Pressure-Compensating and Balanced regs

[AzrealDarkmoonZ]

The PI is fully balanced?

Az

[nicad]

I have not had much time to test the Pi. So far, it seems about par with an old Stabilizer I have had around forever. I would guess it should recharge faster, but have not really had the time to pay with it.


Yes it is fully balanced. Input pressure has no directional force effect on the seat pin.

[UTDragun]

"Pressure-Compensating reg" and "Balanced reg" are both terms for the same thing.

In a reg, you want a high as possible ratio (which can be either inverse or direct, depending on the reg design), but you also want a large as possible reg seat so that it will recharge as fast as possible with minimal seat movement ("fast response"). The larger the reg seat, the lower the ratio or the larger the reg body has to be to maintain a higher ratio.

In theory balanced pin regs do not have a ratio (or it is oo:1), so you can have as large a reg seat as you want and not have to worry about the other parameters.
Typically, however, most "balanced" regs are still slightly un-balanced-- they use the "partially-balance" compensation to help fight for a high ratio AND large reg seat.

The Evolve Pi is a 100% balanced reg.
The 2Liter is a partially-balanced reg.

so the ratio shows the rate at which the pressure changes over the course of emptying a tank, but how would you measure consistentcy of the output during high rates of fire?

so which tank reg would you reccomend then? I have 04 conquest, max-flo and a apoc2k. Conquest needs a rebuild, max-flo doesnt work, and the apoc needs a rebuild and i cant find parts for it

[Ydna]

I was skeptical about the Pi balanced reg before it came out. I had thought about a similar setup but was worried about there being no lift on the piston. But they made it work well using design factors that they traditionally employ on their other stuff, it's a worthy system.

[AzrealDarkmoonZ]

Doesn't the PI use the adjustable reg seat type system, though in this case a stem with orings, Ion regs, CPs, and Sidewinders have used other adjustable reg seat options?

Which should make them immune to input pressure changes but is that the same as balanced?

Az

[Ydna]

The general shape is the same except it doesn't use a "seat", rather a balanced piston (two o-rings of the same size aroudn the input port). So when the air is shut off the piston will only be moving in one direction due to the output air, and the input has no bearing on it in either state.

Here's a model I made http://www.zdspb.com/media/tech/regs_pi.JPG

Like nicad said just about any other reg is technically unbalanced in some direction, but it's small enough that it can be chalked up as a marketing statement...

[AzrealDarkmoonZ]

Input pressure should have no change to a sidewinder regulator either though? Correct? The unbalancing comes from the small pin in most regulators that has air behind it so has the input lowers generally the output increases, whereas in a adjustable regseat that should be a problem since the only force the piston is acting against is the washers/springs in the regulator and it just seals against a reg seat, stem with orings, ect.

Whereas a 2liter's piston is not balanced against the input pressure but the output pressure thus the pin is balanced between pushing the spring and the output pressure.

Hrmmm, or does the PI stem float inside the piston? I did not take the one I had apart while I was testing it.

Az

[Ydna]

On a sidewinder the air won't make much difference if the reg seat is fully broken-in, when the piston is closed. The only surface area that would effect any change would be anything with an upward bias....the bottom of the piston is curved so it'll be exposed if the seat isn't deformed to accept it, but once it is it'll be negledable.

http://www.zdspb.com/media/tech/regs_sidewinder.JPG

For the sake of babling I'd not hesitate to mention even a reg that isn't broken in won't make much difference either. Same thing goes for most other moving base regs...for instance an Ion regulator will always have a small bias upward on the piston when the seal is shut off, but it's only as big as the area made by the input port in the bottom (difference of about 1 pound of upward force per 100 psi input pressure). Compare that to the nearly 300 pounds of downward force on top of the piston (when reg set to 160-psi output) that balances out with the spring.

[AzrealDarkmoonZ]

Just to throw out some more random babbling

The Pi Reg did exceptionally well when I was sent a prototype a while back. So much so that it rivalled the 2liter. I was impressed. And the few gripes I had, such as the adjustment screw being some insanely small easy to strip size have now been fixed.

http://www.ppog.org/results.htm

Az