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how do you make a robot completely waterproof ? Answered

especially the motors , as i am participating in a competition which requires the whole robot to be fully submerged in water
i am looking for it to move freely and without it from getting shot 

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Josehf Murchison (author)2015-11-23

Have you seen the water pumps on Aquariums?

They use water proof brush less motors in the pumps that can be converted for use in the robot drives with a little work.

The electronics can be sealed in resin or a water tight container.

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iceng (author)2015-11-22

Yes !

Fishing Troller Motors for water are prepared by extensive varnish or epoxy encapsulated low voltage wingdings and explosion-proof bearings in a sealed motor enclosure.

You can make a salt water jet propulsion machine with no moving parts. Just an electric current passed through the water in the presence of a magnetic field.

BTW, Use fiberglass Armour to keep it from getting shot.

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Nyxius (author)2015-11-22

The simplest way is to build your robot is such a way as to not need waterproofing.

(i.e. use water rated servos and motors).

In the very probable event that budget restraints prevent you from buying these over priced parts then there are some simple tricks.

1) After you finish your electronics, cast them in a paraffin wax block.

The water will keep the paraffin from melting and the paraffin will keep your electronics dry and safe. You can also use some hydrophobic treatments for this. Note that some are sensitive to high temperatures, so don't let your chips get hot.

2) Use oil baths to protect your motors. This means that your motors and servos operate in a balloon of sorts and do work by stretching the balloon.

One simple example of this would be to use a flipper instead of a propeller. back and forth oscillations through a rubber/foam membrane are easy to waterproof and are ubiquitous in nature. An added bonus in this sort of design is that the oil helps prevent compression in deep depths.

3) use brush-less motors.

They are a little more expensive, but since there are no exposed contacts, there is nothing to short out in water. Note however, that these motors are sensitive to clogging due to junk in the water.

4) completely enclose your robot and fill it with de-ionized distilled water.

Pure water will not conduct a current contrary to popular belief. If you do a good job with tolerances in your enclosure, then the rate of impurity diffusion will be low enough to protect your robot for a long time. You can use an electrode to measure the purity of the water and warn you if it starts becoming unsafe. You will likely have to rinse the robot several times with clean water to get rid of dirt inside it.

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