<div dir="ltr">Hi All,<div>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.</div><div>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.</div><div><br></div><div>No matter what i do, i always seem to end up with a small amount of air in the tube.</div><div><br></div><div>This picture is the only one i can find.</div><div><br>The tube comes out the top, around to a valve secured underneath. Thats it. There is no hole on the underside any more.</div><div><br></div><div>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.</div><div><br></div><div>There appears to be no leaks and no seawater in the motor.</div><div><br></div><div>What am i doing wrong? Its such a nuisance and worry to me.</div><div><br></div><div>I have heard that some people put the prop shaft seals in backwards? I didnt do that, they are just standard.</div><div><br></div><div>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?<br><br>Thanks, </div><div>James</div><div><br></div><div><div><img src="cid:ii_k87b37s60" alt="image.png" width="387" height="516"><br></div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, 25 Mar 2020 at 08:43, Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto"><div></div><div>Brian,</div><div>not sure of your depth but if you are going to 300ft, the air will be compressed to</div><div>1/12th the volume, so the oil overflow reservoir is going to be problematic because</div><div>It's large volume could mean the seawater would come a long way up the tube on</div><div>the seaward side. Also using it as an overflow would create the problem of "how do </div><div>I get the oil back in the motor" & " how do I monitor it".</div><div>I have had rubber perish in WD40 so I would watch that if you are considering using</div><div>a rubber compensator.</div><div>Have a look at the PDF I referenced as that has several options.</div><div>Alan</div><div><br></div><div><br></div><div><br>On 25/03/2020, at 5:40 PM, Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div style="font-family:Arial,sans-serif;font-size:10pt"><font size="2" style="font-family:Arial,sans-serif">Alan, </font><div><font size="2"><font face="Arial, sans-serif"> 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.</font></font></div><div><font size="2"><font face="Arial, sans-serif"><br></font></font></div><div><font size="2"><font face="Arial, sans-serif">Brian</font></font></div><div><font size="2"><font face="Arial, sans-serif"><br></font></font></div><div><font size="2"><font face="Arial, sans-serif"> </font><br></font><br><span style="font-family:Arial,sans-serif;font-size:10pt">--- <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a> wrote:</span><br><br><span style="font-family:Arial,sans-serif;font-size:10pt">From: Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span><br><span style="font-family:Arial,sans-serif;font-size:10pt">To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span><br><span style="font-family:Arial,sans-serif;font-size:10pt">Subject: Re: [PSUBS-MAILIST] motor oil compensator</span><br><span style="font-family:Arial,sans-serif;font-size:10pt">Date: Wed, 25 Mar 2020 17:28:21 +1300</span><br><br><div style="font-family:Arial,sans-serif;font-size:10pt"></div><div style="font-family:Arial,sans-serif;font-size:10pt">Brian,</div><div style="font-family:Arial,sans-serif;font-size:10pt">I wouldn't read a lot in to that experiment as far as heating goes, as when</div><div style="font-family:Arial,sans-serif;font-size:10pt">the motor is under load it will be drawing a lot more amps & develop a</div><div style="font-family:Arial,sans-serif;font-size:10pt">lot more heat.</div><div style="font-family:Arial,sans-serif;font-size:10pt">But people run the Minnkotas with air compensation & get away with it.</div><div style="font-family:Arial,sans-serif;font-size:10pt">Alan</div><div style="font-family:Arial,sans-serif;font-size:10pt"><br></div><div style="font-family:Arial,sans-serif;font-size:10pt"><br>On 25/03/2020, at 2:09 PM, Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote style="font-family:Arial,sans-serif;font-size:10pt"><div><div style="font-family:Arial,sans-serif;font-size:10pt"><font size="2"><font face="Arial, sans-serif"> Alan, </font></font><div><font size="2"><font face="Arial, sans-serif"> 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. </font></font></div><div><font size="2"><font face="Arial, sans-serif"><br></font></font></div><div><font size="2"><font