I am on a Formula Student team and we have decided to design our own brushless AC motor. Our main issue is how we will cool the motor, since we want to keep weight down while also increasing power output. We will be making the rotor from forged Titanium (Ti6Al4V) and the housing from forged 7075-T6 aluminum. We want to use water (or a water/ethylene glycol mix) to cool the aluminum housing which will be cooling the magnets and coils. The main concern is that somehow the polarity of water will affect the workings of the magnets and reduce our power output. Is this an issue? Our other idea was to circulate mineral oil (like the stuff used in transformers) around the coils directly to cool them. Which would be a better method and do we have anything to worry about if we use water/EG to cool it? Second, we are wondering about winding the magnets. If we want a higher power to weight ratio, should we use smaller gauge wire and more winds, or larger gauge wire and few winds around the magnet?