Scubapro O-ring Sizes

[Zung]

Since we're pretty sure the 2.2mm will seal, I'm wondering if the 13% or so oversize of the 2.5mm would create more drag and increase WOB?

NJDiver07866: can you elaborate on the "but"?

 

[redacted]

Since we're pretty sure the 2.2mm will seal, I'm wondering if the 13% or so oversize of the 2.5mm would create more drag and increase WOB?

NJDiver07866: can you elaborate on the "but"?

As long as the "air spring" performance is consistent, I can't see why it would not work. Once pressurized, movement of the o-ring in the balance chamber is probably pretty much unnecessary to sustain high performance.

 

[halocline]

As long as the "air spring" performance is consistent, I can't see why it would not work. Once pressurized, movement of the o-ring in the balance chamber is probably pretty much unnecessary to sustain high performance.

The poppet does move back and forth in the balance chamber, making the poppet o-rings dynamic. So, conceivably, very snug fitting o-rings could increase friction and have at least a theoretical effect on breathing resistance, but I seriously doubt it would be anything measurable unless you really had to jam the poppet in there.

Are we talking about the same thing? The two little o-rings on the s-wing poppet?

 

[NJDiver07866]

Ok to elaborate on the ‘but’ and to man up to my own mistakes in hopes others won’t follow in my footsteps. I installed the white poppet completely in the opposite position in the air barrel turning it 180 degrees. I pushed down on the poppet, the lever moved up and it ‘looked’ like the poppet engaged the feet of the lever ok. Dove the reg this way for the entire season. Only until a few weeks ago I took it apart I noticed the lever was crooked just a bit not much. I pulled the poppet out of the air barrel and said let me try to rotate the poppet so the 90 angle L shapes on the poppet face the other way. When I did this and pushed down on the poppet to see it engage the lever I was like ‘oh that’s a bit better’. It was a more positive feel and more movement in the lever when I had the poppet in this position. So I made a mistake, but found interesting that the reg will breath with the poppet either way in the air barrel.

As for the 2.5 x 1 o-rings. (The tiny ones two of them on the end of the poppet that seal the balance chamber) I have a stash of ‘official’ scubapro o-rings. I can’t freaking tell the difference. After a few seasons I notice all o-rings tend to shrink a bit… could be the 02 I run through them.. or could be that o-rings just shrink over time? I don’t know. Was thinking if the balance chamber did ‘lock up’ on the poppet because of the o-rings were .3 mm larger, gas will still be delivered so I did not see to much of a risk. It bothered me a bit.. so I tried it. I crazy glued a balance chamber to the end of the poppet and dove with it and could not tell the difference. About 100 feet I compared my crazy glued S550 vs a stock ‘scubapro’ s555 and they felt equal. I of course just threw out the crazy glued poppet, was it a waste of parts? I guess, but when you have discovered the secret handshake to get parts, I have a good amount of them now.

Gas density? Again I thought if this would impact the reg if I took it deeper. But the only catch is it’s hard to catch a charter for anything deeper than 150. And If I do.. I’m usually have he in the mix so density would go down.

AWAP hit a good point. That pesky spring on the Poppet. I noticed over time they lose their ‘springyness’ for lack of a better term and the only way to compensate is to tighten the plug at the end of the air barrel (on the s550/555) or tighten down the adjustment knob on the adjustable regs. So also show your secret hand shake and get some spare springs. If the spring is weak it will drive you nuts trying to tune the reg.

And the final swing poppet thoughts… the inner diameter of the balance chamber gets worn out over time or cracks. I know there are a few versions of the chamber and the newest one has reinforced plastic running down the sides, when the older ones I seen only look like a smooth bucket. So get a few of these for your spare parts kit. That’s pretty much all the update info I have with this reg. If I learn more I will post…. Dive safe all.

 

[Couv]

Thanks NJD,

But just to clarify, when you put the poppet in 180 degrees out, do you mean upside down in the barrel? Or do you mean, the soft seat was facing the adjustment screw and the balance chamber faced the orifice?

c

 

[Zung]

mattboy:
Yeah, we're talking about the 2 little o-rings on the poppet. The prospects are pretty good: thanks to everybody's experience, we know that both 2.5 and 2.2mm x 1mm o-rings work: we know that the Trident A148 seat fits. We'll wait a couple of months, and if awap is alive and still posting, we'll know it works too. All these stuff can be bought at places that do not require a contract signed in blood.

