<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Hank,</div><div id="AppleMailSignature">just had another look at a free 150 page ex military document,</div><div id="AppleMailSignature">" Handbook of Fluid-Filled, Depth/Pressure-Compensating Systems</div><div id="AppleMailSignature">For Deep Ocean Applications" ( had it printed & bound) couldn't see </div><div id="AppleMailSignature">any reference to using a weight for over-pressure. The system I drew is </div><div id="AppleMailSignature">pretty typical. <span style="background-color: rgba(255, 255, 255, 0);">The volume of their compensators seemed </span><span style="background-color: rgba(255, 255, 255, 0);">to start at 500ml </span></div><div id="AppleMailSignature"><span style="background-color: rgba(255, 255, 255, 0);">& go up </span><span style="background-color: rgba(255, 255, 255, 0);">from there.</span> An amount of leakage must be expected, or a reserve volume </div><div id="AppleMailSignature">is maintained as a fail safe in case a leak starts. I remember a remark from </div><div id="AppleMailSignature">either Carsten or Emile that they went to one compensator per motor because </div><div id="AppleMailSignature">they couldn't isolate the thruster that was leaking when using one </div><div id="AppleMailSignature">compensator for all thrusters.</div><div id="AppleMailSignature">In the publication I think I can remember piston type systems not being </div><div id="AppleMailSignature">popular because of the low pressures involved & the chances of them</div><div id="AppleMailSignature">sticking because of "crut" in the marine environment. However these subs</div><div id="AppleMailSignature">were going to serious depths. </div><div id="AppleMailSignature">Cheers Alan</div><div id="AppleMailSignature"><br></div><div id="AppleMailSignature"><br></div><div id="AppleMailSignature"><br>Sent from my iPad</div><div><br>On 16/09/2017, at 9:07 PM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div></div>
<div>Alan,</div><div>I don't think there is a need to worry about constant pressure through the diaphragm stroke. You would fill the compensator with fluid to the maximum level. The amount of travel would be equivalent to the amount of air trapped in the system plus any expansion due to temperature change. These two things would be so minimal that the amount of travel would be so small the pressure from the spring would stay quite constant. I can not see the entire drawing because I can not move it over for some reason ;-( . Very clever Idea though using a weight. You could take an air cylinder with a bit of extra length and put a lead weight around the shaft inside the cylinder above the piston, and you would be done.</div><div>Hank</div><div><br></div>
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On Friday, September 15, 2017, 10:27:25 PM MDT, Alan James via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:
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<div><div id="yiv4016051153"><div><div><span></span></div><div><div style="color:#000;background-color:#fff;font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2662"><span>Hank got me thinking about compensators again.</span></div><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2660"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2659">I had made an initial design for a compensator, using a spring</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2679"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2680">to produce over-pressure. This design is pretty standard in operation,</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2691"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2692">with lots of variations.</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2835"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2834">One problem with the spring is that it might be producing 8 pounds of</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2742"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2741">force at the start, but as the oil level goes down & the spring extends,</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2740"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2739">the over-pressure is reduced. Some of the springs I have seen are</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2756"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2755">pretty large, possibly in an effort to keep the pressure range in a narrower</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2757"><span>band. 4-5 psi seems a normal over-pressure.</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2738"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2737">If I replaced the spring with a cylindrical 5lb weight, I would get the same</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2782"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2781">4lb (weight in water) over-pressure throughout the range of the diaphragms </span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2847"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2846">travel. </span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2879"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2878">Can anyone see a problem with this? Any comments. The lead may bounce </span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2879"><span>around a bit</span></div><div dir="ltr"><span>during transport but I don't think this would be a problem. </span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2880"><span id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2920">My initial design is attached!</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2921"><span>Alan</span></div><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2912"><span><br clear="none"></span></div><div class="yiv4016051153qtdSeparateBR" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2658"><br clear="none"><br clear="none"></div><div class="yiv4016051153yahoo_quoted" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2588" style="display:block;"> <div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2587" style="font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2586" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div class="yiv4016051153yqt8015017445" id="yiv4016051153yqt90618"><div dir="ltr" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2585"> <font id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2584" face="Arial" size="2"> </font><hr id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2661" size="1"> <b><span style="font-weight:bold;">From:</span></b> hank pronk via Personal_Submersibles <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>><br clear="none"> <b><span style="font-weight:bold;">To:</span></b> Personal Submersibles General Discussion <<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> <br clear="none"> <b><span style="font-weight:bold;">Sent:</span></b> Thursday, September 14, 2017 12:37 PM<br clear="none"> <b><span style="font-weight:bold;">Subject:</span></b> [PSUBS-MAILIST] oil compensation<br clear="none"> </div> <div class="yiv4016051153y_msg_container" id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2913"><br clear="none"><div id="yiv4016051153"><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2924"><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2923" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div>Hi All,</div><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_3049">Thank you Greg, just sent them a request.</div><div><br clear="none"></div><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_2922">I have tested my air cylinder compensator for my thrusters both in the pressure test and a couple days ago to 100 feet. The set up seems to work with no water intrusion into the motors. I have the cylinder mounted below the motors witch causes a small air pocket in the hydraulic fitting on top of the motor. I am not worried about the small amount of air except the potential of oil being forced up past the air pocket. This makes me think the compensating cylinder should be above the motors. Then I wonder why does the compensating cylinder need oil in it at all. As long as the bore in the cylinder has enough volume so the piston is not bottomed out at max depth. I also have a small spring pushing the cylinder rod to create a small internal pressure above ambient. Is my logic flawed? it would be very convenient to eliminate the oil in the cylinder and would make the compensator faster to react to pressure change say in a fast ascent. </div><div id="yiv4016051153yui_3_16_0_ym19_1_1505530250025_3053">Hank</div></div></div></div>_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" target="_blank" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="http://www..psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"><br clear="none"><br clear="none"></div></div> </div> </div> </div></div></div><div><compensator.jpg></div></div></div><div class="yqt8015017445" id="yqt11027">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org" href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a shape="rect" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div></div>
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