Breathing Resistance- old S.P. REG

[oxyhacker]

Probably a good time to remind everyone that the orifice adjustment doesn't adjust poppet spring pressure/cracking pressure on the 109 and G250 and similar regs the way it does on a basic downstream like the G190, it adjusts lever height. A lot of people, including more than a few reg techs, never notice this because the procedure for adjusting the orifice remains the same regardless of what it is actually doing.

Sure doing so will also effect spring pressure, but only slightly and incidentally - the purpose of the adjustment is lever height. So when you try to reduce cracking pressure too far using the orifice on a 109 or G250 you are actually just putting the lever hard up against the diaphragm, so the diaphragm is contibuting a little pressure of its own, which works to a degree, but, since the dynamics of the diaphragm are a lot more complex than those of a spring, at the cost of adding a certain amount of unpredictability to the reg's behavior. Then when you try desensitize the stage by turning the ext adj knob out you are not actually addressing the problem, but rather trying to compensate for the fouled lever by increasing cracking pressure! The result can be an unstable or hard breathing reg.

The 109 does have a modest, fixed amount of venturi boost built in, and a good breathing 109 can breathe very well indeed. But I think most side by side tests will show that, as much as we love our 109s, that an average G250 will noticeably outperform an average 109.

Oh one other thing all 109 diehards should know is when you do service them, lube the heck out of the adjuster threads, and operate them every so often just to keep them free - since they are metal to metal, and the chrome has usually worn thin on them, freezing of them, and damage resulting from trying to break them free, is probably the most common reason for a 109's demise. I use a food grade antiseize rather than plain silicone grease.

awap once bubbled...
I also decided to bend the lever a bit as it was a good 1/4 inch too high and made reinstalling the cover difficult. Works good in the sink but I'm waiting on a new exhaust valve before I can use it.

Sounds like the adjustments you are making are steps in the right direction. On all 3 of my R109's, the lever (actuator) is in full contact with the diaphram.

 

[ew1usnr]

oxyhacker once bubbled...
.... as much as we love our 109s, .... one other thing all 109 diehards should know ...

Thanks for the tips. I do love my 109's (upgraded to balanced adjustable) and am a diehard fan. Reading these notes has me curious about my lever placements and knob settings. I'll open them up tonight and have a look.

 

[donclaypool]

Guys,

Pardon my ignorance, but is the attached pic, my reg, the aforementioned early 80's 109? And, I can get a balanced kit for it as mentioned below? It's the same as for the 200B and 250?

"The service kit for the older SP balanced barrel poppet regs (Balanced Adjustable, G200B, & G250) is #11-254-041." Thank you AWAP!



Lots of great information here. I was not unloading the seat before making adjustments. I will now. This has a lightweight plastic poppet in it.

I had to bend the demand lever on this one because with the adjuster all the way against the stop as there was still a lot of spring pressure against the seat and the lever was too low for instant air on inhalation. It seemed like the spring was too stiff or long. I'm thinking I'll order the spring and balanced service kit as soon as someone here confirms that I have all the right information. I still need to dive it as is to see where I'm at with it but I'm really enjoying this. And yes, now it breathes MUCH better than my octo, on the surface anyway.

You guys are great.

Don

 

[redacted]

oxyhacker once bubbled...
Probably a good time to remind everyone that the orifice adjustment doesn't adjust poppet spring pressure/cracking pressure on the 109 and G250 and similar regs

This is my third 109 and the first one that was actually difficult to reassemble the diaphram & covers due to the lever being so high. I brought the lever down to a height comperable (a little higher) than my other two which are balanced.

Seems to me that the orifice adjustment is effecting both lever height & spring tension as the orifice applies pressure to the seat. Of course, once the orifice makes contact with the seat, a little movement of the poppet adds a little spring pressure but may move lever height quite a bit more. The adjustment has to add enough pressure to the spring to stop the freeflow. I make that adjustment initially with the covers & diaphram off so the only thing the lever is doing is limiting the travel of the poppet toward the orifice. Then I complete assemby & re-adjust as the front parts have pushed the lever downward. . When I did that with my last one, the lever height was over 1/2 inch higher than the position it would take with the cover installed.

