My new G250Vs and ramblings

[Open Ocean Diver]

You guys ain't going to like this-but if you're using the same seat after all of this swapping out of parts, you may be chasing your tail.

Again, the issue is hard and soft seat separation. This points to the lever and/or seat. <--this presumes the poppet, balance chamber, and orifice are defect free.

So my good unit free flowed with vane in either position. Pulled the poppet, spring, chamber, and knob... only once and tried the parts in the 2nd unit that wasn’t free flowing without success. Reinstalled parts back in the original working unit and guess what it wouldn’t free flow with crescent facing mouthpiece. Ugh

Flipped the crescent toward the diaphragm Shazam free flowing again.

Seems to me this is an edgy test and is not a reliable one. Things can be very very marginal to stop a free flow. Whether it’s the differences in a coarsely machined knob, or spring with marginal differences. Soft seats are fairly new on both units. So I’m not sure are we saying if the seat takes a set the free flow test is hit and missed.

Next I’m going to pull the complete barrel out of the working unit and try in the non working unit and see what happens. All for fun.

 

[Couv]

Flipped the crescent toward the diaphragm Shazam free flowing again.

Interesting! Please, before you disturb anything else re-flip the vane toward the mouthpiece and try again. See if the results are repeatable. If you can confirm the configuration with the crescent toward the diaphragm produces freeflow and toward the mouthpiece it does not I will accept defeat.

Dr. Rob ( @rsingler ) will be able to do his "Superior Dance." Church Lady Dance I'll leave it to him to inform SP that all of their posters are wrong.

Cheers,

Couv

 

[Open Ocean Diver]

Interesting! Please, before you disturb anything else re-flip the vane toward the mouthpiece and try again. See if the results are repeatable. If you can confirm the configuration with the crescent toward the diaphragm produces freeflow and toward the mouthpiece it does not I will accept defeat.

Dr. Rob will be able to do his "Superior Dance." Church Lady Dance I'll leave it to him to inform SP that all of their posters are wrong.

Cheers,

Couv

I did flip it twice...

 

[Open Ocean Diver]

I did flip it twice...

And the results are.... yes free flowed only with crescent facing diaphragm.

 

[rsingler]

@couv , why yes!
Of course you can buy me a beer!

 

[Couv]

@couv , why yes!
Of course you can buy me a beer!

I'll be happy to!

 

[rsingler]

So what we've been looking at here is apples and oranges. Yes, changing cracking effort can affect susceptibility to freeflow.

The three curves above (modeled after Reg Savvy) are all similar. They start at different cracking effort, but all have the same shape. And at a high enough flow rate (e.g., a bang on the purge button) some will cross over into freeflow.

The second group is measured all at the same cracking effort, so instead of stacked curves, they all start at the same point (valve opening).

Now however, the curves are differently shaped, based on how much Venturi suction is generated inside the case. With an old 109, sometimes they'd freeflow and sometimes they wouldn't, based on the shape of the welded case.
Now with identical plastic molds, the Venturi is adjusted with a sleeve or a vane. In those cases, how the vane is oriented determines freeflow, assuming optimal cracking effort.

We still haven't figured out why crescent position is better one way or another, but I'll try to diagram a possibility.

 

[rsingler]

As @Open Ocean Diver points out, this is a subtle effect. Maybe instead of @couv 's airfoil, we have something as inelegant as a barn door.
In one position, the barn door is more in the way of airflow than in the other, and causes more turbulence, less vacuum and hence no freeflow.

The vane above has a semi open side (crescent) and a flat side. Maybe it's as simple as whether the deflector is a little forward, or a little aft in the airflow.

 

[Open Ocean Diver]

Rob, look up crescent shaped airplane wings very complex beyond me but maybe you can gain some insight.

 

[buddhasummer]

So you mean some adjustment knobs have some play or irregularity? Perhaps the surface engaging the balance chamber is not exactly plane/level, and as you turn one direction, the spring load does some back and forth dynamic. And there is one position all the way out where it is actually not releasing spring pressure all the way, but screwed in a fraction it paradoxically releases spring pressure a bit?

I think so yes, you put it more eloquently than I.