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kiwidiver
Lung Diver
Posts: 67
Joined: Thu Nov 29, 2012 9:24 pm
First Name: jeremy
Location: Gosford, Australia

DA Cans

Sun Feb 10, 2013 11:21 pm

Does anybody know if it is possible to mount DAAM internals into one of the plastic cans available from The Scuba Museum?
I realise that the rear can will have to be cut to suit and the Yoke will end up offset, this hopefully won’t be an issue as what wish to do is independently mount the reg between a modern twin set and feed it off a separate first stage via the Hookah port and plug the DA’s first stage. This way I can use the reg with my existing twin set and preserve the original cans.

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luis
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First Name: Luis
Location: Maine

Re: DA Cans

Mon Feb 11, 2013 7:56 am

The lever will not contact the diaphragm in the center. This will affect a little bit how the diaphragm behaves to the suction differential pressures. How much it is affected will depend on several variables including which diaphragm you are using (a new super flexible or other) and how responsive is the regulator (are you using an HPR).

The distance is small, but so are the magnitudes of the forces we are working with.

The regulator performance will be affected a bit more by its orientation in the water (not just its position relative to the diver, as it is normal with any DH).

You may or may not notice a big difference, since there are so many other variables into the equation. This just adds one more.

One more variable in performance as a function of orientation is probably not a big deal unless the regulator is fine tuned. In that situation it could be close to free flowing and it could then free flow in some positions. A free flow in some positions would be my biggest concern.

I have personally tried it with a chest mounted (using the hookah port) regulator. I think I did use an HPR, but I can’t remember for sure… Actually that project might be from before I designed the HPR, but it had to have been one of the prototypes.

When I tried it, I could tell substantial difference of performance with position, but there were so many variables that it was hard for me to isolate the causes. When I have the time I will try it in a more control environment (a pool). The great thing about a chest mounted rig is that I can unhook the straps and change the orientation and the position, independent of each other. The bad thing is that I don’t have any instrumentation that I can use in the water to measure inhalation pressure.
Luis

Buceador con escafandra autónoma clásica.

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Herman
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Location: Raleigh NC

Re: DA Cans

Mon Feb 11, 2013 8:07 am

Possible, yes it is, there just enough room for the hole but there is more to consider. With the body no longer offset, the tabs on the diaphragm are not going to align properly with the lever so you will need to replace the second stage and diaphragm with a HPR and a single stage diaphragm. The HPR does not use the tabs so alignment is less of an issue. The lever will no longer be centered on the diaphragm but is should be OK. The HPR may also solve a second problem. The spacing between the second stage and the horn is critical to keep the venturi assist feature of the reg working properly. Without the venturi working properly, the reg will supply air but there will be a very noticeable degradation in performance. Since the HPR has a fairly strong venturi flow if you set it to max, the flow may be enough to offset the increased distance. This is assuming you barely have enough venturi flow, I am assuming it will be close with the extra distance to the horn. If it proves to be too much, you can always detune the HPR some. In any case, you should keep the alignment of the venturi hole directly down the supply horn. This is a swag (SWAG - scientific wild ass guess ) based on playing with the HPR and the venturi in some other experimental regs but you will be exploring uncharted territory, if you decide to give it a try, take photos and keep us posted. I for one, love to see what others are doing.
A word of warning, DO NOT try breathing off a reg without at least 1 hose, mouthpiece and an exhaust valve installed. Overly aggressice venturis will slam the second stage open and will cause lung damage if it has no place to vent. Experimenting with the venturi of DH regs can be dangerous if you are not careful.
Cutting the cans is not the easiest to do free hand - I cut them for Rob on a mill with a special jig I made just for that purpose and a rotary table. If you are purchasing them new from Rob anyway you might as well get the precut ones, it will make your life easier.
Herman

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kiwidiver
Lung Diver
Posts: 67
Joined: Thu Nov 29, 2012 9:24 pm
First Name: jeremy
Location: Gosford, Australia

Re: DA Cans

Tue Feb 12, 2013 7:21 am

Thank guys, great info. I was planning on upgrading the DA with the HPR and the new diaphragm regardless. Luis I do remember seeing a post ages ago about chest mounting with the plastic cans which sparked off the idea but I couldn't remember who posted it and where now I know cheers. I think with the fact that the leaver and the diaphragm wont line up (even if it doesn't make a big difference it will probably subconsciously bother me) and possible issues with the venturi means I will probably stick with the original cans, do the HPR upgrade, mount it, feed it of the hookah port and see how it goes from there. What I am after really is an everyday DH that will fit in with my current gear. Ultimately I would just buy another set of low pressure tanks with a centre take off manifold like the Sherwood but they are hard to find over here (the manifolds) and as we have to hydro tanks every year in Oz, collecting tanks is not economical.
Thanks again for the help.

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kiwidiver
Lung Diver
Posts: 67
Joined: Thu Nov 29, 2012 9:24 pm
First Name: jeremy
Location: Gosford, Australia

Re: DA Cans

Fri Apr 05, 2013 2:56 am

Well i decided to give it a crack anyway and got a set of Robs pre-cut cans. I will take some pics and let you know how it turns out.

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kiwidiver
Lung Diver
Posts: 67
Joined: Thu Nov 29, 2012 9:24 pm
First Name: jeremy
Location: Gosford, Australia

Re: DA Cans

Wed May 15, 2013 9:20 pm

Well i have completed this project with mixed results. more details here:

viewtopic.php?f=47&t=7027

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