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Six Thruster ROV HDPE Frame Conversion to BlueROV2 Frame


(TCIII) #1

Hi All,

I am constructing a four thruster ROV, with two WTCs, out of 1/2" thick HDPE panels.

You can follow my ROV construction thread on the DIY Drones ArduBoat User Group here

Regards,

TCIII AVD


(TCIII) #2

Hi All,

I have moved my ROV Project discussion to here and have changed the configuration to a vectored six thruster configuration.

I am also using a BBBMINI to control the six vectored thrusters.

Regards,

TCIII AVD






(Paul) #3

Nice!


(TCIII) #4

Hi Paul,

Thanks for the kudos, much appreciated.

Rusty has been a great help in keeping this ROV Project going!

Regards,

TCIII AVD


(TCIII) #5

Hi All,

Recently I have decided to replace my home brew HDPE chassis with a BlueROV2 chassis due to the weight of the HDPE chassis. Since both of the ROV chassis support a vectored six thruster configuration replacing the HDPE chassis with the BlueROV2 chassis should be fairly straightforward. Though I will have to pot the Battery Power Distribution Board, which is presently located in the 4 in diameter Battery WTC, because there will be no room for it in the BR 3 in diameter Battery WTC. Actually BR had originally intended for both the Battery Power Distribution Board and the Signal Distribution Board to be potted (encapsulated) and be mounted externally to the Battery and Navigation Controller WTCs.

The BlueROV2 chassis should be here around the end of November which is just about when I will finish up my BR/OROV Hybrid Three Thruster ROV.

More to come.

Regards,
TCIII AVD


(TCIII) #6

Hi All,

This has been a busy week for me since my BlueROV2 chassis components arrived on Dec 7th.
Upon receipt of the chassis components I proceeded to assemble the basic frame which also included the installation of the Battery WTC by following these instructions.

I then tackled the assembly of the Electronics Tray using the same instructions as above, but not before I had actually assembled the Electronics Tray Frame using these instructions.

The assembly of the Electronics Tray consists of attaching the RPi, the Pixhawk, the 3DR Power Module, and the Fathom-X Interface to the Electronics Tray Frame and then adding interconnecting cables and BECs.

Because I am using the BlueESC thrusters, my Electronics Tray does not include the six thruster ESCs seen in the Port and Starboard Side pictures that appear in the BlueROV2 Electronics Tray assembly instructions.

Tomorrow I plan to move all six BlueESC thrusters from the home brew chassis to the BlueROV2 Frame to see how much excess cable I have to deal with and how the two cables from each thruster will be routed. I have already modified the BlueESC thruster control cables to mate with the Pixhawk Servo Output Bus connectors so my main efforts will be directed towards setting up the BlueESC thruster power cables in order to attach them to the external Power Distribution Board.

More to come.

Regards,
TCIII AVD




(TCIII) #7

Hi All,

On this last Sunday I spent the day moving the six BlueESC Thrusters from the homebrew chassis to the BlueROV2 chassis. It took most of the day as I had to turn each Thruster’s ESC/motor Housing180 degrees in its accompanying Nozzle so that the Control/Power Cables pointed towards the bottom of the Frame Thruster/Faring Plates. Then I proceeded to route the Control/Power Cables to the back of the ROV chassis. The Control Cables appear to be long enough to reach the Electronics Tray WTC and have a sufficient amount of slack. The Power Cables appear to be too long and will have to be trimmed back to be able to connect to the outboard Power Distribution Board.

This morning I began the process of deciding where to mount the outboard Power Distribution Board. I finally ended up deciding to mount the Board on an aluminum/ABS plastic fixture that attaches to the back of the Battery WTC End Cap. The fixture uses three of the lower screws that hold the End Cap plate to the End Cap. I plan to degrease the aluminum part of the fixture and paint it with a good grade of marine epoxy paint to help reduce corrosion. Once the power cables are soldered to the Power Distribution Board pads I will coat the exposed solder joints with a sealing resin. A picture of the Power Distribution Board fixture is below:

Power Distribution Board mounted on Aluminum/ABS Plastic Fixture
More to come.

Regards,
TCIII AVD


(TCIII) #8

Hi All,

I have now soldered the BlueESC power cables to the Power Distribution Board and have also soldered the Power Cable from the Electronics Tray WTC to the Power Distribution Board. Pictures are below:

Power Distribution Board with BlueESC Power Cables Attached

Power Distribution Board with Power Cable Attached

My biggest concern now is sealing the solder joints and cable jacket entry points on the Power Distribution Board. Several Liquid Tape users have had success using it as a form of “conformal” coat. They said to apply thin layers of the Liquid Tape letting it dry thoroughly in between coats. The other approach to sealing would be to make a small dam around the Board and coat it with a layer of epoxy resin.

Comments on how to proceed are welcome.<img src=“http://discuss.ardupilot.org/images/emoji/emoji_one/slight_smile.png?v=3” alt=":slight_smile:"

Regards,
TCIII AVD


(Harold Scadden) #9

Depending on how much pressure your board is going to see, I would not only pot the board but you need to do something with the cables coming into it. I would highly suggest light sanding of the jacket, clean the jacket area with Acetone and encapsulate the whole board / jacket entry points with a semi-rigid material like a polyurethane compound.

I am not familiar with the liquid tape material, if you have a link or a technical data sheet / SDS I wouldn’t mind looking at that. I have had decent luck in the past with polyurethane sealing the ends of connectors / cable entry to depths greater than 2000 feet. The biggest factor in the world is preparing the surfaces to be potted and curing the material correctly.


(undersearobotics.com) #10

Second vote for potting. All it would take is a tiny leak to make quick work of those copper terminals and that would be the end of that.


