<html><head></head><body><div style="color:#000; background-color:#fff; font-family:Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div><span></span></div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3082">Jon,</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3209" dir="ltr">I don't know whether you have followed, but I have made a brushless 2000W thruster</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3266" dir="ltr">which I trialed in a pool for 30 hrs. The glue on the hall sensor board melted</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3353" dir="ltr">& it stopped because the timing went out. Apparently the glue was designed to melt</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3304" dir="ltr">so people could adjust the timing. The thruster got hot because the compensating oil</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3354" dir="ltr">was being forced away from the motor through centrifugal force, & up the wiring tube.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3381" dir="ltr">If I had an overpressure on the system I could have prevented this, but didn't think it</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3412" dir="ltr">was needed in a few feet of water. I was running this motor with 2 lip seals with ambient</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3450" dir="ltr">pressure in between, but have purchased a mechanical seal for the next version.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3451" dir="ltr"> It had a comparable or better thrust to Watt ratio than a lot of the advertised ratings</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3556" dir="ltr">of commercial thrusters.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3568" dir="ltr"> I think it is a matter of time before Minn kota put out a brushless thruster if they haven't</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3569" dir="ltr">yet. Most of the commercial ROV & submarine thrusters are now brushless.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3570" dir="ltr"> If there was enough room to fit a mechanical seal on a Minn kota it would be a big</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3638" dir="ltr">improvement. The white paper suggests grinding the Minn kota shaft to a specific</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3637" dir="ltr">finish, with matching bearing & seal, however a mechanical seal is more tolerant of</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3639" dir="ltr">the shaft surface finish & you could avoid this.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3696" dir="ltr"> Re the heat; one concern is transferring heat off the windings, which oil compensating</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3738" dir="ltr">will do 100 times better than air. However Minn kota motors would have large gauge windings </div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3942" dir="ltr">that can cope with the heat.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3868" dir="ltr">Below is a 2010 thread by Carsten dealing with expansion.</div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3870" dir="ltr">Alan</div><pre id="yui_3_16_0_ym19_1_1491429543317_3883" style="color: rgb(0, 0, 0); text-transform: none; text-indent: 0px; letter-spacing: normal; font-style: normal; font-weight: normal; word-spacing: 0px; orphans: 2; widows: 2; font-variant-ligatures: normal; font-variant-caps: normal; -webkit-text-stroke-width: 0px;">Alan and the other gentlemens,
our expierence with oil filled motors, batterys or even propeller shafts is that the oil expand if the motor is runing longer time.
Simple because its warm up. We had that problem on Eurosub on the first dives.
And on Euronaut we filled the bladder complet up and the get pretty hard in the hot summer just by sun heating the sub.
A full filled bladder with over pressure creates a lot of interal
pressure in the wrong direct - a lot of force for the bladder itself and hose work.
Therefore our bladder are only half expand during the filling. But still free of any air.
An other point is that the bladder has to be not to small.
To create a slightly overpressure on the motorseal you just install the bladder below the motorcasing.
But we found out that on trolling motor (electric outboards) this is not nessesary. There seals are good for some
douzend feets at least - so you can install the bladder else were.
Filling is simpler if the bladder is slightly over the motor - you can vent the system direct on the filling point.
Another point is that we install now one bladder per motor - in the earlier sub (Sgt.Peppers) we install a central
one for all motors. Hard to find a leak after a dive with all the T-crossing piepings and motorseals..
vbr Carsten</pre><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3869" dir="ltr"><br></div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3675" dir="ltr"> </div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3413" dir="ltr"> </div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1491429543317_3382" dir="ltr"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_ym19_1_1491429543317_3045" style="display: block;"> <div id="yui_3_16_0_ym19_1_1491429543317_3044" style="font-family: Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_ym19_1_1491429543317_3043" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_ym19_1_1491429543317_3042" dir="ltr"> <font id="yui_3_16_0_ym19_1_1491429543317_3041" face="Arial" size="2"> <hr size="1" id="yui_3_16_0_ym19_1_1491429543317_3120"> <b><span style="font-weight: bold;">From:</span></b> Jon Wallace 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> Thursday, April 6, 2017 8:31 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Oil Compensator<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_ym19_1_1491429543317_3054"><br><div id="yiv0215708156"><div id="yui_3_16_0_ym19_1_1491429543317_3053">
<div class="yiv0215708156moz-cite-prefix" id="yui_3_16_0_ym19_1_1491429543317_3052">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">
<div class="yiv0215708156yqt6378870078" id="yiv0215708156yqtfd18926"><br clear="none">
On 4/5/2017 4:02 PM, Alan James via Personal_Submersibles wrote:<br clear="none">
</div></div><div class="yiv0215708156yqt6378870078" id="yiv0215708156yqtfd01919">
<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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_3_16_0_ym19_1_1491419564878_2626">Jon,</div>
<div class="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_3_16_0_ym19_1_1491419564878_2775" dir="ltr"><img id="yiv0215708156yui_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="b5eb8d88-55bb-c3d1-90d0-0d40cc80ac95"></div>
<div class="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_3_16_0_ym19_1_1491419564878_2949" dir="ltr">will push
them up against.</div>
<div class="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_3_16_0_ym19_1_1491419564878_3131" dir="ltr">I am not
sure at what pressure the relieving valve opens.</div>
<div class="yiv0215708156qtdSeparateBR" id="yiv0215708156yui_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 clear="none">
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