From RG-UF/M....To RGU-2....And Beyond

DanDunfee

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Thanks for kind words Stefan, I especially appreciate those coming from you. Sorry to hear that you're probably not coming to DEMA,... was looking forward to splitting a brew with you.

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Ken is a better deep-throat technical authority on the RGU CMF regulator than I, so I'll not pre-empt any answers he may offer or add. Ken did an excellent, illustrated teardown article that Tom Rose posted on his website. The URL is below.:

RGU REGULATOR BREAKDOWN

I wish Ken and Beanie would collaborate some to tweak the article format a bit as required to archive it in the Rebreather World Library.
Ken & Beanie....how about it ?? I think its a worthy article to archive as a reference.

My comments (some of which are based on earlier inputs from Ken), are:

* Operated within its design and intended parameters, this inexpensive little integrated pressure and CMF reg is a reliable, 'rock solid' performer, and an good buy at a component price of~ $ 110 USD + S&H. Many have said that its worth the price for a whole RGU unit, just to get the reg...if you can find a really good deal on the rig in the marketplace.

* The 1st stage surface IP typically runs 70-75 psig, only about half that of modern commercial 1st stages. The factory-set surface flow rate for all RGU regulators I know, and have been told of, were essentially right on ~ 0.9 lpm. This means the max depths for full CMF flow at 0.9 lpm is on the order of 90 fsw. Deeper requires progressively more frequent inputting of bypass gas. However, Europeans and Scandanavians (where mods of this rig are quite popular) and others frequently dive mixed-gas variants of the RGU to 125 fsw and beyond. The surface IP can be cranked up to a maximum of ~85 psig, which gives a CMF of ~ 1.2 lpm.

* If the LP output from the regulator gets to be really blocked off, the feedback can sometimes blow out (eject, not severely damage) the rubber diaphram which covers the bypass button, even before the LP pressure release may blow. A tailored washer inserted to partially cover more of the diaphram can substantially increase that blowout pressure, and in any event, a blown-out diaphram is very easy to replace....after one changes their underwear.

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There are 'Bold' divers and old divers, but NO old, ' Bold ' divers

caveseeker7

Thanks Dan.
That first point you made was pretty much the impression I got when I saw the RGU the first time.
Good link, well done Ken and Tom.

Could make a nice offboard/bailout O2 supply valve for mCCR divers ...

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Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

Skipbreather

Hi Stephan-


Dan did a pretty good job of summing things up. Just to put my spin on things:

- Reg is a great donor for homebuilt straight O2 systems. Biggest shortcoming in that usage is that the input side is essentially impossible to modify. On a cold and snowy Saturday last winter I got a wild hair up my *** and decided to cut apart a broken one to see just how the nut was attached for sure. Turns out it is indeed threaded, but it either has the mother of all adhesive thread lockers on it or is assembled w/ a sweat interference of the threads. As is, a brass CGA660 connector is needed at a minimum to get it useable w/ anything other than its original intended valve.

- For use deeper, not so good. W/ the IP adjusted to 80 psi, near max attainable, flow stops completely at about 140 ffw. CMF behavior stops shallower.

- Output connector is fragile, but not terribly so.

- OP valve likewise.

- One must get comfortable w/ fact your gas system has a large (30 mm or so dia) rubber disk (the O2 manual button) sealed w/ just a collar holding it against the reg body. Getting torn or blown out during a dive is highly unlikely, but could happen in some extreme scenario. Result would render reg useless for remainder dive and possibly unrepairable.

Best,
Ken

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"Entropy RULES! Enjoy the interim."

Tom Rose

First a point of order...the breakdown on my website is truly the work of Ken, I had minimal impact, only assembling what he did and very minor editorial input. He did all of that at my request...again a word of thanks to Ken.

Secondly,

While I have 5 RGU units or the remains of those units, only two of the regulators are still alive and kicking. Others have died a death of many cuts (read modifications) and I have long since moved to a critical orifice system using a conventional regulator that is depth compensated. I simply ranged my system so that it never overfeeds at the depths I dive to. This system was discussed to death on another earlier thread.

My current system costs just about what a RGU used to cost...in the range of 150 bucks when they hit the surplus market a few years ago....but all the parts to my system are currently available from the secret yellow book and your lds. I imagine, that Duncan, Dave, or I could whip together one of those systems, in my Duncan's, or Dave's variation in less than an hour from parts in our funshops (it certainly ain't work), This is important in that we are not dependent upon things that are hard to find.

