<div dir="ltr">Cliff knows this first hand, but my experience with the WD40 was similar to his. I found the oil went black after just the shortest of use time, and all my thrusters were generating gas. I'd start the day with just a tiny bubble of air in the accordion bottles, but end it with those bottles stretched taut, and a couple of times they blew off or ruptured due to the pressure. I got the impression the electrical arcs on the brushes might be generating gas. <div><br></div><div>I'm returning to Michigan next week to pick up the sub, which I left behind to a mechanical breakdown of my tow vehicle. Once I have the sub in hand, I'll take a thruster off and use it to research ceramic seals and the design of a custom endcap. Cliff, I know you use a custom endcap already. If you want to send me the CAD file for it, and I used that as a starting point, it's likely the resulting design would maintain compatibility with your Kort struts. </div><div><br></div><div>One thing that perplexes me is that Hank gets good results with WD-40. I really can't think of anything we're doing differently!</div><div><br></div><div>On a positive note, I redid the air compensation for the arm for this trip, and it worked really well. It uses the SS Parker regulator that both Cliff and I used in the past for compensation. My issue with it earlier was that it's OP valve appears to handle only a very low volume, because I was seeing compensation pressure overshoot on ascent. The solution was super simple, I just added a separate OP valve to the compensated line (thanks Alan for the valve suggestion!) This small change makes air compensation attractive again to me, but if we can get 1-atm thrusters to work well, I'd like that even more due to the simplicity. </div><div><br></div><div>Best,</div><div>Alec</div><div><br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Jul 25, 2023 at 6:07 PM Cliff Redus 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><div style="font-family:"times new roman","new york",times,serif;font-size:16px"><div></div>
<div dir="ltr">Good to hear from you my old friend. I stated out with air compensation using the same pressure regulator that you were using. I switch out mainly because I was using too much air on deep dives. At that point I only had 80 scf of HP air. I have since added another 60 scf but still this is not a lot of air for deep dives. Interesting comment about oil impregnating the carbon and then depressurization and getting the "bends".</div><div dir="ltr"><br></div><div dir="ltr">I think Alec may be on to something with the idea of going back to no pressure compensation and using a single mechanical seal. Jon just sent me some pictures of the mechanical seal Kittridge had in the K600. The issue is if there is enough space in the housing to machine out the enclosure. I just don't think there is enough space for the seal without a complete redesign of housing on the Minn Kotas that hold the brushes.</div><div dir="ltr"><br></div><div dir="ltr"> So I am assuming that the 15 seals on Q-Sub are all air compensated with the same regulators you sent me specs on? </div><div dir="ltr"><br></div><div dir="ltr">Cliff<br><div><div dir="ltr" style="color:rgb(38,40,42);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif"><br></div></div></div>
</div><div id="m_-214743638935602065ydp686e84ceyahoo_quoted_1228894202">
<div style="font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:13px;color:rgb(38,40,42)">
<div>
On Tuesday, July 25, 2023 at 04:11:09 PM CDT, via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:
</div>
<div><br></div>
<div><br></div>
<div><div dir="ltr">I noticed that Karl Stanley promotes air compensation. I could never<br></div><div dir="ltr">understand why oil ( WD40 etc) was touted as being the preferred medium. I<br></div><div dir="ltr">would agree with Cliff that the oil has possibly affected the carbon. I<br></div><div dir="ltr">have had a lot of experience with carbon and mechanical seals and now will<br></div><div dir="ltr">not use it. The most successful carbon was antimony impregnated in my<br></div><div dir="ltr">experience. The oils would impregnate the carbon and then with<br></div><div dir="ltr">depressurisation it would get the "bends". i.e. it would be subjected to<br></div><div dir="ltr">minute explosive decompression which would pit the