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<div>Rick, </div><div>Just a further explanation as to why you don't need all the air out of the thruster.... </div><div>If the thruster was 1/4 full of air, and you had a large external bladder full of oil attached; if you descended to 300ft, the air in the motor would be compressed to 1/12 th its original volume and just be replaced by oil from the flexible bladder. The bladder, oil and air in the thruster & surrounding water will all be the same pressure. </div><div>When people used to wrap a tube around the thruster and attach it to two nipples, there was very little volume in the tube to compensate for the air compressing, & so it was critical to get every bit of air out. </div><div>Alan</div><div><br></div>
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On Saturday, September 18, 2021, 05:45:19 AM GMT+12, Rick Patton via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div><div id="ydpe4c21ff6yiv2863543824"><div><div dir="ltr">Hank, I forgot your thrusters don't rotate like mine. I assume you are talking about the Id of the hose being damaged as it collapses if the bubble was at the end? I am still having a hard time wrapping my head around having any air in the system as I would think that when the external pressure increases as you descend, the extra pressure would be pushing on everything evenly and the only things that are weak enough to give are the bubble in a bladder or hose and the extra pressure trying to squeeze the bubble going past the two factory shaft O rings? <div>Rick</div></div><br clear="none"><div class="ydpe4c21ff6yiv2863543824gmail_quote"><div class="ydpe4c21ff6yiv2863543824yqt3882605867" id="ydpe4c21ff6yiv2863543824yqt37297"><div class="ydpe4c21ff6yiv2863543824gmail_attr" dir="ltr">On Thu, Sep 16, 2021 at 11:33 PM hank pronk via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><blockquote class="ydpe4c21ff6yiv2863543824gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;"><div><div style="font-family:Helvetica, Arial, sans-serif;font-size:13px;"><div></div>
<div dir="ltr">Hi Rick, my rubber lines are currently flapping in the breeze sitting on top of my drop weight. Just tie them up, with an arc in the hose, so the bubble is in the middle. This way when the hose collapses it is in the middle, not at the end where it could be damaged by the edge of the plug. Or taper the plug. In my opinion, an air bubble is good in a hose.</div><div dir="ltr">If you have a soft bladder, you can work to get rid of every bubble of air if you want because the bladder will expand and contract as needed.</div><div dir="ltr">I see no point to worry about it, particularly with the bladder because the bubble will simple squeeze to nothing at the highest point of the bladder.</div><div dir="ltr">I am trying to think of a reason why an air bubble outside the motor is a problem. Maybe I am missing something. If I were in salt water with expensive motors, i would try to have a small soft bladder. I like the squeeze ball for individual locations, and an air bag for central location with multiple motors on it.</div><div dir="ltr">I won't be travelling this fall other than local lakes.</div><div dir="ltr">Hank</div><div><br clear="none"></div>
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On Thursday, September 16, 2021, 11:31:26 AM MDT, Rick Patton via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:
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<div><div id="ydpe4c21ff6yiv2863543824gmail-m_4246022930651740812yiv6694623509"><div><div dir="ltr">Hi Hank<div>would love a picture. Do you tie the 1' of vacuum hose to the housing so it's not flopping in the breeze? I thought I had heard conflicting ideas about, "make sure you get all the air out of the thruster and bladder" and others saying that they have a little air left in the bladder to allow for the hot oil expansion so I am confused. My thinking (which is limited) is that you can't have any air in anything because as you know, you can't compress a liquid so any air would compress and push out the factory "0" rings? </div><div>Shoot me a picture if it's not too much trouble. Need to wrap my head around this better so I can pick a method and go for it. </div><div>Are you going to the reunion?</div><div>Rick</div></div><br clear="none"><div><div id="ydpe4c21ff6yiv2863543824gmail-m_4246022930651740812yiv6694623509yqt39212"><div dir="ltr">On Thu, Sep 16, 2021 at 2:27 AM hank pronk via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;"><div><div style="font-family:Helvetica, Arial, sans-serif;font-size:13px;"><div></div>
<div dir="ltr">Hi Rick, the vacuum tube is about a foot long and comes out a threaded fitting in the housing. You can drill and tap either end in most cases. Choose the location well to make sure the fitting does not interfere with the bolts etc. I have a youtube video on how to do this. </div><div dir="ltr">I can email you a picture of the motor with the hose. It is still a good idea to have a bladder, just be sure it is real soft.</div><div dir="ltr">Hank</div><div><br clear="none"></div>
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On Wednesday, September 15, 2021, 03:17:00 PM MDT, Rick Patton via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:
