Clam shell helmet?

Sten · 10th February 2007, 17:46

Quote: (Originally Posted by RAL)

Thanks Alex. Do you have details on the neck damn?

RAL

Is there a separation between the suit gas and the gas in the Isler helmet, around the divers head by some kind of neck seal? Will this be changed?

/Sten

AD_ward9 · 10th February 2007, 19:47

Quote: (Originally Posted by RAL)

The simplest way as I see it would be to use a constricting cam assy like the time proven Superlite 17. Size being the problem I am guessing. If the bottom of the hat is too small to be able to work with a set up that will fit over the divers head could you use a flange rather than the groove on the bottom. Make the flange large enough so that a solid ring that is big enough to fit over the divers head could be used on the neck damn. You could then use a latch assy like the old miller, it seems like it would work with a two part shell.
What ever you use it must be easy for the diver to doff & donn without help IMHO.

RAL

I agree on the bottom line of your post.

There are a few subtle problems that cause a rethink of the clamp. I have a Mk17 here in front of me, with the seal open. The Mk17 assembly is for hot water suits. For a dry suit diver it would pose a serious risk of being pushing into the helmet. The XDH will share the same gas inside it, as used to fill the suit. This means no argon fills, but suit heating and good insulation. It also means the Mk17 seal is not suitable, unfortunately. There is no obvious way to clamp the bottom of the Mk17 clamp to a dry suit neck dam, unless you can think of one.

Cheers,

Alex

AD_ward9 · 10th February 2007, 19:52

Quote: (Originally Posted by Sten)

Is there a separation between the suit gas and the gas in the Isler helmet, around the divers head by some kind of neck seal? Will this be changed?

/Sten

There is no separation. This is where the XDH is very different from existing helmets.

Existing helmets are designed either for Standard Dive Gear or a hot water suit, not modern dry suits. With a hot water suit, there is a latex seal around the diver's neck to stop water getting into the helmet, and it is important the diver has an umbilical supply to ensure there is no possibility of negative pressure in the helmet compared to ambient, otherwise the diver would be squirted into the helmet.

For a dry suit with a free swimming diver, the gas space in the helmet needs to be the same as for the dry suit, so the seal on the XDH uses the neoprene neck seal from the dry suit, simply being squeezed on the outside of the helmet.

The problem with the XDH solution, is if a diver has cold hands with thick gloves, the seal may not be put on properly. Hence a need to change this part of the helmet.

Alex

Sten · 10th February 2007, 21:59

Quote: (Originally Posted by AD_ward9)

There is no separation. This is where the XDH is very different from existing helmets.
Alex

Take a look at the Viking Catalogue page 14 and you will see that that they have many different connection systems avaiable for differet types of helmets. All the way back to the "standad dress". Several of these helmets does not use a neck seal. But they are not for swmming free.

/Sten

AD_ward9 · 11th February 2007, 06:05

Quote: (Originally Posted by Sten)

Take a look at the Viking Catalogue page 14 and you will see that that they have many different connection systems avaiable for differet types of helmets. All the way back to the "standad dress". Several of these helmets does not use a neck seal. But they are not for swmming free.

/Sten

That is the Trelleborg page I was referring to in Post 17 of this thread. As you point out, none of these were intended for swimming free, but we are adopting one of them rather than reinvent the wheel.

Cheers,

Alex

10th February 2007, 17:46	#21 (permalink)
Sten Beeing Visionary Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Göteborg, Sweden Posts: 51	Re: Clam shell helmet? Quote: (Originally Posted by RAL) Thanks Alex. Do you have details on the neck damn? RAL Is there a separation between the suit gas and the gas in the Isler helmet, around the divers head by some kind of neck seal? Will this be changed? /Sten
(Online)

10th February 2007, 19:47	#22 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,862	Re: Clam shell helmet? Quote: (Originally Posted by RAL) The simplest way as I see it would be to use a constricting cam assy like the time proven Superlite 17. Size being the problem I am guessing. If the bottom of the hat is too small to be able to work with a set up that will fit over the divers head could you use a flange rather than the groove on the bottom. Make the flange large enough so that a solid ring that is big enough to fit over the divers head could be used on the neck damn. You could then use a latch assy like the old miller, it seems like it would work with a two part shell. What ever you use it must be easy for the diver to doff & donn without help IMHO. RAL I agree on the bottom line of your post. There are a few subtle problems that cause a rethink of the clamp. I have a Mk17 here in front of me, with the seal open. The Mk17 assembly is for hot water suits. For a dry suit diver it would pose a serious risk of being pushing into the helmet. The XDH will share the same gas inside it, as used to fill the suit. This means no argon fills, but suit heating and good insulation. It also means the Mk17 seal is not suitable, unfortunately. There is no obvious way to clamp the bottom of the Mk17 clamp to a dry suit neck dam, unless you can think of one. Cheers, Alex Last edited by AD_ward9 : 10th February 2007 at 19:55.
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10th February 2007, 19:52	#23 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,862	Re: Clam shell helmet? Quote: (Originally Posted by Sten) Is there a separation between the suit gas and the gas in the Isler helmet, around the divers head by some kind of neck seal? Will this be changed? /Sten There is no separation. This is where the XDH is very different from existing helmets. Existing helmets are designed either for Standard Dive Gear or a hot water suit, not modern dry suits. With a hot water suit, there is a latex seal around the diver's neck to stop water getting into the helmet, and it is important the diver has an umbilical supply to ensure there is no possibility of negative pressure in the helmet compared to ambient, otherwise the diver would be squirted into the helmet. For a dry suit with a free swimming diver, the gas space in the helmet needs to be the same as for the dry suit, so the seal on the XDH uses the neoprene neck seal from the dry suit, simply being squeezed on the outside of the helmet. The problem with the XDH solution, is if a diver has cold hands with thick gloves, the seal may not be put on properly. Hence a need to change this part of the helmet. Alex
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10th February 2007, 21:59	#24 (permalink)
Sten Beeing Visionary Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Göteborg, Sweden Posts: 51	Re: Clam shell helmet? Quote: (Originally Posted by AD_ward9) There is no separation. This is where the XDH is very different from existing helmets. Alex Take a look at the Viking Catalogue page 14 and you will see that that they have many different connection systems avaiable for differet types of helmets. All the way back to the "standad dress". Several of these helmets does not use a neck seal. But they are not for swmming free. /Sten
(Online)

11th February 2007, 06:05	#25 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,862	Re: Clam shell helmet? Quote: (Originally Posted by Sten) Take a look at the Viking Catalogue page 14 and you will see that that they have many different connection systems avaiable for differet types of helmets. All the way back to the "standad dress". Several of these helmets does not use a neck seal. But they are not for swmming free. /Sten That is the Trelleborg page I was referring to in Post 17 of this thread. As you point out, none of these were intended for swimming free, but we are adopting one of them rather than reinvent the wheel. Cheers, Alex
(Offline)

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