[PSUBS-MAILIST] Gauge for outside viewport?

[Alec Smyth via Personal_Submersibles]

Just a follow-up on this. While I'm pretty sure external oil filled gauges
would work outside I find the oil doesn't like staying inside them, so I
ended up bringing the gauges inside the hull. In the end, the majority of
my air system is outside with just the gauges and the BIBS inside the hull.
Apart from hull stops, the valves for operating the sub are outside and
operated via mechanical through-hulls. It's not hard because there's just
three valves total. In my experience most air leaks happen in those valves
that are used routinely, as opposed to hull stops that are left alone. Even
using top quality Swagelok valves, you sometimes have to tighten things up
because a leak develops with use.

One recent design change is that I'm trying air compensation on the
thrusters again. I had originally made them oil compensated because the
thrusters are jettison-able and oil compensation meant one less connection
between thruster and hull, but I'll give air a try because, with big
battery banks and freeboard, I expect this sub to rack up many more hours
of running time than Snoopy did using thrusters just for maneuvering. Air
compensation should mean less brush maintenance.


Best,

Alec

On Wed, Oct 7, 2015 at 6:46 AM, Steve McQueen via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Alec, while I am not 100% sure from the photo I believe these are standard
> ss Ashcroft pressure gauges used in industry.  They are normally oil filled
> to dampen the needle movement.  The oil is added through a rubber plug
> normally that might also act as a compensation diaphragm. Anyway maybe a
> vendor to start having discussion with.
>
> Steve
>
> On Sun, Sep 20, 2015 at 11:03 PM, Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>> I have an interesting thing to think about and wondered if any of the
>> PSUBS brain trust might have a suggestion.
>>
>> One of the simplifications on my new sub is that all HP air lines are
>> external, aside from the BIBS (which is normally shut off anyway). Thus,
>> I'm looking for a 3,000-4,000 psi gauge to mount outside a viewport, like
>> in the Pisces photo that I'll paste below. In case my paste doesn't come
>> through, it is the one at the top of the following article:
>> http://www.nytimes.com/2015/09/15/science/piloted-deep-sea-research-is-bottoming-out.html?_r=1
>>
>> The first thing that came to mind was to use a SCUBA submersible pressure
>> gauge, but the problem is these are normally 1 atm dry enclosures of
>> limited depth rating. There is generally little information posted about
>> how deep they'll go, but what I did find was mentioned 260 feet for the
>> plastic ones and 490 feet for the brass variety. This is a 1,000 foot sub.
>>
>> The second idea was to use oil filled gauges intended for above-water
>> use. But these generally have considerable bubbles in the oil, are not very
>> good at keeping the oil inside, and have other hardware not intended to
>> live long in sea water.
>>
>> Any suggestions would be most welcome!
>>
>>
>> Thanks,
>>
>> Alec
>>
>> [image: Inline image 1]
>>
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>
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