Depth Test X Implosions are still cool

#1

Here is the video showing all 4 e-tubes popping.

The first to go, at ~95m, was the 6 3/4" tube with my original end caps. One of the caps floats around for a bit showing that it failed. (Sadly the bags I put the tubes in also failed and most of the shrapnel is at the bottom of the lake.) The E-tube was also destroyed.

Next at ~103m, is my original e-tube at just over 7" (180mm). Its end caps were the same as the standard OROV 2.4 caps, except:

  1. An additional 1/8" disk on the inside of the cap giving a smooth surface for the additional o-ring placed between the end of the tube and the end cap.
  2. 2 types of o-rings. the original OROV 2.4 type and the one I mentioned above. (though the other end had only the new o-ring)

At 107m, the 6 1/2" e-tube with 1/2" end caps (same as previous), but this only had the 1 o-ring per end cap. This and all the rest have the o-ring I was testing (between the end of the e-tube and the end cap) and they do not have the original o-rings. One more thing, these last 2 tubes had hot glue around the end caps.

At 130m, the 6 1/4" e-tube with 7/8" end caps

At 228m, the last tube passed the test quite well. It was the e-tube on OpenROV#272. :) The tube itself is 6" long and its thickness is 1/4" (twice the thickness of the standard tube. And it doesn't cost much more.) The end caps were 3/4" thick and had the new o-rings.

Video below shows #272 go to the bottom of the lake. Or rather it continues to show everything but itself. Sadly the raspberry pi would not connect. I had a lot of trouble with connections on the 3 previous attempts (I will give details later). The main issue is that I have 2 pairs of homeplug adapters and they will connect to what they want to rather than what you want them to connect to. I had separate power for each but on the last day they would not connect and I was out of time. I adjusted the position of #272 and he went solo. What a champ!

I will update this post later with more details and make sure I answer all of Eric's questions from the first post. :)

This is my science vessel. In answer to your question, I sit right where the orange jacket is. And the plastic bag has my pink laptop in it.

#2

There have been a lot of really incredible posts on OpenROV.com. This is probably my favorite ever. AWESOME!

#3

I noticed something now, looking at pictures I took when I got home from the test, that my tired mind missed at the time. Of the 2 end caps that I managed to retrieve, both had damage:

This is the hybrid cap with both types of o-rings (though the 'new' o-rings are smaller than the ones I used on all the other caps so that there was room for original o-rings as well). Only one edge of this cap broke. It failed along the edge that rested on the e-tube so it seems that it failed before the tube. I think the tube must have been close to collapse as well and broke apart right away since such a small portion of the caps circumference failed.

Here are more pics of the same cap (remember you can click on them to get the full resolution image)

The other cap was the 7/8" thick one. I suspect the damage was either from bouncing around after or from the e-tube shrapnel after collapsing. But, As with all of this, speak up if you disagree.

Must run now, will add more info later.

#4

I scanned through the video and cropped a few images of the End caps floating around from the first pop at ~95m:


It is blurry, but the flange on the right of the photo is the only portion of flange left on the end cap.


Here it is again. Note, the copper tube in the pressure gauge was bent from the rapid decompression/re-compression when the first and last tube popped. The first implosion pushed the needle ahead ~20 psi. the final one pushed it back ~10 psi for a net of ~10 psi above actual pressure. The gauge seems to be linear, and the final depth of the ROV at 228m is close to what we should expect from the neighboring depths on the map. Here are my notes:

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Just more angles on the end cap


This one shows the damage to the underside.


The pictures are probably enough to get the idea, but the video fills in a lot of the blanks.

#5

I have been considering the difference in depth of each tube failure.

Given the first and second(at least partially) were end cap failures, it is not surprising that my original OROV end caps failed first. They were 25% thinner than the second (I will refer to them by number in order of failure) and so the second was 30% thicker than the first. It is interesting that the second was only at ~8m greater depth. That combined with the partial failure of the end cap and the slightly longer tube suggests the e-tube failed as soon as the end cap began to fail. (the second was 1/4" longer than the first, a change I made since my original tube was cut more smoothly) In the first, the e-tube was still strong enough that the end cap failed along ~75% of the flange. In the second failed along ~25% of the flange.

I can only guess about the third failure. It is on the far side of the fourth tube (and raspberry cam had homeplug issues). It occurred only ~4m deeper than the second and ~12m deeper than the first and had the same thickness of end caps as the second, (though one end cap was solid). Its Tube was another 1/4" shorter than the second (so 1/2" shorter than the first). The reason for the shorter tubes is to fit in the OROV housing. I must have thought some of the tubes would survive...

The forth, at ~130m is interesting. It could be that the 6 1/4" tube was stronger due to having less distance between bulkheads (the end caps). But it also could have leaked. If it was half full of water (and if no air had escaped) it would be able to go 10m deeper before failing. It was the raspberry cams job to watch for this as it has a narrower field of view. The ROV was supposed to watch everything with its wide angle lens.

The End caps on OpenROV#272 didn't fail at all. They are 50% thicker than the second or third. Another difference is that they have a 1/2" core rather than a 1/4" core. Either way, ~230m is more than double the depth of the second and third. and less than twice the thickness of end cap. I may have been only a few feet from being ROV dispossessed.

There really is a ton of info left to pass on about the test. I have a lot of work to do (at work) until at least mid January, but i will try to find time to add more bit by bit.

I didn't really have time to write this, so I won't have time to edit it before pressing 'add comment'. sorry!

#6

Thanks for sharing your great data Darcy!