Which BOV (OC/CC DSV)...

Skipbreather · 15th April 2006, 02:16

Quote: (Originally Posted by Rebreatherlab)

Hey Skipbreather!

Im just about to try a similar BOV stunt as you did and assume you went with the no-oring approach as you are talking about 0.001" tolerance. I generally always try to do things with as few orings as possible. Once you got the tolerance where you wanted it, how easy or hard is the spool to turn?

All the best,

Andy

Hi Andy-

There IS one O ring used on the spool of my BOV. The groove placement on the spool is just 0.15 inch inside the front face to effect a positive seal between the loop and the outside world. Also: note that a VERY smooth finish on both the interior of the body and the exterior of the spool are needed w/ clearance not much more than 0.0005 inch (yup, 5 ten thousandths) if you expect to get decent pos + neg pressure checks w/ only Krytox as a lube/ sealant

How hard is it to turn? Not bad at all, though I’d be lying if I said it was an easy flip w/ just two fingers. Think of it this way: it can be turned w/ just a normal effort & grip w/ just one hand if your really hold the mouthpiece well w/ teeth. I normally grip the lever w/ thumb & 2 fingers of right hand and put left thumb under left hose connection to ease the wear & tear on mouthpiece. Done that way it is easy.

Good luck in your efforts and, as a wise man once said, don’t fall in love with your prototype. Be willing to scrap it for a better idea if the first iteration comes up short. Also, I can HIGHLY recommend the check valves sold on the Divematics website. Don’t waste effort trying to reinvent the wheel!

Best,
Ken

Rebreatherlab · 15th April 2006, 06:56

Hi Skip,

Thanks a lot for the advise. I have the front and also a rear oring. The point is that if orings or any other seal is used around the breathing holes of the spool, the diam. of the spool need to be much bigger than i planned.

I will give it a go milling the body holes, but can already foresee a problem with the holes coming out slighly oval, due to clamping. Let's see if light clamping with light cuts does the trick.

The way you describe the "turning the spool" efford it seems very nice. I have a Cis BOV with all soft oring seals and the turning efford is quite similar to your description. so congratulation. It would appear you got the tolerance issue under your belt!

As for the mushroom valve seats I have the programmed already and they work perfect. With CNC it takes only a few minutes to cut them.

Andy

Quote: (Originally Posted by Skipbreather)

Hi Andy-

There IS one O ring used on the spool of my BOV. The groove placement on the spool is just 0.15 inch inside the front face to effect a positive seal between the loop and the outside world. Also: note that a VERY smooth finish on both the interior of the body and the exterior of the spool are needed w/ clearance not much more than 0.0005 inch (yup, 5 ten thousandths) if you expect to get decent pos + neg pressure checks w/ only Krytox as a lube/ sealant

How hard is it to turn? Not bad at all, though I’d be lying if I said it was an easy flip w/ just two fingers. Think of it this way: it can be turned w/ just a normal effort & grip w/ just one hand if your really hold the mouthpiece well w/ teeth. I normally grip the lever w/ thumb & 2 fingers of right hand and put left thumb under left hose connection to ease the wear & tear on mouthpiece. Done that way it is easy.

Good luck in your efforts and, as a wise man once said, don’t fall in love with your prototype. Be willing to scrap it for a better idea if the first iteration comes up short. Also, I can HIGHLY recommend the check valves sold on the Divematics website. Don’t waste effort trying to reinvent the wheel!

Best,
Ken

Skipbreather · 15th April 2006, 15:08

Quote: (Originally Posted by Rebreatherlab)

Hi Skip,

I have the front and also a rear oring. The point is that if orings or any other seal is used around the breathing holes of the spool, the diam. of the spool need to be much bigger than i planned.

I will give it a go milling the body holes, but can already foresee a problem with the holes coming out slighly oval, due to clamping. Let's see if light clamping with light cuts does the trick.
Andy

Hi Andy-

My original prototype also had a rear O ring. I later found it redundant. Think about it: it serves no useful purpose in normal breathing mode. My spool has about 0.35 inches of contact area between the rear of the breathing passage and the rear of the spool. The tolerances that are required for sealing in other areas make this more than adequate for sealing here as well during pos/ neg checks and bailout, and it simplifies the machining process. It may or may not ease effort of turning.

