[PSUBS-MAILIST] instruments, pressure display?

hank pronk hanker_20032000 at yahoo.ca
Sun Dec 22 17:46:31 EST 2013 

Joe,
I would think several prototype parts should be destroyed to determine the average failure point.  Then test the part going into service to the same as other parts 1.5:1 ?  
Hank



On Sunday, December 22, 2013 3:31:43 PM, Alan <alanlindsayjames at yahoo.com> wrote:
  
Thanks Hank.
On this subject. I had some wicking of salt water up 2 foot of wire on
the inside of my sub. It stopped at the through hull. Obviously the
potting of the bare wires in the through hull did a good job holting this.
I am wondering if this wicking occurs on external wires where the
cable  & insulation go in to the potting mix & at the point where a section of 
wire is stripped.  In other words, can the water pressure squeeze the
external wire cladding & get between it & the potting mix, then at the
point where the wire is stripped, turn backward & run up the inside of
the wire sheathing?
Any experience of this?
On my first ever potting attempt, I didn't strip back a section of the wire & 
just ran it through a block of epoxy.
It leaked compensating fluid just with the pressure of gravity.
Alan


Sent from my iPad

On 23/12/2013, at 11:02 AM, hank pronk <hanker_20032000 at yahoo.ca> wrote:


Joe,
>The failure was unremarkable, it was a pin hole size leak through the potting material.  I am not sure if the leak travelled along the bare wire first.  There is no way to tell, I did drill it out and the material was well consolidated and cured.  I have ordered new polyurethane because I suspect my old st material has frozen one to many times.  I think I will stick to tried and true method though.  That is a single threaded rod in a threaded fitting with oversized washer.  I can pressurize one to 3,000 psi to see when and if it fails.  That is the limit of my compressor.
>Hank 
>
>
>
>On Sunday, December 22, 2013 2:48:55 PM, Joe Perkel <josephperkel at yahoo.com> wrote:
>  
>Hank,
>
>
>What was the nature of the failure, leak, extrusion of potting material (epoxy) or a catastrophic mechanical failure? Knowing how things behave in failure is helpful in looking for potential warning signs ahead of time.
>
>
>Your test program is pretty cool, a lot to learn here.
>
>
>Joe
>
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>On Sunday, December 22, 2013 3:35 PM, hank pronk <hanker_20032000 at yahoo.ca> wrote:
>  
>Alan,
>the fitting is tapered, it is pipe thread.  As a safety, I have a  washer of non conducting material under the nut to prevent the rod from pushing through the fitting.
>Hank
>
>
>
>On Sunday, December 22, 2013 12:16:38 PM, Alan <alanlindsayjames at yahoo.com> wrote:
>  
>I follow,
>you are getting wicking down the wires, not a failure from
>the epoxy extruding through the through hull fitting.
>If your design did fail, It could be in a catastrophic manner.
>I would want a bit of inward taper. Their is a perfect inward
>taper angle, but not sure what it is. Aside from stopping the
>potting mix extruding, the taper would compress the potting
>compound around the wires under pressure
>Alan
>
>Sent from my iPad
>
>On 23/12/2013, at 7:49 AM, hank pronk <hanker_20032000 at yahoo.ca> wrote:
>
>
>Hi Alan,
>>There is only thread on the inside of the fitting for the epoxy to grab, but that seem good.  I think the failure is from the smooth copper wire.  If I use threaded rod it works perfect.
>>Hank
>>
>>
>>
>>On Sunday, December 22, 2013 11:45:18 AM, Alan <alanlindsayjames at yahoo.com> wrote:
>>  
>>Hank,
>>so their is no taper or key to hold the epoxy,
>>just a standard tube threaded on the outside?
>>Alan
>>
>>Sent from my iPad
>>
>>On 23/12/2013, at 5:25 AM, hank pronk <hanker_20032000 at yahoo.ca> wrote:
>>
>>
>>I just did a potting experiment, I removed the main  electric penetrator from my little yellow sub and pressure tested it to 1,000psi.  I left it over night and it held 1,000psi with no leaks.  That penetrator is my standard simple threaded rod in poly urethane.  I tried the same technique with 11 bare wires except I started with 5min epoxy for the first .75in  just to seal it to hold the very slow curing poly urethane from leaking out.  Well it failed at 1,000psi, I am not sure if is the small wire versus the larger threaded rod.  More testing :-) 
>>>Hank 
>>>
>>>
>>>
>>>On Saturday, December 21, 2013 10:45:39 PM, Joe Perkel <josephperkel at yahoo.com> wrote:
>>>  
>>>Jon,
>>>
>>>As a diver I would say depth. The reason being that in a blow and go scenario you need to know that last depth and time to blow down to know your bottom time for what would be hopefully, a controlled ascent. Think USN dive tables.
>>>
>>>This is a big reason why I think I personally would limit my own personal maximum operational depth to 250' with a practical use somewhat less. I might design for a 1,000', but I'm not
 going there. I really don't think I would like to go any deeper than say something like the Andrea Doria in a homebuilt non certified sub. Conversely, I'd do Titanic in Alvin, Mir, or Nautile in a heartbeat if I got the chance.
>>>
>>>Pay close attention to that next 25 story building you stand next to and picture yourself ascending from street level to the roof line. You may need to stop at the 24th floor for a while, if you can control that last ten
 feet that is.
>>>
>>>Joe
>>>
>>>
>>>
>>>Sent from Yahoo Mail for iPad  
>>>
>>>
>>>
>>>________________________________
>>> From:  Jon Wallace <jonw at psubs.org>; 
>>>To:  Personal Submersibles General Discussion <personal_submersibles at psubs.org>; 
>>>Subject:  [PSUBS-MAILIST] instruments, pressure display? 
>>>Sent:  Sun, Dec 22, 2013 3:34:24 AM 
>>> 
>>>
>>>
>>>I will be displaying depth in feet.  Is there any practical reason to 
>>>also display pressure?  It's easy enough for me to do so but it seems 
>>>superfluous.  Which do you prefer, depth indicator or pressure 
>>>indicator, and why?
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>>>Personal_Submersibles mailing list
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