Confused with OpenROV Building Tutorial

#1

Step 9 to step 14 in this tutorial describe how to make the brushless motor waterproof by changing the wire, glue the wire joint and applying a shrink tube.

We’ll need to make a few modifications to the brushless motors so that they can work underwater. The main modification we’ll make will be to attach new wire leads with waterproof insulation.

The goal is make no copper wire exposed to water.

In order to keep the motor waterproof there can not be no exposed copper wire. The wire that makes up the windings are covered in enamel to keep them insulated. The ends are the only part where the enamel has been removed and as such can be soldered to.

But at the end of Step 14 there is this line:

Consider potting the motors because they are not waterproof at this point. http://openrov.com/profiles/blogs/dst-70…

Didn’t step 9-14 already make the motor waterproof? So is the motor is now waterproof or not?

#2

Hi,

The modification you make to the wire leads doesn’t really make the motor waterproof. It stops the motor from shorting due to exposed conductors. It will operate this way, but maintenance is needed after submerging the motor to prevent corrosion (clean with distilled water, lubrication, etc) .

The additional step of potting the motor, I believe, is intended to prevent water getting to parts inside the motor which would prevent or slow down corrosion and reduce the maintenance needed to keep the motor clean after use.

Hope this helps,
Lenny

#3

The copper winding is coated with an enamel during manufacturing. The ends that you cut and solder are not enamel coated so you must make a waterproof seal around the connection.

The motor will function in water without “potting” it. However, it will probably last longer if you take certain steps to protect motor components, along with following the post operation cleaning and lubrication procedures.

The armatures upon which the copper motor winging is placed is made of a ferrous material which is NOT coated, so it will corrode after a time. The magnets inside the motor bell are made of neodymium which also corrodes rather quickly in the presence of salt water and other oxidizers. Finally, the motor shaft bearings will corrode after a while as they are steel and difficult to clean.

Here is what I have done in lieu of a full motor potting: I sprayed a very thin coat of rustoleum crystal clear enamel on to the motor winding assembly and the same on the inside of the motor magnets. I allowed this to dry completely. I then assembled the motor parts and made sure that the motor would turn. There was a small amount of binding so I lightly sanded the surface of the just coated motor winding in order to remove a small amount of the coating that I sprayed on. This protects both the winding assembly and magnets from corrosion.

The Bearings can be replaced with ceramic bearings that can be purchased at hobby stores or on-line. Ceramic does not corrode. The procedure for replacing the bearings can be found in these forums.

A good procedure to follow for after operations is to thoroughly rinse the ROV & run the motors for a couple minutes while submerged in a tub of clean fresh water in order to remove all salt water and dirt. Allow the motors to dry completely and then spray the inside of the motor with a silicone based water disbursing lubricant. This should be done after every day of operation.

I have found that coating the motor winding and magnets with a light coat of crystal clear enamel and following the post operation cleaning and lube procedures prolongs the usable life of the motors.

Hope this helps.

#4

We apologize for the confusion. @lenny_m_baker and @Ronald_Peters are correct with their posts. Some community members will pot the motors in order to help slow down the corrosion. Everything we do is open source (including the directions) and that change was a user submitted change that was added. I have removed it in order to reduce the confusion. The ROV will run successfully without potting the motors. You will have to maintain the motors which we talk about in the operations manual.