and solid!


The Laser cutter at VHS (Vancouver Hack Space) was giving us some sassy back talk, cutting circles in a slightly less than circular fashion, but nothing that will impact the Endcaps.


I assembled them and prepared them for potting.


This shows the thickness of the largest one as compared to my original 2.4 endcap. Not including the inner portion (the bit that holds the o-ring) the original was about 3/8" thick. The new test subject in the picture above is 7/8" thick, just over twice as thick. I have not run any math on what thickness should be needed for which depth, I just made the various endcaps that my materials allowed, within reason.

The large endcap paired up with the 1/4" thick e-tube should, I think, survive all the way to the bottom (200-280 meters).


I stripped a gap in the wires to be potted around since A: Deep! and B: the ends of the wires will just be free floating in the ocean and, as has been noted many times, (and experienced by Colin Ho at least) water will treat your wires like tiny little doors!


I didn't pot wires through the smaller endcaps since I expect them to pop...though it may end up that the tubes pop first. I expect a little of each.



Square "O-ring"

Double "O-ring". Shaped like an 'x'

Not sure which will be better. The 'x' has two ridges but the 'square' would be more durable. Ideally a thinner/wider o-ring would be best I suspect, but either of these will likely do the job.

This is how it goes together. The o-ring goes between the endcap and the end of the tube. The ocean should supply all the pressure required to seal the water out. Because the tube is not in the ocean all the time there needs to be some pressure holding the tubes together and I am using an elastic band to do that.


The inner piece is tight fitting to the inside of the tube so that the o-ring can but up against it and does not get pushed in from the pressure.

The edge of the tube needs to be very smooth. I tested it prematurely (1 part curious, 1 part hopeful and lazy)

I have started on the other necessary items like the spool and lights and such but I will post separately about them when I have more to show.

That is all for now!

Darcy

Here is a Pic of Tyson using lasers like they ain't no thing.


And here is the 1/2" acrylic being cut. It cut half way through on the first pass, but it took 4 more passes (total 5) to get all the pieces cut free.



#2

I would apply a fine lay of clear silicone on the outside between the tube and the endcaps. just to prevent the endcaps falling of in 4cm of water


#3

If that is not solid core wire you are using I would suggest filling the small stripped gaps with solder to further reduce the chance of water using your wires as convenient little pipes!

We had that exact problem once we hit about 50' in depth

Cheers,

Chris Caswell
BC Robotics


#4

Alexander,

That is a great Idea. I will try that and hopefully I will be skilled enough to keep the bead smooth!


#5

Chris,

I already potted the wires so I can't solder the gaps, but I will solder the ends and see if that works. I have some hope that the epoxy will have penetrated into the wires because I can see where it penetrated into the endcaps where the glue was missed and it was a very thin space! Your suggestion of solder though is good. Solder definitely penetrates the wires!


#6

For the exposed end: solder, liquid electrical tape, and finally a layer of adhesive heat-shrink has helped ensure a leak free system for now.

We have swapped over to an aluminum / Lexan electronics housing and a 330' tether so we will soon find out if it can handle far greater pressures!