Upgrading R109 to 156

[DA Aquamaster]

Thanks, that's a piece of valuable information: parts #01020216 for/from the R190/290/295/380/390/395 are common as dirt since every SP backed dive club use them.

Now that you got me curious, I checked and the G500, the S550/600 also use the same spring.

People have no imagination.

BTW, I keep one of my 109 unbalanced for an A/B test. I'll report back as soon as the waters hit 70°F. I have the feeling I'll come to the same conclusion as halocline. But then I'm the heretic who dared declare publicly that my G250 breathes better than my 109 BA.

Scubapro is fairly strategic in terms of limiting the number of parts they have to make and stock so if they can re-use a spring or some other part in a new design, they will and the parts commonality between reg models can be pretty high.

On some iterations using the G250 balance chamber you will notice a shim to increase spring pressure. It was done to allow the same parts to be used in some iterations of the G250HP (eliminating the need to design, produce and stock new parts) but that shim itself is just one of the bushings used in the Mk 20/25, so no "extra" part was required, eliminating the need to design a dedicated shim for the design.

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I am also a G250 fan, and to be honest, on average I think the average G250 breathes better, or is at least easier to tune for the same peak performance, than the average 109 or 156, possibly due to accumulated age and wear in many 109s and 156s.

Of course, I also recently rescued a box of retired Air 1's from the shop and had enough parts in my vintage parts bin to put together a few more superb breathing Air 1s (and one that works but is not quite in the same ball performance ball park). I had forgotten how nicely they breathe and I am contemplating what I might do with them now that I have a total of seven of them along with a very nice Pilot.

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I do have a few extra Air 1 diaphragms (used but in very good/excellent condition) and I need a couple of the metal retainer clips to get 2 more of the Air 1s back in service so I am open to a 1 for 1 trade.

 

[DA Aquamaster]

One nit-pick, and I can't believe I'm nit-picking with the all-time scubaboard co-MVP of regulator knowledge, (the other being Luis) is that the forces on the unbalanced and balanced seat are not exactly identical. Because the force on the balanced seat is a combination of spring and air pressure from the balance chamber, when IP drops during inhalation, so does the pressure in the balance chamber, and consequently on the seat itself. This does not effect cracking effort, but does theoretically mean that once inhalation is initiated, effort to keep the seat open is lower. In my meager experience, I do seem to generally notice a difference between my converted 109s and non-converted, but it's very slight and I probably wouldn't notice a difference on a blind test.

I'll have to take some measurements do the math on the net effect of the drop in IP on the force provided by the balance chamber *after* the valve is open and the flow has been initiated (which must occur before the IP and pressure in the balance chamber can drop.) However, I think any effect of the drop in IP and balance chamber pressure acting on the poppet will be more than offset by the venturi effect of the reg which will tend to keep the valve open anyway at higher flow rates.

If there is a noteable difference in effort, it would theoretically be at very low flow rates, and that is negated as at very low flow rates you have almost no IP drop (3-5 psi).

 

[Palindrome]

Any suggestions where to send a 109 in the Pacific Northwest, Vancouver specifically, to get overhauled? Poppet has noticeable wear marks.

Local dive shop says it takes 2 week to service so I am assuming they are sending it out somewhere.

Cheers

Pal,,

 

[wwunder]

Pal,

Robin at Great Pacific Diving in Surrey is the best reg tech in town... He has been around forever and would do an awesome job on your 109 i'm sure. There shouldn't be any problem getting scubapro done locally since the parts are standard.

 

[Palindrome]

Thanks for the quick reply, I will give him a shout

Cheers

Pal

 

[Zung]

... On some iterations using the G250 balance chamber you will notice a shim to increase spring pressure. It was done to allow the same parts to be used in some iterations of the G250HP (eliminating the need to design, produce and stock new parts) but that shim itself is just one of the bushings used in the Mk 20/25, so no "extra" part was required, eliminating the need to design a dedicated shim for the design...

Wow! Yet another gem: part #01060607.

Even though I don't want any G250HP's, I'm very interested in finding alternative parts sources for the MK20/25. Any idea about its mate, the other side of the bushing, part #01700105?