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Re:Rebreather Purchase question - Chuck_Northrup - 04-22-2004
Check the DIR site for the RB80 answer.
Carrying OC travel gas with a low FO2 source gas has been done in the past, but by doing so you loose the RB advantage for ascent and descent.
In addition all orifices available for the Dolphin are calibrated for sonic flow using nitrox mixtures, not trimix. Using helium will result in a less predictable flow rate and a less reliable FO2. It kind of gets back to the different RB's as different tools aspect. If you want to dive 200fsw don't do it with a Dolphin. 
What amazes me most about the homebuilders and modifiers is that many of these guys take a $3,000 rebreather, put in $5,000 worth of time, tools, and machining to achieve a RB unit that can "almost" rival commercially available CCR's which cost less and reduce the "guinea pig" factor.
Chuck
Re:Rebreather Purchase question - ccuda - 04-23-2004
Chuck,
One of the justifications for the modifications is it the size and weight factor versus the big heavy units commercially available like the "turtle". It's what keeps me out of a that CCR - the inspiration is simply too big, too heavy to me. It completely has it's justified place in many areas, just not in my dive locker. I want more steamling, less weight, and given the restrictions that keep increasing for dive travel, the Inspiration is becoming less and less viable as technology improves.
A modified Dolphin can help bridge the gap, but it's a long way from perfect. Drager's lawyers don't want to seem to let diver's know it's full capability, but these more compact CCRs or modified SCR's are the demand. If Drager doesnt want it's product being modified, they need to release units with what they already know is possible and come out with one commercially available for $4 to $5K.
Chuck, why isn't the Prism Topaz marketed in this area, simply CE stamping? This is a sound unit, built with a great deal of forethought, more than the Megladon in my opinion. I'm sure it has a lot ot do with $$$$$$, but I don't see it being any higher than Buddy's. I see it as a clear rival to the Inspiration, and superior in some ways, especially for those not needing as much scubber life and size.
With 6000+ YBOD units sold, Buddy was handed a lot of R & D money to develop the Evloution, and it seems to be a nice unit as well, but there seems to be less support for it from those who are in the Buddy camp? Is that based upon it's price tag? If Buddy would price the Evo for a more attractive price, these chop shops wouldnt even bother with modifying the Dolphins or KISS.
Re:Rebreather Purchase question - Inspirationdiver - 04-23-2004
The Prism Topaz is a pretty good unit. There are some advantages it has over the Inspiration. The problem is a matter of availability and price. I know people have shelled out 5,000 as a deposit to get themselves on the list to accuire one. But 2 years later have still not seen any product. Imagine what it would be like to get service on this unit. The Inspiration is readily available, and has a reputable company to stand behind it's products.
Re:Rebreather Purchase question - ccuda - 04-23-2004
ID,
And the Evolution?
Re:Rebreather Purchase question - Inspirationdiver - 04-23-2004
The Evolution is really a stab at making a Cadillac out of the Inspiration. They are adding a lot of new features that drastically increase the selling price. Some of these include CO2 scrubber temperature monitor, single-wrist mounted display unit, and built in deco software. The tanks contained in the unit are slightly smaller than in the Inspiration(2 litre vs. 3 litre). This makes the unit lighter and smaller but reduces it's capacity for long dives or multiple dives w/o gas fills. I'm not sure what the exact selling price is going to be but I've heard it could be several thousand more than the Inspiration.
Re:Rebreather Purchase question - ccuda - 04-23-2004
several thousand more than the Inspiration? OUCH! :o !
...did my seat just become harder? I need to go out and get me a Cis Lunar for trade in...
Seperate question: We all know Regulators can free-flow, they're designed to do so, but what about Rebreathers? Expectedly or unexpectedly?
Re:Rebreather Purchase question - Inspirationdiver - 04-23-2004
Free flowing regs on a CCR rebreather is really a non-issue. Sure, it can happen but it is really unlikely. The higher the gas flow through a reg, the faster it gets cooled and the more likely it is to freeze up. On a CCR, gas is only injected in small spurts. The only time there is any significant flow is during a fast descent. You have to add diluent to make up for the increase in pressure. Even then, the flow is comparable to when you add air to your drysuit. Most argon regs are unbalanced piston regs and don't have any problems under those conditions, even in really cold water. The Inspiration comes with the DS4 first stage ( balanced diaphram- same as the Apex TX50 first stage) which is a very dependable reg in my opinion.
Re:Rebreather Purchase question - Chuck_Northrup - 04-26-2004
ccuda,
Sorry for the delayed response. If the Inspiration is too big for you (assuming you tried it on?) you may want to take a closer look at the Mini-meg, or when they finally reach production an Evolution. I first thought the Evolution was a "smoke and mirrors" publicity stunt, but now I believe AP is just being careful not to rush it into production. For this and other reasons the Inspiration is going to remain a strong presence in the RB community for some time; after all it does have the current market share. The fundamentals of rebreather technology are almost 150 years old and most of the improvements will change very little in the function (i.e. principles) of CCR.
On a related topic you brought up the travel restrictions. I think the issue here is really about flying with cylinders. A rebreather is no more suspicious looking than scuba gear, but the cylinders send up a red flag in our post 9/11 society. Even with valves removed you need to "prove" that the cylinders do not contain compressed air. ??? With more and more shops in exotic locations becoming "rebreather friendly" these hassles will become less prevalent.
As for the Prism I have to agree with you it is a very well designed unit. In support of its viability, it recently passed US Navy testing. Inspiration Diver is correct by saying production issues and cost are the biggest factors keeping it from our market (the first is probably the more important of the two). Until this weekend I have never actually seen a prism. Much like the evolution I had heard about it, seen pictures of it, but never actually had hands on experience with it. There are still less than 75 units in the field. :'(
There are some features unique to the Prism which are definitely a sign of "thinking outside the box" like an analog PO2 meter that can be used to independently test all 3 sensors and perform battery checks. One 9 volt battery provides up to 40 hours of operation, but even without a battery you can determine your PO2 by checking the mV each cell is producing. The size in comparison to the Inspiration is not a battle it wins, however. The scrubber canister is actually larger, not smaller, but a radial design enhances chemical performance to 6 hours (double the YBOD). I have some picture of the Prism I can post here, or email to you if you would like. I am working on a PowerPoint presentation for upcoming Discover Rebreather events so I am collecting digital images of as many units as I can.
Hope this answers most of your questions.
Chuck