surface. The most<br></div><div dir="ltr">successful seals were bronze and silicon or tungsten carbide. I should<br></div><div dir="ltr">learn from my own mistakes as I have a leaking "carbon"/silicon Carbide<br></div><div dir="ltr">seal. That is only in test mode and has not seen any real pressure. As I<br></div><div dir="ltr">have so many seals, 15 , I once again got conned into a cheaper solution. I<br></div><div dir="ltr">think we all collectively have the answers it is just the in depth reviews<br></div><div dir="ltr">of detailed design that is lacking. Cheers, Hugh<br></div><div dir="ltr"><br></div><div dir="ltr">-----Original Message-----<br></div><div dir="ltr">From: Personal_Submersibles <<a href="mailto:personal_submersibles-bounces@psubs.org" rel="nofollow" target="_blank">personal_submersibles-bounces@psubs.org</a>> On<br></div><div dir="ltr">Behalf Of via Personal_Submersibles<br></div><div dir="ltr">Sent: Wednesday, July 26, 2023 8:03 AM<br></div><div dir="ltr">To: <a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br></div><div dir="ltr">Subject: Personal_Submersibles Digest, Vol 119, Issue 24<br></div><div dir="ltr"><br></div><div dir="ltr">Send Personal_Submersibles mailing list submissions to<br></div><div dir="ltr"> <a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br></div><div dir="ltr"><br></div><div dir="ltr">To subscribe or unsubscribe via the World Wide Web, visit<br></div><div dir="ltr"> <a href="http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles</a><br></div><div dir="ltr">or, via email, send a message with subject or body 'help' to<br></div><div dir="ltr"> <a href="mailto:personal_submersibles-request@psubs.org" rel="nofollow" target="_blank">personal_submersibles-request@psubs.org</a><br></div><div dir="ltr"><br></div><div dir="ltr">You can reach the person managing the list at<br></div><div dir="ltr"> <a href="mailto:personal_submersibles-owner@psubs.org" rel="nofollow" target="_blank">personal_submersibles-owner@psubs.org</a><br></div><div dir="ltr"><br></div><div dir="ltr">When replying, please edit your Subject line so it is more specific than<br></div><div dir="ltr">"Re: Contents of Personal_Submersibles digest..."<br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr">Today's Topics:<br></div><div dir="ltr"><br></div><div dir="ltr"> 1. Re: Minn Kotta 101 - Thruster Reliability<br></div><div dir="ltr"> (Sean T. Stevenson via Personal_Submersibles)<br></div><div dir="ltr"> 2. Re: Minn Kotta 101 - Thruster Reliability<br></div><div dir="ltr"> (Cliff Redus via Personal_Submersibles)<br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr">----------------------------------------------------------------------<br></div><div dir="ltr"><br></div><div dir="ltr">Message: 1<br></div><div dir="ltr">Date: Tue, 25 Jul 2023 19:22:18 +0000<br></div><div dir="ltr">From: "Sean T. Stevenson via Personal_Submersibles"<br></div><div dir="ltr"> <<a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br></div><div dir="ltr">To: <a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a><br></div><div dir="ltr">Subject: Re: [PSUBS-MAILIST] Minn Kotta 101 - Thruster Reliability<br></div><div dir="ltr">Message-ID:<br></div><div dir="ltr"> <br></div><div dir="ltr"><hvwrA_XYbHM4wnAnT6PD23ce1r3TTx98KLljgIsgeatOQqs_ozgPAoDf_LRIrLUnwKqmA7i_6YC<br></div><div dir="ltr">tq3prbN_uGmkJ1pQsRDVuTtWK9_40l-g=@<a href="http://protonmail.com" target="_blank">protonmail.com</a>><br></div><div dir="ltr"> <br></div><div dir="ltr">Content-Type: text/plain; charset="utf-8"<br></div><div dir="ltr"><br></div><div dir="ltr">I have no specific experience with using the WD40 product for pressure<br></div><div dir="ltr">compensating thrusters (or any other volumes, for that matter), but I do<br></div><div dir="ltr">question its efficacy for that purpose on the basis of its known properties.<br></div><div dir="ltr"><br></div><div dir="ltr">WD40 is a proprietary mixture of lubricants and solvents known to have<br></div><div dir="ltr">strong dielectric properties. While the exact formulation is a trade secret,<br></div><div dir="ltr">in general terms the product is an emulsion of oil and alcohol. Marketed as<br></div><div dir="ltr">a penetrant, it has a low viscosity afforded by the substantial fraction of<br></div><div dir="ltr">volatile, lightweight components, which help to allow capillary action to<br></div><div dir="ltr">draw the emulsified product into crevices. In unencapsulated service (open<br></div><div dir="ltr">to atmosphere), typically the lightweight components will evaporate into the<br></div><div dir="ltr">surrounding air, temporarily serving their function as a solvent to dissolve<br></div><div dir="ltr">certain solid or high viscosity residues before leaving behind the heavier<br></div><div dir="ltr">oils which serve the lubrication function.