SP G250V side knob ?

[idive2]

I have looked inside my R190 to see that the dive/predive knob is
simply turning a little deflector in the airway going to the mouthpiece.
Never did figure out how that can affect free flow ? Anyway, I have not
had the cover off my newer G250V to see what that metal knob next to
the dive/predive knob is actually doing ?

 

[redacted]

Buy nor borrow a copy of this: SCUBA REGULATOR MAINTENANCE AND REPAIR by Vance Harlow

It will answer those questions and many more which you should also ask.

 

[DMDavid]

The deflector maximizes or minimizes the opening affecting Bernoulli's Principle.
In short a restricted opening will cause air molecules to flow faster through the restriction and the restriction requires additional force (intake) to create the demand of air thereby lowering the chances of freeflow.

Although as always I may be wrong and it may just be a pretty silver knob to make the reg more expensive.

 

[rcs9250]

The dive , pre-dive knob disrupts the air flow so the air does not come straight out of the air tube outlet inside the reg. It causes the air to swirl around so that a venturi effect is prevented.
The other knob will change the work of breathing. Turn it in a little and breathe it and you may not notice anything. Turn it in a lot or all the way and then breathe the reg, you will notice a mrked difference in the effort to breathe.
Probably 99% of divers never touch it. If you were swimming into a curent the water could push on the diaphragm and make the reg flow air while you are exhaling. If that occurs you just turn the knob in a little till it stops. Don't forget to readjust it when you go with the current.

 

[idive2]

I run the steel knob at about equal turns from full open to full close. It's probably adjusted pretty well because if all the way out it will free flow just as the reg submerges at the surface. I have been in the habit of turning it in and out a bit when I rinse the reg and was just curious what I was actually turning inside the reg. I've been wanting to get that Vance Harlow regulator repair book for some time, maybe soon.

 

[Zung]

You can see how it works here. When you turn it in (clockwise), the knob adds more pressure to the spring (in the middle) and makes the breathing stiffer.

The best setting in all the way out, then back in a fraction if it free flows: that gives you the least effort.

Turning the knob once in a while is a very good idea; it tends to get stuck because of the metal to metal interface.

 

[knowone]

Thanks Zung. It's about time I knew what I've been pulling and pushing and twisting.

No parts left over today.

 

[redacted]

Thanks Zung. It's about time I knew what I've been pulling and pushing and twisting.

No parts left over today.

Have you been using both hands again?

 

[idive2]

Zung, thanks for the working schematic, very nice. Now that i see it is actually
working the spring and interfacing with other parts I'll probably just turn it a bit
from time to time when rinsing. Thanks to the others for your comments as well.