Epoxy filling method for brushless motors


I have 3D printed temporary casings with Water Soluble PVA (Polyvinyl alcohol) filament to assist in encapsulation of the motor windings and magnet housing for brushless motors with epoxy. These parts are slip fit and no post machining required. Some touchup required with brush. This PVA material is somewhat pliable and has a bit of give. This is in evaluation phase. Water test to start next week 1/20. Material list:
Epoxy West System 105 and 205 hardener (looking at different potting compounds)
Water Soluble PVA (Polyvinyl alcohol) filament http://www.matterhackers.com

Pins from Molex connector 1.14mm dia gold over nickel plate

Printer MakerBot Replicator 2 with standard setting @ 215 C extrusion temperature no support



Are you planning to try it without bearings? For me it is the bearings that are the weak point (I can feel some roughness when I turn the props by hand). Our use doesn't put the same type of pressure that an RC car on land would. Especially once you have encapsulated them.

I am excited to see how it works either way!


I am planning on using an underwater rated bushing material in place of bearings.

Looks like the 3mm shaft is chrome plated with a smooth surface finish.

Ingus # H370SM-304-03 will post results :)


Holy Crackers! That is awesome!


Markgawa to the rescue. I can't wait to have some super motors.


Two motors are in the test tank fresh water first than salt.


Do they run properly with the epoxy or are you just first testing to see if they keep the water out?

They look great. :D


How is/did the test going/go?

I am far to excited to wait patiently with my mouth shut. :D


After about 130 hours of continuous cycling zero to full speed operation the control motor failed do to bearing ball bearings lack of lubrication. I have not received my saltwater delivery yet. One motor is still in tank cycling with fresh water 230 hours of operation no failure yet.


Revised test fixture to use less water with open rov parts


Nice test jig, looks like your printer is running 24/7.


This is great work Mark! I'm curious did the motors in the clear epoxy (above) run well in your test tank? Also is the bearing encased in epoxy or can it be re-lubercated?


So far so good. The motors are going to be disassembled and inspected before saltwater testing. On the test motors it is with bushing only so far.

For next test run one motor will have supplied grease and bearing shield removed so the can be filled similar to boat trailer wheel bearings so grease can be purged as required.


I was thinking about replacing the metal bearings with 3D printed plastic. Just a simple friction bushing. The bearings corrode very quickly and ceramic bearings are several times more expensive than the motors, especially when bought in small quantities. I see you have a nice solution - Iglidur bushing inside a brass ring (the outer bushing). I was looking for the outer ring, but I didn't find anything with the outer diameter. Maybe I don't have the right dimensions... according to my measurements, the first metal bearing is 7 x 2 mm and the other is 8 x 3 mm. Am I correct?



You mentioned using the Ingus bushing material. How was the fit for the

H370SM-0304-03 ? And what did you use to replace the 3x8x4 bearing?

Are you using thrust washers as well?


The fit is controlled by holes size in support material nominal shaft clearance is approximately .005mm. Both bearnings have been replaced. Planning on using one thrust washer at rear clip. Waiting on stainless steel clips.


Two of the epoxy coated motors are still running.
230 hours of fresh water mixed speed operation reverse-stop-forward full motor speed. The teardown has shown galling present at front bearing surface at rear slight wear .001mm and retaining ring failure by corrosion. The white paint was also having adhesion problems will omit next test.
The replacement 3mm stainless steel retaining rings have just arrived from Maryland Metrics.
Next run in salt water not to exceed ROV recommended RPM 1600 and also trying different epoxy.




Just received my first 2 mark motors today and am upgrading an ROV with some pretty critical salt water motor damage. The top motor is altogether missing the bottom bearing and the prop is no longer removable. Hoping for the best with these after I get 1 more to be salt resistant and explore the kelp forests trouble free!


For people following along with Marks motors there are two new related posts available here(part 3) and here(part 2 with video playlist).