"Plastic motor"


Hi folks

I saw in tis forum different attempts to waterproof the thrusters. Based on some of those ideas I tried my own way to do this. First I also wanted to seal the the windings with epoxy and replace the ball-bearings with inox bearings. Unfortunately I could not find stainless ball bearings in the correct size. I did find however some plastic ball bearings (spare part for rc-cars), but they have an outer diameter of 10mm and therefore don't fit into the original seatings.

So I decided to move on and make room for those plastic bearings.

my first step was to make a dummy for the motor on my lathe and with help of that I made a silicone mould, where I could place the motor core and pot it with epoxy.

Here you see the dummy and the mould

The dummy and the potted motor, still with the original diameter of the bearing-holder

Here you see the plastic ball - bearings and the already adapted motor as well as the new backplate that has also room for the bearing.

before mounting th new backplate, i had to cut down the aluminum holder for the old backplate. the new one (casted resin, I made a mould also for that) fits into the original hole (see below)

before glueing the backplate, the inside of the aluminum tube in the motor needs to be coated with paint or resin

the finished "plastic motor" without any exposed metal parts. The plastic ball bearings do not run as smooth as the metal ones, but its still ok. In the picure also the motor connections are potted.

Of course you can argue wether it makes sense to do so much work on such a cheap motor, but for me it was just another challenge for my Openrov and a sort of "proof of concept" Now that I know how to do and have the moulds it's quite straightforward.

next thing I want to adress is a new and completely different propeller. I have some ideas there...



This is great!! I'd love to see a video of these props working on the ROV, and see how much it affects performance.

Thanks Hub!


Great work. I think I will be doing a lot of exploring in salt water, so maybe I should waterproof my motors too. Did you just paint the stator with thin epoxy? By the way David Lang - is there a place where all these cool mods are archived? I would hate to lose all these great insights in a mountain of forum comments.


Hi Andrew
If you look through the forum you will find different ways of waterproofing. Some people actually just painted both the stator and the rotor with different coatings. That does however not solve the problem with the bearings.
I placed the stator in my silicone mould after applying a thin layer of epoxy and the filled the mould so I got a nice and round epoxy block around the stator. This epoxy was then reduced a little bit with a lathe which I also used to make room for the new bearings.


Thanks - I should have read your post more closely. Keep us posted on how it performs!


have you looked into ceramic bearings for these?


Actually, no. Do you know a source for them?


They are expensive, but they also have SS.



I purchased hybrid bearings Stainless / Ceramic straight of ebay

3mm shaft 7mm OD 3mm deep bearings

3mm shaft 8mm OD 4mm deep bearings


on ebay,



If you haven't already done so, you may want to check www.Igus.com for possible plastic bearing solutions.

While I do not know the dimensions of the bearings needed (yet, 'm just a newbie in the openROV community) they do have a nice assortment. They also have high quality linkages, bearings, bit and pieces, etc that may come in handy.

Igus has recently made it easy to purchase in small quantities and, will provide samples on request. I have some experience with their products through my work; a great outfit all around.



Hello All,

Could someone please confirm the dimensions need for replacement bearings on the standard motors ? I do not have a caliper handy.




ID on both is 3mm OD on front is 8mm, OD on back is 7mm.


Thanks !!!



What's append If I do not waterproof the motors? (I will dive in salt water).

Thanks for the answers