<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:10pt"><div><span>Hi Jon,</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>I hadn't thought of the possibility of a fire inside a motor.</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>You would have heat, sparking potential, fuel in the form of greece, & plenty of oxygen.</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color:
transparent;"><span>Karl Stanley's air compensated motors have gone down to 2000 ft & regularly go to 1000</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>with his tourist operation, & no fires that I've heard of.</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>Now that you have brought this up I think I will look in to some sought of inflammable grease</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>to replace any existing grease in the motor, & make sure
the motor is cleaned well on the inside.</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>As you say, it's too easy to just use the air supply you already have & you probably wouldn't look </span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>at other gasses unless you were going to have a dedicated tank for compensating.</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span>Alan</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue,
'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-style: normal; background-color: transparent;"><span><br></span></div><div><br></div> <div style="font-family: HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 10pt;"> <div style="font-family:
HelveticaNeue, 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 12pt;"> <div dir="ltr"> <hr size="1"> <font size="2" face="Arial"> <b><span style="font-weight:bold;">From:</span></b> Jon Eide Pettersen 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, July 27, 2014 9:18 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Minn Kota 101 - thread spec<br> </font> </div> <div class="y_msg_container"><br><div id="yiv9128840570"><div>Would it be a good idea to use an inert gas like nitrogen or argon instead of air to pressure compensate thrusters? This is because compressed air will have a high partial pressure of oxygen, making the atmosphere in the thrusters more flammable. Also, if
there is water trapped inside the thrusters, a high pp of oxygen will greatly speed up the corrosion rate.<br>
<br>
The downside is, of course, that air is readily available while an inert gas cost more. <br>
<br>
Regards, <br>
Jon E. Pettersen <br><br><div class="yiv9128840570gmail_quote">On 26 July 2014 22:27:49 CEST, Pete Niedermayr via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv9128840570gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex;">
<pre class="yiv9128840570k9mail"><br>Hank, What is the story behind your magnetic coupler ? You were talking about them on the list and then you had one. Did you buy it ? If so where? Did you build it ? If so from what plans.<br><br>Thanks Pete<br><br><hr><br>On Mon, 7/21/14, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br><br> Subject: Re: [PSUBS-MAILIST] Minn Kota 101 - thread spec<br> To: "Personal Submersibles General Discussion" <personal_submersibles@psubs.org><br> Date: Monday, July 21, 2014, 6:20 PM<br> <br> there is a very nice<br> solution here. Magnetic couplers, it wouldn't take<br> much to convert a minkota to a magnetic coupled<br> thruster.Hank<br> <br> <br> On Monday, July 21, 2014 8:56:11 PM,<br> Jon Wallace<br> via Personal_Submersibles<br> <personal_submersibles@psubs.org> wrote:<br> <br> <br> <br> <br> <br> Dissipation of heat to the water environment
via<br> conduction with<br> the motor housing would help temper overall thermal<br> expansion. <br> The motors are essentially surrounded by an infinite<br> sized water<br> jacket and not typically operated at full speed for<br> long periods<br> of time. I suspect actual thermal expansion of the<br> oil in the<br> motor housing during typical underwater operations is<br> negligible.<br> <br> <br> <br> In regards to viscosity effect on the motors,<br> JimK's GUPPY is oil<br> compensated and three 101's in a K-boat<br> configuration and had no<br> problem moving that heavy (7 ton?) sub. Check out<br> <a rel="nofollow" target="_blank" href="http://www.youtube.com/embed/u0b7NjxttL4?rel=0&vq=hd720">http://www.youtube.com/embed/u0b7NjxttL4?rel=0&vq=hd720</a><br> at<br> 0:20-0:28 where he just about stops the sub on a dime<br> with two<br> forward 101's. Also
