Rebreather modifications.

divetheworld

I'll put that page up shortly, but essentially it is a 250uM 316L gauze on the top and bottom which encapsulates the hydrophobic membrane.

It is soooo much better to pack the stack. Membranes last longer and there is a lot more rigidity in the assembly.

It was the forerunner to the completely new replacement cartridge which doesnt rely on the suicide 'o' ring at the top. This is incomplete until I solve some materials problems. Drawing attached.

Attached Images

inspocart.jpg (173.6 KB, 228 views)

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decoweenie

I just hope you offer in both Inspiration and Evolution scrubber sizes...

One thing to consider as well is make sure it will take the Temp-Stick.

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denzel

Great site, made it into my favorites for future reference.
Have green, it's healthy. (when I discover how....)

denz.

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woody

It is soooo much better to pack the stack. Membranes last longer and there is a lot more rigidity in the assembly.

It was the forerunner to the completely new replacement cartridge which doesnt rely on the suicide 'o' ring at the top. This is incomplete until I solve some materials problems. Drawing attached.[/quote]



I and many others would be very interested in anything that can solve the o ring and packing issues.

What are the material issues? Just being nosey here. My suggestion, for what its worth, would be to concentrate on the complete solution incorporating the membrane and o ring replacement. I understand that the drawing is work in progress, looking at it you only have one o ring on the assembly. I would suggest that 2 would give you a greater stability over the cylinder length if they were equally spaced in a more rigid material. If these o rings were standard items that were of a greater sealing surface area it would help negate any opportunity for gas bypass and would put equal pressure on the outer canister over it's entire length.

There a quite few companies that do work with Perspex and Lexan type materials on the UK south coast (Portsmouth area). Small cylinders with special engineering is there bread and butter. If a design was created and all they had to do was follow it it would be easier to get competitive pricing.

If this was done at the right price you would probably have trouble keeping up with demand.

Hope this helps

R

Mike

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divetheworld

There are some significant design issues with the drawing above and some of your suggestions. The first which has been rightly pointed out is the difficulty in extracting the cart out of the body, this is why the design is as supplied by AP. An imperfect solution, but one that works. The drawing uses a big handle and a structural top to aid removal but there is no doubt that it will suck.
One has to approach alternative designs with respect to those who have been through this so many times before. A redesign had better be the dogs bollocks and solve all problems with minimal cost or there is no point. I'm trying hard not to re-invent the wheel.
To address your ideas, the top section of the outer can (bucket) is the only part which has a suitable surface finnish to accept a sealing 'o' ring, the base of the can is rough cut and would only make the extraction even more difficult without ensuring a good seal. The drawing still incorporates the original 'o' ring at the top (see the chamfer in the OEM position) which would give some order of secondary protection.
There are two main areas of design for this application, confidence and ease of use. The sealing of the stack on the original works, but there is scope for improvement. The packing of the scrubber is a pain, so are most scrubbers. The art is in finding a way for imperfect filling to be inconsequential to its performance. This is the 'self packing' scrubber which has been successfully implemented in many designs. The springs on the base of the cartridge are for this purpose.
To avoid large development costs (i.e. critical testing) it is important to maintain the geometry of the absorbant material in the scrubber or you risk reducing the efficiency of the absorbant. A good example of this is the Extendair cart which, placed as a direct replacement, does not work very well at all, but place the cones on the front and back, the cart performs exeptionally well. The original can has inadequate dimentions to make the EA cart viable in a standard Inspo bucket at the moment. Work in progress at micropore on this as we speak.
There are a number of tricks which improve the efficiency of one approach over another with equal amounts and geometry of absorbant material. It has been proven in testing that expired gas passing through the centre of a system configured like the Meg into the absorbant and out via the outer void would actually improve the efficiency and duration of the bed over gas passing in the other direction.
Another nice example I was informed about is the centre stick in the Inspo cart which actually improved results over one without. This is unverified by AP but I have no reason to doubt where I got this information from.
Much to think about. In the mean time, if I ever get a reasonable prototype made, you will all see it here first. After all, talk is cheap.


Brent.

Oh, the materials problem is fabrication of a part that only lends it self to injection moulding. Other manufacturing methods require second mortgages and create piles of scrap.
This is step one, a long way to go as yet.

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mverick

Maybe not what you're looking for. But if you wanted to used a Oring top and bottom with the bottom one just to stabilize. And you can't because the bucket isn't machined for one.

If the bottom one is just to stabilize. You could put 4 to 6 dimples on the outside of the cannister. That would stabilize the bottom. Like the Meg uses.

Never checked out an YBOD scrubber. So don't know.

Just wondering. What are you using for the Hydrophobic membrane?

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P1010160.JPG (66.7 KB, 164 views)

woody

Hi Brent,

A very interesting and comprehensive post, as you rightly say sometimes it is not worth re inventing the wheel and I forget how much thought and r and d time go into these products. For mere mortals it can very hard to produce prototype products without bankrupting yourself.

Cheers

Mike

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narked at 90

hi mike, you could'nt be more right, i wish others could see how much time and money goes in to this stuff, the money wasted on getting things right will scare the pants off you! when the chance's are you'll get no return, so things like this tend to be hobby's for people, this is where we've been trying to bring stuff to market
Brent's a very clever guy and spends a lot of time thinking about every thing....brent you can go to sleep some times mate
but it does show how good it is to have forums like Rebreather World to test ideas out before you wast the mortgage!!
kindest regards john routley

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