<html><head></head><body><div style="color:#000; background-color:#fff; font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:13px"><div><span>Cliff,</span></div><div dir="ltr" id="yui_3_16_0_ym19_1_1491431690193_3187"><span id="yui_3_16_0_ym19_1_1491431690193_3186">I am confused as to why you would want a 4 psi internal pressure pushing against a spring that is trying to keep the seal tight to the shaft. I would think the seal should be reversed with a 4 psi internal pressure to assist the spring in keeping it tight to the shaft. This will also apply to an oil filled motor, in the case of oil filling, the 4 psi would be beneficial in keeping the seal tight.</span></div><div dir="ltr" id="yui_3_16_0_ym19_1_1491431690193_3187"><span>Hank</span></div> <div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 13px;"> <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 Wednesday, April 5, 2017 3:50 PM, Cliff Redus via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv7911914362"><div><div dir="ltr"><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font face="Calibri"><font size="3"><font color="#000000">I covered this in my Psub presentation at the 2016 PSub
convention.<span> </span></font></font><font color="#000000" size="3">But will hit the highlights.</font></font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font face="Calibri"><font size="3"><font color="#000000">The Minn Kota 101 lower unit (MK part number 2886289) had
a shaft seal on the end of the shaft that is connected to the prop.<span> </span></font></font><font color="#000000" size="3">The seal arrangement consists of two
identical lip seals oriented to see external pressure.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">The inner lip seal lands on a shoulder in the
Brush End Assembly.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">This cast aluminum part
does three things. The first is hold the DC brush assembly, the second to hold
a brass or bronze journal bearing, the third is to provide a cavity to land two
lip seals.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">The stock MK-101 lower unit the
two lip seals separated by a cardboard spacer.</font><span><font color="#000000" size="3">
</font></span><font color="#000000" size="3">This seal arrangement is design for a low differential pressure on the
order of maximum 30 fsw or about 13 psig.</font><span><font color="#000000" size="3">
</font></span><font color="#000000" size="3">Antidotal experience is that this seal assembly has withstood three
times this depth.</font><span><font color="#000000" size="3"> </font></span></font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font face="Calibri"><font size="3"><font color="#000000">For the last two years I have been operating with this
stock seal arrangement on the four thrusters on the R300.<span> </span></font></font><font color="#000000" size="3">I use a WATTS R364-02BSS/M1 REGULATOR part
number 364-02BSS/M1 to do pneumatic pressure compensation of my four thrusters.
I supply pressure to the regulator from the LP pressure side of a scuba first
stage regulator and have it adjusted to supply pressure at 4 psi above ambient
water pressure. The scuba first stage regulator is supplying pressure to this reducing
regulator at 50 psi above ambient water pressure.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">This is a relieving style pressure reducing regulator
meaning that </font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">when you ascend, pressure
vents from the regulator body. The deepest I have had this arrangement is 160
ft.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">To date I have had no thruster
flooding but I don’t have a lot of hours on the units.</font></font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font face="Calibri"><font size="3"><font color="#000000">As both Sean and Alan have pointed out this two lips-seal
arrangement is correctly orient for low pressure applications like the original
intent of the MK 101 units but not ideal for a pressure compensated deep diving
thruster.<span> </span></font></font><font color="#000000" size="3">As Alan pointed out, the 1 atm
air initially between the two lip seals is an issue as well as the cardboard
spacer.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">The outer lip seal will see more
pressure that it was designed for which could lead to it failure with the lip
rim on the ½” shaft being pushed in which could flood the 1 atm space and
damage the cardboard spacer.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">At this
point the inter lip seal is the only seal holding and it is seeing a 4 psi differential
pressure with the pressure inside actually being higher than ambient.</font><span><font color="#000000" size="3"> </font></span><font color="#000000" size="3">I have not torn down my 101s to see if the
space between the lips seals was flooded.</font><span><font color="#000000" size="3">
</font></span></font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font size="3"><font color="#000000"><font face="Calibri">I hope to do some testing of different seal arrangements for
the MK 101 lower unit in my test chamber at some point. I just have not had
time and since my thrusters have been behaving, not strongly motivated.<span> </span></font></font></font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font color="#000000" face="Calibri" size="3"> </font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font color="#000000" face="Calibri" size="3">The idea of using this pressure reducing / relieving regulator
