It is fun to make a toy vehicle with Lego, but it is even more fun to make one that actually works. [PeterSripol] made two Lego submarines, and you can see them in the video below. There isn’t a lot of build information, but watching the subs fire missiles and then getting destroyed by depth charges is worth something.
One of the subs is larger and uses a rudder to steer. It was apparently harder to control than the other smaller sub which used two motors thrusting opposite one another to steer. Looks like fun.
[Peter] found that he had to use lower frequency RC controllers to penetrate the water. The smaller one seems to be trailing a wire, so we think it may not have even used radio control. There were a number of custom 3D printed parts that help motors and other electromechanical devices.
There were a few things we were wondering about, though. The electronics used are pretty conventional, and soaking them in water is probably not great for their lifespan. It wasn’t clear to us also, whether the submarines had any buoyancy control. We think air trapped inside just kept them sort-of floating until the air escaped.
Our favorite model sub is also our favorite starship. If you want an example of buoyancy control, look at this past Hackaday prize entry.
The wire is probably an antenna wire. Longer for low frequency.
I had the same thought. You can see the end of the wire a couple of times, so I think it’s pretty safe to say it’s an antenna.
that would be a 27Mhz radio, I’ve had them working in a big pool, 2 – 3 metres
I don’t think he mentioned how much shorter wavelength is in a medium. It goes by the square root of the dielectric constant. Water is huge: 81. So antennas are only 1/9 the size of what they’d be in air. The attenuation is pretty bad in anything but distilled water though, so you just have to test and see.
Those bricks breaking apart at the end is soooo satisfying though. Good stuff.
would have been interesting to use ultrasonic communication. sub would just need a microphone and a good adc. though signal processing would probably be non trivial and require at least an arm processor or some kind of dsp.
We use acoustic’s to control ours good to a over a kilometer with a single hop horizontally or about 5000 meters in depth