[PSUBS-MAILIST] Thruster bladders

Fri Sep 17 16:56:12 EDT 2021

 Hi Rick, Hugh Fulton who owns a valve manufacturing & importing business first came up with the idea of using a relieving regulator for setting the compensating air slightly above ambient. (Industry standard for oil compensation is about 5psi above ambient.) In a relieving regulator there is a hole that lets excess pressure in the systemEscape out through the handle area. The relieving pressure is factory set to a few psi above your set pressure. Cliff Redus bought a Parker 364 mini stainless regulator as did Brian Hughes, but they are quite pricy unless you pick one up on ebay. Cliff wasn't happy with it as there was a pressure build up due to the relieving hole being too small to exhaust the expanding air volume from all his thrusters. Brian has solved this problem by having a separate relief valve plumbed in to a line from the regulator output. His relief valve is a scuba dump valve that he has fitted in to some pvc pipe. With Brian's system you do not need a relieving type regulator. Just a single stage diaphragm type non corrosive regulator. It does however need at least one hole in the handle /spring area to let water in to give you ambient pressure. Same as a scuba second stage letting water in against the diaphragm. As the components inside the handle area are exposed to water, they need to be non corrosive.You can pick up a second stage octopus regulator for quite cheap. I say octopus because they are less sensitive & prone to free flowing. The Pr364 regulator is very expensive for what it is. I can pick up a much larger item from China for 1/3 the price. With the second stage regulator, I put extensions on the exhaust valve to help stop water getting in the system. I am going with an over-pressure system because I want to air compensate linear actuators in an electric manipulator, and feel they are in more need of over pressure. I have an exhaust valve on the way, but are 3d printing the regulator part, & using a second stage reg valve. Hope that makes it a bit clearer. Let me know if you have any questions. I am looking forward to all the diving videos of those Hawaiian waters! Alan

    On Saturday, September 18, 2021, 05:37:12 AM GMT+12, Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Thanks Alan, it makes it so much easier when I can see a schematic. I am still a little fuzzy though about the hole in the handle. and it seems more complicated and possible more expensive? than using a second stage scuba reg?
Rick
On Thu, Sep 16, 2021 at 7:07 PM Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Rick,

Below is the drawing of the set up I have been talking about.

The regulator is stainless, as is the main adjustment spring in it’s handle. 

With this system & using a relief valve, you don’t need a relieving type regulator.

I am opting for a regulator with an inlet maximum pressure of 500psi which accounts for 130psi system pressure

Plus the pressure at my maximum depth. The outlet has a 0-25psi range. You may get away with an inlet max of 130psi as the regulator 

housing the pressure is also under the inreasing external pressure. I am just concerned about additional pressure on the valve.

If the handle area doesn’t have a hole in it, it needs one for the water to pressurize the diaphragm to give set pressure plus ambient.

A hose extension can be used off the handle area so the water has further to travel and keeps away from the diaphragm which may have

A cap that can corrode. There are regulators with stainless diaphragms . Piston type regulators aren’t sensitive enough.

On the motor side you can have a dedicated nipple for the oil system or run the oil down a tube that contains the wires.

There should be a plug on the manifold for oil filling but forgot to add it. The over pressure valve is also used for manually releasing 

Pressure out of the system.

Hope that all makes sense.

Alan

Sent from Mail for Windows

From: Rick Patton via Personal_Submersibles
Sent: Friday, 17 September 2021 5:32 am
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Thruster bladders

Hi Hank

would love a picture. Do you tie the 1' of vacuum hose to the housing so it's not flopping in the breeze? I thought I had heard conflicting ideas about, "make sure you get all the air out of the thruster and bladder" and others saying that they have a little air left in the bladder to allow for the hot oil expansion so I am confused. My thinking (which is limited) is that you can't have any air in anything because as you know, you can't compress a liquid so any air would compress and push out the factory "0" rings? 

Shoot me a picture if it's not too much trouble. Need to wrap my head around this better so I can pick a method and go for it. 

