Cyklon X, really?

[tmassey]

What you were experiencing were poorly-tuned regulators; that's it. I had a few co-workers over the years, who had echoed your opinion, until they used mine, which I service myself. You can take the finest rigs and make them run like sucking a straw at ten meters; conversely, you can make the purge blow you right out of the water.

Possible. Even likely. Breathing was not bad, just unusual. Purge was... an experience.

Won’t change the bubbles, though, which was my biggest objection. Plus the negative stigma of upstream demand.

 

[Caveeagle]

View media item 203552

 

[Caveeagle]

Possible. Even likely. Breathing was not bad, just unusual. Purge was... an experience.

Won’t change the bubbles, though, which was my biggest objection. Plus the negative stigma of upstream demand.

The servo assisted upstream valve is only an issue if you have swapped around regs and hoses and so now have eliminated an OPV from the configuration.

 

[tmassey]

That is sexy! I imagine the stage bottle hides a lot of the problems with the setup: limited ports, 200 Bar DIN and lower performance at high tank pressure from the unbalanced first stage (as I understand it: you get a lower IP at higher tank pressures with the old Cyklon firsts). Looks sharp though, and the ambidextrous second is nice, too!

And I didn’t say the upstream demand was a problem, I said it was stigmatized! My *understanding* is that there has never been a fatality associated with upstream demand shutting off air. But still a stigma.

 

[Caveeagle]

That is sexy! I imagine the stage bottle hides a lot of the problems with the setup: limited ports, 200 Bar DIN and lower performance at high tank pressure from the unbalanced first stage (as I understand it: you get a lower IP at higher tank pressures with the old Cyklon firsts). Looks sharp though, and the ambidextrous second is nice, too!.

That was just a buddy bottle set up I was using for OW/ cavern dives with kids and a coupe friends. I don’t like triple buddy pairs as a general rule, so I would just go solo if we didn’t have an even number that day. And that rig is very streamlined and easy to carry.

 

[tbone1004]

@tmassey that's a balanced first stage

 

[Eric Sedletzky]

And I didn’t say the upstream demand was a problem, I said it was stigmatized! My *understanding* is that there has never been a fatality associated with upstream demand shutting off air. But still a stigma.

My understanding about the upstream valve, based on the knowledge of my former tech instructor, was that there were two schools of though regarding upstream valves. “If” the reg fails shut then you go to your alternate and you still have gas, you haven’t lost anything. If a downstream reg fails and you get a free flow and lose your gas and happen to be deep with a deco obligation you’re fcked.

 

[RainPilot]

The servo assisted upstream valve is only an issue if you have swapped around regs and hoses and so now have eliminated an OPV from the configuration.

Agreed, fortunately the OPV is now part of the 1st stage eliminating that issue, along with the need for special hoses etc. Still something to look out for when diving older Poseidons.

 

[IslandKraut]

...there's always been one more oring in the 3960 for the Jetstream.

I've always wanted to know what the purpose of that oring is...
Certainly not to make more IP as the Cyklon's is higher anyway.
And would it hurt to have it on the Cyklon first?

 

[rsingler]

I've always wanted to know what the purpose of that oring is...
Certainly not to make more IP as the Cyklon's is higher anyway.
And would it hurt to have it on the Cyklon first?

I believe it's to ensure a more rapid pressurization of the upstream valve stem inside the second stage. Without the oring, IP flows first and more easily into the space under the first stage diaphragm.
As you know, the Jetstream hisses until the upstream valve stem has enough pressure to force the valve closed. That o-ring makes it happen fractionally faster.
I can't think of any reason it would hurt to leave it on a first tuned to the higher IP of a Cyklon, but Poseidon engineering has always been very meticulous, so maybe? But then if it really mattered, the 3950 wouldn't have the land for the oring, and the 3960 would. They're EXACTLY the same regulator, but for the oring and the number stamped on the DIN wheel.