kevorkian breakdown

rhelsley · 26th October 2007, 04:45

As promised here's a breakdown of kevorkian. Kevorkian is a manually-operated CMF Rebreather that I designed & built between 2004-2005. This RB has taken me to depths down to 250' and around 200 dives. Kevorkian was designed to be very simple & streamlined, and I like to think I succeeded on that design theme.

Considering that this Rebreather uses a single bag-style CL, I made an effort to maximize scrubber function using a co-axial design scrubber housing that is wrapped in a neoprene insulating jacket, and with insulated breathing hoses & CL. Even 2 hours after a dive I can feel warmth between the outer scrubber wall & the insulating jacket!

This post will cover the basics of kevorkian, and I'll post another later that shows more component detail.

Here's a front-top view of kevorkian. O2 & diluent is plumbed in through standard BCD fittings; to prevent the fittings accidentally being knocked off (& flooding the loop) I place small zip ties around the recession behind the release collar to prevent their release.

Here's a rear view of kevorkian. You can see that the center section holds the scrubber & counterlund internally, and the 40cf tanks are mounted externally with titanium bands & brackets (courtesy of Boeing surplus). The center section is an 8" diameter acrylic 1/4" wall tube wrapped in epoxy-carbon fiber for strength & rigidity.

The breathing loop consists of a counterweighted bag-style bottom-mounted CL, the head & scrubber housing made from a large ABS water filter housing, corrugated breathing hoses with 1-3/4" cuffs, and a PVC 1/4 turn ball valve DSV from Tom Rose (thanks!)-CEDU inspiration. The breathing loop fits down into the center section and locks into place with nelson latches. The CL is made of heat-sealable urethane coated nylon and has lead "medallions" attached on the outside to provide weight which counteracts upward hydrostatic pressure. Over the medallions is neoprene insulating material. The open end of the CL is ringed with a 1/8" thick EPDM rubber flange which seals around the bottom of the scrubber housing with a large hose clamp. The bottom of the CL is fitted with a purge valve--simply going upright and pressurizing the loop with diluent flushes any liquid out.

The PO2 meters use lascar meters and is of similar circuitry to the old-style KISS meters, but are laid out in a single tubular polycarbonate enclosure with a single battery. The meters are activated by turning the endcap of the tube which has a stud that actuates a microswitch--no magnetic reed switches for kevorkian. In addition to my tubular meter I have a single Jetsam KISS meter that reads a 3rd cell. Kevorkian was originally fitted with 2 KISS brand meters, but repeated water-integrity problems prompted me to design & build my own.

The Constant-Mass-Flow system uses a .0035" screened stainless steel orifice, and because the orifice is fitted with an internal 15 micron screen the possibility of not being able to add O2 due to a blocked filter is non-existent. Simply pressing the O2 add button bypasses the orifice/screen & injects directly into the loop. These orifices are cheap at $12 so replacement is not an issue if necessary. I'm still using the original orifice, and a recent inspection showed no need for replacement. I designed the O2 flow path myself & machined the valve stem & valve housing from 304 SS, machined on my taig micro-lathe. You can see a 1/4 turn ball valve to cut O2 flow, which is necessary if breathing open circuit from the O2 tank in the event of a bail-out. The O2 1st stage is fitted with a 2nd stage for this scenario.

The non-compensating O2 1st stage regulator is a modified scubapro MK14. You can see I drilled out & threaded the hex IP adjustment, that a machined delrin cap threads into. The cap seals on an o-ring below the ambient pressure ports when screwed down. IP is adjusted with a spanner with holes drilled on either side of the original hex adjustment.

In my simplicity design theme I elected to go without an ADV on kevorkian. Diluent is added through a high-flow-capacity push-button valve that I designed & built. Diluent can be breathed open circuit with a 2nd stage worn on a necklace, and diluent supply to the valve can be cut by releasing the AP valves quick-connect. The AP quick-connect also facilitates plumbing in alternate diluent mixes, injected with the same diluent valve.

More detailed photos & explanation to come in my next post.

russell helsley

rhelsley · 26th October 2007, 04:50

Oops, my photos didn't come through. Here they are in attachments.

russell

rhelsley · 26th October 2007, 04:55

...and more photos.

russell

rhelsley · 26th October 2007, 05:04

Here are more detail shots of kevorkian.

russell

Drmike · 26th October 2007, 05:07

interesting stuff - thanks for sharing

rhelsley · 26th October 2007, 05:14

oops, photos didn't come through again...

rhelsley · 26th October 2007, 05:20

...and lastly...

The circular silver gadgets I'm holding are .0035 orifices. They came from O'keefe controls at OKC Home Page and were $12.00 ea.

You can see the placement of the orifice (only the center wrench section shows) in the close up photo to the right of the O2 shut-off valve.

russell

kiwi_diver · 26th October 2007, 09:54

Super bit of DIY engineering Russell. The carbon fibre is an especially nice touch, adding strength without excessive weight and looks good too.

You've obviously spent a bit of time thinking this project through and can be proud of the result. Great unit, hope you enjoy many more dives with it.