<br></div><div dir="ltr"><br></div><div dir="ltr">When you encapsulate WD40 in a closed volume, the lightweight components do<br></div><div dir="ltr">not evaporate, leaving them to perform their solvent function on any soluble<br></div><div dir="ltr">material in contact for as long as the equilibrium concentration gradient<br></div><div dir="ltr">supports that. Additionally, you hold these lightweight components with low<br></div><div dir="ltr">viscosity / high volatility (remember, this product is marketed as a<br></div><div dir="ltr">penetrant) in contact with whatever sealing arrangements are designed to<br></div><div dir="ltr">keep it contained, where these seals would otherwise perform much better in<br></div><div dir="ltr">contact with a higher viscosity oil or grease which augments the seal<br></div><div dir="ltr">performance.<br></div><div dir="ltr"><br></div><div dir="ltr">In short, for any compensation of electronics in static applications, I<br></div><div dir="ltr">would consider only the dielectric properties and dimensional stability<br></div><div dir="ltr">(bulk modulus) of the compensating fluid. In a dynamic application, such as<br></div><div dir="ltr">with a drive shaft seal, I would also pay attention to viscosity and<br></div><div dir="ltr">lubricity. Material compatibility, however, is critically important in both<br></div><div dir="ltr">cases, and I would be much more comfortable with a product for which the<br></div><div dir="ltr">chemical makeup (and thus the material compatibility matrix) is known and<br></div><div dir="ltr">available on a technical datasheet, versus a proprietary product that has no<br></div><div dir="ltr">such publically available information.<br></div><div dir="ltr"><br></div><div dir="ltr">Similarly, with regard to compensating a Minn Kota motor specifically, I<br></div><div dir="ltr">would want to know what all of the internal materials that may be in contact<br></div><div dir="ltr">with the compensation fluid are, to make sure I was specifying a compatible<br></div><div dir="ltr">fluid. I have no idea what information is available in that respect.<br></div><div dir="ltr"><br></div><div dir="ltr">Finally, I do wonder how much fluid breakdown is occurring not as a result<br></div><div dir="ltr">of chemical incompatibility, but rather as a result of the brushes lifting<br></div><div dir="ltr">from the armature due to the journal effect of the compensating fluid<br></div><div dir="ltr">forming a boundary layer in between the two parts as they rotate, and a<br></div><div dir="ltr">consequent electric arc forming which jumps the gap and cooks the fluid in<br></div><div dir="ltr">the process. The combination of fluid breakdown and ablation of the brushes<br></div><div dir="ltr">from such arcing could possibly be the source of the blackened fluid, as<br></div><div dir="ltr">opposed to dissolution of the components due to chemical incompatibility.<br></div><div dir="ltr"><br></div><div dir="ltr">I find myself wondering if there might be a sweet spot with respect to the<br></div><div dir="ltr">compensating fluid viscosity where the rotor is actually slowed by the fluid<br></div><div dir="ltr">to the extent that the brush contact is actually better than it would be<br></div><div dir="ltr">when rotating faster in a lesser viscosity fluid.<br></div><div dir="ltr"><br></div><div dir="ltr">Sean<br></div><div dir="ltr"><br></div><div dir="ltr">-------- Original Message --------<br></div><div dir="ltr">On Jul. 25, 2023, 12:11, Cliff Redus via Personal_Submersibles wrote:<br></div><div dir="ltr"><br></div><div dir="ltr">> The point of the thread is Psubbers like to use the Minn-Kotta 101 lower<br></div><div dir="ltr">units as a starting point for thrusters because they are cheap, simple to<br></div><div dir="ltr">control, quiet and simple to work on.For my boat I have used these with both<br></div><div dir="ltr">air and oil compensation and have now lost a thruster using each of these<br></div><div dir="ltr">pressure compensation strategies.Typical run lives of trolling motors are on<br></div><div dir="ltr">the order of 5-10 years for boaters. This thruster had less than 20 hours of<br></div><div dir="ltr">run time.How can we boost the reliability of these thrusters?