Honkers and Slipping Diaphrms

[Nemrod]

Honkers and slipping diaphrams, a bi-modal thread.

Honkers, like the regulator at SDIV that when heeee, haaawwww, heeeeee, haawwwwww all the way through every dive . what causes that? I have always thought it a resonance in the first stage, possibly a vibration of the springs caused by the airflow past the HP seat.


Slipping diaprhams, I have worked on several dh regs that had warped cans. I set them on a flat surface and could clearly see that the can sealing surface was deformed. Such a situation would result in uneven clamping force on the diaphram and possibly unseating.

Just spoke briefly to Luis, got to get to work.

James

[Turtleguy9]

Aloha Nemrod
Some of the old diaphragms we have had to use for years, were so thick and stiff, they could not slip if we wanted them to. I am looking forward to the better response from the silicone ones.
I know some modern single hose regs that honk, and I think you are right, its a harmonic thing.
Turtleguy9

[SDAquamaster]

It's most likely a sympathetic resonance caused by vibration of the moving parts.

Resonance can occur in piston first stages where a lack of lubrication of the piston stem or piston head o-rings can cause the piston to vibrate slightly as it moves back and forth.

It can also occur on a few piston models at certain intermediate pressures where the spring pressure is exactly right to cause a resonance with some other part of the system. If the IP is not adjustable with a spring pad, addition or deletion of a shim is required.

It is less common on diaphragm designs. But the latter issue caused by spring pressure is most likely to occur in a double hose reg (although on a balanced diaphragm first stage it is still possible for the seat carrier to vibrate slightly due to inadequate lubrication of the seat stem and/or the o-rings that seal it in the spring block/seat carrier.)

The fix is usually to increase or decrease the IP by 5 or 10 psi which is done by altering the spring pressure which in turn usually changes the frequency enough to eliminate the resonance issue. Although while you are in there, it is worth it to also ensure proper lubrication of any moving parts as well. The first stage adjustment should warrant a second stage adjustment as well for peak performance and that will normally ensure the problem is resolved if it was a case of the second stage seat retainer and spring creating the resonant vibration.

The above adjustment will usually resolve a higher pitched honk or whistling sound but much lower freqency honk is often caused by a second stage diaphragm with abnormal tension on it. If the diaphragm has been installed in a manner that has resulted in tension around it's circumference in an area, it can create tension across the surface of the diaphragm that increases when the diaphragm moves inward. The stretching that results can cause it to flutter in the airflow and produce an extremely annoying honk. The honk is almost always much less noticeable to non existant underwater due to the dampening that occurs and it will often go away with use as the diaphragm slips back into a less stressed position. But sometimes it will require removal and re-seating of the diaphragm to resolve.

[Bryan]

Great information....Thank you! Gives me some more things to experiment with.....

Two things.....USD never used any lubricant on their double hose regulators as far as the info I have goes....

The regulator that was making all the racket was a DA Aqua-Master...If I follow your ideas that would lead me to believe that it was a problem with the main diaphragm as the 1st stage is unbalanced and has no nylon bushing or o-ring?

[boogerdave]

That was the first time that reg had been dove in a very long time as far as I know. I have it on my bench now and it was very dirty inside so It may just be . . . , lack of "slideability". That was also the case on another DA and I found that after cleaning, the honk went away. Dunno . . . just what I've found has worked for me.

[Bryan]

That was the first time that reg had been dove in a very long time as far as I know. I have it on my bench now and it was very dirty inside so It may just be . . . , lack of "slideability". That was also the case on another DA and I found that after cleaning, the honk went away. Dunno . . . just what I've found has worked for me.

I was not aware that you had a honker as well Dave? The one I was talking about belonged to someone else...

[boogerdave]

It was the one Charlie bought down there - not mine. I finally talked him into diving my Royal until I could look at it.

[pescador775]

I owned a SP MK10 which developed a first stage "honk" which was noticable only under water. The second stage had a slight chatter which was noticable only on the surface. The regulator was found to have an intermediate pressure of 165 and, moreover, the second stage spring was suspect. The original spring had a rate which was too low (weak) and SP tech support advised to replace it with a later model spring. My impression was that this problem was known already to SP. The changes were made and cured the problem. My opinion is that the high IP was the main problem causing an annoyance during the dive.

I have neither heard of strains occuring across the diaphragm of a DH regulator nor any chatter resulting from such a problem. Every diaphragm that I have seen bulges or dimples out slightly when clamped in place. This results in a slight slant or bias to the diaphragm which is unnoticable in action except for the fact that, on the surface, the diaphragm's contacts will strike the demand lever at different intervals when inhaling on the mouthpiece. I have never heard of an AM or RAM honking so this is news to me. However, I don't necessarily have access to this type of info except on vintage boards and my own experiences.

[SDAquamaster]

The Mk 10 is a good example of a regulator that will develop a whistle or honk during inhalation if the high pressure piston stem o-ring and piston stem are not adequately lubricated.

One of the cures for this problem that was frequently promoted was flipping the mainspring over. It usually worked, but only because the piston has to be emoved to flip the piston and when properly done, the o-ring and stem are re-lubricated - solving the actual problem. The spring really did not care which way was up.

Several years ago SP started including 3 seats in the MK 10 annual service kits. This was done to allow more range of adjustment, especially downward, as it appears that the Mk 10 main springs get stiffer with age causing a gradual IP increase over the 25 plus years they have been in service. Including taller seats with a slightly reduced working range was a cheaper way to get the IP back into the normal range than replacing all those main springs and it works for all but the stiffest Mk 10 springs.

I had one case in the late 1980's where a Mark 10 and it's frustrated owner (a spearfishermen who did NOT appreciate the noise) came back several times reporting an intermittent problem with honking. We finally determined it only did this when the reg was on one particular tank and discovered that the problem was resonance in the J valve on the tank, not the regulator. This strikes me as a possibility that may become common again in the vintage dive community.

[Turtleguy9]

Aloha SD Aquamaster
Quoting your post.

I had one case in the late 1980's where a Mark 10 and it's frustrated owner (a spearfishermen who did NOT appreciate the noise) came back several times reporting an intermittent problem with honking. We finally determined it only did this when the reg was on one particular tank and discovered that the problem was resonance in the J valve on the tank, not the regulator. This strikes me as a possibility that may become common again in the vintage dive community.

This problem with the tank valve, is one I have had in the past. I have one pipe thread post style J valve, that makes a sqeaking sound as air moves through it at certain pressures. It probably needs a rebuild.
Aloha Turtleguy9

[pescador775]

A comment on resonance. Every spring has a natural frequency which can be calculated using several factors. Springs also have resonant frequencies which are multiples or harmonics of the natural frequency. There is also a sister phenom called sympathetic vibrations. I doubt that a regulator mainspring ever produces resonant frequencies but under certain circumstances can undergo oscillations which may or may not approach the natural frequency. This is much like the reed in a trumpet or a duckbill in a regulator which vibrates due to airflow (quack). Sympathetic vibration occurs when two bodies vibrate, one in response to the other when the natural frequency of the second body is excited indirectly by the first. If I were describing the behavior of a naughty regulator, the terms "oscillation" or "vibration" might come to mind but not necessarily "resonance". The reasons are simple; a resonance is not required to produce a noise or flutter in the airflow, and a regulator piston is not likely to create sympathy in other parts. The original vibration might be felt but not qualify as "sympathy". However, it might be hard to convince a diver who suspects Spike Jones' musical saw is inside his regulator. FWIW
Pesky