cold water use and most robust

[rsingler]

All of the Apeks regs perform very well in cold water, and they are one of the most common regs here in Norway.

I have JUST gotten word that Scubagaskets now has 1.6mm thick diaphragms back in stock in the Apeks diameter (~39mm?).
I have had more than one seminar participant from your cold northern waters who has commented on "champagne bubbles" from the Apeks diaphragm clamp at around the 1-2 year mark. That scares me.
The Apeks design is constrained by a metal to metal contact limit when screwing the diaphragm clamp onto the body. That means that diaphragm compression by the two halves is limited to the milled distance between the two parts (~0.8mm). For a spec 1.16mm Apeks diaphragm, that is only 28% compression. That's not enough, IMO. Perhaps adequate at the start, but when the diaphragm takes a "set" from the clamp, its seal weakens. Hence, the leak at the clamp.
But I have had consistent success using the Scubagaskets diaphragm. Because of the thickness, I don't go to metal to metal contact - the thread torque becomes excessive. But clamping to 266 in-lb (30 Nm) gives the best of both worlds: 40-50% compression and room to play.
And at €7.25, it's very reasonable

Diaphragm for 1st Stage Apeks scuba gear as SGAP 1478 (1,6mm thikness )

Scuba Gaskets - Diaphragm for 1st Stage Apeks scuba gear as SGAP 1478 (1,6mm thikness ). ap1478, APEKS, apeks service kit 0219, RG912062, scuba orings service kit.

scubagaskets.com

 

[Scuba fryd]

My personal stance on knobs/levers is knob good, combo knob boo (that changes both Cracking effort and Venturi at the same motion) but better than no knob/lever

just to be sure the standart apek with a knob and a lever is good and dosnt add any unessecary risk og breaking the reg or getting sand and so stuck?. but the ones were its jus tone thing that adjust both ventui and cracking presure is not good?

might just be me then but i would actuly have thougt that the adjustment would be another way of risking faster degrading of a reg

 

[Mobulai]

just to be sure the standart apek with a knob and a lever is good and dosnt add any unessecary risk og breaking the reg or getting sand and so stuck?. but the ones were its jus tone thing that adjust both ventui and cracking presure is not good?

might just be me then but i would actuly have thougt that the adjustment would be another way of risking faster degrading of a reg

I might have mixed a few things in one go:
The knob that does both is NOT an Apeks feature so don’t worry about that (some aqualung and Sherwood regs have that); they are not a good practice as they detune regs in an intense way
Nothing to do with sand (ok inherently they have a sand issue, next point)

Then, there is the style of Venturi; either a separate vane (at the mouthpiece) or a deflector around the barrel; the 2nd type is where sand can get stuck; again not the end of the world with regular cleaning but I try to avoid them

Cracking effort knobs also get sand stuck in them — if you wanna avoid that risk then avoid them; but I find the benefit of having one worth having a knob

 

[Scuba fryd]

Cracking effort knobs also get sand stuck in them — if you wanna avoid that risk then avoid them; but I find the benefit of having one worth having a knob

might just be me but i actuly dont remember when it is used heh.
but i like the thougt of having it since i go from 1c water to 18 so i would belive i would be using the ajustment as the water gets colder and warmer but dose cracking presure anything to do with water temp?

i see some say that the MTX-r can be ajusted with a 5mmhex key but somthing tells me that it is not agood idea hope

i hope you can help me understand it a bit better so i can decide if the extra 150 usd is worth it just for the knob and lever adjust.

 

[Mobulai]

Starting with the most important:

lever adjust.

You don’t adjust the lever… only in service

The poppet seat seals against the orifice, and the lever moves the poppet to open it up, them air flows to you
You want max(possible) lever height so that you get „instant“ transmission from diaphragm to open up the valve for breathing

Now that this part is cleared up (I hope):
The orifice will make an imprint with time onto the seat and eventually it will be deep enough to freeflow (not violently at 1st, but eventually)

Now when that happens you have 2 (3 really) options:
- You can adjust the orifice (lowers lever, not recommended)
- you can tighten the spring pushing the poppet, so that you increase the cracking effort without lowering the lever
- you can change the seat to a new one (service the reg)

Option 2 is achieved with either the knob or (if it’s a balanced but without knob like xtx40) with a hex key

see some say that the MTX-r can be ajusted with a 5mmhex key but somthing tells me that it is not agood idea hope

It’s alright to do that, and not complicated

A strategy some of diy users is to tune the reg so light that it barely free flows, but the orifice isn’t touching the seat; so the seat doesn’t wear quickly; and when they are dive „ready“ they tighten the knob a bit to get a seal — I learned about this here on scubaboard and I adopted that

(The knob is extra control in case you want instant access to the spring, it is your preference to have one or not of course, some people never touch them and are doing well )

Re: water temperature:
I would say I wanna have lowest (easiest) cracking effort (the sucking effort you have to apply to get a breath) regardless of temperature; but (uneducated) guess is that you want to restrict the flow a little bit in real cold water
Again I did like 5 dives only in water colder than 15degC so… this is something for experienced cold water divers to answer

Edit: in case you wanna know more about the internals/mechanisms of a 2nd stage; here’s a great in depth by the wizard @rsingler

 

[grantmac]

Having the adjustment is useful for high current or scootering to prevent freeflow. Also common to detune a little in cold water, especially on your secondary reg.

I find the Apeks venturi knob much easier to use with dry gloves compared to Scubapro. They also seem much harder to provoke a freeflow for a given cracking effort but maybe my SP regs are just getting tired.

 

[Scuba fryd]

high current or scootering to prevent freeflow.

i am quessing it becuse large amounts of water will be enough to reach cracking pressure ?

 

[admikar]

You are starting to overthink this.
Both regs you have mentioned are good for what you need them to do.