After a particularly long dive (7+ hours) we were decontaminating the BROV2 and heard some rattles. Loose objects rolling around somewhere in the ROV. Weird. We thought it was debris, but the unit was otherwise clean.
After rolling, shaking, etc to find the culprit we took an end cap off a vertical thruster and a shaft collar was laying in the housing. No biggie, at least it wasn’t lost.
After checking, five of the eight had fallen off. We couldn’t be certain, but there didn’t appear to be any thread locker on the setscrews. We replaced them all, and set the shaft axial play at about 0.5mm. The bushings all felt ok.
We will add a prop free play check to our preflight list, but wondering if this is just an anomaly? Any suggestions for more or less play?