<br></div><div dir="ltr">><br></div><div dir="ltr">> R300 Thruster Failure, Beaver Island Expedition July 15, 2023<br></div><div dir="ltr">><br></div><div dir="ltr">> We had a great IS Expedition at Beaver Island on Lake Michigan.Water was<br></div><div dir="ltr">blue, visibility was great, support excellent.Dives were great!That?s the<br></div><div dir="ltr">good news.The bad news is that after a submerged two mile transect when I<br></div><div dir="ltr">surface, I lost the port stern horizonal thruster. Alec?s son Treavor was<br></div><div dir="ltr">the safety diver for the expedition.I asked him to swim over and<br></div><div dir="ltr">inspect.There were no obvious issues like had occurred last year at Lake<br></div><div dir="ltr">Charlevoix when a limb got lodged between the prop and ducted nozzle and<br></div><div dir="ltr">lockrf up rotation.After recovering the boat, I disassembled the<br></div><div dir="ltr">thruster.These are Minn-Kotta 101 lower units that have been modified by<br></div><div dir="ltr">adding hydraulic pressure compensation with WD-40 for the fluid and a small<br></div><div dir="ltr">bellow style bladder for thermal expansion.Before disassembly, I noticed<br></div><div dir="ltr">that the bladder for this unit was completely compressed.The bladders on the<br></div><div dir="ltr">three remaining thrusters were expanded almost to the point of rupture and<br></div><div dir="ltr">were black in appearance.Also, before I di!<br></div><div dir="ltr"> sassembly, I pushed radially on the prop shaft and was rewarded with a<br></div><div dir="ltr">squirt of black 10WD-40.The shaft had a lot more radial play than<br></div><div dir="ltr">normal.From this I could tell the shaft bushing was worn and that both the<br></div><div dir="ltr">thruster lip seals had failed.Upon disassembly, I drained the contents of<br></div><div dir="ltr">the remaining fluid into a plastic pail.See picture at the Psubs web<br></div><div dir="ltr">site.What came out was black WD-40 fluid and a lot of loose black sludge<br></div><div dir="ltr">which was a portion of the brushes.Trolling motors are typically made of a<br></div><div dir="ltr">blend of carbon and graphite also known as carbon-graphite.Upon pulling off<br></div><div dir="ltr">the bow cap and brush end of the trolling motor I found that the surfaces<br></div><div dir="ltr">were caked with black sludge.See picture.Inspecting the brushes showed the<br></div><div dir="ltr">cause of failure.Both brushes were about half the thickness of a new brush<br></div><div dir="ltr">set.One of the brushes springs had bottomed out thus no spring force was<br></div><div dir="ltr">being applied to the brush and thus loss of electrical contact.The WD-40<br></div><div dir="ltr">fluid had been in the thruster since la!<br></div><div dir="ltr"> st year?s Psub convention in Lake Charlevoix.According to the manufacturer<br></div><div dir="ltr">MSDS sheet, WD-40 consist of 30-60% petroleum distillates, 10-30% petroleum<br></div><div dir="ltr">base oils and 5-15% Naptha.My working hypothesis is that one or more of the<br></div><div dir="ltr">components in the WD-40 reacted with the binding agent in the<br></div><div dir="ltr">carbon-graphite brushes and reduced the mechanical strength of the brush<br></div><div dir="ltr">thus leading to accelerate wear.Over the two years period (17,500 hours),<br></div><div dir="ltr">the thrusters had two main dive events with a total of no more than 20 hours<br></div><div dir="ltr">on the units.The balance of the time, the thrusters were sitting on the boat<br></div><div dir="ltr">in my shop soaking in this WD-40 at elevated Texas temperatures.BTW, the<br></div><div dir="ltr">driver for using WD-40 is that is a very low kinematic viscosity (2.8 cSt at<br></div><div dir="ltr">100 F or 38C). Note water is about 1 cSt.