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Jun 19, 2019, 09:53 PM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Originally Posted by Trisquire
Curious why the ROV guys are unconcerned about silty water. I can’t imagine they like replacing bad motors any more than we do.

Because the ROV guys use motors in protective housings, often with seals for dealing with silt, salt or whatever. I've NEVER seen an exposed motor on a pro-quality ROV. Submerging a motor is not a problem though. Oddly enough, my last car had it's fuel pump mounted and submerged in the fuel tank itself. Gasoline actually flows through the electric motor to keep it cool. That's brave engineering.

This would be an example of a properly sealed and protected thruster: Example: https://ae01.alicdn.com/kf/HTB17S48J...er-ROV-AUV.jpg

Pro level thrusters aren't cheap though..Got 6 bills laying around?



Here's a a place to look around for whatever fits your budget. Some are just hobby motors placed in some kind of protective jacket or printed shell and are poorly sealed, so be wary: https://www.ebay.com/sch/i.html?_fro...Motor&_sacat=0
Last edited by AirDOGGe; Jun 19, 2019 at 10:09 PM.
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Jun 19, 2019, 10:44 PM
Intermediate Multi
Trisquire's Avatar
Quote:
Originally Posted by ZZ56
I'm sure the ROV guys are also concerned with silty water. If they're buying those AliExpress hackjobs posted above, its likely because they're cheap enough to be disposeable.
I see. Thanks.
Last edited by Trisquire; Jun 19, 2019 at 11:50 PM.
Jun 20, 2019, 02:31 AM
Registered User
I guess that it is a matter of perspective.


If you seal the rotor with epoxy and sort out the bearing issues ( both of which are easy & cheap) then you have a a $10 motor that lasts a year which is fine. Just have a few in a drawer ready to go. They are consumable items like propellers (& sometimes motors) on my model aircraft.
Last edited by ChrisE; Jun 20, 2019 at 03:08 AM.
Jun 20, 2019, 06:09 AM
Latitudes vs Attitudes
Bob Gaito's Avatar
I'd be curious to see a test-as to how long it would take for a ceramic bearing'd outrunner to fail when run in silty water, or salt water for that matter-I would bet that Joe average modeler would give up on the test long before it failed..
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Jun 20, 2019, 07:52 AM
Registered User
As I am sure you know most outrunner motors have 2 ball race bearings. In theory these are sealed & full of lubricant but neither is normally true and any lubricant that exists will not be waterproof (in cheap motors often very little lubricant).

In use water gets into the bearings and simply washing the motor after use will not remove it. Salt water left in a bearing will obviously not do any good.

The quick solution is to vacuum fill the bearing with marine grease but the better solution is to replace the ball bearing with a sleeve plastic bearing that will like the water lubrication and will not corrode nor retain water after rinsing.

Unless you run in incredibly gritty water I too suspect that it will not be a significant problem.
Jun 20, 2019, 11:27 AM
Registered User
Sure it probably won't fail the first year but what about when you take it out next year or 3 years from now? An o-ring is 50 cents compared to trying to source an identical $10 dollar motor a couple of years from now. I keep seeing this kind of logic on sub builds, sounds like people are trying to justify be lazy to me. I spend enough time replacing servos and speed controls that have died in sealed compartments to not want to go down this path.
Jun 20, 2019, 11:51 AM
Latitudes vs Attitudes
Bob Gaito's Avatar
[QUOTE=ChrisE;42132307]As I am sure you know most outrunner motors have 2 ball race bearings. In theory these are sealed & full of lubricant but neither is normally true and any lubricant that exists will not be waterproof (in cheap motors often very little lubricant).

In my above post-I mentioned ceramic bearings-either race ball bearings or bushing type...these are almost indestructible even without lubricant although they would be lubricated by the water that they would run in-winter storage..no problem.
I do suggest using a motor with a stainless steel shaft or replacing a steel shaft with stainless..
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Jun 21, 2019, 06:59 AM
Registered User
Gammon Iron's Avatar
Thanks for this discussion. I have very limited electrical skills. I sail large scale RC sailing ships. During the winter, I'd like to attach a pod motor to the false keels of my models for indoor display events.
Jun 21, 2019, 10:52 PM
Intermediate Multi
Trisquire's Avatar
I guess if it's easy enough to create a waterproof stuffing tube, you might as well just enclose the motor inside something. I remember owning one of these as a kid. A little waterproof pod that contains a dry cell and a motor.


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