Custom sealed stepper motors for rotating thruster

propulsion
water-proofing

#1

I’m working on a small ROV for shallow waters (max ~3m), requiring precise manoeuvring in 3D in tight spaces. To achieve that I want to use fully sealed thrusters that can be rotated a full 360 degrees.

To keep things mechanically simple and affordable the plan is to use a stepper motor with a hollow shaft for the motor phase wires and added sealing features, bolted into the side of the ROV. The stepper motor itself will be in a dry space, the shaft will protrude and hold the thruster assembly.
This is the generic use-case I have in mind (don’t mind the thruster itself, it’ll be replaced by a sealed unit with mounting flange, etc):

The ESC (and stepper driver) would be mounted in the chassis, feeding the phase wires through the shaft. The shaft can the be filled with a sealing agent, if required.

Potential issue is still the screw holes, they require using some form of thread sealant for properly closing off the whole thing.
I’d love to hear any other possible pitfalls or change suggestions (provided they don’t hugely increase the motor costs or weight).

These can be made for around 30-45 USD a piece in sample quantities according to quotes I got on Alibaba. If anyone else finds these motors interesting I’d be happy to arrange introductions to the supplier I’ll end up choosing to tag along in some form.


#2

Base drawing (one image per post limit):


#3

Interesting concept. For an ROV, wouldn’t you need 2 motors for balance? I would think the drag of the unit would cause constant drift for the motor and you would not have 3 axis movement.


#4

The idea is to use multiple of these indeed, in my case 4 of them, one on each corner of a relatively flat rectangular ‘box’, with the stepper axis horizontal and perpendicular to the longest axis of the box. I don’t need very high speed operation, so a little friction is fine in this case.
Depending on what you require you can also make only one or two thrusters rotating, of course.