Need help regarding rebreather ideas I have...

MPJScuba

I haven't wrote for awhile and I apologize. I've had a very busy schedule
of late. I just recently dived in the ocean at Key Largo. I am seeking info,
suggestions and/or feedback for help in the final stages of design for my
re-breather that my friend Jere (who recently passed away) and I have been
working on. I've attached a diagram as to how the re-breather and ventilator will work side by side (together). The vent box is already completed. A re-breather is needed to complete all of this...thoughts are leaning toward an evolution rebreather. Again, if you have any ideas, questions or concerns, please feel free to contact me at: roadrunnermatt@yahoo.com or cell is: 651.248.2326

Respectfully,
Matt Johnston

Attached Images

CCR_Vent2.jpg (112.4 KB, 280 views)

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Genesis

Matt! Wow! Seeing you here... cool....

IMHO using something like an Evo for this is gross overkill. If you're limited to 20fsw then a pure oxygen rebreather is going to be a MUCH simpler, lighter and easier to manage system.

Do you really need all the other complicated - and expensive - bits?

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AD_ward9

If you give me a call on Skype (Deeplifeltd), I would be happy to share our experience of testing and building RBs with ventilators: on our case, for extremely deep diving. We have built several breathing assistance units, and also been involved with the company that has promoted breathing assistance on RBs who had 20 years experience with these, down to 450msw, and our own tests to 500msw.

It is essential to measure carefully the pressure to the diver. These units are very dangerous in a closed loop diving situation if not very carefully designed and verified.

Remember, your lungs are very bad at sensing overpressure. What may feel like super low breathing resistance, can in fact be a dangerous underpressure. You can do permanent lung damage with just 120mbar.
The over and underpressure safety valves are essential when experimenting with these things.

Alex

rdmmdr

karl has the right idea

how about taking the mk15/mk16/biopak system and power the clung plate with an air motor with a cam. it would replace your vent and give you a powered rebreather with the option of manual override. we could do this with surface supplied air for the motor or use the piston design i sent you months ago. spring power one way and air power the other.

rick

MPJScuba

Hello and thanks for your input. This is what I seek most, information!
I will catalog your input (w/name) and enter into my resource database.
One question, do you think by looking at my diagram that it's doable? My
quest is to dive beyond 30ft plus. Again, thanks for taking the time to
respond to my quest for help.

Regards,
Matt Johnston

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lizardland

Wouldn't a RB80 clone like an EDO4 Swiss Technical Diving Equipment be a good option for a powered rebreather? The bellows move in a straight line, should be fairly easy to power it.

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AD_ward9

Stuart kindly filled me in with what you are wanting.

I have been involved with build, verification and test of powered breathing assistance for rebreathers, for very deep diving rather than to assist people diving with a breathing handicap, but the mechanics are the same.

There are some important things to note:

1. A ventilator on an open circuit regulator is simple, and can work if properly engineered. It will use a lot more gas than for a normal open circuit stage.

2. A ventilator on a closed loop is unstable if it uses any pressure measurement device to switch directions. We have done extensive mathematical modelling and actual testing of this type of equipment. If you contact me directly, I can discuss this with you.

3. If you use a sensor to detect lung position, then the ventilator can work on a closed loop. The best way to do this, is to use a variable resistance fabric in a vest. There are some special materials which exhibit very large changes when pulled. Another method is to weave a cable in a zig-zag into a vest, then use it in the tuning loop of an oscillator, and measure the frequency. Oscillators of around 8KHz are used for this.

4. If someone has lost all power over their lungs, then the ventilator can be set to a continuous cycle. This involves no feedback, and works.

As regards driving the bellows, a pneumatic piston works but uses a lot of gas. A DC brushless motor with a 4 Quad controller works better: less power and can be made safe. We found it better to use a piston than a bellows: more control. The problem with bellows in a rebreather, is preventing it moving to either end position.

It is very important to fit over and underpressure valves, otherwise this equipment can cause serious lung damage.

Alex

MPJScuba

Thanks for the idea Rick. I never received your idea, I can't find my previous post on here.

Matt

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rdmmdr

Matt

i need the tidal volume your vent is set to and the respiratory rate.
rick

MPJScuba

Hey Alex, I would love to hear how you guys do it with the RBs with a ventilator. I would love to call you but I don't have access to Skype. Is there another way to contact you? Do you have Yahoo messager? Or we could talk back and forth on my e-mail at Yahoo.com

I'am really intriged by what you guys have done in the past. I love working with this stuff, it's an awesome chanallange.

In your opinion what type of a rebreather would be good to use with a HT 50 ventilator. I know an oxygen rebreather would probably be more simpified.

I'll you around,

Matt

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