[PSUBS-MAILIST] motor oil compensator

Fri Apr 3 14:41:21 EDT 2020

 David, there is too much concern around having a small amount of air in the system.  As long as you have sufficient volume in your tube or bellows or hose or what ever then it's fine.  I think you have a super slick set up indeed, just no need for pulling a vacuum.Hank
    On Friday, April 3, 2020, 9:53:39 AM MDT, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Hank, I've been thinking about this oil compensatation issue. On the seaQuestor, I did not want to side tap my thrusters, but wanted to have the ability to go with oil compensatation in the future. So I designed a coupler made out of uhmw. I had it machined to thread into the 1" thruster shaft location, and to have threaded in the opposite direction a seaconn wet mate  connector and that would plug into the pressure hull via what ever cable lenght I need. In the coupler there are other side taps that are for other sensor wires( ie: temp, pressure). One tap is reserved for future use as the port for oil compensatation. The average lenght from my thrusters to hull body is about 48". My future plan would be to fill the thruster thru the largest port of the coupler. Take the thruster, place in a plastic bag so that the seal seams have a way to sealed temporarily and place the unit into a vacuum chamber. Pull a vacumm like we do with epoxy, remove the unit, cap off the end of the 5/8"x 48" tube,  and install in the sub. My assumption is there is no hidden air now in my thruster, and I have 48" long bellows to compensate should the oil expand. Do you see any issues with my thoughts?David
On Fri, Apr 3, 2020, 5:26 AM hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 James, you could have the bellows attached to the bottom side of the motor and a fill plug on top.  Hank
    On Thursday, April 2, 2020, 10:21:56 AM MDT, James Frankland via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Hi All who replied to me.
Many thanks, i am investigating what I can find.  I want to keep it really simple.  Ideally just oil compensated, sealed with a suitable bladder.  Im nearly there with my existing setup, I think i just need some sort of bellows or super soft bladder in the line.  The accordian bladder Cliff mentioned looks good but i need one with a connection at both ends so I can run a tube to my filling valve.
I will keep searching.  
On Thu, 26 Mar 2020 at 21:21, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

James,If you go with the regulator method make sure it is a relieving regulator thatcan let overpressure out on assent.In general in the relieving regulators there is a hole in the valve spindle portionthat allows an overpressure down line to escape, & also allows water pressure at ambient depth to maintain the set pressure above ambient. You need to mount withthe handle down or water will ingress through the valve. If you set it for say 5psi pressure, the down stream pressure ( in the motor housing) may jump a lot higher when relieving due to the fixed overpressure setting. I oiledthe regulator piston with silicone & this helped make the differential just a few psi.I bought a number of regulators & pulled them apart looking for a cheap plastic option with view of changing out parts in the handle that are exposed to water, but toomuch work & Hugh found that regulator that Cliff referenced.The system below is filled with 5 cst silicone oil. The oil runs down the wiring tubeto the T & continues up to within a couple of inches of the regulator.This gives room for any oil expansion but leaves only a couple of inches of air thatwill be compressed when diving.Even if all the oil leaked out there would still be air compensation.Alan

On 27/03/2020, at 6:53 AM, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 James, the pressure reducing/relieving regulator I used for pressure equalization of my thrusters until recently was the Parker - PR364-02BSS - Regulator Port size 1/4" NPT, stainless steel body.  Parker has a number of PR364 regulators that show up on ebay all the time .  Make sure you get the SS version.   
Would be similar to this one https://www.ebay.com/itm/PARKER-R364-02B-1-4-MINIATURE-REGULATOR-NEW-IN-A-BOX-0-60-PSI/252360167538?hash=item3ac1d69072:g:EckAAOSwubRXFSSP  but his one not SS.

Hugh Fulton was the the first in the Psub group to adopt this pressure compensation device for his Q-Sub.
I used this regulator quite successfully to pressure compensate my Minn Kota 101s for many years.  I abandoned the regulator about 8 months ago and switch to oil pressure compensation.  The reason I switched is that I did not like the amount of air it used in my HP air bank on repeated deep dives to 300 to 400 ft.  I ran these with 4 psi differential positive pressure.  I left the lip seals in my 101's oriented as per the original manufacturer ( oriented to withstand external pressure).  I don't have enough run time on my new oil compensation method which is WD-40 with small accordion plastic bladders I got from Alec to argue which technique is better.
Best Regards
Cliff

    On Thursday, March 26, 2020, 12:15:51 PM CDT, James Frankland via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Also interested in Cliff's compensator regulator that was mentioned.  Any info on that.
Many thanks
On Thu, 26 Mar 2020 at 17:08, James Frankland <jamesf at guernseysubmarine.com> wrote:

Hi Alan,
Im using silicone oil.  
I deliberately kinked the hoses for the very reason you say.  I initially used silicone hose which is much softer and flexible, but it reacted with the oil and expanded, quite a lot.
I think I might see if i can get some thinner walled tube (but not silicone) and wrap it around the motor a couple of times, to give it a bigger compensator.  
Can other people confirm that a small amount of air in the tube is acceptable?  I have been constantly trying to remove every bubble.  If a small amount is ok, im pretty good to go.

