[PSUBS-MAILIST] Brushless thruster test

[Alan James via Personal_Submersibles]

I had an initial pool test of my brushless thruster yesterday.Thruster is on projects page http://www.psubs.org/projects/1235435392/brushlessthruster/A bit of a mixed bag. Firstly I was testing it on 36-37 V & not 44 that it was designed for,due to size restrictions on import of Lithium polymer batteries. I will buy the additional voltage.   I was getting 5kg (11lb) thrust off 150W & 10kg (22lb) off 515W, which is comparable &better than some commercial direct drive BLDC thrusters that I have specs on.However I got to 13kg thrust & the propeller seemed to slip at that point & even though it was running at 2,200W I wasn't getting any more thrust. I was only a couple of feet out from the pool edge when testing, so that could be contributing.Another factor could have been that the seal leaked badly & the motor was short circuiting through the water. Why did the seal leak? Possibly I damaged it hammering it in to it's housingor because I didn't polish up the propeller shaft. I have other motors I will be testing, so a lot more work & learning to do on this one.I did notice I had the same problem as  Cliff, with the motor wiring starting to wear throughwhere it comes out of the housing.Cheers Alan
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