@ROVthruster.com - Thanks for sharing! @kaosrulz is right that this is fairly close to direct advertising, but we do like to support anything that encourages more people to get involved in marine robotics. Congrats on putting this together and sharing it!
Since most of your claims are directed towards our T200, I’d like to take a second to address some of the reasons why your thrust/efficiency performance numbers are similar to ours.
Max Thrust: With a similar diameter propeller and similar power output, I’d expect you to get similar thrust. We generally get a little performance hit when using 3d printed stuff because of the rough surface but it looks like your propeller area might be a little greater, which would make up for that difference.
I’d also like to note here that to get to your max thrust you are going way beyond the ratings for this motor. According to the HobbyKing page, the motor is rated for 13A max. I’m sure it will run at 25A for a little while, but it will likely burn out pretty quickly. I’d recommend being very careful with that. I think a more realistic and sustainable “max thrust” is probably around the 6.5 lbs / 13A point.
Efficiency at Low Power: I’m not sure about the details of your design, but there are a few factors that could contribute to that:
It looks like you’ve got a little larger propeller area, which will almost always lead to more efficiency. There’s always a trade-off between thruster size and efficiency.
We have a larger than normal air gap on our motors, which decreases efficiency a bit but prevents sand from jamming the motor. We’ve tested the DT700 before and it can’t handle sand at all - it will jam almost immediately.
For anyone here doing thruster research, I’d like point out a few other things:
The DT700 (and most other brushless motors) don’t have any corrosion resistance. I see that you’ve added epoxy to it, which will definitely make an improvement but the rotor and magnets will start corroding after a few uses in saltwater.
This motor also has both steel, stainless steel, and aluminum parts in contact with one another, so there will be pretty rapid galvanic corrosion one submerged in water.
This motor has unsealed ball bearings (as opposed to plastic bushings in the T100/T200), which degrade pretty quickly and will either break or severely decrease the efficiency.
This design likely has low insulation resistance to the water, which is important for safety and galvanic corrosion reasons. Most off-the-shelf motors we’ve tested have nearly direct electrical contact with water. That also prevents them from being used in MATE competitions according to the MATE rules.
Again, nice work on putting together this design! We strongly encourage all DIY marine robotics efforts and I’m sure these will be helpful to others. I only share this info to make it clear to anyone else who happens to be reading this. Keep it up!