Ken (Skipbreather makes a very important point, to make the RGU work with tanks you can ship by air, you need to connect the regulator to a brass fitting or you are gonna mess up something. (one of those regulators bit the dust because I was given a stainless fitting, being such a good customer of the gas supplier).

By the time you add the RGU valve, the adaptor, etc, you can almost take one weight off your belt. Do I still dive a RGU, yeah, but not much. I would dive Dans version of the RGU much more than the RGU if I had one. Even accounting for some different ideas and my ego, I think Dan is really on to something.

Nuff Said,

See you guys at DEMA....make sure you bring those Rube Goldbergs to the Rebreather Party...The grand master of rebreather world is giving us some space to show off.

Consider shipping to the motel if you do not think you cannot get past TSA.

Tom

__________________
The 50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong the first time.

www.atlimp.com

DanDunfee

The Input connection thread on the RGU reg is a standard European G3/4 thread, the old std German Oxygen thread, ... Dave Sutton had pointed out in his original RG-UF/M teardown article that the same thread is found on a number of Draeger O2 rigs, including early US Navy-destined LAR Vs.

I personally have no experience with substituting a CGA 660 thread at this interface, but several people have said it works OK.

I think I've found a source for a brass, G3/4 Male X G5/8 DIN Male, short-coupled adapter that I hope to use to mate the RGU reg to the DOT-approved, 2 liter, DIN-valved cylinder that I'm integrating into some of the RGU-2 config variants. I'll let you know how that all turns out.

__________________
There are 'Bold' divers and old divers, but NO old, ' Bold ' divers

DanDunfee

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Tom........Or Ken Swain:

What would it take to induce you to part with a set of the components for the RG-UF/M orifice assembly from one of your 'dead soldier regulators.???
Before long, I want to experiment some with an SCR variant of RGU-2 , so I want to get intimately familiar with that component set, but don't want to be tearing out, or buggering up my only orifice set right now.

__________________
There are 'Bold' divers and old divers, but NO old, ' Bold ' divers

Tom Rose

Hi Dan,

No problem if I can find it easily in my pile of stuff. You gonna be at DEMA, I will bring it down. No charge.

Tom

__________________
The 50-50-90 rule: Anytime I have a 50-50 chance of getting something right, there's a 90% probability I'll get it wrong the first time.

www.atlimp.com

DanDunfee

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I received the adapter above from W+S Water Safety
W+S Water Safety GmbH - Sauerstoff-, Nitrox-, Luft-Adapter ( Item 300490 )
They're a bit pricey, esp. with Handling & Shipping to the US, but the close-coupled adapter does the job beautifullly !! I'll soon do an update and pic spread on integrating the DOT-approved, 2-liter, belly-mounted cylinder variant into the RGU-2

BTW... Just did the first of the 12-ft pool test trials on the RGU-2 Oxygen system module. First trial dealt with: search for leaks: buoyancy and weight & balance: flow rates, etc. All went very satisfactorily. Very few minor leaks, one small mod required to the Catenary Panel suspension of the Counterlung, good WOB, etc. There will be Several more 12-ft pool trials, in preparation for first ocean trials at Key Largo, Florida, probably near the end of November.

__________________
There are 'Bold' divers and old divers, but NO old, ' Bold ' divers

DanDunfee

Got in a couple more 12 ft pool dives with the RGU-2 Oxygen Module just before heading out to DEMA. Essentially all initial trials had been done in horizontal, ~ 0 to 30 degree, swimming attitude. Initial reports of good WOB were optimistic. Positive hydrostatic head drove gas thru the scrubber and down divers throat.....goood !! ..but exhale WOB was higher than desired. .

Most recent trials, mostly in ~ vertical attitude, found continued very goood inhale WOB, but the vertical exhale WOB was quite high, due to the same positive hydrostatic head that makes the inhale WOB so effortless. To me, the exhale WOB is not acceptable for routine, and especially longer dives (fatigue). The initial scrubber & counterlung configurations are being modified.

Changing internal scrubber canister flow & porting.... and counterlung shape ...to better balance the inhale / exhale WOB components. Both are minor physical detail changes, but expected to have substantial effects. Plan to go to Key Largo, Florida for first open water trials the end of November..... Will report after...

Dan

__________________
There are 'Bold' divers and old divers, but NO old, ' Bold ' divers

gco-cs

Any news ?