Tuning Larger calibers seem much more efficient?

[explorer]

Anyways, its great to see for me this brainstorming and to get to know im not the only one who is trying to have scientific way of thinking regarding the airguns. The above mentioned stuff and messing with barrel volume I dont think its a good to go. I think the projectile surface and barrel length should get managed as two separate variables as the projectile diameter/surface is not going to make any "trouble" with the calculation if reaching some extreme not as the barrel length which at very low length is lowering the efficiency significantly and at very high length when there is no or very low pressure slowing down the projectile, etc.
@Stubbers For me it looks that you are trying to get some universal formula for this but I dont really think it is possible due to thermodynamics and rifle differences in (valve,port,etc) solutions.
But guys, we know that higher cal are more efficient if we need a lot of energy and also know why. EZPZ.
But have you anybody thinked about projectile efficiency how to get as high bc as possible with as low pressure as possible?
I mean, regarding my calculations and researches higher calibers are having often higher BC compared to smaller ones at the same or very similiar cross section density and similiar shape and/or form factor. But why the hell if the BC is given by density and form factor?

 

[Stubbers]

Anyways, its great to see for me this brainstorming and to get to know im not the only one who is trying to have scientific way of thinking regarding the airguns. The above mentioned stuff and messing with barrel volume I dont think its a good to go. I think the projectile surface and barrel length should get managed as two separate variables as the projectile diameter/surface is not going to make any "trouble" with the calculation if reaching some extreme not as the barrel length which at very low length is lowering the efficiency significantly and at very high length when there is no or very low pressure slowing down the projectile, etc.
@Stubbers For me it looks that you are trying to get some universal formula for this but I dont really think it is possible due to thermodynamics and rifle differences in (valve,port,etc) solutions.
But guys, we know that higher cal are more efficient if we need a lot of energy and also know why. EZPZ.
But have you anybody thinked about projectile efficiency how to get as high bc as possible with as low pressure as possible?
I mean, regarding my calculations and researches higher calibers are having often higher BC compared to smaller ones at the same or very similiar cross section density and similiar shape and/or form factor. But why the hell if the BC is given by density and form factor?

I am not trying to get a universal formula, OP was, and I concluded its not easily possible outside the one I provided in its simplest form imo, and if anyone does come across one better and more precise, I'll slow clap for their accomplishment. (its possible but very complex)

I could come up with one (probably requiring lots of sweat), but its not my drive/goal, all the variables are easy to consider and wrap up with a pretty bow in some form of mathematical expression. To refine the calculation you'd need so much data about the gun, that its basically given at that point to know its capable efficiency, because you know everything about the gun, my current spreadsheet already does this, but its not simple at all.

-Matt

 

[weevil]

Im not sure, if this approximation is right. Okay if we are talking about pressure assisted valve like RTIs it can be a mess like this but in a case of normal valve i think the plenum pressure is much more dominating the valve speed and/or opening depth than the barrel/port pressure.

it’s not an approximation, it’s physics. Pressure is relative. If you really want to test it, run a shot count shooting pellets vs. dry firing.

 

[explorer]

it’s not an approximation, it’s physics. Pressure is relative. If you really want to test it, run a shot count shooting pellets vs. dry firing.

Yeah physics but by what reason the non pressure assisted valve is closing faster without pellet than with?
I dont want to test it but understand it

 

[Stubbers]

Yeah physics but by what reason the non pressure assisted valve is closing faster without pellet than with?
I dont want to test it but understand it

Non pressure assisted valve? Does this mean conventional poppet valve or pressure relief valve such as balance valve or pilot valve?

The larger the load/parcel (pellet mass) the faster the valve will close, or the lighter the load/parcel (no pellet or very light pellet) will result in slower closing valve due to less back pressure...a heavy enough projectile in the bore and you will have a valve that won't even want to open very far at all...

This is why you'll emit a lot more air in a dry fire than you will if you fire a heavy pellet...or light pellet vs heavy pellet, less resistance in the barrel = more air into the barrel given the same hammer strike. Any valve that defies this would shoot lighter pellets more efficiently...

-Matt

 

[explorer]

Non pressure assisted valve? Does this mean conventional poppet valve or pressure relief valve such as balance valve or pilot valve?

The larger the load/parcel (pellet mass) the faster the valve will close, or the lighter the load/parcel (no pellet or very light pellet) will result in slower closing valve due to less back pressure...a heavy enough projectile in the bore and you will have a valve that won't even want to open very far at all...

This is why you'll emit a lot more air in a dry fire than you will if you fire a heavy pellet...or light pellet vs heavy pellet, less resistance in the barrel = more air into the barrel given the same hammer strike.