came from Hugh Fulton as he has installed the system on the Q-Sub.</font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font color="#000000" face="Calibri" size="3"> </font></b></div><font color="#000000" face="Times New Roman" size="3">
</font><div style="margin:0in 0in 10pt;"><b><font color="#000000" face="Calibri" size="3">Cliff </font></b></div><font color="#000000" face="Times New Roman" size="3">
</font></div><div class="yiv7911914362gmail_extra"><br clear="none"><div class="yiv7911914362gmail_quote">On Wed, Apr 5, 2017 at 3:29 PM, Jon Wallace via Personal_Submersibles <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:personal_submersibles@psubs.org" target="_blank" href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>></span> wrote:<br clear="none"><blockquote class="yiv7911914362gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="yiv7911914362yqt4424373173" id="yiv7911914362yqt18415"><div>
<div class="yiv7911914362m_-7977742677370067463moz-cite-prefix">Hi Alan,<br clear="none">
<br clear="none">
Yeah, that white paper pretty much just states fill it with oil
and you're good to go. It doesn't address some of the issues that
have come up on the list regarding heat and expansion, inter-seal
cavity, etc. I understand the drive to find a perfect solution
and that minn-kota oil compensation is not perfect, I'm just
trying to understand the real-world ramifications of using it as
that white paper suggests and most psubbers have implemented.
Given that water is such a good heat sink, are the heat and
expansion issues of the oil really that serious? I know Alec
wrote something about his experience with this some time ago but
am having a hard time finding that thread. Pretty sure SNOOPY is
still using simple oil compensation regardless.<br clear="none">
<br clear="none">
Jon<br clear="none">
<br clear="none">
<br clear="none">
On 4/5/2017 4:02 PM, Alan James via Personal_Submersibles wrote:<br clear="none">
</div>
<blockquote type="cite">
<div style="color:rgb(0,0,0);font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;background-color:rgb(255,255,255);">
<div><span></span></div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2626">Jon,</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3309">Cliff has been doing
a lot of work on Minn kota modifications & has the hands</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3310">on
experience. If he's not tuning in it would be worth contacting
him privately.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2892">The
Minn-kota seal set up is not ideal, with the gap between the
two seals</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2719">meaning
one or the other seals will fail when their pressure rating is
exceeded.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2720">The outer
seal seems to serve a double purpose, being the first line of
defense</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2815">against
water ingress & also a sacrificial seal that will see all
the abrasive muck stirred up by the prop.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2774">Noticed in
this kit that the outer seal has a shield to protect it.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2775"><img id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2777" src="http://cdn3.bigcommerce.com/s-9zqwsza/products/284334/images/633/880-006__65028.1446824316.1280.1280.png?c=2"></div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2850">Historically
in deep diving set ups they have had dual seals, but with
either ambient pressure between them,</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2867">or a
cascaded pressure system, and normally mechanical seals. The
outer seal was regarded as sacrificial.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2911"> Maybe
you could pack between the seals with grease to reduce the air
gap. </div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2950">I am not
sure whether you could simply reverse the inner seal or not as
they need a shoulder that the pressure</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_2949">will push
them up against.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3128">Cliff is
using a small relieving air regulator to compensate his
motors. The regulator is fed air from your tanks</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3107">& is
set at an overpressure of about 4psi. The regulator is
orientated upside down as the relieving air feeds</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3129">out
through the handle portion & the orientation will stop
water entering when this valve opens.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3142">This
system was suggested by Hugh, & Cliff is trialing it. It
has the advantage that you could either air or oil</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3130">compensate.
If your motor ran out of oil it would just be replaced with
air above ambient pressure.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3131">I am not
sure at what pressure the relieving valve opens.</div>
<div class="yiv7911914362m_-7977742677370067463qtdSeparateBR" dir="ltr" id="yiv7911914362m_-7977742677370067463yui_3_16_0_ym19_1_1491419564878_3233"> There
is this very good Psub resource from an expert in modifying
Minn kotas for underwater use.</div>
</div>
</blockquote>
<br clear="none">
</div></div>
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