<div dir="ltr"><div>Hi Jon,</div><div>I did an experiment with this recently for my underwater caving light:</div><div>- Cable gland (no-name Chinese brass one, which I have since successful tested to 160m!) </div><div>- 2-core (1mm2 I think) twisted pair cable with pretty solid sheath (ie. no air spaces), ~6mm/1/4" OD</div><div>- External pressure: 80m water depth</div><div>- Pressurising medium: air</div><div><br></div><div>The cable didn't extrude or otherwise move, but the leakage through the wire strands was significant (ie. comfortably audible without being too loud, and slightly too much to blow bubbles in soapy water).</div><div><br></div><div>I didn't measure it, but the flow would be less for water, and probably wouldn't be filling up your sub too quickly.</div><div><br></div><div>Something to point out on the inside/outside cable glands is that the loading on them is much different with external vs internal pressure. Ie. for external all the force is compressing the fitting against the hull, whereas for internal the threaded section is in tension (and some are not very thick). I don't think typical cable glands are meant for internal pressure, but the Blue Globes are probably good for it.</div><div><br></div><div>If anyone is interested, the cable glands I used and tested are these:</div><div><a href="http://www.aliexpress.com/snapshot/6439871078.html?orderId=65381957659001">http://www.aliexpress.com/snapshot/6439871078.html?orderId=65381957659001</a><br></div><div>(the O rings are a bit average, and I doubt they would be much good for internal pressure, but otherwise shiny and good quality, with 100% success on sealing for 4 of them to 160m)<br></div><div><br></div><div>Cheers,</div><div>Steve<span id="goog_1732964246"></span><a href="/"></a><span id="goog_1732964247"></span></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Apr 17, 2015 at 8:23 AM, Jon Wallace via Personal_Submersibles <span dir="ltr"><<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div><br>
Alan,<br>
<br>
The best approach is to use threaded rod with the potting, if
possible. My question is probably better stated in the context of
whether air trapped between a multi-wire cable and the surrounding
sheath is an issue to be concerned about. Some cables have a good
tight sheath but others such as CAT-5 is pretty sloppy.<br>
<br>
A potential concern of the blue globe gland since it seals around
the cable sheath is what happens if the sheath gets damaged and
cut underwater. Water pressure will allow creep to flow between
the wires and sheath bypassing the gland. However the same would
be true of a home-made potted penetrator as well. What type of
inflow should we expect from such a breach? Minor?<span class="HOEnZb"><font color="#888888"><br>
<br>
Jon</font></span><div><div class="h5"><br>
<br>
<br>
<br>
On 4/16/2015 4:46 PM, Alan James via Personal_Submersibles wrote:<br>
</div></div></div><div><div class="h5">
<blockquote type="cite">
<div style="color:rgb(0,0,0);font-family:HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif;font-size:16px;background-color:rgb(255,255,255)">
<div dir="ltr"><span>Jon,</span></div>
<div dir="ltr"><span>I noted that the lights
on "I think" a dual DW at Nuytco</span></div>
<div dir="ltr"><span>had oil in the wiring
tubes to the lights, which were a clear plastic.</span></div>
<div dir="ltr">I
compensated a linear actuator & didn't strip the wires
inside the potting.</div>
<div dir="ltr">I filled it
with WD40, & it just ran out between the epoxy & the
wires when</div>
<div dir="ltr">I tipped it
upside down. No pressure applied. </div>
<div dir="ltr">I think it
was Hank that suggested untwisting the wires so the potting
mix </div>
<div dir="ltr">can get
around them. On the through hulls, Carsten & Emile are
using</div>
<div dir="ltr">blue globe
cable glands with one outside the hull & another inside
for</div>
<div dir="ltr">double
security.</div>
<div dir="ltr">Alan</div>
<br>
<div style="font-family:HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif;font-size:16px">
<div style="font-family:HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif;font-size:16px">
<div dir="ltr">
<hr size="1"> <font face="Arial" size="2"> <b><span style="font-weight:bold">From:</span></b>
Jon Wallace via Personal_Submersibles
<a href="mailto:personal_submersibles@psubs.org" target="_blank"><personal_submersibles@psubs.org></a><br>
<b><span style="font-weight:bold">To:</span></b>
Personal Submersibles General Discussion
<a href="mailto:personal_submersibles@psubs.org" target="_blank"><personal_submersibles@psubs.org></a> <br>
<b><span style="font-weight:bold">Sent:</span></b>
Friday, April 17, 2015 12:06 AM<br>
<b><span style="font-weight:bold">Subject:</span></b>
[PSUBS-MAILIST] minn-kota cabling to hull<br>
</font> </div>
<div><br>
<br>
I think Emile had details of potting the minn-kota.
Anyone know where <br>
this might be located?<br>
<br>
Anyone waterproofing their cabling by oil-compensation
through a poly <br>
tube? If I remember correctly, Aquarius uses this method
for the <br>
electrical wires to the lights and vacuum.<br>
<br>
Jon<br>
<br>
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