Ok, tear it apart (New Home Build Design)

canetoad

On again, off again Home build project. Cant decide on name; HBAM1 (Home Build, Available Materials) or Canetoad1. Leaning toward the later. Not too pretty @ the moment & havent decided on encasing it in a hard or soft shell, or just leave it as is. As can be seen from the images below, unit is starting to come together but still some work to do. I wanted to build a unit with as many off the shelf parts as possible. I also want to test a few ideas. Mainly; scrubber design. I wanted a semi pendulum type scrubber configuration that balances scrubber shape & gas flow to extract maximum scrubber duration & performance. I know the scrubber shown here is not likely to achieve this goal but thought it would be a good 1st practical test as it's gas flow is roughly similar to the idealized shape I have in mind. That design will need to be custom molded & gas flow studies conducted. That will be for a later date, of course. The current design, below, actually utilizes 3 CLs. The 2 CLs on either end of the scrubber are more water traps than actual CLs. The main CL is mounted to the center section of the scrubber as shown in the line drawing below. Other details: O2 injection is via a modified "Dave Sutton" KISS valve assembly. (Dave, your KISS part's list, photos & website have been a big help. Thanks). CLs are made from Auto inner tubes & will be manually sealed by being clamped between aluminum, brass, or stainless bar stock bolted togather. This unit is intended to be used as a Pure O2 rig with the possibility of going mixed in future if it proves successful. Comments/criticisms accepted.

Thanks,
PM
P.S. I appologize for the quality of the artwork & photos.






Basic Unit without main CL




Basic Unit without main CL from another angle




Modified "Dave Sutton" KISS




Modified "Dave Sutton" KISS detail




Also, a couple of pics of the meter I may use. Seems to work fine but no in water test yet & only a very informal pressure test so far. It uses a PM 128E. Real easy to work with, only 1 resistor to be removed which is replaced by a 10K pot. And every thing else set via jumper. Yes, I know it is verbotten to use leads of the same color, but was only decent wire available @ the time. This will change, as will the jumper for the decimal.




Meter circuit board detail. I added a 10k load resister on Cell leads. Will add heatshrink later.

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PM

Ben Field

Looks interesting, well done for actually building something, good start!

One question- exhale gas goes in one end of the scrubber then what? It can go straight past the O2 cells into the CL on the other side or make a 90degree turn and go past the cells? Or is there are baffle in the centre like the SK scrubber?

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www.hugsac.org.uk

canetoad

Thanks. Gas flow will be split but there is no baffle. Part of the gas will go straight through like any axial scrubber & the rest will go to the main or central CL & thereby past the cells. I guess I'll see what works in actual practise. If it doesn't , I have room to relocate the cells to one of the CLs, etc. Hope this posts properly, doing it from a mobile PDA.

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PM

Lure_Angler

From what limited knowledge I have, here's my take on this system:

It seems to me that you've created an axial flow (and not semi-pendulum flow) which has 2 CL to it. The advantage of that is that you get reduced WOB and flood tolerance.

However, if a semi-pendulum flow is to be achieved, I don't think its possible with a dual counterlung system. That's because a system requirement of pendulum flow is that the DSV hose, single or dual, must connect directly to the scrubber.

On top of that, if a dual hose DSV is used, I believe, the inhale and exhale hose must be connected to the scrubber, as close together as possible. (side by side) This is to ensure that gas enters, and exits the scrubber from almost the same point. Only then can you achieve pendulum flow (better scrubber efficiency), minus the dead space issue.

I believe Mr Dave Sutton's website has excellent photos of a semi-pendulum rebreather.

Hope it helps.

Tian Chang.

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2LT Lure_Angler minus 3 months

canetoad

Lure Angler, always liked the name, if you look @ the line drawing you can see there are actually 3 CLs. I captioned the photos to indicate that they are without the main CL. The main & centrally located CL is what allows some of the gas to move over part of scrubber bed more than once. Maybe not a true pendulum effect but close enough. If I recall you are also in the midst of a Homebuild, hope it is going well.
Thanks,
PM

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PM

Lure_Angler

I get your point.

The pendulum effect is there but only the lime in the center of your scrubber is exposed to it.

A clever trick indeed.

Another question though: For the system to be effective, when you exhale and inhale, most of the gas must move into and out of the central CL, instead of bypassing it. How did you ensure that happens?

My own system's a pendulum O2. Somewhat along the lines of Frenzy Frenzy. Progress is slow but moving along.

Tian chang.

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2LT Lure_Angler minus 3 months

Ben Field

Ah... are we to assume you don't have any one-way valves in the DSV then?

When I first looked at this I assumed it was a loop running one way, which is why I couldn't understand the 3rd lung at the back!

In which case you have alot of "deadspace" between the mouthpiece and scrubber to hold unscrubbed gas you'll inadvertantly rebreath won't you?

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www.hugsac.org.uk

canetoad

Ben, You were correct the 1st time; flow is one way. See image below. Threw the picture togather in about a minute so it is a little sloppy but should clear things up.
Lure Angler; Good eye; gas flow to the main CL is partial & only over the center section of the scrubber will some of the gas be rescrubbed. I will make the 2 end CLs as small as possible so the main center CL will take most of the gas. This is mainly a proof of concept, by no means do I represent it to be totally efficient as a semi pendulum but I think it should exhibit some improvement over a axial flow scrubber of the same dimentions. May be wrong on that but sounds good in theory.

Thanks,
PM

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PM

Lure_Angler

A mentor once told me this: Gas flows to where there is least resistance.

Keeping that in mind, the qs now is: Would differentiating the CL volume direct the most gas into the central CL? As compared to say, differentiating the diameter of the outlets leading to the respective CL?

Tian Chang

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2LT Lure_Angler minus 3 months

teomannaskali

Looks really nice and diveable.

Do you see where you have written SCRUBBER. I think that just under the ``U`` you will not have good scrubber usage. The gas may bypass that part. Its just a feeling.

Does it work? I htink that you sould check it with that coloring sorb.

how did you stick the tire together?


Teoman