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ianmarsh

Member Since 15 Jan 2012
Offline Last Active Nov 10 2013 08:06 AM
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Posts I've Made

In Topic: New Housing "Airlock" Vacuum from Backscatter

17 September 2013 - 09:11 AM

I put a hair across my main o-ring, and pumped down my system to 10" Hg.  It took almost 10 minutes for the vacuum to fall below 5" Hg.  So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.

Doug,

 

Good point, indeed.

 

I have the non electronic version... seems like a solid piece of gear. Very reassuring, but:  With that model, a STABLE vacuum reading is critical.

 

If the vacuum is changing, the housing is leaking.

If you start out at -10in/Hg and it "drops" to -5in/Hg the absolute value doesn't matter. It doesn't start to leak when it gets to 0in/Hg.

The ∆ indicates a leak, and if its leaking air, it is leaking water.

 

The point is, with a non monitored system, stability of the initial reading is key. Don't fool yourself into thinking a small change doesn't matter. It does.

 

However, be aware of temperature/pressure fluctuation.

 

ian


In Topic: Nikon 20-35mm f2.8 in Subal ND3

14 June 2013 - 02:10 PM

I'm feeling a rain cloud forming over my little parade...  :)


In Topic: Subal C10 parts

14 June 2013 - 08:53 AM

I had a similar event with my ND2 housing. Depending on your strobe set up, you may or may not need all connections. You only need two wires to shoot manual. Can't remember which two, but there is a thread somwhere on Wetpixel regarding the pins and wires...

 

It is an easy repair for someone skilled with a soldering iron. Saves a bundle of cash too!

 

In addition, when I fixed mine, I encased the wires and solder on both sides of the board in clear silicone caulk to provide water resistence and strain relief to the solder joint. Otherwise it is pretty exposed.

 

ian


In Topic: Housing Sentry Vacuum Seal

31 May 2013 - 10:26 AM

I maybe way off base (and somewhat off topic) on this but maybe Bill or someone else with an engineering background could answer:

 

With any of the currently discussed devices (Sentry, Airlock, Hugy) would there be any utility of using a low positive internal pressure to test seal integrity? I am thinking bike pump, 2-3 psi differential and dunk tank looking for bubbles. This might be a useful way localizing leaking seals. 

 

Or would this be completely facticious, based on how the o rings are designed to work. It would simulate taking the housing to altitude, and most housings warn against flying with a sealed housing...


In Topic: Went with Backscatter's Airlock

22 May 2013 - 08:47 AM

I would suggest spraying a soap / water mixture on the housing and watch for a bubble.

 

When I installed on my Aquatica the washer went on the inside and I used a wrench to tighten slightly. less than 1/8 turn.

 

Problem is, you need to spray the solution INSIDE the housing!! :)

 

I suppose you could put a small positive pressure in with a bike pump and check for bubbles, but that does not mimic how the "o"rings are designed to work.

 

Not sure if this would produce "false positive" results:(