<br></div><div dir="ltr">><br></div><div dir="ltr">> One other observation on the failure was the wear on the armature shaft.It<br></div><div dir="ltr">has a visible wear ring and the shaft bushing went from a snug fit to a<br></div><div dir="ltr">loose fit.Working hypothesis is that the carbon-graphite particles in<br></div><div dir="ltr">suspension were acting like an abrasive polish.<br></div><div dir="ltr">><br></div><div dir="ltr">> The question is how can we improve the reliability? Should we investigate<br></div><div dir="ltr">a different seal and try to get by with 1-ATM operation or investigate a<br></div><div dir="ltr">different oil or go back to air compensation? What Alec and I discussed at<br></div><div dir="ltr">the Expedition was to try a single mechanical carbon seal or a high<br></div><div dir="ltr">pressure-rated lip seal. If we can come up with something to try, I am<br></div><div dir="ltr">willing to put a Minn-Kotta 101 in my test chamber, power it up so that the<br></div><div dir="ltr">seal in a dynamic mode and increase pressure to failure. A control would be<br></div><div dir="ltr">to run an off-the-shelf MK 101 with no pressure compensation to failure.<br></div><div dir="ltr">><br></div><div dir="ltr">> Any thoughts?I would like to hear what experience others have had with oil<br></div><div dir="ltr">compensation on MK 101?s.<br></div><div dir="ltr">><br></div><div dir="ltr">> Cliff<br></div><div dir="ltr">-------------- next part --------------<br></div><div dir="ltr">An HTML attachment was scrubbed...<br></div><div dir="ltr">URL:<br></div><div dir="ltr"><<a href="http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230725/" rel="nofollow" target="_blank">http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230725/</a><br></div><div dir="ltr">93cfbc41/attachment-0001.html><br></div><div dir="ltr"><br></div><div dir="ltr">------------------------------<br></div><div dir="ltr"><br></div><div dir="ltr">Message: 2<br></div><div dir="ltr">Date: Tue, 25 Jul 2023 20:02:55 +0000 (UTC)<br></div><div dir="ltr">From: Cliff Redus via Personal_Submersibles<br></div><div dir="ltr"> <<a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br></div><div dir="ltr">To: "Sean T. Stevenson via Personal_Submersibles"<br></div><div dir="ltr"> <<a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>><br></div><div dir="ltr">Subject: Re: [PSUBS-MAILIST] Minn Kotta 101 - Thruster Reliability<br></div><div dir="ltr">Message-ID: <<a href="mailto:1367956435.5158416.1690315375216@mail.yahoo.com" rel="nofollow" target="_blank">1367956435.5158416.1690315375216@mail.yahoo.com</a>><br></div><div dir="ltr">Content-Type: text/plain; charset="utf-8"<br></div><div dir="ltr"><br></div><div dir="ltr"> Minn Kota is very tight lipped about any of the design aspects of their<br></div><div dir="ltr">products.? I guess they are fending off cheap knockoffs.? As such I can find<br></div><div dir="ltr">no real data on materials such as make-up of the brushes.? I am looking at<br></div><div dir="ltr">transformer dielectric oil as a possible replacement<br></div><div dir="ltr">like?<a href="https://phillips66lubricants.com/wp-content/uploads/2019/12/Transformer" target="_blank">https://phillips66lubricants.com/wp-content/uploads/2019/12/Transformer</a><br></div><div dir="ltr">-Oil.pdf. As to arcing being the possible cause of the blackened fluid, it<br></div><div dir="ltr">is possible, but my guess is a suspension of brush particles given the<br></div><div dir="ltr">amount of sludge left on all the parts and the wear pattern on the shaft.?<br></div><div dir="ltr">What would support arcing hypothesis is that all of these thrusters were<br></div><div dir="ltr">filled using a vacuum pump.? Yet all the bladders experienced gas pressure<br></div><div dir="ltr">build-up.? Likewise, Alec filled all his thrusters with WD-40 and saw<br></div><div dir="ltr">similar blackened WD-40 in bladders and similar gas built up past what you<br></div><div dir="ltr">would expect from thermal expansion of fluid.<br></div><div dir="ltr">Cliff<br></div><div dir="ltr"><br></div><div dir="ltr"> On Tuesday, July 25, 2023 at 02:23:16 PM CDT, Sean T. Stevenson via<br></div><div dir="ltr">Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote: <br></div><div dir="ltr"> <br></div><div dir="ltr"> I have no specific experience with using the WD40 product for pressure<br></div><div dir="ltr">compensating thrusters (or any other volumes, for that matter), but I do<br></div><div dir="ltr">question its efficacy for that purpose on the basis of its known properties.