Absolutely, no question to the full and safe abort part. Rod

On Wed, 4 Sep 1996, Roderick Farb wrote:

> Absolutely, no question. Rod
> 
> On Tue, 3 Sep 1996, Richard Pyle wrote:
> 
> > 
> > Yeah, but are computers on fully-closed rebreathers truely "life-support" 
> > equipment - or can any well-trained diver do a full and safe abort with 
> > any well-built rebreather without the aid of computers? That's the 
> > question I wanted John to ask you.
> > 
> > Rich
> > 
> > > Computers are very convenient and I always carry tables as backup. I cut
> > > my own using Decomm which is the best program for what I do. The computer
> > > uses the Buhlman ZHL16 algorithm with a little conservatism added in (I
> > > can change this on my laptop and download the changes to the dive
> > > computer. The dive computer will keep track of ten different gas mixes and
> > > do gas switches; I can change these on the laptop as well. The only switch
> > > I do on deep dives is from trimix to OEA running both at a pO2 of 1.4. The
> > > computer handles this readily. If the O2 sensors crap out then the
> > > computer will default to a preset pO2, usually 1.3. The computer can be
> > > used attached to the rebreather and monitor O2 sensors or as a stand alone
> > > computer with preset pO2 or fO2 for rebreather or open circuit. Computers
> > > can and will fail so I always carry tables. For a while I had problems
> > > with the computer and quit using it because I didn't trust it. These
> > > problems have been ironed out and I trust the computer implicitly. But, I
> > > still cut tables as backup. Decomm and computer differ on same dive
> > > because I cut Decomm so that when I enter the water I am at the bottom
> > > instantly. I used to cut Decomm by treating a rebreather descent as an
> > > open circuit descent for fO2 purposes. I would input a new fO2 every 30
> > > feet until the bottom. On the bottom it takes about 5 minutes for you to
> > > metabolize O2 in excess of set point, so I would factor that in. I found
> > > from experience that you get nearly the same tables if you cut decomm as
> > > if you were at the bottom instantly at the fO2 of the setpoint. So now I
> > > cut the tables the easy way. For a mixed gas dive with the rebreather, the
> > > fO2 in the diluent tank at maximum depth is the same as the set point
> > > fraction, so I never go over the set point. For most dives that I make
> > > over and over again to the same depth and for similar times I know what
> > > the deco is without the computer or tables. But, computers make all of the
> > > above much simpler to deal with and makes diving more convenient. George's
> > > point is well taken in that computers can and will fail. BTW, Decomm can
> > > be used in a constant pO2 mode by trickery because Abdur hasn't built me
> > > Decomm to do it automatically. 
> > > 
> > > 
> > > 
> > >  On Tue, 3 Sep 1996, Richard Pyle wrote:
> > > 
> > > > 
> > > > >    anyone who ever ran windows 3.1 should be able to tell you that
computers
> > > > > crash fairly often.as a result i dont want to trust my life to a
computer
> > > > > system. - jt
> > > > 
> > > > If a rebreather is designed right, and if the user is trained right,
then 
> > > > computers on a fully-closed rebreather are a convenience, not a 
> > > > life-support system. If you don't believe me, as Farb.
> > > > 
> > > > Rich
> > > > 
> > > > > 
> > > > > 
> > > > > On Mon, 2 Sep 1996 gmii@in*.co* wrote:
> > > > > 
> > > > > > 
> > > > > >    In reading this account of another electronic rebreather
nightmare I am 
> > > > > > amazed at the sheer stupidity and arrogance of the "tech"
"engineers"  who come 
> > > > > > up with this crap. Clearly anything in the breathing loop of any
rebreather is 
> > > > > > by definition at the same number of atmospheres as the diver -
obviously whoever 
> > > > > > designed this is one dumb fuck.
> > > > > > 
> > > > > >    For you dumb fucks out there, that means that the chips are
compressed, the 
> > > > > > batteries are compressed, and the besides the obvious chance to
short circuit as 
> > > > > > they are squeezed, some components, like dry cell nicads, can not
tollerate 
> > > > > > compression. It is no wonder , however, that the same crowd that
went for square 
> > > > > > lights fell for this bogocity.
> > > > > > 
> > > > > >     Most computer chips are hermeticly sealed, which means that
they may retain 
> > > > > > compression in their voids and explode when the pressure is
lowered. I do not 
> > > > > > know much about rebreathers or computers, but I think NOVRAM chips
have their 
> > > > > > own batteries, so that means the chip and the battery are being
compromised. 
> > > > > > 
> > > > > >     Trying to encase this crap in gell would not alleveiate any of
these 
> > > > > > problems, and would add the problem of water wicking down the wires
and causing 
> > > > > > the endless electonic mystery. 
> > > > > > 
> > > > > >   Just like most dive equipment, these devices are clearly created
by people who 
> > > > > > do not actually dive for people who need a magic carpet, and the
only commercial 
> > > > > > use for a piece of shit like what is described here is for
instructors to teach 
> > > > > > wannabees and strokes yet one more merrit badge specialty.
> > > > > > 
> > > > > >     But, what else is new? - G
> > > > > > 
> > > > > > 
> > > > > >   
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > 
> > > > > --
> > > > > Send mail for the `techdiver' mailing list to `techdiver@terra.net'.
> > > > > Send subscription/archive requests to `techdiver-request@terra.net'.
> > > > > 
> > > > 
> > > > Richard Pyle
> > > > deepreef@bi*.bi*.ha*.or*
> > > > *******************************************************************
> > > > "WHATEVER happens to you when you willingly go underwater is
> > > > COMPLETELY and ENTIRELY your own responsibility! If you cannot
> > > > accept this responsibility, stay out of the water!"
> > > > *******************************************************************
> > > > 
> > > > --
> > > > Send mail for the `techdiver' mailing list to `techdiver@terra.net'.
> > > > Send subscription/archive requests to `techdiver-request@terra.net'.
> > > > 
> > > 
> > > 
> > 
> > Richard Pyle
> > deepreef@bi*.bi*.ha*.or*
> > *******************************************************************
> > "WHATEVER happens to you when you willingly go underwater is
> > COMPLETELY and ENTIRELY your own responsibility! If you cannot
> > accept this responsibility, stay out of the water!"
> > *******************************************************************
> > 
> > 
> 
> --
> Send mail for the `techdiver' mailing list to `techdiver@terra.net'.
> Send subscription/archive requests to `techdiver-request@terra.net'.
> 

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]