When I turned the DSV body I did it in a 4 jaw. I used shim plates of stainless on all 4 sides between the jaws and the body. Idea was to spread the clamping force & minimize distortions to the stock. Might work for you as well.

Best,
Ken

Rebreatherlab · 15th April 2006, 19:35

Hi Ken,

Is your mouth piece boss machined seperately from the body? I would guess not. My plan is to make that as a separate part which would then need sealing just as the front would to keep the water out. Did you machine the retaining rim on the mouth piece boss with a manual rotary or CNC?
I have a Bridgeport mill but no rotary, so I was planning on doing the mouthpiece plate on a small Taig that has a tiny 4th axis rotary. There is a 3 jaw chuck on it which means I can't center the square DSV body, but I could center the internal round boss that portrudes into the DSV body.
The picture shows how the seal works, (I hope!).

Andy

Quote: (Originally Posted by Skipbreather)

Hi Andy-

My original prototype also had a rear O ring. I later found it redundant. Think about it: it serves no useful purpose in normal breathing mode. My spool has about 0.35 inches of contact area between the rear of the breathing passage and the rear of the spool. The tolerances that are required for sealing in other areas make this more than adequate for sealing here as well during pos/ neg checks and bailout, and it simplifies the machining process. It may or may not ease effort of turning.

When I turned the DSV body I did it in a 4 jaw. I used shim plates of stainless on all 4 sides between the jaws and the body. Idea was to spread the clamping force & minimize distortions to the stock. Might work for you as well.

Best,
Ken

Rebreatherlab · 15th April 2006, 19:47

Hmm,

For some reason the rear oring seal is not on the picture. Maybe it was masked in the program. Anyway it is the same as the front groove.

Andy

Quote: (Originally Posted by Rebreatherlab)

Hi Ken,

Is your mouth piece boss machined seperately from the body? I would guess not. My plan is to make that as a separate part which would then need sealing just as the front would to keep the water out. Did you machine the retaining rim on the mouth piece boss with a manual rotary or CNC?
I have a Bridgeport mill but no rotary, so I was planning on doing the mouthpiece plate on a small Taig that has a tiny 4th axis rotary. There is a 3 jaw chuck on it which means I can't center the square DSV body, but I could center the internal round boss that portrudes into the DSV body.
The picture shows how the seal works, (I hope!).

Andy

Skipbreather · 16th April 2006, 04:32

Quote: (Originally Posted by Rebreatherlab)

Hi Ken,

Is your mouth piece boss machined seperately from the body? I would guess not. My plan is to make that as a separate part which would then need sealing just as the front would to keep the water out. Did you machine the retaining rim on the mouth piece boss with a manual rotary or CNC?

Andy

Hi Andy-

Think WAAAAAY lower tech, one off production. The only milling capacity I have is via a Palmgren attachment for my lathe, and that is as basic as it gets.

My BOV’s body and mouthpiece are PVC. The mouthpiece is bonded into rear of body w/ 3M Scotch-Weld 2216. Mouthpiece itself starts out in life round w/ lip turned to the correct size. I did some close tolerance wood working w/ a thick block of oak and made an oval hole the exact size and shape of the mouthpiece oval needed. Holes were drilled for guide pins (large nails w/ heads cut off). Block was then band sawed in half longitudinally. Round mouthpiece blank was heated w/ heat gun and then formed (OK, squished) in oak block halves when closed in a large vice. Crude but effective, not unlike me!

Parts came out looking rather professional given their humble origins.

Best,
Ken

Rebreatherlab · 16th April 2006, 15:23

That's fantastic! My first DSV took a similar approach but even lower than your low tech. For the mouthpiece tube I used round pvc and a blow gun. Once hot shaped it until fingers got burnt, dipped fingers in water and repeat. This was made of a 1" PVC ball valve which later got a 2nd added under it. The epdm seals are the best. Easy turning and now leaks whatsoever. The only problem is the internal bore of some 23 mm that give a bit resistance at deep air depths. Still use it alot out of sentimental reasons. The thing was made in baby blue PVC, but I spent three late nights sanding it and spraying it flat black for the proper Batman look!

Long live the home builders!

Andy

Quote: (Originally Posted by Skipbreather)

Hi Andy-

Think WAAAAAY lower tech, one off production. The only milling capacity I have is via a Palmgren attachment for my lathe, and that is as basic as it gets.

