<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1480187447224_5856" dir="ltr"><span id="yui_3_16_0_1_1480187447224_5900">Hi Hank,<br id="yui_3_16_0_1_1480187447224_5884">Wouldn't you have to exhaust the air as in a pneumatic system?<br id="yui_3_16_0_1_1480187447224_5885">Also air would have to displace the volume of oil in the cylinder<br id="yui_3_16_0_1_1480187447224_5886">as the piston moves in & out, so there would be marginal benefits<br id="yui_3_16_0_1_1480187447224_5887">over a pneumatic system. It would also be spongy like a pneumatic <br id="yui_3_16_0_1_1480187447224_5888">cylinder because any bouncing force on the cylinder would compress the air<br id="yui_3_16_0_1_1480187447224_5889">that is the source for the movement.<br id="yui_3_16_0_1_1480187447224_5890">You were talking about saving space with this idea, but if compressed<br id="yui_3_16_0_1_1480187447224_5891">air was a good form of power we would have pneumatic thrusters <br id="yui_3_16_0_1_1480187447224_5892">instead of batteries & electric motors..<br id="yui_3_16_0_1_1480187447224_5893">I once did the maths on how much energy was stored in a dive tank;<br id="yui_3_16_0_1_1480187447224_5894">can't remember the result, but there was at least 3 x more energy in<br id="yui_3_16_0_1_1480187447224_5895">a battery of an equivalent size.<br id="yui_3_16_0_1_1480187447224_5896">WD40 as hydraulic oil? It is flammable with a reasonably low flash point.<br id="yui_3_16_0_1_1480187447224_5897">Also at that viscosity you would be more prone to leaks wouldn't you?<br id="yui_3_16_0_1_1480187447224_5898">https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf<br id="yui_3_16_0_1_1480187447224_5899">Cheers Alan</span></div><div class="qtdSeparateBR" id="yui_3_16_0_1_1480187447224_5684"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_1_1480187447224_5714" style="display: block;"> <div id="yui_3_16_0_1_1480187447224_5713" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_1_1480187447224_5712" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_1_1480187447224_5711" dir="ltr"> <font id="yui_3_16_0_1_1480187447224_5710" face="Arial" size="2"> <hr size="1"> <b><span style="font-weight: bold;">From:</span></b> hank pronk via Personal_Submersibles <personal_submersibles@psubs.org><br> <b><span style="font-weight: bold;">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Sunday, November 27, 2016 4:59 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Hydraulic idea<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1480187447224_5717"><br><div id="yiv9627893211"><div id="yui_3_16_0_1_1480187447224_5716"><div id="yui_3_16_0_1_1480187447224_5715" style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px; background-color: rgb(255, 255, 255);"><div id="yiv9627893211yui_3_16_0_1_1480175087437_3060"><span>Sean,</span></div><div id="yiv9627893211yui_3_16_0_1_1480175087437_3060"><span id="yiv9627893211yui_3_16_0_1_1480175087437_3181">The receiving tank will take the full depth pressure and be large </span>enough to take all the oil without building up excess air pressure, no need to vent off, since it is only receiving oil and displacing air. I need a balance with two tanks to maintain neutral buoyancy.</div><div id="yiv9627893211yui_3_16_0_1_1480175087437_3060" dir="ltr">I am not worried about oxidation of the oil because the oil is not going through a pump and the flow rate is so small. I ordered air cylinders for the manipulator with a 5\8 rod to reduce the back pressure. Gamma's manipulator operated at 1,100 psi when the sub was at 1,000 feed of depth. The arm will loose power, but I don't expect that to be an issue, because the oil tank will be powered from a separate bottle of air. </div><div id="yiv9627893211yui_3_16_0_1_1480175087437_3060" dir="ltr">I have to work with what I have to keep the cost in check, so I can modify an open centre valve by blocking the final pressure port drain. I also have some HP tanks. If it does not work out easily, I have a few electric pumps I can use. </div><div id="yiv9627893211yui_3_16_0_1_1480175087437_3060" dir="ltr"><br clear="none"></div><div id="yiv9627893211yui_3_16_0_1_1480175087437_3060" dir="ltr">If I go electric, I intend to submerge the motor pump unit in the oil reservoir with a bladder top to compensate. That means I will use WD40 as hydraulic fluid.</div> <div class="yiv9627893211qtdSeparateBR" id="yui_3_16_0_1_1480187447224_5800"><br clear="none"><br clear="none"></div><div class="yiv9627893211yahoo_quoted" id="yui_3_16_0_1_1480187447224_5722" style="display: block;"> <div id="yui_3_16_0_1_1480187447224_5721" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div id="yui_3_16_0_1_1480187447224_5720" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div class="yiv9627893211yqt2382799783" id="yiv9627893211yqt36000"><div id="yui_3_16_0_1_1480187447224_5719" dir="ltr"><font id="yui_3_16_0_1_1480187447224_5718" face="Arial" size="2"> On Saturday, November 26, 2016 6:25 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br clear="none"></font></div> <br clear="none"><br clear="none"> <div class="yiv9627893211y_msg_container" id="yui_3_16_0_1_1480187447224_5803"><div id="yiv9627893211"><div id="yui_3_16_0_1_1480187447224_5802"><div id="yui_3_16_0_1_1480187447224_5801" dir="ltr">How do you intend to control the pressure on the receive tank? Just vent it through a check valve to the water? You need to design carefully to prevent contamination in either direction.</div>
<div id="yui_3_16_0_1_1480187447224_5804" dir="ltr">I wouldn't use air as the drive gas under high pressures, in order to prevent oxidation of the oil. Charge with nitrogen if you intend to do this.</div>
<div id="yui_3_16_0_1_1480187447224_5805" dir="ltr">To generate the same drive capability as a hydraulic pump, you are talking about very high precharge pressure - approaching the pressure at which HP bottled gas is supplied, unless you can source e.g. 6000 psi nitrogen and regulate it down to 2500-5000 depending on your manipulator requirements. In any case, if your cylinders are single acting, or even dual acting with a single rod, you have to contend with the force from the ambient water pressure, so your receive tank pressure needs to be this at minimum, and with a pressure reservoir source instead of a pump, that available delta-P is further reduced the moment you demand any fluid from the system (i.e. HP bottle pressure will drop), so your manipulator becomes weaker over time.</div>
<div dir="ltr">Just a few things to think about.</div>
<div dir="ltr">Sean</div>
<br clear="none"><br clear="none"><div class="yiv9627893211gmail_quote">On November 25, 2016 5:25:47 AM MST, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv9627893211gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;">
<div class="yiv9627893211yqt2885590970" id="yiv9627893211yqt95748"><div style="color: rgb(0, 0, 0); font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px; background-color: rgb(255, 255, 255);"><div id="yiv9627893211yui_3_16_0_1_1480075807070_2825">Hi All,</div><div id="yiv9627893211yui_3_16_0_1_1480075807070_2825" dir="ltr">I have an idea to replace the hydraulic pump for my new manipulator with a air over hydraulic system. It is quite simple, the hydraulic oil reservoir is a hp tank that can be pressurized from a designated HP supply. The oil return goes to another HP tank to receive the oil. This eliminates the pump completely and that is a dream. The manipulator can go through 54 complete extensions and retractions, that is 54 complete movements of all functions. </div><div id="yiv9627893211yui_3_16_0_1_1480075807070_2825" dir="ltr">After the oil is used up, the oil can be returned to the pressure tank by reversing the air flow.</div><div id="yiv9627893211yui_3_16_0_1_1480075807070_2825" dir="ltr">Hank</div></div></div><div style="margin-bottom: 1em; border-bottom-color: rgb(0, 0, 0); border-bottom-width: 1px; border-bottom-style: solid;"></div><pre class="yiv9627893211k9mail"></pre><hr><br clear="none">Personal_Submersibles mailing list<br clear="none">Personal_Submersibles@psubs.org<br clear="none"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" rel="nofollow" shape="rect">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></blockquote></div></div></div><br clear="none"><div class="yiv9627893211yqt2885590970" id="yiv9627893211yqt00964">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a href="mailto:Personal_Submersibles@psubs.org" target="_blank" rel="nofollow" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" rel="nofollow" shape="rect">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><br clear="none"><br clear="none"></div></div> </div> </div> </div></div></div></div><br><div class="yqt2382799783" id="yqt04851">_______________________________________________<br clear="none">Personal_Submersibles mailing list<br clear="none"><a href="mailto:Personal_Submersibles@psubs.org" shape="rect" ymailto="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a><br clear="none"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" target="_blank" shape="rect">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></div><br><br></div> </div> </div> </div></div></body></html>