Effective DSV designs?

[rjack321]

The bright orange visual indicator idea was just meant to be an additional 'reminder' from the diver's POV... in some other DSV designs they can be partially open or closed and it is difficult to tell at a glance. Most current lever or rotary knob DSV's only indicate their status when viewed from the front, or by feel.

The golem DSV leaks via the vent holes if the knob is not turned completely to closed loop mode. The bubbling when you exhale is immediately noticeable. The BOV version is not as sensitive to not completely turning the knob into CC mode.

 

[rjack321]

Also critical is the design of the spiders, the WOB on the flapper valves, the total dead space volume, how water is cleared before opening the DSV, and how a HUD can be attached and HUD position adjusted.​

Good points, many of the CNC machined spider designs seem to be more oriented for ease of manufacture than minimal obstruction for efficient gas flow.

The ISC DSV spiders are really cleverly designed so it takes serious effort to assemble things backwards. I'm not even sure its possible to reverse the flow at all.

The Golem spiders are quite ingenious in the way they are not reversible by accident through routine disassembly and cleaning. But if you break the DSV or BOV down completely to the overhaul level of disassembly you are able to reverse the flow direction.

The Kiss DSV I used for ~6 months was finicky, the flappers were excessively delicate, and it didn't have these subtle safety features. Both the ISC and the kiss DSVs are in my spares box. I would use the ISC DSV but the flow direction is wrong for my Kiss.

I dive with a golem BOV or DVS depending on the unit (Meg 2.7 or kiss sidewinder) I'm using. I like the golem knob, the way the hoses attach/detach for cleaning, and the ability to rotate a hose during the dive. I don't like the golem HUD attachment that I'm stuck using for my shearwater HUD. The ISC HUD attachment when used on a golem BOV is less than ideal as well.

 

[happy-diver]

Plugs and more

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[happy-diver]

It's not to lube the mouthpiece stem. It's to seal the sealing surface to hedge bets against a torn mouthpiece of a broken zip tie.

Inside German and Russian rebreathers and stuff I've seen this, with lungs and stuff
I've done a couple of mouthpieces and all my double enders just in case of mix up

Very tough stuff, as tight as you do or don't want it


but what I'm using is some kind of fine woven nylon or polyester builders line

 

[txaggie08]

Inside German and Russian rebreathers and stuff I've seen this, with lungs and stuff
I've done a couple of mouthpieces and all my double enders just in case of mix up

Very tough stuff, as tight as you do or don't want it


but what I'm using is some kind of fine woven nylon or polyester builders line

For doing what he did, I'd go get some 60# power pro fishing line and a bit of ca glue or head cement. I use that not all over the place in whip building, fishing rod building, and general rigging.

 

[Brad_Horn]

Spun off the previous thread to allow it to keep focus without an interesting sidetrack...

Just wondering what features experienced rebreather divers look for in an effective DSV?
Most appear to follow similar executions, but specifically I'm wondering:

• Is the front vertically moving lever style of shutoff valve more intuitive or easy to use vs the rotary knob?
• Would an additional brightly coloured indicator (easily visible from the rear) be a useful feature?
• Ease of breakdown for cleaning and transport... most DSV's feature a threaded collar to connect the hoses but these do not always seem to be keyed so that the mouthpiece consistently points in the right orientation on reassembly.
• Ease of service... uses snap rings and standard o-ring sizes?
• Should the mouthpiece connection also be modular or are standard cable ties OK?
• Is a 1.5" or bigger hose connection a disadvantage as it makes the entire DSV more bulky vs gas flow at depth?
• What current DSV's do rebreather divers rate highly? Drager looks pretty good, but...

If you're interested in a bit more depth regarding what makes an effective DSV from an engineering perspective and the opportunity cost of certain design decisions see pages 30-50 http://www.deeplife.co.uk/or_files/FMECA_OR_V4_140831.pdf
That also includes the respective WOB of a number of DSV with relevant bore and flapper valve sizes for comparison.

Also a bit more on why the fine detail of the testing of the DSV and the specific flapper valves used may be important. http://www.deeplife.co.uk/or_files/Fault_Study_CO2_Bypass_110314.pdf

 

[Fibonacci]

These sort of empirical data and detailed FMEA studies are exactly what I am after.
Very interesting, will read in detail over the weekend, thank you VERY much...!

 

[JohnnyC]

These sort of empirical data and detailed FMEA studies are exactly what I am after.
Very interesting, will read in detail over the weekend, thank you VERY much...!

If only they were from a trustworthy source. There's not a damn thing that Open Safety/APOC/Deep Life/Alex Deas/Brad Horn puts out that should be trusted.

 

[Brad_Horn]

These sort of empirical data and detailed FMEA studies are exactly what I am after.
Very interesting, will read in detail over the weekend, thank you VERY much...!

Fibonacci, You're most welcome.

Don't know if your interest is just theoretical but if you want to buy any of the components: flappers, spiders, breathing hoses or complete ALVBOV for comparison purposes contact sales@opensafety.eu They've supplied these parts to a number of rebreather manufacturers and homebuilders who just want individual parts are happily supported. While OSEL sell DSVs for military users, they don't have an application for these for the recreational market, but do have them in stock and the CC mode WOB is the same as the ALVBOV.

 

[megmofo]

I've got the Golem BOV for my meg and it's about as good as it gets regarding maintenance (apeks parts), ease of breathing, and modularity; you can take the base model and do just about anything you want to tweak it.

I don't mean to hijack your thread but what Sidemount DSV/BOVs have you guys found to work the best?
I like the MAV integration from Divesoft but the hose routing of the SF2 and Golem SM appeals as well? Thoughts?