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<div class="moz-cite-prefix">Hi Alan,<br>
<br>
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>
<br>
Jon<br>
<br>
<br>
On 4/5/2017 4:02 PM, Alan James via Personal_Submersibles wrote:<br>
</div>
<blockquote cite="mid:1321807755.50605.1491422577614@mail.yahoo.com"
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<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2626">Jon,</div>
<div class="qtdSeparateBR"
id="yui_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="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3310" dir="ltr">on
experience. If he's not tuning in it would be worth contacting
him privately.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2892" dir="ltr">The
Minn-kota seal set up is not ideal, with the gap between the
two seals</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2719" dir="ltr">meaning
one or the other seals will fail when their pressure rating is
exceeded.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2720" dir="ltr">The outer
seal seems to serve a double purpose, being the first line of
defense</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2815" dir="ltr">against
water ingress & also a sacrificial seal that will see all
the abrasive muck stirred up by the prop.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2774" dir="ltr">Noticed in
this kit that the outer seal has a shield to protect it.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2775" dir="ltr"><img
moz-do-not-send="true"
id="yui_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"
data-id="27fba912-f492-82f7-b4e7-4937b3395b2d"></div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2850" dir="ltr">Historically
in deep diving set ups they have had dual seals, but with
either ambient pressure between them,</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2867" dir="ltr">or a
cascaded pressure system, and normally mechanical seals. The
outer seal was regarded as sacrificial.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2911" dir="ltr"> Maybe
you could pack between the seals with grease to reduce the air
gap. </div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2950" dir="ltr">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="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_2949" dir="ltr">will push
them up against.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3128" dir="ltr">Cliff is
using a small relieving air regulator to compensate his
motors. The regulator is fed air from your tanks</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3107" dir="ltr">& is
set at an overpressure of about 4psi. The regulator is
orientated upside down as the relieving air feeds</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3129" dir="ltr">out
through the handle portion & the orientation will stop
water entering when this valve opens.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3142" dir="ltr">This
system was suggested by Hugh, & Cliff is trialing it. It
has the advantage that you could either air or oil</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3130" dir="ltr">compensate.
If your motor ran out of oil it would just be replaced with
air above ambient pressure.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3131" dir="ltr">I am not
sure at what pressure the relieving valve opens.</div>
<div class="qtdSeparateBR"
id="yui_3_16_0_ym19_1_1491419564878_3233" dir="ltr"> There
is this very good Psub resource from an expert in modifying
Minn kotas for underwater use.</div>
</div>
</blockquote>
<br>
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