Puncturing Co2 Carts

[arkmaker †]

Big hole, little hole? Does it matter? Since we are talking gas, once it escapes the cart and settled in the valve, I would think the size of the hole it came from would make no difference.
Just me thinking
Rich

[Crosshairs]

Big hole, little hole? Does it matter? Since we are talking gas, once it escapes the cart and settled in the valve, I would think the size of the hole it came from would make no difference.
Just me thinking
Rich

I would agree with that Rich but does it fill the valve slower with a small hole, just me trying to think.
                                  Mike

[quickster47 †]

I would agree with that Rich but does it fill the valve slower with a small hole, just me trying to think.
                                  Mike

Doesn't fill the valve any slower because it's under pressure and the shot is using gas already in the reservoir.

The 22xx valve does double duty as it acts as both a reservoir and a gateway between the powerlet and the transfer port, and ultimately the barrel with a pellet in the chamber.  The firing process is activated by the hammer striking the valve stem assembly which opens the reservoir portion of the valve to allow the metered charge of gas in the chamber to escape out the transfer port and ultimately propel the pellet.

On the other end of this arrangement is the piercing pin which will only at the limit of its travel, when the valve is fully open, close the hole in the cap of the powerlet.  The entire rest of the time as the valve is opening and closing gas is both flowing out of the valve into the transfer port and barrel, while at the same time gas is dumping out of the powerlet into the valve.  When the valve re-seals it finishes refilling from the powerlet to prepare for the next shot.

Carl

[Crosshairs]

I would think just like any liquid it would move slower with a smaller hole I know it turns to a gas but that only happens when it hits the air so you would think the small hole less volume. 

[quickster47 †]

I suppose it is possible to only puncture the powerlet cap and create a micro hole and that could inhibit flow.  You would also notice that immediately because you would have essentially no velocity to speak of.

Not sure how small is too small.  Something to investigate one of these dark and stormy winter nights in the near distant future. 

Carl

[arkmaker †]

This is one of those times that I would like to pick the brain of the engineer that designed the 22xx valve.


Is the valve system  designed to dump gas only from the valve (from tip of cart to TP) or is it designed to dump gas from the valve body and also added gas from the cart? If the latter were true, then I think a larger hole will make a difference. If not, then I do not think the hole size makes much difference, since we are taking the reaction of a liquid turning to gas and the flow of that gas would be pretty quick, I would think.


In my thinking (and I am no expert), but in my thinking, I would design the valve to hold a certain amount of gas and then for each shot to expel only that amount of gas only. This way FPS/FPE would be controlled and consistent for the life of the cart. It is accomplished by use of a known hammer weight and known hammer/valve spring and known TP opening size along with known caliber, which allows the gas to escape through the TP for a pre-determined known time. That time is calculated from the consistency of the know factors of hammer weight, spring tension and TP/barrel opening size. To me, that is the only way to determine a consistent shot to shot FPS/FPE.


If anything, I would want to have enough gas available in the valve, so that once the time factor has expired (valve stem closes) there would be a tiny bit of gas left from the starting amount, which would then be replaced from the cart for the next shot.


Of course this is talking of a stock gun. Bulk filling and modding the valve for performance brings on a whole new set of factors. Which is why we experiment with Boss Valves, TP size, grinding valve stems, polishing internals, heavier and lighter springs, etc.....


Again, just thinking and typing. Does any of it make sense? Who knows, but like I said, I sure would like to talk to the original designer and hear first hand how he thought it should all work.


Rich

[Crosshairs]

All true but remember it's the the liquid going through the hole not the gas so if that's true then a small hole would let less liquid out. 
This is a good one for picking our brains.
                   Mike

[arkmaker †]

All true but remember it's the the liquid going through the hole not the gas so if that's true then a small hole would let less liquid out. 
This is a good one for picking our brains.
                   Mike

No, I don't think it is liquid going through the cart hole but gas. Remember, the cart itself is only partially filled with liquid and a portion of it is space which becomes gas immediatly, so the flow from cart to valve would be gas, not liquid.
Rich

[quickster47 †]

At 70 degrees F, CO2 obtains a gas pressure of 852.8 psi when confined in a vessel. If there is more CO2 in the vessel, it will be have to be in liquid form. So, the state of CO2 in a pressure vessel, such as a powerlet at room temperature, is a pressurized gas above a liquid. If the gas is released, such as through the operation of an airgun valve, some of the remaining liquid flashes to gas until the pressure is equalized for that temperature.

It's important to understand that CO2 pressure is determined by temperature, not by mechanical compression. If you were to compress gaseous CO2 by mechanical means, it would turn into liquid when the right pressure was reached.  The pressure in a 12-gram powerlet remains constant until all the liquid is gone. A powerlet has the same internal pressure as a 10-oz. bulk CO2 tank when both are at the same temperature. Therefore, CO2 guns do not lose velocity as you shoot them until all the liquid is gone and they start to run out of gas.

Also, keep in mind that CO2 is a refrigerant gas. That means it cools when it expands by flashing from liquid to gas. Therefore, when you shoot a CO2 gun rapidly, the gas will cool the gun parts considerably. Because CO2 pressure is based on temperature, the pressure in a CO2 gun will drop if a series of shots are fired in rapid succession. In practical testing, I've seen velocities decrease by more than 100 fps over a long string of shots. That will affect where the pellet strikes the target unless it's very close to the shooter. So, if you want to shoot accurately with a CO2 gun, do not shoot rapid-fire. With a target pistol, I like to allow at least 15 seconds between shots so the gun's temperature can cycle back to where it was before the shot. But, if you're just plinking, you can shoot faster than that.

Carl

[Gareth]

In the movie "Where Eagles Dare", Major Smith (Richard Burton) said,  "A hole is a hole is a hole, as they say". 
I've noticed this seeming anomaly with some of the CO2 cartridges I've used. But, unless the seal was not entirely punctured, performance has always appeared to be the same.

[BDS]

JEBert's comments were on a 1377, not a 22XX gun...

I'm with the "crushed" seal or a seal that has taken a "set" and is now shaped like the co2 cap

[Baltim0re28]

JEBert's comments were on a 1377, not a 22XX gun...

I'm with the "crushed" seal or a seal that has taken a "set" and is now shaped like the co2 cap

It was actually that I had the trigger over travel screw in too far where the trigger wasn't fully letting the seer move away from the hammer. The seer was dragging the on the hammer and wasn't striking as hard as it should which was making it not puncture the c02 cart all the way. I'm thinking the seer dragging like that was also the reason that it seemed my fps had dropped because I was shooting low from where I had previously sighted my scope. After I fixed the problem and went back out to shoot, I was now hitting high from re sighting the scope for the lost power from before.

[mr007s]

By golly, wheres Ed when ya need him?

[Crosshairs]

By golly, wheres Ed when ya need him?

LOL I have to stick to my guns, small hole less big hole more.
                                     Mike

[JEBert]

I was indeed talking about the sear drag on my hammer in a 1377 gun causing the valve not not release more than 6 pumps when I had the over-travel screw adjusted too tight.  I would think that it would have the effect of not holding the valve open as long in a 22XX gun the same as it did in my 1377 in addition to not piercing as big of a hole in the cart in a 22XX gun.
Cheers,