[Spitlebug]

Originally Posted by y0da900

I'd rather have a ginormous dump chamber that I could drop inserts in to tune than too small a one and wish I could cram an extra 50psi in there to reduce shootdown issues without it shooting hot or being wasteful.

^^ This, but at least for initial prototyping...

[desertT1]

Spools aren't my thing, but I still 'get' them. Can somebody explain the difference between metered and non?

[Spitlebug]

Originally Posted by desertT1

Spools aren't my thing, but I still 'get' them. Can somebody explain the difference between metered and non?

Metered spool has a main air shutoff during the firing sequence so that only the same volume of air is used per shot.

A 'Mag is a prime example of this, as is an ION.

[desertT1]

Perfect, thanks. So there are some spools that rely on solenoid dwell to control firing volume? Seems silly when you have other options.

I modeled up a spool idea that I had a few weeks ago and metering is something I was focused on without even knowing it :p

[Spitlebug]

Originally Posted by desertT1

Perfect, thanks. So there are some spools that rely on solenoid dwell to control firing volume? Seems silly when you have other options.

I modeled up a spool idea that I had a few weeks ago and metering is something I was focused on without even knowing it :p

Yes, a stock Shocker SFT for example and a G3/G4, SLG etc...

[y0da900]

Ions are not metered with the stock bolt, but there are upgraded, third party, and modified bolts that are. Matrix family guns are metered as well.

I think you meant PMR bug, SLG only cares about dwell to catch the sear.

[Spitlebug]

Originally Posted by y0da900

Ions are not metered with the stock bolt, but there are upgraded, third party, and modified bolts that are. Matrix family guns are metered as well.

I think you meant PMR bug, SLG only cares about dwell to catch the sear.

Yes, I was referring to two O-ring ION bolts.

The SLG is NOT metered. The dwell does refer to the clapper noid operation, but the bolt is returned by back pressure from a small hole in the bolt. Without this hole the marker would just dump air all day long.

The PMR is metered.

[y0da900]

Not metered, but it operates on a dynamic mechanical dwell which is very different than the other systems that rely on electronically controlled dwell.

You're right, the PMR is metered, I don't know why I kept thinking it wasn't.

[desertT1]

Is the pressure:dump volume linear? You have 200 psi for .5 cubic inches, so if you have .25 cubic inches you will need around 400 psi?

[y0da900]

For a comparison of stored energy for our purposes, yes. There is actually compressibility because atmospheric air is not an ideal gas, but that can be largely ignored.

As far as energy useful to the gun, it is not a linear relationship most of the time.

[desertT1]

Hmm. I just did a little playing with the model and I can only squeeze out .09ci for now. Not good. It's literally right behind the ball though, sommaybe I can tweak sizes to get more volume.

[rjones1213]

This thread makes me want an ion so I could make it closed bolt.
Closed bolt and 105psi I don't care what marker it is in, sounds like fun.

[Spitlebug]

IONs are great project markers.

[y0da900]

Cheap, easy to work with, and nobody cries when you kill one with fire - or machine tools.

[Spitlebug]

Originally Posted by y0da900

Cheap, easy to work with, and nobody cries when you kill one with fire - or machine tools.

FIRE!!!!!


That makes me happy.

[pbjosh]

I will catch up with BfA here and take a look at his kit here soon, since we have plans to get a beer here soon. If I get my garage finished, I might even get him setup and take some video. I will get energy calcs for you guys. But no, the flow path is far more important then the dump chamber size, up to a certain point.

1) In most systems I have built the last 50psi in an 'unmetered' or not cut off dump chamber gun doesn't really affect velocity. I noticed this from several energy calculations I did before I cycled any of my prototype guns vs their pressure needed to cycle. It is wasted air, not helping the velocity.

2) Air path is more important to being efficient then volume, but the lower the air pressure the more likely a bad airpath is to be a factor in the effect.

3) Total of energy usage can often be figured if you include the volume of air of the bolt, valve and dump chamber in most guns if you include 8-12" of barrel and multiplying it by 50psi. Total energy for and Old School Shocker, a Cocker, a mag, new shocker, the Shiva, a spyder, Ion can all be figured this way. Take total volume (bolt, valve, body, dump chamber, barrel) multiply by 50, and you have about the right amount of in*lbs of energy.

4) Most guns dump the entire valve chamber. Metered or not. And small retainment of about 50psi normally doesn't effect velocity. It is wasted none the less. Only systems that through timing or mechanical means (AKA valve design, for example) that retain this air are ones that will have better efficency.

So, in BfA's gun, if the air path is clean, I have no doubt it will totally ruin my calculations in some manner or form. In addition, with a small (.25") clean airpath in the original Shiva I was only using 165in*lbs of energy per shot on a sub 200psi gun. In the SPI bolt I have for the Ion and Epiphany the energy usage is even lower, and I think the BfA gun has a larger port, allowing similar ratings with airpath design, it just depends on the gun suffering the lost 50 psi I have in previous designs of mine.

Guess I have to have a beer with Bob next week, eh?

[jonotwist]

Originally Posted by Spitlebug

Y
The SLG is NOT metered. The dwell does refer to the clapper noid operation, but the bolt is returned by back pressure from a small hole in the bolt. Without this hole the marker would just dump air all day long.

i pretty sure its metered, its just that without the sear catching the bolt it will continue to cycle in full auto. either way others have probably said this lol

[bobfromaccounting]

port = .58 doesn't get much better then that with a "conventional bolt" configuration.

[pbjosh]

Bob:

You busy Wednesday? If not, Wednesday next week-

Josh

[Spitlebug]

Originally Posted by jonotwist

i pretty sure its metered, its just that without the sear catching the bolt it will continue to cycle in full auto. either way others have probably said this lol

That doesn't make it metered. Metered would be the air source blocked during firing cycle.

[Leafy]

Yes yoda, working on it. I'll have tubing so I can make a mech setup without leaks although even with leaks I got an absurd efficiency number which I wont post because I kind of forgot what it was.