[PSUBS-MAILIST] motor oil compensator
hank pronk via Personal_Submersibles
personal_submersibles at psubs.org
Thu Mar 26 14:18:41 EDT 2020
James a small air bubble is fine but use the softest tube possible
Hank
Sent from my iPhone
> On Mar 26, 2020, at 11:15 AM, 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.
>>
>> Regards
>> James
>>
>>
>>
>>
>>
>>
>>
>>> 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 water
>>> would push past the seals before there was any compensation.
>>> I don't know whether you are still getting trapped air in the system coming out
>>> or 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 the
>>> seals when you transit & it heats up, & then causes a vacuum when you take the sub
>>> out 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 WD40
>>> or similar, perhaps it is pushing past the seals with the hot cold variation over
>>> each 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 to
>>>>> 1/12th the volume, so the oil overflow reservoir is going to be problematic because
>>>>> It's large volume could mean the seawater would come a long way up the tube on
>>>>> the 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 using
>>>>> a 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 when
>>>>>> the motor is under load it will be drawing a lot more amps & develop a
>>>>>> lot 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.pdf
>>>>>> I printed it out & had it bound.
>>>>>> I found that the rotation of the motor was throwing the oil out of the motor
>>>>>> housing & up in to the compensating tube. If you dived there would be added
>>>>>> pressure to keep the oil in the motor housing, but this wouldn't happen transiting
>>>>>> on the surface. As the oil also keeps the Motor cool, there may be a danger of
>>>>>> the 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 dialled
>>>>>> up 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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>>>>>>
>>>>>>
>>>>>> --
>>>>>> Vennlig hilsen
>>>>>> Øystein Skarholm
>>>>>> 91369599
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