My BOV’s body and mouthpiece are PVC. The mouthpiece is bonded into rear of body w/ 3M Scotch-Weld 2216. Mouthpiece itself starts out in life round w/ lip turned to the correct size. I did some close tolerance wood working w/ a thick block of oak and made an oval hole the exact size and shape of the mouthpiece oval needed. Holes were drilled for guide pins (large nails w/ heads cut off). Block was then band sawed in half longitudinally. Round mouthpiece blank was heated w/ heat gun and then formed (OK, squished) in oak block halves when closed in a large vice. Crude but effective, not unlike me!

Parts came out looking rather professional given their humble origins.

Best,
Ken

15th April 2006, 02:16	#41 (permalink)
Skipbreather Reads the fine print Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet MK 15.X Home Build Join Date: Mar 2005 Location: Chicago, Illinois, USA Posts: 557	Re: Which OC/CC DSV.. Quote: (Originally Posted by Rebreatherlab) Hey Skipbreather! Im just about to try a similar BOV stunt as you did and assume you went with the no-oring approach as you are talking about 0.001" tolerance. I generally always try to do things with as few orings as possible. Once you got the tolerance where you wanted it, how easy or hard is the spool to turn? All the best, Andy Hi Andy- There IS one O ring used on the spool of my BOV. The groove placement on the spool is just 0.15 inch inside the front face to effect a positive seal between the loop and the outside world. Also: note that a VERY smooth finish on both the interior of the body and the exterior of the spool are needed w/ clearance not much more than 0.0005 inch (yup, 5 ten thousandths) if you expect to get decent pos + neg pressure checks w/ only Krytox as a lube/ sealant How hard is it to turn? Not bad at all, though I’d be lying if I said it was an easy flip w/ just two fingers. Think of it this way: it can be turned w/ just a normal effort & grip w/ just one hand if your really hold the mouthpiece well w/ teeth. I normally grip the lever w/ thumb & 2 fingers of right hand and put left thumb under left hose connection to ease the wear & tear on mouthpiece. Done that way it is easy. Good luck in your efforts and, as a wise man once said, don’t fall in love with your prototype. Be willing to scrap it for a better idea if the first iteration comes up short. Also, I can HIGHLY recommend the check valves sold on the Divematics website. Don’t waste effort trying to reinvent the wheel! Best, Ken
(Offline)

15th April 2006, 06:56	#42 (permalink)
Rebreatherlab RebreatherWorld Sponsor Current Rebreather/s: Pelagian Other Rebreather/s: Not Bought Yet Classic Kiss Pelagian Join Date: Sep 2005 Location: Thailand Posts: 202	Re: Which OC/CC DSV.. Hi Skip, Thanks a lot for the advise. I have the front and also a rear oring. The point is that if orings or any other seal is used around the breathing holes of the spool, the diam. of the spool need to be much bigger than i planned. I will give it a go milling the body holes, but can already foresee a problem with the holes coming out slighly oval, due to clamping. Let's see if light clamping with light cuts does the trick. The way you describe the "turning the spool" efford it seems very nice. I have a Cis BOV with all soft oring seals and the turning efford is quite similar to your description. so congratulation. It would appear you got the tolerance issue under your belt! As for the mushroom valve seats I have the programmed already and they work perfect. With CNC it takes only a few minutes to cut them. Andy Quote: (Originally Posted by Skipbreather) Hi Andy- There IS one O ring used on the spool of my BOV. The groove placement on the spool is just 0.15 inch inside the front face to effect a positive seal between the loop and the outside world. Also: note that a VERY smooth finish on both the interior of the body and the exterior of the spool are needed w/ clearance not much more than 0.0005 inch (yup, 5 ten thousandths) if you expect to get decent pos + neg pressure checks w/ only Krytox as a lube/ sealant How hard is it to turn? Not bad at all, though I’d be lying if I said it was an easy flip w/ just two fingers. Think of it this way: it can be turned w/ just a normal effort & grip w/ just one hand if your really hold the mouthpiece well w/ teeth. I normally grip the lever w/ thumb & 2 fingers of right hand and put left thumb under left hose connection to ease the wear & tear on mouthpiece. Done that way it is easy. Good luck in your efforts and, as a wise man once said, don’t fall in love with your prototype. Be willing to scrap it for a better idea if the first iteration comes up short. Also, I can HIGHLY recommend the check valves sold on the Divematics website. Don’t waste effort trying to reinvent the wheel! Best, Ken
(Offline)