Are you going to the reunion?

Rick

On Thu, Sep 16, 2021 at 2:27 AM hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Rick, the vacuum tube is about a foot long and comes out a threaded fitting in the housing.  You can drill and tap either end in most cases.  Choose the location well to make sure the fitting does not interfere with the bolts etc.  I have a youtube video on how to do this. 

I can email you a picture of the motor with the hose.  It is still a good idea to have a bladder, just be sure it is real soft.

Hank

On Wednesday, September 15, 2021, 03:17:00 PM MDT, Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org> wrote: 

Hi Hank.

Do you happen to have a good picture of your set up? Not clear what you are saying. How long is your vacuum tube and I assume it comes out of the can but not back in? I woldn't think a rubber hose could inflate enough to allow the heated oil to expand it enough before pushing out the two factory "0" rings? 

Rick

On Wed, Sep 15, 2021 at 3:31 AM hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Rick.  I have oil filled at the moment because they jettison.  I use a length of vacuum hose from a car engine because it is soft.  I intended to install a car suspension air bag and connect all the motors to that.   I don’t worry much about an air bubble because it will just compress to nothing.   

Sent from my iPhone

On Sep 15, 2021, at 7:18 AM, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi Rick,

You'll find people here who love oil compensation, and others who love air. They both work, so I guess it's just a matter of what has worked for each person. 

I used oil initially. The method was to put two 90 degree nipples in the motor can, and attach about a foot of plastic hose to them. To fill, you disconnect the top nipple and add oil through the hose until it comes out the top nipple. The hose wraps around the can and with that extra length is supposed to act as a bladder. I found it worked, but only until I started diving my K250 to 250 feet. Then, I was getting internal build-up of pressure in the motors. In the end, I figured what was going on was that the compression of the hose was insufficient for the thermal contraction between the surface, where I'd filled the motors, and the very cold ambient temperature at 250 feet. At depth, water was forcing its way past the shaft seals, and then the seals would keep the motors pressurized as I rose. My solution was to go to a larger bladder, namely this:

https://www.google.com/search?q=squeeze+bottles&rlz=1C1CHBF_enUS807US807&sxsrf=AOaemvLRC6ixUOHC7wIDhQcAL78ShVP-Sw:1631711091091&source=univ&tbm=shop&tbo=u&sa=X&ved=2ahUKEwig_9a_hYHzAhUgF1kFHRK2AW0Q1TV6BQgBEKkC&biw=1536&bih=664#spd=4605806885737196691

That said, the larger bladder was something I implemented just before selling that sub, so never got to dive it. It was also always a problem getting every last bubble out. I'd spend ages doing that, then come back the next day and find a bubble in the hose. I was never able to solve that issue, and I think the only way would have been to assemble the motor in a bucket of oil. The other problem was that if there was an issue, such as the over-pressurization one above, my sub created an oil slick. That is NOT good, and can attract the wrong sort of attention even if you were to use an oil that is harmless.

Now I use air compensation. So far, so good. On my first dive with the mechanical arm, I noticed bubbles coming from a hose when I extended the arm. The bubbles would cease when I retracted the arm. Closer examination showed a nick in the hose, which got pinched closed when the arm was retracted. The beauty of air is that if there's a leak, you can see and trace it immediately. With oil, I'd have had a small slick but no idea where it was coming from. Also, it worked well in the sense that no water entered the arm. I have a shutoff valve, so that a leak won't drain the sub's air supply, or another way would be to supply the air comp with a small independent cylinder. 

Best,

Alec  

On Wed, Sep 15, 2021 at 12:13 AM Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

I am re thinking what to use for my oil expansion bladder. Would love to hear from everyone who chose to go with an oil filled thrusters on what they used and how they liked it. I remember someone saying that they used a squeeze ball gas tank primer which I like because it is small but I just spoke with someone who didn’t use a bladder and had never had a problem.
Rick 

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