Cheers, Ray.

fin · 26th October 2007, 12:36

Despite the fact that I don't like back mounted cl so much I say it is an excellent point of view and choices that i see at this homebuilt unit.
I will come up with more questions about it when I get down to mine.
It looks that you are studying hard and make few compromises for safety.
Very matching name for an Rebreather also and a good way to keep ckecklisting serious.
Sincerely thank you very much and best luck with testing-diving.

silentscuba · 26th October 2007, 13:58

Nice Job Russ- Thanks for putting the time in to explain your creation

26th October 2007, 04:45	#1 (permalink)
rhelsley New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: May 2005 Location: seattle, usa Posts: 36	kevorkian breakdown As promised here's a breakdown of kevorkian. Kevorkian is a manually-operated CMF Rebreather that I designed & built between 2004-2005. This RB has taken me to depths down to 250' and around 200 dives. Kevorkian was designed to be very simple & streamlined, and I like to think I succeeded on that design theme. Considering that this Rebreather uses a single bag-style CL, I made an effort to maximize scrubber function using a co-axial design scrubber housing that is wrapped in a neoprene insulating jacket, and with insulated breathing hoses & CL. Even 2 hours after a dive I can feel warmth between the outer scrubber wall & the insulating jacket! This post will cover the basics of kevorkian, and I'll post another later that shows more component detail. Here's a front-top view of kevorkian. O2 & diluent is plumbed in through standard BCD fittings; to prevent the fittings accidentally being knocked off (& flooding the loop) I place small zip ties around the recession behind the release collar to prevent their release. Here's a rear view of kevorkian. You can see that the center section holds the scrubber & counterlund internally, and the 40cf tanks are mounted externally with titanium bands & brackets (courtesy of Boeing surplus). The center section is an 8" diameter acrylic 1/4" wall tube wrapped in epoxy-carbon fiber for strength & rigidity. The breathing loop consists of a counterweighted bag-style bottom-mounted CL, the head & scrubber housing made from a large ABS water filter housing, corrugated breathing hoses with 1-3/4" cuffs, and a PVC 1/4 turn ball valve DSV from Tom Rose (thanks!)-CEDU inspiration. The breathing loop fits down into the center section and locks into place with nelson latches. The CL is made of heat-sealable urethane coated nylon and has lead "medallions" attached on the outside to provide weight which counteracts upward hydrostatic pressure. Over the medallions is neoprene insulating material. The open end of the CL is ringed with a 1/8" thick EPDM rubber flange which seals around the bottom of the scrubber housing with a large hose clamp. The bottom of the CL is fitted with a purge valve--simply going upright and pressurizing the loop with diluent flushes any liquid out. The PO2 meters use lascar meters and is of similar circuitry to the old-style KISS meters, but are laid out in a single tubular polycarbonate enclosure with a single battery. The meters are activated by turning the endcap of the tube which has a stud that actuates a microswitch--no magnetic reed switches for kevorkian. In addition to my tubular meter I have a single Jetsam KISS meter that reads a 3rd cell. Kevorkian was originally fitted with 2 KISS brand meters, but repeated water-integrity problems prompted me to design & build my own. The Constant-Mass-Flow system uses a .0035" screened stainless steel orifice, and because the orifice is fitted with an internal 15 micron screen the possibility of not being able to add O2 due to a blocked filter is non-existent. Simply pressing the O2 add button bypasses the orifice/screen & injects directly into the loop. These orifices are cheap at $12 so replacement is not an issue if necessary. I'm still using the original orifice, and a recent inspection showed no need for replacement. I designed the O2 flow path myself & machined the valve stem & valve housing from 304 SS, machined on my taig micro-lathe. You can see a 1/4 turn ball valve to cut O2 flow, which is necessary if breathing open circuit from the O2 tank in the event of a bail-out. The O2 1st stage is fitted with a 2nd stage for this scenario. The non-compensating O2 1st stage regulator is a modified scubapro MK14. You can see I drilled out & threaded the hex IP adjustment, that a machined delrin cap threads into. The cap seals on an o-ring below the ambient pressure ports when screwed down. IP is adjusted with a spanner with holes drilled on either side of the original hex adjustment. In my simplicity design theme I elected to go without an ADV on kevorkian. Diluent is added through a high-flow-capacity push-button valve that I designed & built. Diluent can be breathed open circuit with a 2nd stage worn on a necklace, and diluent supply to the valve can be cut by releasing the AP valves quick-connect. The AP quick-connect also facilitates plumbing in alternate diluent mixes, injected with the same diluent valve. More detailed photos & explanation to come in my next post. russell helsley
(Offline)

26th October 2007, 05:07	#5 (permalink)
Drmike RBW Member Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,378	Re: kevorkian breakdown interesting stuff - thanks for sharing __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
(Offline)

26th October 2007, 09:54	#8 (permalink)
kiwi_diver Alias - Ray Mansell Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: Aug 2007 Location: Auckland, New Zealand Posts: 157	Re: kevorkian breakdown Super bit of DIY engineering Russell. The carbon fibre is an especially nice touch, adding strength without excessive weight and looks good too. You've obviously spent a bit of time thinking this project through and can be proud of the result. Great unit, hope you enjoy many more dives with it. Cheers, Ray. __________________ Ray. == Latitude 36 South, where the deeper you dive, the warmer it gets! ==
(Offline)

26th October 2007, 12:36	#9 (permalink)
fin New Member Current Rebreather/s: Megalodon Dolphin Other Rebreather/s: Megalodon Dolphin Join Date: Jul 2006 Location: Thessaloniki, Hellas (Greece) Posts: 49	Re: kevorkian breakdown Despite the fact that I don't like back mounted cl so much I say it is an excellent point of view and choices that i see at this homebuilt unit. I will come up with more questions about it when I get down to mine. It looks that you are studying hard and make few compromises for safety. Very matching name for an Rebreather also and a good way to keep ckecklisting serious. Sincerely thank you very much and best luck with testing-diving.
(Offline)

26th October 2007, 13:58	#10 (permalink)
silentscuba rEvo CCR Driver Current Rebreather/s: Classic Kiss rEvo Other Rebreather/s: Inspiration Classic rEvo Join Date: Jun 2005 Location: Mill Creek, WA USA Posts: 612	Re: kevorkian breakdown Nice Job Russ- Thanks for putting the time in to explain your creation __________________ Curt McNamee rEvo CCR Diver KISS CCR Diver www.silentscuba.com
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode