[PSUBS-MAILIST] air compensation

Tue Aug 1 12:24:15 EDT 2023

 I would figure out why the lip seal was pushed out.  Sounds like the OP valve was not venting the pressure correctly.  It would take quite a bit of pressure to unseat one of these lip seals.  You would have thought that with the lip seal oriented to see higher pressure from outside that an overpressure event would send air out as a leak from around the lip seal.
Cliff
    On Tuesday, August 1, 2023 at 10:10:05 AM CDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

  A new development to consider with air compensating.  I just removed one of my vertical thrusters that was on air because it was making a noise.  The magnet detached, but was still running.  The glue let go, maybe from the oil from previous use?  or from the rough bush road?  Also the seal has push out until it hits the prop pin.  I will have to put some SS washers in to hold it down.  It was not leaking but should be secured.Hank
    On Tuesday, August 1, 2023, 06:46:11 AM MDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

  Alec, I was looking at small cartridge seals on my favourite site, Amazon.  They have some real nice little seals there.  Hank
    On Tuesday, August 1, 2023, 05:33:38 AM MDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 I originally used the little Parker SS pressure relieving regulator to compensate everything, which included four Minnkota 101s. I had a differential pressure gauge in the sub so I could see the delta between ambient and compensation pressure in real-time. It had no problem at all keeping up when submerging, but the delta would overshoot surfacing.  My first attempt at resolving that was to use a SCUBA 2nd stage, but I kept getting water in the system. I still have no idea why, the entire PSUBS brain trust at last year's convention couldn't resolve that maddening leak despite the approach having worked fine for countless other people. 
This year I went back to oil, and had the same maddening issues as Cliff. But I retained the air compensation for the arm, because the motors there are so small I didn't like the idea of the tiny brushes swimming in oil. The volume being compensated is far smaller than with the thrusters, but just in case I added a pressure relief valve to the compensated line, as I thought the actuators might blow up if I surfaced fast. If ever anything should leak it's the arm, because there's a lot of seals, and there's movement. The junction box is intended for electronics on land, it's sealed with a little rubber gasket but it's a square box, so although the gasket has a round section, calling it an O-ring would be a bit of a stretch. Yet the air compensation worked perfectly, I never got a drop of water in any of it. It was pressurized at 3psi. That system will now stay as it is.
I should mention that both the thrusters and arm are jettisonable. The arm is pressurized by a little pony bottle on the arm itself, like Hank used to have on Gamma. If I jettison the arm, the air compensation setup goes with it. But on the thrusters, I need to disconnect the air supply if jettisoning. That could be done without much difficulty, but I tried oil because it has no tubing at all in an area that I'm trying to keep hydrodynamically clean.  
I'm going to research putting a ceramic seal on the 101's and running them at 1 atmosphere. If that doesn't work, then it's back to air. Either with a Parker and OP valve, or using the SCUBA 1st stage method Hank described, with disconnects for the thrusters to jettison. But the 1 atm solution would be so clean and tidy, I'd like to at least explore it first.

Best,Alec
On Mon, Jul 31, 2023 at 10:47 PM Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

I would be inclined to use a Tescom 44-4069 regulator for this purpose. Not sure what these sell for.

Sean

-------- Original Message --------
On Jul. 31, 2023, 20:37, Cliff Redus via Personal_Submersibles < personal_submersibles at psubs.org> wrote:

My original air competition for the R300 used the regulator that Hugh Fulton has on QSub.  These are pricey new but you can get them used on eBay.  I was operating all four of my Minn kotas 101 off this single regulator.  It was a special ss pressure reducing/pressure releasing regulator.  I had it installed on my last Florida dive which I went down about 100 ft .  Unit worked fine.  My first failure was on Flathead lake expedition in which one of my aft thrusters flooded.  After that I switched to oil compensation.  Alec is using same regular on his articulated arm and not the thrusters. He felt issue with the regulator was that the port for releasing pressure on ascent was too small.  I believe he has addressed this by adding a pressure release valve or OP valve.  He can elaborate more on his current strategy.
Cliff

Sent from my iPhone

On Jul 31, 2023, at 9:14 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

John,I am happy with both air & oil. Am intending to fill my thrusters with oil, but have the oil pressurized off my air comp system. This will reduce air use to just whats in the lines.My electric manipulator will be air compensated off the same unit. Putting oil in it adds another layer of complexity.I think I need to put out a long video once I've finished thisair compensator.From what I am hearing from Cliff, he didn't get enough air delivery from the single regulator he was using. However I thought this was the same unit that Alec is using & was now happy with.Alan

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