<br></div><div dir="ltr"><br></div><div dir="ltr">WD40 is a proprietary mixture of lubricants and solvents known to have<br></div><div dir="ltr">strong dielectric properties. While the exact formulation is a trade secret,<br></div><div dir="ltr">in general terms the product is an emulsion of oil and alcohol. Marketed as<br></div><div dir="ltr">a penetrant, it has a low viscosity afforded by the substantial fraction of<br></div><div dir="ltr">volatile, lightweight components, which help to allow capillary action to<br></div><div dir="ltr">draw the emulsified product into crevices. In unencapsulated service (open<br></div><div dir="ltr">to atmosphere), typically the lightweight components will evaporate into the<br></div><div dir="ltr">surrounding air, temporarily serving their function as a solvent to dissolve<br></div><div dir="ltr">certain solid or high viscosity residues before leaving behind the heavier<br></div><div dir="ltr">oils which serve the lubrication function.<br></div><div dir="ltr"><br></div><div dir="ltr">When you encapsulate WD40 in a closed volume, the lightweight components do<br></div><div dir="ltr">not evaporate, leaving them to perform their solvent function on any soluble<br></div><div dir="ltr">material in contact for as long as the equilibrium concentration gradient<br></div><div dir="ltr">supports that. Additionally, you hold these lightweight components with low<br></div><div dir="ltr">viscosity / high volatility (remember, this product is marketed as a<br></div><div dir="ltr">penetrant) in contact with whatever sealing arrangements are designed to<br></div><div dir="ltr">keep it contained, where these seals would otherwise perform much better in<br></div><div dir="ltr">contact with a higher viscosity oil or grease which augments the seal<br></div><div dir="ltr">performance.<br></div><div dir="ltr"><br></div><div dir="ltr">In short, for any compensation of electronics in static applications, I<br></div><div dir="ltr">would consider only the dielectric properties and dimensional stability<br></div><div dir="ltr">(bulk modulus) of the compensating fluid. In a dynamic application, such as<br></div><div dir="ltr">with a drive shaft seal, I would also pay attention to viscosity and<br></div><div dir="ltr">lubricity. Material compatibility, however, is critically important in both<br></div><div dir="ltr">cases, and I would be much more comfortable with a product for which the<br></div><div dir="ltr">chemical makeup (and thus the material compatibility matrix) is known and<br></div><div dir="ltr">available on a technical datasheet, versus a proprietary product that has no<br></div><div dir="ltr">such publically available information.<br></div><div dir="ltr"><br></div><div dir="ltr">Similarly, with regard to compensating a Minn Kota motor specifically, I<br></div><div dir="ltr">would want to know what all of the internal materials that may be in contact<br></div><div dir="ltr">with the compensation fluid are, to make sure I was specifying a compatible<br></div><div dir="ltr">fluid. I have no idea what information is available in that respect.<br></div><div dir="ltr"><br></div><div dir="ltr">Finally, I do wonder how much fluid breakdown is occurring not as a result<br></div><div dir="ltr">of chemical incompatibility, but rather as a result of the brushes lifting<br></div><div dir="ltr">from the armature due to the journal effect of the compensating fluid<br></div><div dir="ltr">forming a boundary layer in between the two parts as they rotate, and a<br></div><div dir="ltr">consequent electric arc forming which jumps the gap and cooks the fluid in<br></div><div dir="ltr">the process. The combination of fluid breakdown and ablation of the brushes<br></div><div dir="ltr">from such arcing could possibly be the source of the blackened fluid, as<br></div><div dir="ltr">opposed to dissolution of the components due to chemical incompatibility.<br></div><div dir="ltr"><br></div><div dir="ltr">I find myself wondering if there might be a sweet spot with respect to the<br></div><div dir="ltr">compensating fluid viscosity where the rotor is actually slowed by the fluid<br></div><div dir="ltr">to the extent that the brush contact is actually better than it would be<br></div><div dir="ltr">when rotating faster in a lesser viscosity fluid.