Test dove 4 DH regs today, 3 for the first time.

[elmer fudd]

I'm pretty sure the exhaust valve was a rotten design. HW's themselves dumped it pretty quickly and nobody else ever picked it up. The problem is, where do you fit a working diaphragm in that tiny exhaust chamber? Also, the fact that the exhaust tube is part of the can really limits what you can do.

I got my silicone sheeting from Granger. There's one a few miles from me. They're not really in the business of dealing with the general public, (mainly commercial accounts), but the guy behind the counter was pretty good about letting it slide. It cost me something like $10 for 1 square foot of sheeting.

 

[Double Diver]

Congratulations! You have one of the only working Northhills in the country. They are a rare beast and have some very unique features including a type of compensation for the changing pressure in your tank. That's why the HP seat which is part of that pin that can be seen from the yoke side moves forward when you crack the valve, it changes the spring tension on the diaphragm.
So next time check the pin before and after your dive.
Have fun!

BTW you can search the patent number and find the original patent filled in 1954.

 

[John C. Ratliff]

Elmer,

I thought when you said you had a "Blue Label Scuba" that you had the second generation. But it appears that you have this one, which is the original:

The exhaust on this one used a combination of a duckbill and the membrane. The use of the membrane alone will product the problems you described with the water entering the hose when you go head-down. The membrane works very well when level, or facing up, but water enters the hose when head down. So Healthways installed a flat duckbill valve. The duckbill was internal, and had an internal "C" clamp. This was a thin, red outside & white inside (as I remember) duckbill valve. For those who have never seen it apart, here are the components:

I would not worry a bit about the "membrane" as it is neoprene-impregnated nylon, and won't give way. I am using a much thinner nitril rubber (from clean room gloves) just to try to see what the valve is capable of, and it has held too. I do dive it with a backup regulator on my other Sherwood post, though.

SeaRat

 

[Eric Sedletzky]

Elmer,

I thought when you said you had a "Blue Label Scuba" that you had the second generation. But it appears that you have this one, which is the original:

The exhaust on this one used a combination of a duckbill and the membrane. The use of the membrane alone will product the problems you described with the water entering the hose when you go head-down. The membrane works very well when level, or facing up, but water enters the hose when head down. So Healthways installed a flat duckbill valve. The duckbill was internal, and had an internal "C" clamp. This was a thin, red outside & white inside (as I remember) duckbill valve. For those who have never seen it apart, here are the components:

I would not worry a bit about the "membrane" as it is neoprene-impregnated nylon, and won't give way. I am using a much thinner nitril rubber (from clean room gloves) just to try to see what the valve is capable of, and it has held too. I do dive it with a backup regulator on my other Sherwood post, though.

SeaRat

Well that makes me feel better. At least I know the membrane won't blow out and send me to the surface sucking water!

 

[elmer fudd]

Thanks for the photos and the explanation. Mine doesn't have the duckbill inside of it, and after removing the "membrane" I found that the rubber band that surrounds the metal exhaust horn inside the can was mostly disintegrated. The screw that held the clamp was rusted so that I couldn't loosen it while it was in the can. I didn't want to introduce any petroleum based penetrating oils either, so I eventually ended up prying off the clamp, which created a tiny hole in the membrane.

My plans at this point are to replace the exhaust diaphragm with silicone sheeting and find a rubber band of the correct size to replace the one around the exhaust horn, (maybe a ring off a trimmed duckbill?).

Should it have the additional duckbill inside too, or is this unnecessary?

 

[elmer fudd]

Well that makes me feel better. At least I know the membrane won't blow out and send me to the surface sucking water!

When you mentioned that earlier, for some reason I was envisioning water running down the exhaust hose and into the mouthpiece. Now I realize you really were concerned about water entering the cans and flowing down the intake.

 

[elmer fudd]

Congratulations! You have one of the only working Northhills in the country. They are a rare beast and have some very unique features including a type of compensation for the changing pressure in your tank. That's why the HP seat which is part of that pin that can be seen from the yoke side moves forward when you crack the valve, it changes the spring tension on the diaphragm.
So next time check the pin before and after your dive.
Have fun!

BTW you can search the patent number and find the original patent filled in 1954.

It actually breathes pretty well too, although it still needs a little work. Between SH's and DH's now, I've got about a dozen regulators, and for practical purposes almost all of them are better than the Northill, but it's still my favorite regulator. It's beautiful, heavy, over-engineered and was obviously a high end product in it's day. There are probably half a dozen strange design quirks with the Northill. Whether it's that floating valve, the exhaust hose activating the diaphragm, the exhaust flowing through the diaphragm or the rotating mouthpiece, it's a strange piece of work.

 

[John C. Ratliff]

This is from Basic Scuba by Fred Roberts:

The rubber band was on the holes because Healthways was concerned that if the membrane adhered to the exhalation horn, there would be no way to exhale. So these little holes are a backup exhaust, with the rubber band around them to keep water out of the exhaust hose.

I think a regular duckbill can be cut down to fit into the exhaust chamber and provide the balance that the original one had. It may even breath easier, as the original duckbill was not very big. Here's a commercial duckbill site, and it shows what the original looked like (not like the USD type of duckbill).

Duckbill Valves

It may even be possible to call Elder Rubber and get something like it, but I'm not sure how you would secure it into the exhaust horn. But it is the duckbill that "balanced" (to use Fred Roberts' word) the exhaust system for all positions. Without the duckbill, it works well in all but the head-down position. Here is what the inside look like for those who have not seen it. I'm also showing that one option to limit the amount of water into the exhaust hose is to put a mushroom valve in the hose right on top of the exhaust horn. This was the exhaust disc from a Snark III regulator's mouthpiece, which I had removed from that regulator's intake side (they breath easier without this mushroom valve).

I made a hybrid Healthways SCUBA, using the original with the Gold Label innerds. I used a latex rubber diaphragm from a clean room glove for the membrane, and it functioned very well. There was just a bit of seepage past the seal when it was used, but not much at all. I'm going to be curious about how your silicone sheet works.

Here is the evolution of the exhaust for the Healthways SCUBA double hose regs.

Note that I needed to cement a nut near the exhaust for the second generation. The reason was that I did not use non-return valves with this regulator, as it breathed easier without them. But it also blew the diaphragm against the mushroom exhaust, completely occluding it and preventing exhaust. The third generation actually had a metal tab fitted near the exhaust mushroom to prevent that from happening in the Gold Label Healthways SCUBA.

Elmer, you need to post some photos of your Northill Air Lung. I have never seen one close-up. I have only seen the photos and drawings in Basic Scuba.

SeaRat

 

[elmer fudd]

I just did a little testing with a USD duckbill and I'm pretty sure that's not going to work. The duckbill is too long and since it can't lie flat it can't vent easily. I was just testing it by blowing through it and adjusting the duckbills position. It really didn't breathe well in any position, but what made it particularly bad IMO was that sometimes you would move the duckbill just a little and it became almost impossible to exhale through it.

I actually think that what might work best would simply be a plastic tube that extends the exhaust horn until it makes light contact with the exhaust diaphragm. I think that combined with a silicone diaphragm would likely work pretty well.

 

[Eric Sedletzky]

I'm going to get to work on finding a way to modify it to put a mushroom valve in that chamber and then come up with a secure and water proof cover plate where the membrane was that can be removed for access to service the exhaust valve.