Also I will be making some progress on my new sub pretty soon.  Just getting a heavy hoist sorted, which at the moment is difficult as all the shops are shut.
RegardsJames

On Wed, 25 Mar 2020 at 21:38, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

James,that method with the hose wrapped around has come under criticism previously.Fortunately you have a kink in the hose which initiates a collapse of the hose to provide some equalisation. We calculated that the hose may take over 100psi external pressure before it collapsed to provide equalisation. So at depth waterwould push past the seals before there was any compensation.I don't know whether you are still getting trapped air in the system coming outor whether expansion & contraction when out of the water is sucking air in.But for air to get in, oil would have to get out. Maybe oil expands out through theseals when you transit & it heats up, & then causes a vacuum when you take the subout of the water & the motors cool down, thus sucking air in.Perhaps you could run the motors out of the water for a while untill they feel hot, & see if any oil comes out. Another thought is that if you are using WD40or similar, perhaps it is pushing past the seals with the hot cold variation overeach day, & evaporating away so that there's not much evidence of a leak.Alan

On 26/03/2020, at 1:35 AM, James Frankland via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi All,This is a really interesting topic for me.  I have been meaning to ask this for a while but been a bit busy with other stuff.I need to modify my motors again somehow.  I have a simple tube coming from the top of the motor with a valve that i can shut, so i can seal the motor and close it off.
No matter what i do, i always seem to end up with a small amount of air in the tube.
This picture is the only one i can find.
The tube comes out the top, around to a valve secured underneath.  Thats it.  There is no hole on the underside any more.
I fill it, it seems fine.  The next day there are a few bubbles, which i would expect from just sticking to things.  So i clear that.  However, after either a dive or some time, a small amount of air gets in the tube.
There appears to be no leaks and no seawater in the motor.
What am i doing wrong?  Its such a nuisance and worry to me.
I have heard that some people put the prop shaft seals in backwards?  I didnt do that, they are just standard.
I suspect im getting pressure differences and its sucking air past the seal.  Maybe some sort of 5 psi pressure system is required, as per cliffs method?  Any more info on that?

Thanks, James
<image.png>

On Wed, 25 Mar 2020 at 08:43, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Brian,not sure of your depth but if you are going to 300ft, the air will be compressed to1/12th the volume, so the oil overflow reservoir is going to be problematic becauseIt's large volume could mean the seawater would come a long way up the tube onthe seaward side. Also using it as an overflow would create the problem of "how do I get the oil back in the motor" & " how do I monitor it".I have had rubber perish in WD40 so I would watch that if you are considering usinga rubber compensator.Have a look at the PDF I referenced as that has several options.Alan

On 25/03/2020, at 5:40 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Alan,                So do you see any issues with the way I have my compensator set up?   I've been trying to see a scenario where it wouldn't work, but I don't see one.  One reason I like it is because there in no over or under pressure in the system.
Brian

--- personal_submersibles at psubs.org wrote:

From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] motor oil compensator
Date: Wed, 25 Mar 2020 17:28:21 +1300

Brian,I wouldn't read a lot in to that experiment as far as heating goes, as whenthe motor is under load it will be drawing a lot more amps & develop alot more heat.But people run the Minnkotas with air compensation & get away with it.Alan

On 25/03/2020, at 2:09 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Alan,                     In my case my motor pod contains about 8 gallons of WD40   .  I ran the motors the other day , all day long for about 10 hours straight .  The temp outside was around 60 F  so it sort of simulated our water temperature here.   I was surprised to discover that the expansion of the oil was not as much as I thought it would be , it was about 1/2 gallon.  It reached a point where it stopped expanding, so I guess it reached a point of equilibrium with respect to the temperature.    One problem I have is in the summer the oil actually expands more than when the motor is running just sitting there heating up from the ambient temperature.    I think in the summer I'm going to disconnect the hose and put it into a bucket when sitting.  
Brian

--- personal_submersibles at psubs.org wrote:

From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] motor oil compensator
Date: Wed, 25 Mar 2020 13:25:53 +1300

Brian,there is this military de-classified 1972 document on pressure compensating.https://apps.dtic.mil/dtic/tr/fulltext/u2/894795.pdfI printed it out & had it bound.I found that the rotation of the motor was throwing the oil out of the motorhousing & up in to the compensating tube. If you dived there would be addedpressure to keep the oil in the motor housing, but this wouldn't happen transitingon the surface. As the oil also keeps the Motor cool, there may be a danger ofthe motor overheating in this instance.As you will find in the linked manual, a minimum of 5psi over pressure is the norm.I am going to use the same system as Cliff, with the relieving regulator dialledup to 5psi to give an overpressure. However my system has oil in it so I get it's cooling advantages & eliminate large air volume changes.Alan
On 25/03/2020, at 11:19 AM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Seawater gets compressed up the hose, so never goes above the highest point of the hose.  When oil heats up it spills into trap and cannot escape to the sea. 
Brian

--- personal_submersibles at psubs.org wrote:

From: Øystein Skarholm via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] motor oil compensator
Date: Tue, 24 Mar 2020 22:21:15 +0100

You should avoid contact between the seawater and the oil. The oil will contaminate quickly and it will no longer be dielectric. Just the hose from the motor to the tee is enough to compensate. You do not have to have a large volume of oil. Fill the hose with oil and cap it off, done. or make a neat yet more sophisticated solution. Make the end lid of the motor as a flange assembly and instead of a lid, use a rubber diaphragm. This will then act as a compensator. You can even install a light spring pushing down on the diaphragm  if you want a slight internal overpressure. <image.png>

tir. 24. mar. 2020 kl. 21:28 skrev Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>:

Here is a drawing for my oil compensator

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