Hi,

Welcome to the Build Log! This week, we thought we could show you the first ever underwater drones we've built.

You might have heard us mention multiple times that we've been working on underwater drones for the past 7 years (it's true). We started this journey with very little knowledge about building anything really. Today we'll show you our first ROV prototypes, tell you exactly what we've learned from building each one and how we improved later on (so you don't have to make the same mistakes yourself).

First prototype

This prototype was supposed to be a very simple "proof of concept". It only had one horizontal thruster and one vertical thruster. We intentionally used very simple electronics (just off the shelf RC reciever and some ESCs) - to make sure that our ideas about how to build these things were correct.

What we've learned from building it:

• We need a cable connected to the drone and the reciever on the surface, so that you will not lose signal when you submerge the drone,
• We need to choose the motors carefully and make sure that their torque is large enough to operate in the water instead of the air. In this prototype, none of the motors did spin (because the drag underwater was too large),
• It's important to make the drone neutrally buoyant so that it doesn't float, like this one did,
• We need to develop a better process for sealing the drone, because this one leaked

Second prototype (CPS Micro)

For this one, we decided to simplify the idea even further. We created a design, which uses a printed shell that is as small as possible - so that the buoyancy would be smaller. We even chose better motors and used a cable. Since the drone was small, it sank and wasn't neutrally buoyant, like we intended.

What we've learned from building this prototype:

• When we used only one power thruster for the drone, it rotated around it's axis while swimming forward. You can see this effect in the video below:

• We need at least a 3-motor configuration for an underwater drone to be truly controllable,
• We need to develop a better process for sealing the drone, because this one leaked (once again),
• We need to develop a process for ballasting the drone so it will be neutrally buoyant instead of negatively buoyant

Third prototype

This prototype was the extension of the CPS micro idea. We fixed the issue where the drone rotated around it's axis of rotation by having a 3 motor configuration. The drone could turn from side to side now and even regulate it's depth by using a vertical thruster.

We only tested this drone in a bathtub but it worked really well compared to all the other prototypes. It was pretty tricky to steer and it didn't submerge very well, but it definitely was the best so far.

What we've learned from building this prototype:

• We need a better ballasting system than filling up the bottom of the drone with sand (we actually thought that this was a better idea than metal weights),
• We need a better electronics system, because the very simple system with an RC reciever and ESCs required a lot of manual control and skill to operate the drone,
• We need to develop a better process for sealing the drone, because this one leaked (once again!),
• We finally need to integrate a camera,
• This drone looked very basic, we needed to make a much prettier design (what were we thinking lol

What we needed

What we would've loved during those first couple of months is guide to getting started with underwater robotics. And about 7 years later we've realized our dream of making an assembly Kit for those of you getting started now - we call it the CPS 3 Kit. It also comes with the CPS 3 course, which will teach you everything about how the drone that you'll be building works.

You don't have to buy any components separately, because they're all in the one box delivered to you.

Cheers,

Piotrek, CPSdrone

PS: You can access all of the previous releases of the newsletter here.

PS2: Those of you who are with us the longest might have noticed that this is a re-relase of a newsletter we wrote almost 4 years ago :)