in<br> <a rel="nofollow" target="_blank" href="http://www.youtube.com/embed/9Vaq4JK9wVs?rel=0&vq=hd720">http://www.youtube.com/embed/9Vaq4JK9wVs?rel=0&vq=hd720</a><br> at<br> 3:39 he pulls out of the boat lift with just one 101<br> aft, and at<br> 4:02 he pulls out with two forward 101's. Alec<br> has smaller motors<br> on SNOOPY but they still have enough power to move it<br> around. I'm<br> sure viscosity effect on the motors are measurable but<br> from<br> practical application it doesn't appear to be much<br> of an issue<br> when two or more motors are used. There's enough<br> power to move<br> the subs as desired even with any viscosity effect<br> that is<br> present.<br> <br> <br> <br> Jon<br> <br> <br> <br> <br> <br> On 7/21/2014 10:22 AM, Cliff Redus via<br> Personal_Submersibles<br> wrote:<br> <br> <br> <br> <br>
<br> <br> <br> <br> James, a couple of points. First, to<br> me the fewer<br> the leak paths the better so I would not<br> install the<br> added plug. The issue is how to get traped<br> air out of<br> the Md-101 when using oil compensation. <br> I like Alec<br> and Hanks ideas for removing trapped air due<br> to nipple<br> protruding into body. The other point is<br> the wrap<br> around tube volume can compensate for the<br> small amount<br> of air that remains trapped. To deal with<br> thermal<br> expansion of the oil, first of all you are<br> dealing with<br> a small volume to start with so the<br> tube/reservoir does<br> not have to be all that large. If you do a<br> quick back<br>
of the envelope calc on the required volume<br> to compensate for only thermal expansion of<br> the oil you<br> about need 3 US teaspoons for a MK 101 (<br> Assume oil has<br> a thermal expansion coefficient of 0.00056<br> 1/F and that<br> there is one US pint of oil in the body of<br> the 101 and<br> that the temperature swing is 70F to 130F. <br> Delta volume<br> is 0.125 gal * 0.00056 1/F * 60F = 0.0042<br> gal*128 OZ/gal<br> *6 US TSP/OZ = 3.2 teaspoons). <br> To me the design pressure inside the ME<br> 101 should be<br> ambient pressure as they have lip seals on<br> shafts. Lip<br> seals are design to take external<br> pressure. They re not<br> designed to take internal pressure. So a<br> simple wrap<br> around tube
for oil compensation with say a<br> volume of 5<br> US teaspoons should work just fine as this<br> would allow<br> for thermal expansion of the oil and a small<br> volume of<br> trapped air and because the tube is<br> flexible, the<br> pressure inside the 101 is ambient which<br> makes the lip<br> seal happy. As to Alan's suggestion on<br> omitting all<br> pressure compensation and only relaying on<br> the lip seal<br> without any pressure compensation, I am not<br> wild about<br> this idea unless the boat is only designed<br> for shallow<br> water. MK designers when they speced the<br> lip seals for<br> MK were designing shallow submergence of a<br> trolling<br> motor with a factor of safety. So as you<br> get deeper and<br> deeper, you are
starting to expose these<br> lips seals to a<br> significant differential pressure which<br> causes them to<br> overheat and fail at some point. Is this<br> 10ft or 50 ft<br> or 100 ft. Don't know but to me this<br> exposes the boat<br> to some risk particularly if use the<br> 101's for depth<br> stability rather than a VBT and dive the<br> boat negatively<br> buoyant, i.e., vertical thruster fails,<br> boat starts to descend and pilot is<br> forced into dropping<br> ballast. <br> <br> <br> <br> To me a bigger question on air vs oil<br> compensation is<br> how much power are you giving up with oil<br> compensation<br> due to viscosity difference between oil and<br> air. <br> <br> <br>
<br> As both Alec and Vance point out, there<br> has been a<br> lot of bottom time on MD-101s with oil<br> compensation<br> without a lot documented failures. <br> <br> <br> <br> I have not decided in my own mind which<br> compensation<br> method I will use on my MD-101's for<br> future boats. <br> <br> <br> <br> Cliff<br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br><hr><br> Personal_Submersibles mailing list<br> Personal_Submersibles@psubs.org<br> <a rel="nofollow" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br> <br> <br> <br> <br> -----Inline Attachment Follows-----<br>
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