NJDiver07866:
Very interesting experiments. I lament the passing of a poppet: they retail for $20 a piece around here. And crazyglueing the thing turns it into a non-balanced reg, right?

I'm intrigued by the positioning of the poppet; I assume you mean up side down like couv said. According to my experience (gigantic, all of 2 units serviced, metal adjustment knob vintage G250), only one way goes without forcing.

 

[NJDiver07866]

To clarify... the correct way is the l shaped dogs to face towards the mouthpiece. By mistake I rotated it 180 and the L shaped dogs faced the purge cover.

I took it apart and noticed the purge lever actually gets hung up on this part of the poppet allowing it to work in the incorrect position. But just learn from my mistakes.. I know it seems like it should have been caught.... but it 'felt' ok to me until I took it apart a season later and the light bulb went on.....

Zung.... my thoughts exactly about the unbalanced 2nd stage...and one of the reasons I glued the balance chamber to the poppet. I'm a bit extreme in my thinking, but I wanted to test a few things.

1. Will the reg breathe like crap if the balance chamber jams on the poppet? Will I even notice if I use the wrong sized o-ring and have it jam up? After gluing the balance chamber to the to the poppet intentionally, it taught me that even though it's cool looking and in theory it's a great sales pitch to say to a customer 'get this regulator because it's balanced!' In reality it does not do too much.

2. Was it the balance chamber that made the reg breathe smooth VS the hockey puck style valve on the 190/290/390? After experimenting, I believe it's the length of the spring that gives the swing it's smooth draw not the balance chamber. If you look on the 190 type, it has a very tiny spring on the poppet held on by a nut.

There is a good amount of tension on the tiny spring length. When you compare it to the G250/S550/S555 etc it has a huge spring in comparison. Just thinking about physics energy displaced over a longer amount of time/distance (bigger spring with less tension) gives it a less 'Jerky' feeling compared to a smaller spring with incredible tension and more 'Jerky' feeling. Kinda like long plush shocks VS Stiff short shocks on a car. Both can absorb the bumps but the longer plush shock is smoother. The bumps being the drop in IP and recovery of IP from the 1st stage.

Just thinking out loud. I share this because I'm open to people questioning this and would like their ideas. If you never question anything then Nitrox will still be on the ban (for those who remember way back when..)


Dive safe..

 

[halocline]

NJDiver, did you say you glued your G250 poppet to the balance chamber? If the balance chamber and poppet were one rigid piece, the reg should no function. The back of the balance chamber rests against the adjustment knob, and the other end sits against the orifice. When the lever depresses, it pushes the poppet back off the orifice, into the balance chamber. The balance chamber can't move. On the S600 and newer versions of the G250HP, there might be a second balance chamber; I don't know much about those.

On a recent thread, one of the usuals on this forum pointed out that the G250 and R190 use the same spring, it's just that the R190 compresses it much further.

 

[redacted]

Yes, there has to be movement of the poppet stem in the balance chamber for the poppet to be pulled from the orifice, but not much.

BTW, the the Trident cave cone seat, p/n A-242, fits and functions in a Mk5. I probably will not get to dive this stuff until next week. Lockup was a little mushy but this was an untested Mk5 so it may not be a problem with the seat. It is improving with more break in. I also tried it with a different seat retainer and an old flat HP seat and they behave pretty much the same. When I say mushy, it recovers instantly to about 120 psi, then another second or 2 to 130 psi. And then maybe 2 or 3 psi creep over the next minute. I have not gotten back with Scubatoys on the prices yet.

 

[Couv]

....unless you place the spring between the balance chamber and adjustment knob, like the 109. NJD....could we impose on you to take pictures of the parts as you had them arranged, except of course outside of the barrel? I have a feeling you basically rearranged the parts into a 109 configuration.

We need to get this guy into our other thread and hook him and his experiments up to some telemetry equipment.

c