I have been asked by Open ROV to share my experience with my new OpenROV 2.7.
I assembled my ROV and vacuum tested it, -0.5bar for 30 min – All OK. After this I ran it in my bathtub. All worked well and as expected. I was unable to do more tests on functionality since I´m waiting for the battery chargers to arrive.
I decided to do a real life pressure test at sea, so I removed all electronics and batteries. I had 3x30m of line for this test. My dive computer and a led weight was attached to the hull. The led weights were needed to make the ROV slightly negative buoyant.
First test was to 30m. All well and no leaks. Second test was the full length 90m. I was very surprised when I pulled it back to see that is had imploded completely both main tube and both battery tubes. The implosion of the main tube was so powerful that it ripped apart the whole structure. Absolutely all acrylic part except from the battery end-caps with the O-rings was broken, including the ROV hull?!
I have taken some pictures of this. When reviewing the log on the computer I could see that the decent from the surface down to approx… 60m were slow and fine, but after that the speed increased rapidly. This indicates to me that the implosions happened at 60m.
The battery tubes weren’t actually imploded. They where squeezed flat and ruptured along the squeeze line.
I contacted OpenROV support, and they quickly replied –
“Sounds incredible! I’m guessing that the implosion of the battery tubes occurred around 60m which made the ROV sink faster to implode the main E-Tube. With batteries inside the battery tube, it’ll prevent the battery tubes from imploding at that depth and should be stable beyond the E-Tubes failure point. We would love to see and hear what you found out through this test on our forums. That being said, we can send you the replacement parts that you need in exchange for a forum post of your test! It’s always helpful to hear these things.”
Excellent support, thanks!
In the after math of this one could say that I should know that the battery tubes needed some support inside before this test could be done, but after seeing the last video I thought I was safe. In that test there is no extra support in the battery tubes. Is the video showing an earlier design with thicker walls in the battery tubes?