Whaddaya know about Northill Air Lungs?

[elmer fudd]

I just ordered one the other day from the Scuba Museum, (1969ivan1 over on VDH), and if possible I'd love to put it back into diving condition.

Looking over the schematics in Basic Scuba, it appears that the only really difficult items would be those oddball diaphragms.

Anyone ever dive with one of these things or try to rebuild one?

 

[knowone]

Where are these schematics?

 

[elmer fudd]

Basic Scuba has the schematics and a pretty detailed explanation of how they work.

Amazon.com: Basic Scuba: Self-Contained Underwater Breathing Apparatus: Fred M. Roberts: Books

Unfortunately, it doesn't give any kind of subjective appraisal of how well they breathe or compare them to any other regulators. It was written back in the era when parts were still available, so there's no information on how to restore them. Also, while Roberts did an outstanding job of listing the available regulators of the day and explaining their mechanical function, he didn't give any real tips or suggestions at all for tuning them. There were a couple of regulators that he discouraged, but for the most part he just printed the schematics of all the available regulators and then wrote about a three page explanation of how each one worked with no criticism pro or con.

 

[Greg Barlow]

See if you can obtain a copy of the HDS (Historical Diving Society) magazine Volume 9, Issue 2, Spring 2001. Kent Rockwell wrote an informative article on the reg, and its operation.

I've rebuilt many different vintage double hose regulators. You would be hard pressed to find parts for the Northill. I've personally seen, and handled, the reg that you purchased. It is a very nice example that will be a great addition to your collection.

Greg Barlow

 

[Double Diver]

I just ordered one the other day from the Scuba Museum, (1969ivan1 over on VDH), and if possible I'd love to put it back into diving condition.

Looking over the schematics in Basic Scuba, it appears that the only really difficult items would be those oddball diaphragms.

Anyone ever dive with one of these things or try to rebuild one?

I own three of them and have restored one. They are quite unique in their design and operation, and here's some trivia. The manufacture was Garrett, ever here of a Garrett turbocharger? they supplied them for most of the planes in WWII which is probably why they they look like a turbo. Anyhow the key is the compound diaphragm and whether it is it good or not. If it's good then all you need is a hardware store with a big O-ring selection. The mouthpiece will most likely have turned to stone so the easy fix is to get a straight aqualung MP from VDH and cut the MP flush to the round body then remove part of the center support and it will fit perfectly on the Northill rotating MP barrel. Northill wagon wheels are very different from the norm, they are held in-place by the corrugation of the hose so they are hard to get out (I used soapy water) These will also have turned to stone and can be replace with the exhaust valves from a Micra. Now when you replace these you must use a hole punch on the exhaust valve so when you inhale the negative pressure is drawing on the exhaust side which is what will pull the diaphragm down. Setup is simple just screw down the center toggle plate screw until it starts to bleed when you place the diaphragm on it with the cover held tight as if it was screwed down, then back it of until it stops.

I have found them to breath better in shallow water (6'-15') than my Mistral. It has a down stream first stage and so the more pressure the better, in fact they were tested up to 3000PSI by the Navy. But it is a wet breather so be prepared to roll to the left. And one last thing, because of the angle of the yoke it will not mount on a K or J valve, only to a post. So that's about it.
Good luck!

 

[elmer fudd]

Thanks, that's exactly the kind of information I was looking for.

I guess I'll discover the condition of the diaphragms when I get the regulator. If they're bad perhaps I can fabricate something.

I hadn't considered the post valve issue, but fortunately I do have a tank that has one..

 

[knowone]

Look up Normalair.

Dan Barringer Vintage Scuba Supply - Antique Diving Gear Two Hose Regulators

has a couple of repro manuals.

 

[Ben Dugger]

I just ordered one the other day from the Scuba Museum, (1969ivan1 over on VDH), and if possible I'd love to put it back into diving condition.

Looking over the schematics in Basic Scuba, it appears that the only really difficult items would be those oddball diaphragms.

Anyone ever dive with one of these things or try to rebuild one?

Yes, at one time I had one of these damed things. They were the noisest regulator I ever saw. They were eqipped with a shut off at the mouthpiece. The unit exhausted under and through the diaphram, a dangerous arrangement. If you lost the mouthpiece without shutting it off the entire system would flood! Then lifting the hoses above one's head would not stsrt the air flowing. The only way to get air flowing was to pinch the hose at the mouthpiece and extend it upward. Sometimes this would start the air flowing. Then you would get about half air and half water. Start rolling and blowing and maybe you gould clear it. Aside from that it was well built from brass castings. Only dive it in a swimming pool.

 

[elmer fudd]

That's good information to have as well, but not exactly what I was hoping to hear. Much better than finding out unexpectedly at 80' however.

I've got the regulator now and I think I'll probably have it working and ready for a test dive within a week or two. The diaphragms were totally shot. The only part of that that was salvageable was the plastic center piece. The rest of the reg is pretty good though. It all seems to be there except for the wagon wheels. Somebody adapted a different valve seat to fit at some point in the past one of the small screws was bent and the yoke screw was from an Aqualung.

After disassembling everything, replacing all the o-rings, cleaning, polishing, lubricating, etc... I have the valve and the reserve working fairly well. I have a slight free flow on the valve, but it's very slight and I'm going to see if it goes away in the next couple of days before I add a little bit more tension to the spring. I'm thinking that as the seat conforms a bit better to the orifice that it will likely resolve itself.

So the next task is to make a diaphragm. My plan is to sandwich a piece of 1/32" silicone sheeting between a couple of compact discs, with the exhaust valve from my old Seaquest inflator reg attached in the center.

 

[knowone]

Have you thought about using diaphragm material.