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<div><div id="ydpe4c21ff6yiv2863543824gmail-m_4246022930651740812yiv6694623509gmail-m_-8648065951920121099yiv8598992633"><div><div dir="ltr">Hi Hank.<div>Do you happen to have a good picture of your set up? Not clear what you are saying. How long is your vacuum tube and I assume it comes out of the can but not back in? I woldn't think a rubber hose could inflate enough to allow the heated oil to expand it enough before pushing out the two factory "0" rings? </div><div>Rick</div></div><br clear="none"><div><div id="ydpe4c21ff6yiv2863543824gmail-m_4246022930651740812yiv6694623509gmail-m_-8648065951920121099yiv8598992633yqt74949"><div dir="ltr">On Wed, Sep 15, 2021 at 3:31 AM hank pronk via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;"><div>Hi Rick. I have oil filled at the moment because they jettison. I use a length of vacuum hose from a car engine because it is soft. I intended to install a car suspension air bag and connect all the motors to that. I don’t worry much about an air bubble because it will just compress to nothing. <br clear="none"><br clear="none"><div dir="ltr">Sent from my iPhone</div><div dir="ltr"><br clear="none"><blockquote type="cite">On Sep 15, 2021, at 7:18 AM, Alec Smyth via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"><br clear="none"></blockquote></div><blockquote type="cite"><div dir="ltr"><div dir="ltr">Hi Rick,<div><br clear="none"></div><div>You'll find people here who love oil compensation, and others who love air. They both work, so I guess it's just a matter of what has worked for each person. </div><div><br clear="none"></div><div>I used oil initially. The method was to put two 90 degree nipples in the motor can, and attach about a foot of plastic hose to them. To fill, you disconnect the top nipple and add oil through the hose until it comes out the top nipple. The hose wraps around the can and with that extra length is supposed to act as a bladder. I found it worked, but only until I started diving my K250 to 250 feet. Then, I was getting internal build-up of pressure in the motors. In the end, I figured what was going on was that the compression of the hose was insufficient for the thermal contraction between the surface, where I'd filled the motors, and the very cold ambient temperature at 250 feet. At depth, water was forcing its way past the shaft seals, and then the seals would keep the motors pressurized as I rose. My solution was to go to a larger bladder, namely this:</div><div><br clear="none"></div><div><a shape="rect" href="https://www.google.com/search?q=squeeze+bottles&rlz=1C1CHBF_enUS807US807&sxsrf=AOaemvLRC6ixUOHC7wIDhQcAL78ShVP-Sw:1631711091091&source=univ&tbm=shop&tbo=u&sa=X&ved=2ahUKEwig_9a_hYHzAhUgF1kFHRK2AW0Q1TV6BQgBEKkC&biw=1536&bih=664#spd=4605806885737196691" rel="nofollow" target="_blank">https://www.google.com/search?q=squeeze+bottles&rlz=1C1CHBF_enUS807US807&sxsrf=AOaemvLRC6ixUOHC7wIDhQcAL78ShVP-Sw:1631711091091&source=univ&tbm=shop&tbo=u&sa=X&ved=2ahUKEwig_9a_hYHzAhUgF1kFHRK2AW0Q1TV6BQgBEKkC&biw=1536&bih=664#spd=4605806885737196691</a><br clear="none"></div><div><br clear="none"></div><div>That said, the larger bladder was something I implemented just before selling that sub, so never got to dive it. It was also always a problem getting every last bubble out. I'd spend ages doing that, then come back the next day and find a bubble in the hose. I was never able to solve that issue, and I think the only way would have been to assemble the motor in a bucket of oil. The other problem was that if there was an issue, such as the over-pressurization one above, my sub created an oil slick. That is NOT good, and can attract the wrong sort of attention even if you were to use an oil that is harmless.</div><div><br clear="none"></div><div>Now I use air compensation. So far, so good. On my first dive with the mechanical arm, I noticed bubbles coming from a hose when I extended the arm. The bubbles would cease when I retracted the arm. Closer examination showed a nick in the hose, which got pinched closed when the arm was retracted. The beauty of air is that if there's a leak, you can see and trace it immediately. With oil, I'd have had a small slick but no idea where it was coming from. Also, it worked well in the sense that no water entered the arm. I have a shutoff valve, so that a leak won't drain the sub's air supply, or another way would be to supply the air comp with a small independent cylinder. </div><div><br clear="none"></div><div><br clear="none"></div><div>Best,</div><div>Alec </div></div><br clear="none"><div><div dir="ltr">On Wed, Sep 15, 2021 at 12:13 AM Rick Patton via Personal_Submersibles <<a shape="rect" href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br clear="none"></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex;">I am re thinking what to use for my oil expansion bladder. Would love to hear from everyone who chose to go with an oil filled thrusters on what they used and how they liked it. I remember someone saying that they used a squeeze ball gas tank primer which I like because it is small but I just spoke with someone who didn’t use a bladder and had never had a problem.<br clear="none">
Rick <br clear="none">
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