Another Ida71 Question

robertfondren

In Dave Sutton's descrition of Franken-son, he describes using 6mm compression fittings to feed diluent and o2 to the small metal pipes connecting to the counterlungs. I've been unable to source the 6mm fittings so far, but have heard that 1/4'" compression fittings can be used in place of 6mm fittings. Is this true? Has anyone else used the 1/4" compression fittings to good effect? Are the fittings indeed 6mm, as another source said the pipes are 8mm? I do not, in fact have the rig with me (on order), but wish to be prepared on day one!
GKAM, if you see this, what fittings did you use to connect 02 and diluent on your Olive Green Ida?
Thanks one and all!

GKAM

Hi Robert, I can confirm the pipes (at least on my IDA71) are 8mm dia. I used the following part from Swagelok : B-8M0-7-6RG Brass Female Connector, 8 mm OD - 3/8 in. Female ISO Parallel. Please note that although the compression fitting is correct, the thread on the opposite side was not UNF 3/8.

What I ended up doing was to machine a copy of 1/2 the Swagelok part to get the UNF 3/8 thread on the other side using a brass hex bar. In fact, I machined 3 pieces : one for the flowmeter and two for O2 and DIL.

Note that I used two different CEJN fittings. The O2 feed is the standard "BCD inflator type" and the DIL is larger bore to feed the ADV better.



More details can be found here

(btw, I am looking to sell my complete IDA71 KISS. I would be interested in swapping it with a "virgin" IDA71 plus some cash difference. The unit is in VGC, but I am on assignment in Munich for 3 years and my poor IDA is just gathering dust in Athens)

/GKAM

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robertfondren

Thank you very much. That is extremely useful information, GKAM. I'm still (obviously) waiting for the arrival of mine.
I may modify mine if/when it arrives in a slightly different fashion, as Dave Sutton mentions keeping the system truly modular, that is, the ability to use both scrubbers. Initially I was firmly in the one-scrubber camp, since I have used one IDA-59 scrubber in a homebuilt to good effect, but after reading the posts here, I've developed just enough doubt to keep me wondering.
I'd also like to maintain the utility of the offboard nitrox connection. I'm considering installing a barbed brass fitting in the LP hose between the O2 tank and the internal quick-connect manifold, and feeding diluent there, and possibly cutting only the left tube in order to inject o2.
In all honesty, it's probably best it hasn't arrived yet, as I'm still resolving these issues.
GKAM, thanks again for the info!

Dave Sutton

Metric tube fittings are sourced from McMaster-Carr for about 1/4 the price of Swagelok. Come next day. Manufacturer is generally Parker and they interchange with Swagelok mechanically. Recommended.

I bought metric tube to SAE female adapters and then worked from there with standard fittings.


Dave

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robertfondren

Thank you, Mr. Sutton!
Though it's been done before, if anyone else wishes to weigh in on the gas plumbing, wing and harness mounting, or the eternal one vs. two-scrubber debate, please don't hesitate!
Regards

Packhorse

I silver soldered a barb fitting on to the stock ADV pipe. But I am currently awaiting some BC QD's that I will swap over.

As the harness I used a transpac but will change that to a custom plate. Divelermintov gave me a few ideas today.

As for the scrubber I am using the single square one. Its slightly larger as far as I can tall and twice the path legnth. I think (hope) it will be adaquite for 30 meters. 2.5 hours max

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robertfondren

Hey, Packhorse.
That's exactly the sort of info I'm looking for. 6 months ago, I'd have just built a Franken-son clone and been done with it, but when Dave Sutton himself said use two scrubbers, I had to rethink, as I had a delrin blanking plugs for one scrubber, with one plug tapped for 3/8 UNF, but if I use both scrubbers, I've got to re-route O2 feed. I may just feed O2 straight to the bag with a slightly modified drysuit valve since my soldering skills are theoretical, at best, but it would have been nice to feed O2 before the scrubber...
Most of my diving is to little more than 40m, so I'm PROBABLY good either way, but uncertainty is uncomfortable.
Thanks!

GKAM

I am not sure about the need for two scrubbers for air DIL dives. I have taken my unit to 50m way too many times and never had any signs of hypercapnia.

I can confirm however, that the scrubber limits are at around 120min. I had a really unpleasent experience on a shallow dive once... I will never forget the feeling of high CO2 in the loop.

Also, as far as the weight and trim is concerned, at first I copied David's suggestion for the 4x1kg weights in the lid but found the CL volume to be affected, esp with the hose routings I had. I now have 2x2kg weights high up on my harness and trim is perfect.

/GKAM

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Dave Sutton

Warm Water.


These WILL break thru in cold water with one scrubber and a diver HARD at work. Light swimming in warm water they will 'probably' be OK.

The thing is this:

IF you carry a bailout bottle,

AND you want to live long enough to die of old age,

WHY NOT use the offboard bottle for the diluent source and keep two scrubbers? I mean, what's the down side to this? None? There's your answer.

But WHEN you want to dive the thing shallow (like 10 metres) without offboard bailout why not just remove one scrubber and add the internal cylinder for internal diluent?


Make it able to be used either way and it'll be perfect.


The square scrubber does have twice the dwell time of the gas on the 'sorb.


Dave

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GKAM

Probably right.

My dives were in 18-25C water in the summer and I am of medium built. I have nothing against using two scrubbers other than the fact that I wanted to house everything inside the unit and have an external tank for bailout keeping things separate.

However if I were to build the IDA again, I would keep the two scrubbers and use a 1-1.5 L tank for O2 where the original russian tank sits. The DIL would then come from a sidemount S40 that also carries my bailout.

ah, the joy of homebuilding ! The combinations are almost infinite...

/GKAM

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