Hardware

Chassis

The main chassis is made of King Marine Starboard. It's an HDPE plastic designed for marine environments. It's slightly buoyant and easy to work with. I believe this is the same material used in the BlueROV2. You can cut it as if it were wood. It's a bit expensive but you should be able to get all the material you need for about $60.

I was able to mill the smaller top plates on my 3018 CNC router. Which is definitely the way to go. The larger side panels I had to cut by hand with a jigsaw and a drill and router. It was a much bigger task than I expected. My solution was to print out the templates and glue them to the board as you can see to the right. As you can imagine this was less than ideal.

Here are the SVG files I used to create the templates and GCODE for the CNC.

Electronics tray / Camera gimbal

The electronics tray is where all of the internal electronics are mounted to inside the main enclosure. Although the official tray from Blue Robotics is made of aluminum I laser cut mine from acrylic. You will need to either purchase the long blue standoffs that you see in the image below to complete the tray or come up with some other solution to secure the 3 cut pieces together. The acrylic material I used isn't quite the right thickness and I needed to sand out the tab locations on the end pieces slightly to get it together.

Here are the SVG files for cutting the main tray

STL files for the camera gimbal. These have been slightly modified to fit my particular camera.

Thrusters

Finding good affordable underwater thrusters is almost impossible. The T200 thrusters sold by Blue Robotics are amazing feats of engineering but at $179.00 a pop that's a significant chunk of change when you buy 4 - 6 of them. While my thrusters aren't quite as good, at $20 each the compromises are worth it... Sort of.

You can read more about programming the ESCs here.

Motors

The motors I used for these thrusters are the BRF2838 350kv. So far, they are the only brushless motors I've found that are specifically designed for underwater use. Technically any brushless motor can be used underwater, however these are designed with a completely sealed armature which helps to keep out particulates and protects from corrosion.

They are not perfect, however. They have 2 critical defects that I think will need to be addressed.

The motor bell is steel and is not well coated. This will allow corrosion and rust. Another coat of paint on the outside may help but I don't know how well I can protect the inside of the bell where the magnets are.
The motor uses standard bearings. While this works fine in air, high pressure water quickly removes any lubrication and likely causes rust as well. I can already hear the bearings going bad after only a few hours of use. My solution will likely be to replace the bearings with bushings which is what the T200 thrusters use.

Fairings

I designed these 3D printed fairings to be quick and easy to print in a single piece, without the need for supports. I was hesitant to use 3D printed PLA parts for underwater use but so far, they have been holding up very well.

Thruster fairing STL

Propellers

I'm using the Blue Robotics propellors used on their T200 thrusters. They are a bit too large for the motors I'm using. The BRF2838 motors are usually paired with a 60mm propeller but those are almost impossible to get. They don't fit on the motors as they are but only require a tiny bit of filing to get the mounting holes to line up.