On and off I’ve been working on adapting OpenROV pieces for deeper-diving ROVs. Here are the dxf files for some battery tubes I made that can go much deeper than stock OpenROV units:
Deep Battery Tube DXFs.zip (64.5 KB)
The design is similar to tubes I built and tested a year and a half ago at Lake Tahoe, but those were based on the OROV 2.7 battery tube. These are based on the 2.8 battery tube, with the nice twist-lock on the front.
Here are the pieces all laid out and ready for assembly. Note that you need to cut two of the 3mm discs for each forward endcap:
There are three differences between these tubes and the stock 2.8 tubes- the forward and aft flanges are now 6mm acrylic vs. 3mm, the PETG tubing is twice the stock thickness, and the clearance for the 3mm discs on the forward endcap has been reduced, to minimize the chance of extruding an O-Ring.
Here’s a shot of the thicker PETG tubing. It’s available from McMaster-Carr, here:
To eliminate the chance of water hosing through a wire and into the tube, I stripped off some of the insulation on the (+) lead wire, and soldered the strands together to fill the space between the strands:
The lead wire is then adjusted so that this soldered area is inside the potted area of the aft endcap. Here’s a picture of the aft endcap, just before attaching the spring terminal:
Other than this modification to block water, assembly of the battery tubes is identical to the 2.8 units. Here are shots of the potted tubes and forward endcaps. The thicker flange pieces are noticeable in the photos:
Before taking these to Tahoe, I decided to do a test run of the tubes in our pressure chamber, which can go to a pressure equivalent to 200m depth. Here are the tubes prepped for the test. Note the hot glue on the ends of the wires, since I want to use these tubes on an ROV, and didn’t want to push water up into the wire strands:
Here are the tubes in the test chamber. Thanks to Brian Grau for helping me with the test.The tubes went to 200m and back, with no trace of moisture inside the tube.
The earler 2.7-style tubes survived a dunk to 280m in Lake Tahoe. Once the weather clears in Tahoe I plan on testing these to failure, initially with a test to 300m.
If you decide to copy this design for your own ROV, please write back and let us know how they work!