help on my own diving helmet!

[ironzorak]

hey, i've always loved the concept of the metal deep sea diving helmets, but the only problem is, they are incredibly expensive and being a student i can't afford too much.
So i had the idea of making my own diving helmet from varnished marine plywood or possibly fiberglass. Now i've worked most of the issues out, but i need to know what kind of valve i would need to let air out of the helmet, but not in the helmet. if someone could weigh in and give me some help i would really appreciate it!

 

[Thalassamania]

First be sure that you have a non-return valve, at the helmet, on the inlet side. As far as exhaust is concerned, you could just let it bubble out the bottom.

 

[ironzorak]

thanks! but is it a specific kind of non-return valve, or should any one generally work?

 

[Thalassamania]

You can get one from most any commercial diving supply house, there may be substitutes, but I don't know what they'd be.

 

[vshearer]

Please make a video of your progress on this project.

 

[cool_hardware52]

hey, i've always loved the concept of the metal deep sea diving helmets, but the only problem is, they are incredibly expensive and being a student i can't afford too much.
So i had the idea of making my own diving helmet from varnished marine plywood or possibly fiberglass. Now i've worked most of the issues out, but i need to know what kind of valve i would need to let air out of the helmet, but not in the helmet. if someone could weigh in and give me some help i would really appreciate it!

My grand father used to make his from the end of old water heater tanks.....

Tobin

 

[Ben Dugger]

If you are building an open helmet you don,t need a check valve. Just bring the air inlet in just above shoukder level. That way, if the hose blew out the helmet would only flood up to the inlet leaving your head in the bubble.
Also direct the incoming air across the windows to keep them clear.
In order to see how much weight one would need, invert the helmet and fill it with water. Weigh this and it will give you a ball park to start with.
I started diving with one of these made from a hot water tank many, many years ago. They are fun to use. In fact, tomorrow I an letting my grandkids try my Miller Dunn #2.

 

[DCBC]

Good luck with your efforts. I think I'll just stay with my KM.

 

[Akimbo]

Will you actually dive the hat? If so, will it be attached to a deep sea suit (drysuit open to the hat)? If yes, the exhaust valve is basically a large adjustable low pressure relief valve.

If it will not be attached and open to a drysuit, there is no need as the adjustable exhaust. The exhaust valve is designed to control the inflation level of the suit by holding some pressure back. It is also common to have a mushroom end on the inside stem of the valve so you can grab it with your mouth to momentarily override the valve closed in order to inflate the suit above normal — like if you are moving something heavy and need added lift. I can probably find an exploded view of it in an old Navy diving manual if you don’t have access to one. You may also be able to find assembly drawings on the Desco site (one of the few people still making heavy gear):

https://www.divedesco.com/

Don’t forget you need a lot of air to supply heavy gear. We used 6 ambient CFM as a rule of thumb. There is also a lot of displacement to heavy gear. Typically a pair of shoes was 35 Lbs, the weightbelt was 85 Lbs, and the copper hat was around 50 Lbs.

You may also want to Google: "swindell diving helmet" if your are interested in a fiberglass hybred. The Swindell offered a neck dam and a breast plate to attach to heavy gear suits.

Swindell helmet

If you have any doubt about the importance of a check valve on the supply umbilical, read this:

http://www.scubaboard.com/forums/commercial-divers/333195-deadly-helmet-squeeze.html

 

[The Blue Whale]

Any open bottom design will work fine so you can't exceed the ambient pressure regardless of depth. You'll know you're too deep when you feel like your sucking air through a straw. The non-return valve must be at the helmet and you should have a valve to control the flow from the surface supplied air. I'll post a collection of open bottom helmets from the 20s in an upcoming post.