What factors should be considered in choosing the brushless motor to prevent rust and damage in long-term use?
We considered two motor brushless
Our first choice
Our second choice
Which one can be more suitable and if not, what do you suggest other than your own brushless motor
I recommend you to use brushless motors build for the marine enviroment for example those you´ve posted are related to the flying commercial drones not to submarine applications althought they might work but theyre life span will be less than expected. The motor should be magnetically coupled and the stator might be potted with resin to avoid direct contact with water.
I can tell you Bluerobotics offers one of the best motors for harsh marine enviroments talking about relation between price and quality, but if you want to find cheaper and make some experiments take a look at alibaba we´ve tested a few with one of our clients from a research institute and we have no doubt that BR motors are better.
A submersible brushless motor is a compromise between reliability and motor output.
To be reliable the gap between the magnets and the rotor should be large enough not to be abraded by sand or small rock that can get in the gap between the magnets and the rotor.
However, too large a gap can affect motor performance in that the wider the gap the lower the magnet field felt by the rotor and vice versa the narrower the gap the higher the magnet field felt by the rotor.
Therefore submersible brushless motor design is a compromise between motor reliability and power output.
As Luis mentioned, neither of the two motors you posted would be appropriate for use underwater without extensive modifications. They may be lightly water resistant, but they would likely corrode very quickly and become unsafe to use or completely unusable after some time underwater. If you are unable to use our motors/thrusters, you can try potting/coating the rotor and stator of a motor on your own. You would also need to replace the bearings, going with a full ceramic set or with plastic bushings.
An interesting site, but some of the available products are overpriced.
They appear to get their maximum thrust of 4.25kg at an insane current draw of 25 amps!
They are still using brushless hobby quad types of motors (DT-700/750) like the original OROV2.X project which will eventually corrode/degrade when used in chlorinated water or salt water even with lubrication after every dive.
I have converted an OROV2.8 to BR M100 motors and it is very fast even on a motor thrust setting of one!