Conversion to new penetrators

hey folks, I have been lurking for some time now, thought I would throw out some advice on my conversion to the new wetlink penetrators on the BlueROV2. I have a heavy unit with gripper, 4 lights and also adding on a ping today and a TriTech Micronav USBL modem unit.

  1. First I removed the entire housing from the frame by removing the 4 screws that hold the end caps to the frame.
  2. Then remove the vent caps and take the end caps off and slide the electronics tray from the tube.
  3. MARK all of your cables with tape and number the thrusters and lights, etc.
  4. Take a photo of the end cap and print the photo if you can.
    • Write all the numbers of the cables on the photo, so you can re-assemble later in the same spots.
  5. MARK with a sharpie on the ESC’s the number of the thrusters, same as on the cables.
  6. Take a photo of where and what orientation the gripper, and lights connect to the Pixhawk and the power strips.
  7. Use an ice tray for all the small parts, hopefully in order of how you removed them
  8. Using a heat gun, heat up the old red alum penetrators, one or two at a time,
    • if you have an IR gun or FLIR camera, heat until the penetrator is about 190F-200F,
    • using a glove, hold the end cap with one hand and firmly pull the cable out of the penetrator with the other, the potting will be soft and flexible if you have heated it enough,
    • if it is still very solid, heat some more.
    • Large heat gun on low setting took about a minute.
    • Work your way around the perimeter of the end cap removing all the cables you want to replace.
  9. Using a cable stripping tool, (see Rusty’s video) make a light pass just up cable from any left over potting, be sure to cut the insulation square to the cable.
    • Don’t worry if you don’t go all the way through, in fact, best to not go all the way.
    • Then bend the cable at the cut and take a sharp razor blade and just barely touch the remaining insulation, DON’T saw at it, just a light touch will finish it off,
    • work your way around in a similar manner.
    • Don’t nick the inner wires.
    • Clean up the filler material carefully.
  10. From there on, with the help of Rusty’s penetrator video, you will fit the cables into the new penetrators and reassemble in reverse.

Two extra things…
Notice that you would have to remove all the thrusters so the cables will spin into the end cap threads, you may think, hey, if I just drill out the threads on the outer perimeter, I can dispense with that nonsense and put a nut on the back side. Won’t work, the nut on the back will interfere with the ring the end cap screws onto and you won’t have a seal.

So…, what I am doing is

  1. putting the penetrators on the cables, but not quite tight to compress the seal,
  2. once they are all on, I can thread them in to the end cap, as the penetrator will still spin around the cable, tighten up the body, then finish compressing the seal to torque specs.
    • I suspect some dielectric grease on the seals might help that process.

I am not recommending this last bit as a for sure thing, I am just being lazy and not wanting to pull all the thrusters off. Warning, this may not work, but I am gonna give it a try.

Hi @RV_Zephyr, welcome to the forum :slight_smile:

Thanks for writing out this guide!

I’ve added some formatting to your post to make it a bit easier to follow. I’d recommend having a read through the How to Use the Blue Robotics Forums post if you haven’t already done so.

It’s worth noting that the torque spec for tightening the penetrators onto the end cap is significantly lower than the torque spec for tightening the plug into the penetrator. If you’re going to do this you’ll want some way of preventing the penetrator from rotating into the end-cap while you’re tightening the plug to compress the seal :slight_smile:

Thanks for the edit Eliot, looks much better now. I took a short video of the insulation removal, is there a way to post it?

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Video files can’t be directly posted on the forum, but if you post a video on YouTube you can post the link to it here and it’ll be watchable from within the forum - that’s likely the most accessible option. Otherwise you can put it in cloud storage (e.g. google drive, dropbox, one drive, etc) and then post a link to it here :slight_smile: