<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1480249331941_4890"><span>Alan,</span></div><div id="yui_3_16_0_1_1480249331941_4890" dir="ltr"><span id="yui_3_16_0_1_1480249331941_5254">Think of it as a hydraulic system, not an air system. The arm is identical in every way except it is powered by air pushing the oil instead of a pump. It would not be spongy because the cylinders are full of oil. The air never leaves the pressurized oil tank. </span> When the valve is activated, the oil moves as if it had a pump. Instead of the oil returning to the pump reservoir, it is sent to a holding tank that is a HP bottle. The air in the receiving tank compresses as the oil flows into it. Nothing is vented, it can not vent because I need to maintain a balance between the two tanks for buoyancy. As the oil leaves the pressure tank, the tank gets lighter. At the same time the receiving tank gets heavier, so they are balanced. </div><div id="yui_3_16_0_1_1480249331941_4890" dir="ltr">I am not worried about space, it is weight I am thinking about and complexity. Of coarse if you were doing construction with the arm it would need to be electric. But to grab one gold bar it can be air driven. Air drive saves battery power also. Having said all that, it may have a problem I have not expected, so speak up and save me some trouble anyone. </div><div id="yui_3_16_0_1_1480249331941_4890" dir="ltr"> I don't see a problem with a motor submerged in WD40, my vertical thrusters are full of it. I could use something else as long as it has a low enough viscosity for the motor to run. </div><div id="yui_3_16_0_1_1480249331941_4890" dir="ltr">Hank</div> <div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"><font size="2" face="Arial"> On Saturday, November 26, 2016 8:03 PM, Alan James via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv2665961427"><div><div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480187447224_5856"><span id="yiv2665961427yui_3_16_0_1_1480187447224_5900">Hi Hank,<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5884">Wouldn't you have to exhaust the air as in a pneumatic system?<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5885">Also air would have to displace the volume of oil in the cylinder<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5886">as the piston moves in & out, so there would be marginal benefits<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5887">over a pneumatic system. It would also be spongy like a pneumatic <br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5888">cylinder because any bouncing force on the cylinder would compress the air<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5889">that is the source for the movement.<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5890">You were talking about saving space with this idea, but if compressed<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5891">air was a good form of power we would have pneumatic thrusters <br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5892">instead of batteries & electric motors..<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5893">I once did the maths on how much energy was stored in a dive tank;<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5894">can't remember the result, but there was at least 3 x more energy in<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5895">a battery of an equivalent size.<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5896">WD40 as hydraulic oil? It is flammable with a reasonably low flash point.<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5897">Also at that viscosity you would be more prone to leaks wouldn't you?<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5898">https://www.wd40company.com/files/pdf/wd_40tec16952473.pdf<br clear="none" id="yiv2665961427yui_3_16_0_1_1480187447224_5899">Cheers Alan</span></div><div class="yiv2665961427qtdSeparateBR" id="yiv2665961427yui_3_16_0_1_1480187447224_5684"><br clear="none"><br clear="none"></div><div class="yiv2665961427yahoo_quoted" id="yiv2665961427yui_3_16_0_1_1480187447224_5714" style="display:block;"> <div id="yiv2665961427yui_3_16_0_1_1480187447224_5713" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div id="yiv2665961427yui_3_16_0_1_1480187447224_5712" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div class="yiv2665961427yqt5393059757" id="yiv2665961427yqt26177"><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480187447224_5711"> <font id="yiv2665961427yui_3_16_0_1_1480187447224_5710" face="Arial" size="2"> </font><hr size="1"> <b><span style="font-weight:bold;">From:</span></b> hank pronk via Personal_Submersibles <personal_submersibles@psubs.org><br clear="none"> <b><span style="font-weight:bold;">To:</span></b> Personal Submersibles General Discussion <personal_submersibles@psubs.org> <br clear="none"> <b><span style="font-weight:bold;">Sent:</span></b> Sunday, November 27, 2016 4:59 AM<br clear="none"> <b><span style="font-weight:bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Hydraulic idea<br clear="none"> </div> <div class="yiv2665961427y_msg_container" id="yiv2665961427yui_3_16_0_1_1480187447224_5717"><br clear="none"><div id="yiv2665961427"><div id="yiv2665961427yui_3_16_0_1_1480187447224_5716"><div id="yiv2665961427yui_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="yiv2665961427yui_3_16_0_1_1480175087437_3060"><span>Sean,</span></div><div id="yiv2665961427yui_3_16_0_1_1480175087437_3060"><span id="yiv2665961427yui_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 dir="ltr" id="yiv2665961427yui_3_16_0_1_1480175087437_3060">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 dir="ltr" id="yiv2665961427yui_3_16_0_1_1480175087437_3060">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 dir="ltr" id="yiv2665961427yui_3_16_0_1_1480175087437_3060"><br clear="none"></div><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480175087437_3060">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="yiv2665961427qtdSeparateBR" id="yiv2665961427yui_3_16_0_1_1480187447224_5800"><br clear="none"><br clear="none"></div><div class="yiv2665961427yahoo_quoted" id="yiv2665961427yui_3_16_0_1_1480187447224_5722" style="display:block;"> <div id="yiv2665961427yui_3_16_0_1_1480187447224_5721" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"> <div id="yiv2665961427yui_3_16_0_1_1480187447224_5720" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div class="yiv2665961427yqt2382799783" id="yiv2665961427yqt36000"><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480187447224_5719"><font id="yiv2665961427yui_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="yiv2665961427y_msg_container" id="yiv2665961427yui_3_16_0_1_1480187447224_5803"><div id="yiv2665961427"><div id="yiv2665961427yui_3_16_0_1_1480187447224_5802"><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480187447224_5801">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 dir="ltr" id="yiv2665961427yui_3_16_0_1_1480187447224_5804">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 dir="ltr" id="yiv2665961427yui_3_16_0_1_1480187447224_5805">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="yiv2665961427gmail_quote">On November 25, 2016 5:25:47 AM MST, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv2665961427gmail_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="yiv2665961427yqt2885590970" id="yiv2665961427yqt95748"><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="yiv2665961427yui_3_16_0_1_1480075807070_2825">Hi All,</div><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480075807070_2825">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 dir="ltr" id="yiv2665961427yui_3_16_0_1_1480075807070_2825">After the oil is used up, the oil can be returned to the pressure tank by reversing the air flow.</div><div dir="ltr" id="yiv2665961427yui_3_16_0_1_1480075807070_2825">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="yiv2665961427k9mail"></pre><hr><br clear="none">Personal_Submersibles mailing list<br clear="none">Personal_Submersibles@psubs.org<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"></blockquote></div></div></div><br clear="none"><div class="yiv2665961427yqt2885590970" id="yiv2665961427yqt00964">_______________________________________________<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"></div><br clear="none"><br clear="none"></div></div> </div> </div> </div></div></div></div><br clear="none"><div class="yiv2665961427yqt2382799783" id="yiv2665961427yqt04851">_______________________________________________<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"></div><br clear="none"><br clear="none"></div></div> </div> </div> </div></div></div></div><br><div class="yqt5393059757" id="yqt62639">_______________________________________________<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><br><br></div> </div> </div> </div></div></body></html>