GRAEY Thruster Issues- 9/10/26
We have been encountering many thruster issues with our Sub Graey. This is a series of events that went wrong, and how we overcame those challenges.
Opening #1 (August 23)
Hot glue over ESC 1
Graey was encountering issues with two of its thrusters. Thruster 5 was unresponsive, while Thruster 1 stuttered and sounded as if stalled. After confirming that the thrusters themself were fine, it was narrowed down to an ESC issue. Opening up the sub, the solder joint going to the Pixhawk for ESC 1 (for thruster 1) was weak and easily tugged it loose. However, I did not yet have the scope of looking down and checking the phase wire. This would come back to haunt me more than once. After soldering it back on, I figured since ESC 5 had everything soldered on nicely, the ESC itself must have been ruined. I took an ESC off of our sacrificial boat J Boog and replaced ESC 5. Running motor tests proved ESC 5 to work but the ESC 1 thruster stalled and stuttered in place. Thruster 5 would be fixed, by the other thruster still had a long way to go.
Opening #2 (August 28)
On the second opening, I was able to find out that the phase wire for ESC 1 had also come loose. I soldered it back on, as well as implementing strain relief by extending all the wires from ESC to Pixhawk and adding stress points with zip ties that tied to bulkier power and ground wires of the PDB. Unfortunately, running motor tests proved ESC 1 to be completely responsive this time.
Opening #3 (August 29)
Loose phase wires
The plan this time was to check all the continuity and wires. After this was confirmed to be fully continuous, I decided to take another ESC from J Boog. This time thruster 1 worked! But it was not over.
Opening #4 (September 5)
The day after the third opening, Graey was declared ready for water testing. However, during water time that day, the thruster stopped once again. It stalled and stuttered once again. By now, I had caught on that if you could hear the thruster struggling, it was most likely the phase wire, and if the thruster was completely dead, most likely the ESC itself was fried or the solder joints came loose. My assumptions were proven right after opening Graey once more. I found one of the phase wires of ESC 1 loose and flooded it with solder. Then, to make sure this never happens again, I did pull tests on all the phase wires for each thruster, and guaranteed that there would be no strain on any of the ESC solder joints. I also put hot glue over ESC 1. Thruster 1 was finally, truly was fixed.
Zip ties help provide strain relief
