General motor question


#1

I have the Hobby Wing motors and just took my ROV out for a dive this weekend (In Tahoe with the OpenROV gang!)

I noticed just now when I got home, one of the rear motors wasn't spinning when I tried a thrusters check. I pulled it off and it's all ground up inside. The ROV had hit the sand a few times so I'm figuring it was the result of the motor spinning with sand inside the motor. How can I prevent this and has this happened to anyone else?

Thank god these parts are so cheap, I just want to know if there is a way to keep the motors lasting longer or if anyone has any tips on preventing this from happening?



#2

Hi Anthony:

We had a similar problem with our breathing apparatus during a dive in "dark waters".

The solution was quite simple.

We used the final end of a stocking (that which goes around the foot toes), and wrap the regulators up with it.

The same solution can be applied to the motors.

A kind of cage must be built around the motors for preventing the stocking from tangling up around them.

Regards

-Ion-


#3

Thanks for your response Ion! Are you saying that you literally just cut the toe section off of a sock and (ziptie?) cover the motor entirely minus the output shaft? Sorry for my confusion, this sounds like something I should be doing :)


#4

Hi Anthony:

We used that "invention" in order to prevent our breathing regulators from being filled with solid particles while diving into a cave.

And yes, it was made by cutting the toe section of a stocking and covering the whole apparatus with it.

For the motors, a kind of cage must be built before setting the stocking (not a sock that is too thick and heavy), or it would get tangled up on the motor rotor. (Remember you are using "OUTRUNNERS").

In the attached pic there is a proposal:

An acrylic 3mm thick exagonal plate is set between the motor and the propeller.

Exagonal better than circular: Less interference in the propeller flow.

The hole diameter in the center is big enough for avoiding touching the shaft.

Six copper bars are set at six holes made at each corner of the exagon, and a fourth copper wire makes a ring, sorrounding the six bars, and welded to each one.

Finally the six bars are attached to the motor mounting plate, by drilling holes and epoxy.

Once this cage built, just put a piece of a stocking or similar "silk like" fabric around the copper bars.

Copper wire: At least 1mm diameter.

If the bars are changed by brass screws, the cage will be easily mounted and dismounted by means of nuts at the end of each one. (Brass, not steel, for making welding easier and colder)


Minimum exagon radius: 18mm

Minimum center exagon to center of bars: 16mm

- Regards


#5

Sounds like a job for Marks 3d printed sand guard too??


#6

Wow Ion, that looks like a fantastic idea! I'll have to 3d print a prototype and test this out :) Thanks a lot for your insight and recommendations!


#7

Hi Mathew:

May you provide the link to Mark's guards thread ?

Anthony:

Thanks for your appreciation.

Kind regards

Thanks