15th April 2006, 15:08	#43 (permalink)
Skipbreather Reads the fine print Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet MK 15.X Home Build Join Date: Mar 2005 Location: Chicago, Illinois, USA Posts: 557	Re: Which OC/CC DSV.. Quote: (Originally Posted by Rebreatherlab) Hi Skip, I have the front and also a rear oring. The point is that if orings or any other seal is used around the breathing holes of the spool, the diam. of the spool need to be much bigger than i planned. I will give it a go milling the body holes, but can already foresee a problem with the holes coming out slighly oval, due to clamping. Let's see if light clamping with light cuts does the trick. Andy Hi Andy- My original prototype also had a rear O ring. I later found it redundant. Think about it: it serves no useful purpose in normal breathing mode. My spool has about 0.35 inches of contact area between the rear of the breathing passage and the rear of the spool. The tolerances that are required for sealing in other areas make this more than adequate for sealing here as well during pos/ neg checks and bailout, and it simplifies the machining process. It may or may not ease effort of turning. When I turned the DSV body I did it in a 4 jaw. I used shim plates of stainless on all 4 sides between the jaws and the body. Idea was to spread the clamping force & minimize distortions to the stock. Might work for you as well. Best, Ken
(Offline)

15th April 2006, 19:47	#45 (permalink)
Rebreatherlab RebreatherWorld Sponsor Current Rebreather/s: Pelagian Other Rebreather/s: Not Bought Yet Classic Kiss Pelagian Join Date: Sep 2005 Location: Thailand Posts: 202	Re: Which OC/CC DSV.. Hmm, For some reason the rear oring seal is not on the picture. Maybe it was masked in the program. Anyway it is the same as the front groove. Andy Quote: (Originally Posted by Rebreatherlab) Hi Ken, Is your mouth piece boss machined seperately from the body? I would guess not. My plan is to make that as a separate part which would then need sealing just as the front would to keep the water out. Did you machine the retaining rim on the mouth piece boss with a manual rotary or CNC? I have a Bridgeport mill but no rotary, so I was planning on doing the mouthpiece plate on a small Taig that has a tiny 4th axis rotary. There is a 3 jaw chuck on it which means I can't center the square DSV body, but I could center the internal round boss that portrudes into the DSV body. The picture shows how the seal works, (I hope!). Andy
(Offline)

16th April 2006, 15:23	#47 (permalink)
Rebreatherlab RebreatherWorld Sponsor Current Rebreather/s: Pelagian Other Rebreather/s: Not Bought Yet Classic Kiss Pelagian Join Date: Sep 2005 Location: Thailand Posts: 202	Re: Which OC/CC DSV.. That's fantastic! My first DSV took a similar approach but even lower than your low tech. For the mouthpiece tube I used round pvc and a blow gun. Once hot shaped it until fingers got burnt, dipped fingers in water and repeat. This was made of a 1" PVC ball valve which later got a 2nd added under it. The epdm seals are the best. Easy turning and now leaks whatsoever. The only problem is the internal bore of some 23 mm that give a bit resistance at deep air depths. Still use it alot out of sentimental reasons. The thing was made in baby blue PVC, but I spent three late nights sanding it and spraying it flat black for the proper Batman look! Long live the home builders! Andy Quote: (Originally Posted by Skipbreather) Hi Andy- Think WAAAAAY lower tech, one off production. The only milling capacity I have is via a Palmgren attachment for my lathe, and that is as basic as it gets. My BOV’s body and mouthpiece are PVC. The mouthpiece is bonded into rear of body w/ 3M Scotch-Weld 2216. Mouthpiece itself starts out in life round w/ lip turned to the correct size. I did some close tolerance wood working w/ a thick block of oak and made an oval hole the exact size and shape of the mouthpiece oval needed. Holes were drilled for guide pins (large nails w/ heads cut off). Block was then band sawed in half longitudinally. Round mouthpiece blank was heated w/ heat gun and then formed (OK, squished) in oak block halves when closed in a large vice. Crude but effective, not unlike me! Parts came out looking rather professional given their humble origins. Best, Ken
(Offline)

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