Musings about a homebuild BOB & pendulum rebreathers

SteveL

Interesting Dave - I like the idea but I also like having the 4th cell as a completely independent backup - It's not something to plan a whole dive around but if the whole system goes down for some reason this is the get out of jail card.

Its a bit like the alpinist idea - or to give it an aeronautical flavor - any landing you can walk away from is a good landing - so I fugere if you can get out of the water kicking even a bit bent from and "event" then you are out of the water.

I used to dive an inspo and have had both handsets die inside a wreck once - NOT HAPPY - but the 4th cell was enough to know the PPo2 was breathable flying manually - enough to get out of jail!

I have been thinking about the fischer bulkhead connector as well - but I heard the other day that besides the self imposed psycological problem of drilling a hole in a nearly 'unobtainable if you bugger it up' -centre section - the material from which it is made may tends to flake and chip rather than make a nice hole - that wouldn't be good - Im sure there is a way to do it though.

Anyway I thought that if you can get a fischer bulkhead connector in then it would be nice to mount a small K1 sensor inside the plastic ring at the inhale port. That way you can actually get the sensor out of the inside of the CL to clean it or whatever - and it would be small enough not to bugger the gas flow. I thought you could mount it in a piece of small diameter pvc tubing - maybe this should be split to facilitate removal / insertion.

Now I have those cooper hoses on my rig it is much more difficult to put in a T piece

Pondering........

Steve L

Marc T

What about a very small cell housing for a K1 close to the mouthpiece?

Marc T

Hum sorry badly reading your thread, think whe are saying the same thing in fact .
One step further small housing closed to the mouthpiece 3 K1, electronic of a hud included in the same plastic part so no cable, easy external calibration...
Sort of a dream

Dave Sutton

Both of you have good points. Let's address them in order:

(1): The 3 vice 4 cell issue is one that can be debated ad infinitum. I agree with the reliability increase regarding the 4th cell, if in fact a position can be found to mount one internally. There are several places that come to mind.

(2): The cabling is an issue, and as you say drilling a hole in the center section takes a leap of faith. Remember that I have a metal center section not a plastic one so multiply the problem. But it can be done. A good sharp drill with the correct angle will drill that plastic no worries.

(3): I have been toying with the idea of a cell mounted in the DSV with a built in HUD... funny that it's mentioned here is a "bailout rebreather" thread, because that's *exactly* the application I want to use it for. Way back when, Will Smithers made up some circuit boads that ONLY drive a LED in his color coded and flash-cycle coded PP02 scheme and I have one here that I've never used. I've also a Halcyon OC/CC DSV that has the appropriate internal volume to mound a cell, if the open circuit feature is disabled and some new internal parts made. I hve not figured out how to do it with an OC/CC DSV that continues to work as that though, oter than building a new DSV from scratch. Something to think about. This is a huge part of finishing up the bailout rebreather project for "prime time" use.

(4): I also use Cooper hoses and still have a Tee for the 4th cell, it's a metal tee that threads to the center section, a cell is placed internally and the Cooper hose threads to it. Works fine.


Think it's time to again study the DSV placement scheme. Might kill several birds with one stone. Ideas anyone?

Dave

__________________
"Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com

SteveL

Dave, with the metal Tee do you notice any increase in condensation ?? I would have thought that an aluminium or brass T would conduct heat or cold in this case and make the warm moist loop gas bead up nicely in this area??

Will ponder the DSV option and let you know - conceptually its easy but gets bulky fast - thats the kicker -

If you just have 3 LEDs though they would give limited but vital info +/- setpoint - but the question is - do you want more from your 4th cell ?? - do you need the NUMBER ....

mmmmm

Steve

Dave Sutton

Condensation is not an issue. The part is acrtually an original military one.

The single LED (dual color) has a flash sequence that alllows you to determine PP02..... Solid Green is "on setpoint" and it then flashes green "flash..... flash" if you are 0.1 high and the same in red "flash...... flash....." if you are 0.1 low. double flash green "flash flash...... flash flash........" = 0.2 high and doubld flash "flash flash....... flash flash........" in red is 0.2 low. Continue the number of flashes for the PP02 high and low in 0.1 increments. Works great and the circuit board can be used single, double, or triple cell.

Bottom line is that you know the PP02 in 0.1 ATMA increments in relationship to desired setpoint.


Dave Sutton

__________________
"Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com

Duncan Price

In order to throw this back on track I'd like to flag up that most of my P1SS is now surplus to requirements due to me having another version on the blocks. No unreasonable offer - even if someone want's to "borrow" it - refused.

See: http://www.rebreatherworld.com/rebre...ss-takers.html

Duncan Price

As as suggestion (bearing in mind I'm on my second glass of Cabernet Sauvignon):

Blue/Green/Red LED's

Flashing Blue < 0.6
0.6 < Blue < 0.8
0.8 < Blue & Green < 1.0
1.0 < Green < 1.2
1.2 < Green & Red < 1.4
1.4 < Red < 1.6
1.6 < flashing Red

(special - 0.2 ish - all flashing - to calibrate in air.)

you make it - I might buy it.