 

[redacted]

donclaypool once bubbled...
Guys,

Pardon my ignorance, but is the attached pic, my reg, the aforementioned early 80's 109? And, I can get a balanced kit for it as mentioned below? It's the same as for the 200B and 250?
Don

Thanks to DA, I now have some idea of the vintage of my 109's. The two adjustables that I got have no rib and my balanced adjustable has a very large rib. It sure does purge easily - whether you meant to or not. The case assembly (main body) should be the same reqardless of vintage so those parts should do the job. New service kits (11-254-041) should all have the new, one piece plastic poppet with 2 o-rings into the balance chamber. My 1999 schematics still shows the 2 piece poppet assembly in the BA, G200B & G250, so the poppet upgrade is fairly new. That poppet change also went through a 1 piece poppet version that only used a single o-ring. My 1999 G500 was configured that way. When it started leaking from that single o-ring (after almost 4 years), I upgraded to the newer poppet and recycled the old one with a new o-ring into my R109 conversion where it is working OK.

 

[oxyhacker]

The orifice is effecting both, yes, but its only adjusting one. That is to say, you can't adjust two things simultaneously with one adjuster - one will always have to defer to the other. The 109/G200/G250 are single adjustment regs. There's no cracking pressure adjustment other than the lever height, which some people consider cracking pressure but I don't (I consider it lever height).

The correct way to adjust a 109/250 is to rough set the lever height, assemble the stage, turn the ext knob all the way out, then fine tune the lever height so the lever won't foul. This is done exactly in the same way that one adjusts poppet spring pressure on a two adjustment 2nd, but it's not the same thing.

awap once bubbled...


This is my third 109 and the first one that was actually difficult to reassemble the diaphram & covers due to the lever being so high. I brought the lever down to a height comperable (a little higher) than my other two which are balanced.


Seems to me that the orifice adjustment is effecting both lever height & spring tension as the orifice applies pressure to the seat. Of course, once the orifice makes contact with the seat, a little movement of the poppet adds a little spring pressure but may move lever height quite a bit more. The adjustment has to add enough pressure to the spring to stop the freeflow. I make that adjustment initially with the covers & diaphram off so the only thing the lever is doing is limiting the travel of the poppet toward the orifice. Then I complete assemby & re-adjust as the front parts have pushed the lever downward. . When I did that with my last one, the lever height was over 1/2 inch higher than the position it would take with the cover installed.

 

[DA Aquamaster]

No disrespect to oxyhacker but the orifice adjustment does affect spring pressure, not just lever height. And like awap indicates this can be easily demonstrated by adjusting the orifice with the cover off.

I do agree the design is different though. It is not as linear in function or adjustment as a std downstream design. It is more of a "system" in terms of operation as the orifice, spring and lever all feedback into the system and if any of the parts are out of tolerance, the reg cannot be tuned properly for optimum performance.

In any system with a feedback loop, you are in fact adjusting two (or more) things with one adjuster. It's just that most wetern people don't think that way. With the subject-verb relationships common to western languages we are steeped a linguistic tradition that is biased toward linear cause and effect thinking and we tend not to look at things in a more circular or dynamic fashion.

I also would agree that in side by side performance numbers and on a breathing machine, the G250 will kick BA butt with it's high VIVA settings. But from a subjective standpoint, that additional performance comes at the cost of a less "natural" feeling breathing response from the reg. And I don't think many divers actually dive the G250 in that max performance but touchy condition.

Some divers don't mind a positive pressure phase in the inhalation cycle but I do not like it and prefer a more measured, controlled and predictable response from the reg.

Besides, I can drop a tank on my metal cased BA and then go diving. Drop a tank on a G250 and you are out of business until you replace the graphite/resin case.

The 109 second stages also came with a little blue key the fit inside the "S" to keep the lever depressed and lift the poppet off the seat. This allowed an almost indefinite storage life for the reg without the poppet taking a set from constantly being pressed against the seat.

I don't think SP makes them any more and they have a habit of breaking, so in a pinch you can insert a quarter between the metal and rubber purge covers to accomplish the same thing. This is very close to what SP originally used with the rounded blue tab that was used prior to designing the key. This does however leave the system open so it is something you want to reserve for clean and dry storage areas.

