A few thruster questions

[marine+man]

I'm a real novice when it comes to ROV's but it seems the propulsion system is the heart of the whole machine. I'm looking to build my first and have decided to build around the thrusters once I've chosen them. I kind of like the idea of brushless motors in oil and have a few questions:

1) From what I have read here, a problem with oil bath motors is the slight leak around the shaft seals due to pressure differential. Could one not incorporate a diaphragm to the motor housing which would equalise the internal pressure to the external?

2) If so, would the extra work of adding a diaphragm be worth it? I mean how much of a problem are the leaks in reality?

3) The engineer in me tells me that an equalised pressure system would allow for a more gentle shaft seal which would in turn allow for less power wastage on what is a very small motor. Relevance?

Thanks in advance

[rossrov]

Welcome Marine-Man. Yes, Yes, and Yes