face="Arial, sans-serif">Brian</font></font></div><div><font size="2"><font face="Arial, sans-serif"><br></font></font></div><div><font size="2"><font face="Arial, sans-serif"> </font></font><br><br><span style="font-family:Arial,sans-serif;font-size:10pt">--- <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a> wrote:</span><br><br><span style="font-family:Arial,sans-serif;font-size:10pt">From: Alan via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span><br><span style="font-family:Arial,sans-serif;font-size:10pt">To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span><br><span style="font-family:Arial,sans-serif;font-size:10pt">Subject: Re: [PSUBS-MAILIST] motor oil compensator</span><br><span style="font-family:Arial,sans-serif;font-size:10pt">Date: Wed, 25 Mar 2020 13:25:53 +1300</span><br><br><div style="font-family:Arial,sans-serif;font-size:10pt"></div><div style="font-family:Arial,sans-serif;font-size:10pt">Brian,</div><div style="font-family:Arial,sans-serif;font-size:10pt">there is this military de-classified 1972 document on pressure compensating.</div><div style="font-family:Arial,sans-serif;font-size:10pt"><a href="https://apps.dtic.mil/dtic/tr/fulltext/u2/894795.pdf" target="_blank">https://apps.dtic.mil/dtic/tr/fulltext/u2/894795.pdf</a></div><div style="font-family:Arial,sans-serif;font-size:10pt">I printed it out & had it bound.</div><div style="font-family:Arial,sans-serif;font-size:10pt">I found that the rotation of the motor was throwing the oil out of the motor</div><div style="font-family:Arial,sans-serif;font-size:10pt">housing & up in to the compensating tube. If you dived there would be added</div><div style="font-family:Arial,sans-serif;font-size:10pt">pressure to keep the oil in the motor housing, but this wouldn't happen transiting</div><div style="font-family:Arial,sans-serif;font-size:10pt">on the surface. As the oil also keeps the Motor cool, there may be a danger of</div><div style="font-family:Arial,sans-serif;font-size:10pt">the motor overheating in this instance.</div><div style="font-family:Arial,sans-serif;font-size:10pt">As you will find in the linked manual, a minimum of 5psi over pressure is the norm.</div><div style="font-family:Arial,sans-serif;font-size:10pt">I am going to use the same system as Cliff, with the relieving regulator dialled</div><div style="font-family:Arial,sans-serif;font-size:10pt">up to 5psi to give an overpressure. However my system has oil in it so I get it's </div><div style="font-family:Arial,sans-serif;font-size:10pt">cooling advantages & eliminate large air volume changes.</div><div style="font-family:Arial,sans-serif;font-size:10pt">Alan</div><div style="font-family:Arial,sans-serif;font-size:10pt"><br>On 25/03/2020, at 11:19 AM, Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote style="font-family:Arial,sans-serif;font-size:10pt"><div><div style="font-family:Arial,sans-serif;font-size:10pt"><font size="2">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. </font><div><font size="2"><br></font></div><div><font size="2">Brian</font></div><div><font size="2"><br></font><br><span style="font-size:10pt">--- <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a> wrote:</span><br><br><span style="font-size:10pt">From: Øystein Skarholm via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span><br><span style="font-size:10pt">To: Personal Submersibles General Discussion <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span><br><span style="font-size:10pt">Subject: Re: [PSUBS-MAILIST] motor oil compensator</span><br><span style="font-size:10pt">Date: Tue, 24 Mar 2020 22:21:15 +0100</span><br><br><div dir="ltr" style="font-size:10pt">You should avoid contact between the seawater and the oil. The oil will contaminate quickly and it will no longer be dielectric. <div>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. </div><div>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. </div><div><div><image.png><br></div></div></div><br><div style="font-size:10pt"><div dir="ltr">tir. 24. mar. 2020 kl. 21:28 skrev Brian Cox via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>>:<br></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="font-family:Arial,sans-serif;font-size:10pt"><font size="2">Here is a drawing for my oil compensator</font><div><font size="2"><br></font></div><div><font size="2"><br></font></div></div>_______________________________________________<br>
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