RB 80

[Chuck_Northrup]

This post disappeared from the "dressing for tech" thread so I thought I would start a new thread for the RB80. This is a very DIR specific rebreather so I believe this section is where it belongs.

Quote from FreediveWI
"Not being an expert on all forms of rebreathers I'll still take a stabe at the RB80 question. It's my understanding that the gas usage,and dosage, on the RB80 is directly tied to the divers own work of breathing. This cannot be said for other SCR's, like the Dolphin or the Ray, which can have widely fluctuating F02's in the bag due to work load. The RB80 is tied to the workload so the F02 stays much more constant. From what I understand this is the reason for one rebreather over the other.

Maybe you can help me out with this. I "thought" that the Gator, or the Frog, was suppossed to work on hte same prinicple, but can't remember for sure."



Jon,

You are pretty much on the money with the RB80. It is the only true RMV keyed rebreather on the market. What is unique about it is a bellows designed counterlung which sits on the bottom of the canister. When the diver exhales the bellows fills and a portion of the exhaled gas is trapped (with moisture) in a series of check valves and then jettisoned with the following inhalation.

The greatest advantage of this system, as you mentioned, is a much more stable FO2. This can be within 8% variation on the surface and as low as 2% over 80fsw. The disadvantages are the amount of offboard gas needed for optimum PO2, and a "relative" loss of efficiency compared with other RB's because gas use is directly related to the divers breathing rate. At least one of the deaths on an RB80 was due to an OOG situation.

To a diver used to wearing doubles the RB80 will seem very intuitive. As was mentioned it is noticeably larger and more cumbersome than many other RB's, but nevertheless still a viable player in the RB market. If it was priced more reasonably it would likely be more popular but $8,000 is a bit high for an SCR. It has a built in OC DSV (open circuit dive surface valve) which means to go "off the loop" from SCR and OC is merely the flip of a switch. Definitely a nice feature, but it does add bulk to the mouthpiece.

As for the FROG it is a complete POS! I have seen the unit at a number of trade shows and how people are not killing themselves on the unit is a mystery to me. The design flaws in the unit are too many to list here, but the scrubber is the biggest concern. The canister is roughly the size of a large soup can, contains about 1/5 the amount of scrubber material than the Inspiration yet they claim a 3 hour duration? :o The canisters themselves are "disposable" and look like they were made in arts and craft time at the local kindergarten. To answer your question the FROG runs more along the lines of a KISS style rebreather and is not RMV keyed.

Chuck