Be careful when putting the motor bells back on: don't let them "snap" into place


#1

I accidentally knocked out the ball bearing on the back side of one of my motors ... I suspect because I was careless in letting the magnets "snap" the bell back on. If you do that, and if the center shaft is not perfectly well aligned, it can push the ball bearing out.

The symptom in my case was that it became very tricky to get the motor bell back on such that it rotated freely.

And then, even once you get it back on, under load (out in the pond yesterday) it can come right back out, and cause bad things to happen (the motor uses much more current than it should, the magnets bang against the electro magnets, the bell/prop shake and don't really turn very well).

I noticed something was wrong because when I asked the ROV to go straight, it would curve very strongly left because my right motor was messed up.

Anyway, I unscrewed the motor mount, saw that the ball bearing had nearly fallen out in the back, pushed it back in, remounted the motor, and very slowly put the bell back on.

It could be I have a bad motor (whose ball bearing falls out too easily) ... has anyone else seen this?


#2

From what you said there is a few things you can do. One is to replace the C-ring that came with the motor, as this will hold the assembly together. Alternatively you can use something like blue loctite to keep the bearing in, but with this method you need to be very careful not to get any inside the bearing itself. Hope this helps!


#3

Thanks Jacob. For now, I just pushed the ball bearing back in, re-mounted the motor, and then very carefully put the motor bell + propellor back in (not allowing it to "snap"). I'm hoping it just stays in place; it is in the other two motors ...

I agree re-installing the C-clip would be best, but I don't think it's possible (easy?) to then re-mount the motor, because the bell blocks access to the screws? And also, I like being able to pull the bells off and blow the water out of the motors / let them air out. Even when I spray with silicone before the dive, the motors still get rusty ...

Blue loctite is a neat idea. I agree the risk of accidentally getting it inside the bearings is scary though...


#4

we replaced my bearing with brass bushing. Mostly because my investigations are in salt water and the open bearings would be near immediately fused anyway. Brass bushing seem to work very well :)


#5

Thanks, which brass bushings / from where did you buy? This seems like a useful upgrade!


#6

we machined them. I didn't check to see if there were any commercially available...