help on my own diving helmet!

[The Blue Whale]

Here's a picture showing a wide variety of the helmet designs from the 20s for recreational diving. They were real popular in Miami and the Keys at many of the resorts. This picture was taken at the History of Diving Museum in Key Largo.

 

[elmer fudd]

If you look closely, you'll notice that a lot of the helmets in the last post were homemade. I'm too lazy to find the link for you, but the History of Diving Museum has a webpage where they showcase them each individually.

Even that plastic, Fischer Price looking thing, in the photo is an actual diving helmet intended for real use. Kind of makes me wonder about making a helmet out of acrylic.

 

[muddiver]

My personal favorite is the Kirby Morgan KHX-13

"The Bucket Hat. This helmet was made as a joke, but several important findings were made as a result of water testing this unit. The helmet dives quite well and is surprisingly comfortable." - from the Kirby Morgan web site.

The non-return valve everyone is talking about is just a check valve on the air supply inlet. You can probably use one of these:

2200 Series Check Valves

 

[The Blue Whale]

Funny how that Kirby Morgan KHX-13 never went into production... wonder how they got to '13' or if that was the number of fatalities to get that design down to a science.

I like this one with the girl included...

 

[ironzorak]

i'm not going to attach it to a dry suit, i will just weigh the helmet down and then strap it to my shoulders

 

[Aceboyd]

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.

The "sucking air though a straw" analogy only applies to regulated hats. This happened to me in a Superlite 17 once when the reg was acting up. The hat draws down on our head and the neck dam pulls up with every breath. I had to free-flow the thing to get through the dive. With an open-bottomed hat, the air flow displaces water out the bottom of the hat. As you exceed the volume of your compressor, the water would begin to come up inside the helmet as you inhale.

 

[Akimbo]

i'm not going to attach it to a dry suit, i will just weigh the helmet down and then strap it to my shoulders

In that case, you might consider a padeye on the top so you can suspend it over the side and enter the hat in the water rather than try to carry the heavy puppy up and down a ladder. Basically, it will have to weigh at least 64 Lbs/Ft³ in salt water and 62.4 Lbs/Ft³ in fresh water. Depending on your skill level, wearing a small Scuba bottle and carrying a mask might be worth considering.

I couldn't tell from your profile if you are trained in Scuba and familiar with Air Embolism and related events. If not, an air hat like this, or any other underwater breathing apparatus, can be extremely dangerous; even in swimming pool. Forgive me if I am stating the obvious.

 

[Aceboyd]

As Akimbo says, you need wieght to counteract the inherent bouyancy so a low internal volume is desirable. Less volume means less bouyancy so less weight. Make it big enough to comfortably turn your head and not hit anything. Most early air hats had no straps at all. Varying degrees of negative bouyancy kept them in place. If feasible, try to incorporate some kind of bib to add depth to your air bubble and distribute the weight on your shoulders for comfort. An adjustable inlet valve is not necessary but highly recommended. Any extra air volume would just bleed out the bottom but it's desirable to be able to control the flow rate. Excessive flow causes the hat to bounce around as it bubbles out and makes an awful racket as well. A check valve or non-return valve is not critical with an open-bottomed hat but again, highly recommended. With the valve, a loss of air pressure or busted hose would just stop the air flow, the air in the hat would remain. Without it your engineered air bubble would disappear up the hose immediately.
Your inquiry has gotten my wheels turning again. I may just take up the challenge myself and see what I can come up with. ; ) Feel free to post any more questions and by all means good luck with the project and document your efforts so we may all share your experiences. If I do decide to start a project of my own, I will do the same.

 

[Aceboyd]

I need to add this as well. I have visited the History of Diving Museum in Islamorada, Florida Keys and would HIGHLY recommend it to anyone remotely interested in diving. Very informative and educational. They even have a few Mark V hats for sale in the gift shop, if you happen to have several thousand extra dollars in your wallet that day. ; )

The Florida Keys History of Diving Museum

 

[SangP]

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!

I'm sure you'll be able to find some cheap helmets on ebay, garage sales, antique shops or the like. You can then add additional valves instead of making one yourself.

SangP