 

[redacted]

DA Aquamaster once bubbled...
No disrespect to oxyhacker but the orifice adjustment does affect spring pressure, not just lever height. And like awap indicates this can be easily demonstrated by adjusting the orifice with the cover off.

snip

The 109 second stages also came with a little blue key the fit inside the "S" to keep the lever depressed and lift the poppet off the seat. This allowed an almost indefinite storage life for the reg without the poppet taking a set from constantly being pressed against the seat.

I don't think SP makes them any more and they have a habit of breaking, so in a pinch you can insert a quarter between the metal and rubber purge covers to accomplish the same thing. This is very close to what SP originally used with the rounded blue tab that was used prior to designing the key. This does however leave the system open so it is something you want to reserve for clean and dry storage areas.

Damn, enter key does not move you from title to msg, it sends.

The primary function of adjusting the orifice is to adjust lever height. If the lever is correctly positioned and the system does not freeflow, the cracking pressure is then controlled by the spring. But I figure any excess compression on the spring just detracts from performance.

To reduce the tendency of the 109 seat to take a set in storage, I removed all my retaining clips after the reg is adjusted. When they are stored, I back off on the adj knob till it is almost ready to fall out. This reduces or elinminates the pressure on the seat. And in that I usually forget to crank it back in before I set it up on a tank, it also reduces the shock of first opening the valve as I crank it back in to stop the freeflow. It does mean you have to be a little careful not to do anything real stupid with the adjuster during a dive. It really isn't a problem since a well tuned metal should start to freeflow lightly within about 1/2 turn beyond the stop. That is another check I make when tuning.

 

[oxyhacker]

Of course orifice adjustment effects both lever height and spring pressure - I've said so several times in this thread. Though demonstrating it with the cover off gives an exaggerated view of its range and significance, which may be where some of the misunderstanding comes in.

However the effect on spring pressure is only incidental, and largely irrelevant, because proper lever height is so much more important to the stage's functioning that a tiny bit more or less spring pressure.

Re the cultural biases of my western mind, I alway hated ZEN AND THE ART OF MOTORCYCLE MAINTENANCE so I may be hopeless in this regard. But to me adjusting means the ability to tune something to the setting I want, not just the ability to make random changes. When two variables are controlled by one adjuster, then there is no way to optimize them both other than dumb luck. Either one must be given priority, as it is in this case, or the error has to be split between them.

DA Aquamaster once bubbled...
No disrespect to oxyhacker but the orifice adjustment does affect spring pressure, not just lever height. And like awap indicates this can be easily demonstrated by adjusting the orifice with the cover off.

 

[ElectricZombie]

donclaypool once bubbled...

1. Has new technology- venturi assists, and all the bells and whistles virtually eliminated breathing resistance?

I've never thought that the venturi assist did much of anything to improve breathing. It does seem to help prevent freeflow when the reg is out of your mouth.

2. Can I gain the benefits of a new reg by replacing only my
second stage.

I don't think you'll tell a whole lot of difference. The SP balanced adjustable is a good reg. Maybe yours just needs some tuning.

3. Do I need to buy new regs due to the age of these ones? I stay within rec. limits, but still want an excellent cold water reg. should I move north again. I don't believe in replacing with the newest and best simply for that reason.

No. Your setup seems fine to me. The Mk5 is a good reg. The balanced adjustable 2nd stage is a good breather in my experience.

I know this reg is the granddaddy of the balanced piston design and all the old commercial guys tell me to keep this reg.

The Mk5 is really simple and works great. ScubaPro got it right with the Mk5/Mk10 first stages. Keep it.

So, I guess I'll do a little buddy breathing on my next dive to compare something newer to mine at depth, or rent some new gear for comparison.

Good idea...might save you some money...you may not need to upgrade.

I really don't need to hear "Go get an Apeks or Posideon and forget about it". What I need is a few educated opinions from you old timers and reg rebuilders.

I'm not an "old timer", but I'm pretty familiar with SP regs. Your setup is still a good reg...I wish I had a Mk5 actually. You may want to take it apart and check it out if it's breathing hard.