<br></div><div dir="ltr"><br></div><div dir="ltr">Sean<br></div><div dir="ltr"><br></div><div dir="ltr">-------- Original Message --------<br></div><div dir="ltr">On Jul. 25, 2023, 12:11, Cliff Redus via Personal_Submersibles <<br></div><div dir="ltr"><a href="mailto:personal_submersibles@psubs.org" rel="nofollow" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr"> <br></div><div dir="ltr">The point of the thread is Psubbers like to use theMinn-Kotta 101 lower<br></div><div dir="ltr">units as a starting point for thrusters because they arecheap, simple to<br></div><div dir="ltr">control, quiet and simple to work on.? For my boat I have used these with<br></div><div dir="ltr">both airand oil compensation and have now lost a thruster using each of<br></div><div dir="ltr">these pressure compensationstrategies.? Typical run lives of trollingmotors<br></div><div dir="ltr">are on the order of 5-10 years for boaters. ?This thruster had less than 20<br></div><div dir="ltr">hours of runtime.? How can we boost the reliability ofthese thrusters?<br></div><div dir="ltr"><br></div><div dir="ltr">R300 Thruster Failure, Beaver Island Expedition July 15,2023<br></div><div dir="ltr"><br></div><div dir="ltr">We had a great IS Expedition at Beaver Island on Lake Michigan.? Water was<br></div><div dir="ltr">blue, visibility was great, supportexcellent.? Dives were great!? That?s the<br></div><div dir="ltr">good news.? The bad news is that after a submerged twomile transect when I<br></div><div dir="ltr">surface, I lost the port stern horizonal thruster. Alec?sson Treavor was the<br></div><div dir="ltr">safety diver for the expedition.? I asked him to swim over and inspect.?<br></div><div dir="ltr">There were no obvious issues like had occurredlast year at Lake Charlevoix<br></div><div dir="ltr">when a limb got lodged between the prop and ductednozzle and lockrf up<br></div><div dir="ltr">rotation.? After recoveringthe boat, I disassembled the thruster.? Theseare<br></div><div dir="ltr">Minn-Kotta 101 lower units that have been modified by adding<br></div><div dir="ltr">hydraulicpressure compensation with WD-40 for the fluid and a small bellow<br></div><div dir="ltr">style bladderfor thermal expansion.? Beforedisassembly, I noticed that the<br></div><div dir="ltr">bladder for this unit was completely compressed.? The bladders on the three<br></div><div dir="ltr">remaining thrusterswere expanded almost to the point of rupture and were<br></div><div dir="ltr">black in appearance.? Also, be!<br></div><div dir="ltr"> fore I disassembly, I pushed radiallyon the prop shaft and was rewarded<br></div><div dir="ltr">with a squirt of black 10WD-40.? The shaft had a lot more radial play<br></div><div dir="ltr">thannormal.? From this I could tell the shaftbushing was worn and that both<br></div><div dir="ltr">the thruster lip seals had failed.? Upon disassembly, I drained the contents<br></div><div dir="ltr">ofthe remaining fluid into a plastic pail.?See picture at the Psubs web<br></div><div dir="ltr">site.?What came out was black WD-40 fluid and a lot of loose black sludge<br></div><div dir="ltr">whichwas a portion of the brushes.? Trollingmotors are typically made of a<br></div><div dir="ltr">blend of carbon and graphite also known ascarbon-graphite.? Upon pulling off<br></div><div dir="ltr">thebow cap and brush end of the trolling motor I found that the surfaces<br></div><div dir="ltr">were cakedwith black sludge.? See picture.? Inspecting the brushes showed<br></div><div dir="ltr">the cause of failure.? Both brushes were about half the thickness ofa new<br></div><div dir="ltr">brush set.? One of the brushessprings had bottomed out thus no spring force<br></div><div dir="ltr">was being applied to the brushand thus loss of electrical contact.? TheWD-40<br></div><div dir="ltr">fluid had been in the!