I was approached by a gentleman who is a research scientist working with organisms that live in and under Arctic ice.. Most of the work is off the northern coast of Alaska near Barrow.
The water he works in is typically shallow (between 15' and 45'). He had purchased an Aquavu camera system (http://www.aquavu.com) and wanted to have me construct a platform that would allow him to move it around under the ice.
The insertion hole in the ice could be only 12" in diameter, so the ROV needed to be very small. Other design considerations included high reliability, ease of maintenance and repair, and cold climate compatibility.
Here is what I came up with:
April 20, 2012
The basic outline of the unit took a few hours to work out to my satisfaction. Propulsion is from standard 1100gph 12V bilge pumps and the main body is constructed from 3/4" PVC pipe and fittings.
The way I envisioned it to work is that it will settle naturally on the ocean floor, being ballasted slightly negatively. No thrusters will be needed that will stir up sediment and mean that you'll need to wait for it to settle before you get meaningful video. To move around, you just use the "up" thruster, which is vented near the rear of the unit. This was done so that the ROV will get pushed up and forward at the same time, allowing it to "hop" forward to re-settle in better position if needed. With the outlets to the rear, the sediment should be directed aft of the model, keeping the video clear (or that's the thinking, anyway!).
The camera is mounted on a threaded rod that can be adjusted up or down approximately 15 degrees according to your needs.
Once complete, I will create a complete list of materials used so that anyone interested in trying out this fun little project can follow in my footsteps.
These photos do not show the flotation pods that will be going on the top of the unit. Stay tuned for final photos and video!
April 24, 2012
I've added some nozzles on the two vertical outlets to bring the pressure back up to what is originating at the pump itself. My preliminary tests showed that the pressure from the two full-sized outlets were not sufficient to bring the model up from the bottom in a timely manner.
My PVC float at the top of the model was also not sufficent to float the ROV, and I am now looking to fabricate a styrofoam flotation module that will be mounted to the top of the ROV to offset its weight. The tricky part in this build is the 12" size constraint, otherwise I'd have based the model around a larger PVC tube that would have had a lot of flotation.
I've also started on the control box. Look for more updates probably by early next week (hopefully wet-testing!)
May 18, 2012
This project is complete (and should actually be shipping out today!).
Wet tests went perfectly and the model is a great, stable platform for the little camera system. I will say, however, that I'm disappointed in the thrust generated by the three RULE bilge pumps. With the heavy duty silicone cable, the model tends to "bind up" as it tries to twist the thick cable. In hindsight I should have just cut the impellor shroud off and attached a propeller, but that would have affected the ease of mounting and replacement, so there are gives and takes.
Check out the video!