Saturday, January 2, 2010

Mindstorms + Water ????

I think you probably feel the same way that I do about getting your Mindstorms electronics close to water. You don’t even want to chance it. But I would love the chance to build a robot that isn’t restricted to movement in two dimensions. I think I could create some really interesting stuff. The whole shape of a submarine robot would be completely different that things I make now. It would also take some calculations to get the buoyancy correct so it doesn’t float or sink too much.

Parts would likely be an issue. You might have to create non-Lego parts for ballast tanks. Not to mention the mostly ineffective propellers and screws that Lego makes.

I was looking around the other day, and I found three videos of people who don’t feel the same way about sinking their Mindstorms in water. It appears that all of these videos were made at institutions of higher learning so the possible loss of high dollar electronics would be covered by the school.

One thing I found really interesting is that in two of these videos, the 9-volt gear motors are fully exposed to the water. Reading some of the comments, the poster says that the motors are almost completely waterproof and very little water enters the housing. I still don’t know if I would take the chance with my own stuff.



  1. Before I saw the third one I was already thinking about the idea of using the LEGO pneumatic tanks as ballast. I don't know if they would provide more buoyancy if the tanks are left at atmospheric pressure, or if the pressure in each was really cranked up as high as it could go, and then capped off. What would be really cool would be to use the LEGO pneumatics system to pump up or discharge the tanks as necessary to allow the sub to go to different depths. More work, but that is how real submarines do it. I guess that might require a long hose/snorkel to the surface. But what a cool idea!

  2. I think you could easily use the pneumatics to adjust the ballast tanks, but increasing or decreasing the air pressure won't change the buoyancy. You would need to pump water (or air to displace the water) in and out of the ballast tanks to do that. Basically, high pressure air is no more buoyant than air at atmospheric pressure if the volume is the same.

    It would be very interesting to try to achieve neutral buoyancy, which is just hanging in the water, not floating or sinking. You would need a pressure sensor to do that along with control of the ballast tanks. Then be able to 'drive' around at that depth. There would be a whole new set of interesting challenges.

  3. I believe that Direct Current motors aren't as prone to water damage as AC current, and you could safely submerge them. Not going to try it with mine quite yet.

    Pressurising a tank with air makes it heavier (ever so slightly) so it would be less buoyant. Real submarines use tanks of compressed air to blow out water from other tanks, this might work in lego if your air pressure was high enough to displace the water and the air didn't just escape as well.