<br></div><div dir="ltr"> thruster since last year?s Psub convention in Lake Charlevoix.? According<br></div><div dir="ltr">to the manufacturer MSDS sheet, WD-40consist of 30-60% petroleum<br></div><div dir="ltr">distillates, 10-30% petroleum base oils and 5-15%Naptha.? My working<br></div><div dir="ltr">hypothesis is that oneor more of the components in the WD-40 reacted with<br></div><div dir="ltr">the binding agent in the carbon-graphitebrushes and reduced the mechanical<br></div><div dir="ltr">strength of the brush thus leading to acceleratewear.? Over the two years<br></div><div dir="ltr">period (17,500hours), the thrusters had two main dive events with a total of<br></div><div dir="ltr">no more than 20hours on the units.? The balance of thetime, the thrusters<br></div><div dir="ltr">were sitting on the boat in my shop soaking in this WD-40at elevated Texas<br></div><div dir="ltr">temperatures.?? BTW,the driver for using WD-40 is that is a very low<br></div><div dir="ltr">kinematic viscosity (2.8 cStat 100 F or 38C). Note water is about 1 cSt. <br></div><div dir="ltr"><br></div><div dir="ltr">One other observation on the failure was the wear on the armatureshaft.? It<br></div><div dir="ltr">has a visible wear ring andthe shaft bushing went from a snug fit to a loose<br></div><div dir="ltr">fit.? Working hypothesis is that the carbon-graphiteparticles in suspension<br></div><div dir="ltr">were acting like an abrasive polish.? <br></div><div dir="ltr"><br></div><div dir="ltr">The question is how can we improve the reliability?? Should we investigate a<br></div><div dir="ltr">different seal andtry to get by with 1-ATM operation or investigate a<br></div><div dir="ltr">different oil or go back toair compensation?? What Alec and I discussedat<br></div><div dir="ltr">the Expedition was to try a single mechanical carbon seal or a high<br></div><div dir="ltr">pressure-ratedlip seal.? If we can come up with somethingto try, I am<br></div><div dir="ltr">willing to put a Minn-Kotta 101 in my test chamber, power it up sothat the<br></div><div dir="ltr">seal in a dynamic mode and increase pressure to failure.? A control would be<br></div><div dir="ltr">to run an off-the-shelf MK101 with no pressure compensation to failure.<br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr">Any thoughts?? I wouldlike to hear what experience others have had with oil<br></div><div dir="ltr">compensation on MK 101?s.<br></div><div dir="ltr"><br></div><div dir="ltr">Cliff<br></div><div dir="ltr"><br></div><div dir="ltr">_______________________________________________<br></div><div dir="ltr">Personal_Submersibles mailing list<br></div><div dir="ltr"><a href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br></div><div dir="ltr"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br></div><div dir="ltr"> <br></div><div dir="ltr">-------------- next part --------------<br></div><div dir="ltr">An HTML attachment was scrubbed...<br></div><div dir="ltr">URL:<br></div><div dir="ltr"><<a href="http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230725/" rel="nofollow" target="_blank">http://www.whoweb.com/pipermail/personal_submersibles/attachments/20230725/</a><br></div><div dir="ltr">4691a505/attachment.html><br></div><div dir="ltr"><br></div><div dir="ltr">------------------------------<br></div><div dir="ltr"><br></div><div dir="ltr">Subject: Digest Footer<br></div><div dir="ltr"><br></div><div dir="ltr">_______________________________________________<br></div><div dir="ltr">Personal_Submersibles mailing list<br></div><div dir="ltr"><a href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br></div><div dir="ltr"><a href="http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.whoweb.com/mailman/listinfo.cgi/personal_submersibles</a><br></div><div dir="ltr"><br></div><div dir="ltr"><br></div><div dir="ltr">------------------------------<br></div><div dir="ltr"><br></div><div dir="ltr">End of Personal_Submersibles Digest, Vol 119, Issue 24<br></div><div dir="ltr">******************************************************<br></div><div dir="ltr"><br></div><div dir="ltr">_______________________________________________<br></div><div dir="ltr">Personal_Submersibles mailing list<br></div><div dir="ltr"><a href="mailto:Personal_Submersibles@psubs.org" rel="nofollow" target="_blank">Personal_Submersibles@psubs.org</a><br></div><div dir="ltr"><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="nofollow" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br></div></div>
</div>
</div></div>_______________________________________________<br>
Personal_Submersibles mailing list<br>
<a href="mailto:Personal_Submersibles@psubs.org" target="_blank">Personal_Submersibles@psubs.org</a><br>
<a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles" rel="noreferrer" target="_blank">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br>
</blockquote></div>