DST-700+ motors for salt water (Mark motors part 3)


#1


Before(on the left) and after photo of the Turnigy DST-700 with Marks latest potting procedure.

Hello ROVers,

I live down near Monterey so I'm only really interested in a sturdy salt water ROV. Mark has been nice enough to help out with motor trials to make that happen. (see previous posts here and here) Previously we were using the stock OpenROV 2.6 motor and a 3d printed mold. This latest test was done using the DST-700 motors by turnigy, renamed the DST-700+ for their upgraded bushings and potting along with some tape. The new motor has long magnet wire leads so you don't have to cut the wire at the motor and have a nice pin.

Here is the process we used for this round of testing (they will be going on my ROV soon and in to the ocean).

Supplies

  • Rustoleum self-etching primer (this will probably rub off but trying on the bells)
  • Cheap mini paint brushes
  • West marine epoxy (the slower the better)
  • 2 of Marks bushings per motor
  • Cheap plastic cups (for epoxy)
  • Scale (for epoxy)
  • Blue painters tape(makes the epoxy mold)
  • Toilet bowl wax(Keeps epoxy out of the top motor bearing hole)

Procedure


1) Remove the C-clips, motor bells, and bearings from the motors.


2) Fill the top bearing hole(it will be facing down when you epoxy the motor) with toilet bowl wax, making sure not to get it on anything else or the epoxy won't stick then give the motor a nice wipe with isopropyl alcohol to make sure it's clean.

3) Make a mold out of blue tape, wrapping around the outside of the motor first and then the bottom to keep the epoxy from leaking out


4) Heat up the motors a bit under a light to get the epoxy to flow really well into everything (or use the slowest epoxy

5) Measure out 10g resin and 2g hardener, mix

6) Pour in to each mold until a little bit over the height of the coils


7) Let sit over night, then demould and trim off the excess

The critical dimension is really just around the diameter of the motor. So the top and bottom can be a bit messy, wavy, etc but try to make it nice.

8) Super glue in the new bushings



9) Use a mini lathe to clean up the outside diameter of the motor since this is the critical dimension. Don't go crazy and make sure you center everything on the lathe so that you don't cut in to the windings.


10) Paint the coils and any missing parts with a new batch of epoxy, if you scraped the core with the lathe you can put a thin coating on outside of the core as well but keep it thin!


11) Give the motor bells a coating on the inside with some self-etching primer. This may just get scraped off but we're testing here!

12) Give the shaft a little sanding to clean off excess paint, you should probably tape it or something instead...but I'm new.

13) Make sure your motors spin cleanly (sand if they don't or go back to the lathe), add them to the ROV, and go back in the ocean!

Let us know what you try, I am interested in making the ROV really nice so people can just use it and not have to mess with it!

Have a good one,

Matthew


#2

This is what I was thinking of doing to my stock motors. Any reason why it shouldn't work?

Instead of using epoxy, I was going to use a two part resin.

How would I get hold of some of Marks bearings for the stock motor?


#3

I think he is making a run of bushings. We did a similar process on the stock ones as well (my ROV has one of those that is really nice). The stock motors won't fit the new bushings though because they are a different size I believe.


#4

Hi

A question about the West marine epoxy, is it a specific one from them?

As here in Denmark it's difficult to find West products..


#5

We are going to give this a try with the stock motors. How do we go about getting a set of Mark's motors, in case that doesn't work?


#6

Why isn't there a reply button?

We sealed up the stock motors using the tape epoxy mold. It took a few tries but now the motors show no continuity to water! Hooray!

http://jacobswellproject.blogspot.com/2014/07/motoring.html

http://jacobswellproject.blogspot.com/2014/08/excuse-me-while-i-drip-this-out.html

http://jacobswellproject.blogspot.com/2014/08/grinding-for-mine.html

I would recommend that everyone do this as part of the assembly of the OpenROV. There is no reason to stick motors into water if you don't know if they are sealed as it is only going to cause pain and confusion later.