(TCIII) #11

@Harold/Undersearobotics,

Thanks for the responses gentlemen, much appreciated.

Rusty has recommended this insulating compound: MG Chemicals 4229

I have attached the MG Chemicals 4229 insulating compound spec sheet below.

I will probably never dive below 100 ft.

Comments please!

Regards,

TCIII AVD

254229-55ml (245 KB)


(Harold Scadden) #12

@TCIII AVD considering your depth, this should work. I would still clean it with a zero residue solvent. The chemical that is in the TDS that you attached is a thinner more than anything.

So, if you wanted to use this stuff … kind of reminds me of coal tar! … take a lint free cloth and wipe everything with the Acetone and then apply this stuff.

Now the cure schedule is weird. Allow four hours per coat with 20 minutes dry time between coats. I think if you are coating definitely do the 20 minute between coats and don’t let it set up to much before applying. I would play it safe and give it a couple of days to do a total cure.

The electrical and mechanical properties are decent and it should work just fine for shallow depths.

 


(TCIII) #13

@Harold,

Thanks for the insights and encouragement, much appreciated.

Regards,

TCIII AVD


(TCIII) #14

Hi All,
Due to the holidays, progress has been somewhat spotty, but I have made some progress nonetheless.
I have coated the Power Distribution Board with eight coats of MG Chemicals 4229 Connector Coating allowing at least four hours of curing time between coats. The connector coating was recommended by Rusty at BR and went on quite easily and has formed a firm rubbery finish on the exposed areas of the board.

Coated Power Distribution Board

In between waiting for the coatings to cure I proceeded to being to attach the BlueESC Control Cables, the Battery Cable, and the Lumen Power Cable to the Electronics Tray End Cap. I will still need to attach the Tether Cable, Power Distribution Board Power Cable, and the Pressure Sensor.

Electronics Tray End Cap Cable Routing

I have also had a chance to communicate with the Electronics Tray over the Fathom-X ROV Side/Topside Interfaces. Using the latest Daily Build of QGC I was able to view the RPi HD Camera and view the ArduSub parameters. I also took the time to update the Pixhawk ArduSub firmware to rc3 which corrected the Pressure Sensor issue where the Pressure Sensor was set to the Firstbaro and not the Secondbaro all of the time. This week I plan to configure the Pixhawk various operating parameters and sensors and prepare for the ROV’s first dive in my 38 gallon test tank.

More to come.

Regards,
TCIII AVD


(TCIII) #15

Hi All,

I have completed the calibration of the Electronics Tray which included the accelerometers, compass, and battery monitor. I also verified the functionality of the baro 30 external pressure sensor, added the SOS Leak Sensor board and mounted the four Leak Sensor probes on the Tray. Now I am ready to attach the Electronics Tray to the End Cap, but not before testing the integrity of the Cable Tray and Battery WTC cable penetrators and End Cap O ring seals.

To test the WTC cable penetrators and End Cap O ring seals I followed the instructions in the BR BlueROV2 Assembly instructions except that I used a motor driven diaphragm vacuum pump and did not have the Electronics Tray in the main WTC during the vacuum testing. BR recommends pumping both WTCs down to 10 inches of vacuum, wait 15 minutes, and then verify that the vacuum has dropped no more than 1 inch and is 9 inches or greater. I took the vacuum to 22.25 inches and after 15 minutes, I had lost only 0.5 inches of vacuum which I consider to be acceptable given the vacuum test setup.

Now, I will attach the Electronics Tray to the its respective End Cap, make all necessary cable connections to their respective connections in the Tray, and then proceed to tidy up the external wiring, add the Fairings/Buoyancy, and the Ballast, and then prepare for the first dive in my 38 gallon test tank.

More to come.

Regards,
TCIII AVD


(TCIII) #16

Hi All,
Finally got the Electronics Tray all cabled up, the buoyancy fairings, and the ballast weights installed on the Frame and a vacuum test of the two WTCs.So I was ready to put the ROV in my 38 gallon test tank. The biggest problem I had prior to being ready to test was getting the Power Cable from the Electronics Tray WTC to the Thruster Power Distribution Board to be watertight. It took about two weeks of experimenting and testing to achieve a waterproof seal.

I charged up the two 3S 5000 mah LiPos that I am running in parallel and stuffed them into the Battery WTC and let the ROV run for a while to heat up the air in the Electronics Tray WTC prior to sealing the vent plug. I then put the ROV into the test tank and added water. When the test tank was 2/3 full the ROV began to float and according to the QGC HUD, the Frame is stable in both pitch and roll.:slight_smile:

I then tested the functionality of the Thrusters, Camera Servo, and the Lumen Lights. All of the components worked as expected. It is kind of wild to watch the ROV Frame move sideways (strafing) as I have only been used to three thruster ROV Frames. Even with only the BlueESC T100 Thrusters at 50% drive, the ROV seems pretty powerful.

Pictures below show the finished ROV Frame:


Front View showing RPi Camera and Lumens

Rear View showing BlueESC Thruster Power Distribution Board and temporary Tether

Side View

I believe that this project proves that the BlueESC Thrusters can be used in a BlueROV2 Frame, but it is not the easiest project I have tackled especially getting the Power Distribution Board Power Cable watertight.

I will grab a shot of the ROV in the test tank to show how well balanced the Frame is due to Rusty’s (BR) ballasting scheme.

More to come
Regards,
TCIII AVD


(TCIII) #17

Hi All,
Here are a couple of shots of the Conversion BlueROV2 in my 38 gallon test tank:


BlueROV2 Front View

BlueROV2 Side View

Regards,
TCIII AVD