One day I was randomly browsing the I Want One Of Those website when I stumbled upon a tiny cheap radio-controlled submarine. I just couldn't resist it. When the package arrived and I opened it, I immediately realised that the submarine did not have any pitch control. In fact, it only had these functions: full forward, full backward, rotate left, rotate right, plus the combined movement and rotation.

It was hugely disappointing. Here it was, a submarine floating in a 3D pool of water but behaving like a car driven on the floor.

My first thought was to buy another one and concoct a hybrid monster which would have all the necessary controls. But then I decided to design one from scratch. Here's a couple of drafts I came up with:

submarine3.jpg thumbnail submarine2.jpg thumbnail

The diameter of the body is slightly bigger than the diameter of a 1 pound coin. This is not just a random design - I actually found the smallest engine and battery I could, and designed the smallest hull possible around them. It's designed for these:

  • Micro DC 1.3 0.03 (x3) - miniature coreless 1.2g motor
  • Kok145 - 3.7V 145mAh Lithium Polymer cell
  • LB1836 (x2) - dual H-bridge IC (each drives two motors)
  • The brains of the submarine was going to be a tiny Wi-Fi radio chip made by the company I work for (way smaller than the motor driver IC). It was going to run all the (small amount of) control code + the radio link to the transmitter, which was also going to use another one of those chips.

It's been more than 6 months since then, and I can see some really nice tiny motors on Precision Microdrives website now, and cheaper too.

The most expensive part in this project is the hull - since it has to be custom made in a small quantity. I was going to get one made using Selective Laser Sintering, but never got round to getting a quote and gradually lost interest in this project. Which is a pity since the hull design is finished - all the supports for components are there. There's even a hole for the wires running from the body to each engine, which can be seen in the right image (if you click on it).

I'll post pics if I ever build this one!

Update - a friend of mine has bought a CNC router and has generously offered me to get the hull machined from acrylic. Unfortunately the above design is not machineable. I recently redesigned the hull around the same motors and batteries to make it CNC machineable:

sub2-front-side.png thumbnail sub2-vertical.png thumbnail

More images of this design: Submarine2