-Matt

Non pressure assisted valve? Does this mean conventional poppet valve or pressure relief valve such as balance valve or pilot valve?
Indeed
Maybe im missunderstanding but he told "With the lighter projectile, the differential needed to close the valve is arrived at in a shorter time, hence less air is used in spite of having the same hammer strike."
So he is telling the oposite, that with dryfire we are using les air and however i never tested but i also think the dryfire is using less of the air. Isnt it?

 

[explorer]

Non pressure assisted valve? Does this mean conventional poppet valve or pressure relief valve such as balance valve or pilot valve?
Indeed
Maybe im missunderstanding but he told "With the lighter projectile, the differential needed to close the valve is arrived at in a shorter time, hence less air is used in spite of having the same hammer strike."
So he is telling the oposite, that with dryfire we are using les air and however i never tested but i also think the dryfire is using less of the air. Isnt it?

Now after a short thinking i think @weevil is correct. And indeed, its because of the pressure differential. The lighter pellet "goes away" sooner and not making so high chamber pressure as the heavy pellet. Higher chamber pressure=less pressure difference=longer valve opening.

 

[Stubbers]

Non pressure assisted valve? Does this mean conventional poppet valve or pressure relief valve such as balance valve or pilot valve?
Indeed
Maybe im missunderstanding but he told "With the lighter projectile, the differential needed to close the valve is arrived at in a shorter time, hence less air is used in spite of having the same hammer strike."
So he is telling the oposite, that with dryfire we are using les air and however i never tested but i also think the dryfire is using less of the air. Isnt it?

Incorrect, if you leave the gun unchanged and dry fire from 3000 down to 2000 psi, you will get less shots than if you fire with a pellet from 3000 to 2000 psi, this is confirmed, likewise the heavier pellet you go the more shots you'll obtain in that same range...

-Matt

 

[Motorhead]

Yeah physics but by what reason the non pressure assisted valve is closing faster without pellet than with?
I dont want to test it but understand it

Sail effect most likely modeling your above statement.
When the HP air does little to actually pressurize the transfer path being there is no Cork ( pellet ) in place, the air flow past poppet head is at a higher velocity threw the system looking for a way out. Air passing around the poppet head DRAGS it back to seat faster than it does when there is pressure within throat/transfer stalling flow for a small period of time.
* There is always some poppet sail effect in non assisted systems. The air has no choice but to flow AROUND the poppet head & it just increases with velocity.

 

[Stubbers]

Sail effect most likely modeling your above statement.
When the HP air does little to actually pressurize the transfer path being there is no Cork ( pellet ) in place, the air flow past poppet head is at a higher velocity threw the system looking for a way out. Air passing around the poppet head DRAGS it back to seat faster than it does when there is pressure within throat/transfer stalling flow for a small period of time.
* There is always some poppet sail effect in non assisted systems. The air has no choice but to flow AROUND the poppet head & it just increases with velocity.

If this were the case lighter pellets would be more efficient than heavy, its simply not the case in any valve that I am aware of....

Drag on the poppet doesn't change when you change pellet weight to 0, 1gr, or 20gr....

And if drag IS going by the poppet faster (more air flow) on the no pellet scenario, well you just proved me right that its less efficient, letting more air by, its dwell/duration however is not less or "closing faster", dry fires don't 'snap' closed, anyone with 2 sets of ears knows they're obnoxiously loud...if they snapped shut the pressure gradient would result in less pressure at the end of the shot cycle, simple physics. "faster closing" = less muzzle report due to Lagrange.

Simple resistance.

 

[explorer]

Sail effect most likely modeling your above statement.
When the HP air does little to actually pressurize the transfer path being there is no Cork ( pellet ) in place, the air flow past poppet head is at a higher velocity threw the system looking for a way out. Air passing around the poppet head DRAGS it back to seat faster than it does when there is pressure within throat/transfer stalling flow for a small period of time.
* There is always some poppet sail effect in non assisted systems. The air has no choice but to flow AROUND the poppet head & it just increases with velocity.

The sail effect also can help to it but personally (without any evidence) think its more because of the pressure differential.
Just remarking that for the sail effect we need fast airflow but in this kind of high pressure system when you remove the wall between a 100bar and 0bar chamber the flowing air next of the valve also has a pressure. You need to think about the high pressure air as about something between gas and liquid.
If you open the valve quickly and depending on design of course you have a big valve enough without after restriction (lower cross section than valve itself) the air passing the valve has a pressure for example 50 bars and expanding to 0bar after the valve in the port. This i modelled with flow simulation software.

