I came up with the ROVVor after thinking about how to create a minimalist, cheap, and easy to build ROV. I figured the first thing I would try would be an aquatic version of the popular land-based 'brushbot' which can be built with just a toothbrush head and a vibrating pager motor.
So I put a pager motor into a centrifuge tube (see figure I
), and put it into a pool of water. It vibrated and I could see standing waves created all around it, but it didn't translocate (it didn't move through the water).
So then I tried adding little bristles to its sides (see figure II
) and still nothing happened.
Finally, I starting thinking about adding a 'wave-sail' to the robot (see figure III
) to take advantage of the waves created by the vibrations. I based this idea on the fact that one can use a fan on a sailboat to push the sailboat (see this great video: http://www.youtube.com/watch?v=0CrXvOKPymk
). When I added this 'wave-sail' the robot started moving through the water
However, when I trimmed the 'wave-sail' down a bunch (see figure IV
) the robot still moved through the water, even faster than it had before
. That's when I realized that the trimmed down 'wave-sail' was not acting as a wave sail at all. So I added sawdust to the water and saw a bunch of standing vortices all around the sides of the vehicle. I drew the vortices as I saw them as can be seen in figure IV
). I then added some weights into the tube (little pebbles) and saw that the ROVVor could move even when completely submerged
Then I thought that maybe if I put the same bendy straw on both sides of the vehicle that it would move even more powerfully through the water (see figure V
) ,but when I did that it didn't trans-locate anymore! So it seems like the ability to move through the water is dependent on the vehicle's asymmetry and on the standing vortices created around it.
In the future I'm planning on trying a design in which multiple ROVVors are attached to each other (see figure VI
) via a semi-flexible connection. In this way, by selecting which ROVVors to activate or deactivate one could selectively steer the whole structure in a desired direction. Because the connections are semi-flexible they would not propagate the vibrations from one vortex-drive subunit to another.Note:
I haven't yet created a fully self contained version of the ROVVor because I couldn't find batteries small enough to fit into my centrifuge tube, and it's hard finding a water-tight tube that would fit a battery and the motor. I'll update this instructable if I find a right-sized tube and am able to implement a fully self contained version.