 

[Motorhead]

If this were the case lighter pellets would be more efficient than heavy, its simply not the case in any valve that I am aware of....

Drag on the poppet doesn't change when you change pellet weight to 0, 1gr, or 20gr....

And if drag IS going by the poppet faster (more air flow) on the no pellet scenario, well you just proved me right that its less efficient, letting more air by, its duration however is not faster, dry fires don't 'snap' closed, anyone with 2 sets of ears knows they're obnoxiously loud...if they snapped shut the pressure gradient would result in less pressure at the end of the shot cycle, simple physics. "faster" = less muzzle report due to Lagrange.

MATT .. if only you read the first BOLD part of statement. Was not agreeing, just expanding Sail effect.

Nothing said of "total" DWELL, only that the flow around poppet head. And am going to agree absolutely that system uses more air shot empty than with a pellet. Why .. because the air flowing around poppet head keeps the poppet off the seat longer and more total air exits.

Taken a look at another way ... If & when a pellet is in place & throat actually gets pressurized, the opposing size to seat will get its area pressurized and for a moment counter the pressure coming threw the seat side. ( minus area of stem & poppet spring ) Which in turn will speed up the speed poppet returns to seat.
Now whats not being talked about here is "Total" dwell of the open / close cycle and that is another conversation entirely.

You want to have a conversation about valves & air flow ... IT ALL needs to be dissected into sub cause & effects before a general blanket statement of It works like this because

 

[Stubbers]

MATT .. if only you read the first BOLD part of statement

I read that, and responded directly that the sail effect DOES NOT CHANGE BASED ON PELLET WEIGHT, resistance does...most importantly Lagrange.

Explain how the sail effect or drag on a poppet changes based on pellet weight? I can provide the logic, reasoning and formula's as to why no projectile and lighter projectiles are less efficient simply due more air escaping in near equal or longer dwell. If it were any other way the Pressure Gradient going down the barrel would be much LESS on lighter projectiles or NO projectile which would result in a MUCH quieter muzzle report, this is simply not the case. Dry fire a gun that is typically 'mouse fart quiet' at 12 fpe shooting 10 gr for example, and it will be LOUD, why? If it shut faster it should be quieter?

 

[Stubbers]

If the sail effect were enough to close poppet valves effectively all by it's lonesome, the simple balance valve wouldn't need proper venting...the Cothran valve wouldn't be known to blow open until the throat pressure drops...they aren't less susceptible to 'sail' effect unless you're shielding it...

-Matt

 

[Stubbers]

What happens if you plug the transfer port (immovable object) and try to fire? Nothing...

Resistance

-Matt

 

[Motorhead]

I'm going to bow out ....

Not worth it.

 

[Stubbers]

I'm going to bow out ....

Not worth it.

"Not worth it" - Motorhead


Simple question and you bow out? What happens when you plug the transfer port, you can do it very easily on marauders...takes a whole 30 seconds to test.

How about if I do shield the SAIL EFFECT that you suggest closes dry fires faster in a typical poppet valve (like a cobra valve...), why does it dry fire the same way as an non shielded poppet Scott? I love to learn, and am here to if you are up to the task, however based on your reasoning the cobra valve should close much slower with lighter pellets and or dry fire with the absence of sail effect...

(I know some people are more hard headed than others, stubborn and unwilling to learn new concepts or ideas, but trust me I am willing and receptive!)

-Matt

 

[explorer]

because the air flowing around poppet head keeps the poppet off the seat longer and more total air exits
Im not sure if the effect does something but if do its definietly the opposite, the flowing gas between two surfaces creating lower pressure, blow air into the inside of paper V (between two pieces of paper)
@Stubbers Explain how the sail effect or drag on a poppet changes based on pellet weight?
As with pellet weight the flow is changing also the sail effect needs to change but as most probably this effect is not even noticable the change is also not doing a much.
Dry fire a gun that is typically 'mouse fart quiet' at 12 fpe shooting 10 gr for example, and it will be LOUD, why? If it shut faster it should be quieter?
I think too this one is because of the intensity of the air releasing gradient. If you release slowly the air from a baloon its not loud but if it blows its loud but the released energy is the same. Same stuff why the fast train tunnel exits are not straight vertical.
Anyways, unfortunately today i had no opportunity to try it but i really believe that in some cases (rifle/valve types) the dryfire is less air consuming than the fire with projectile. I have never tryied to measure but i have memories that a time ago on one of my rifles (there was some) during the de-gasing i experienced that the pressure was droping slower than with pellet. Remember this only because it was getting me annoyed. Maybe this one i think depends on the "balance" (design) ?

 

[Stubbers]

because the air flowing around poppet head keeps the poppet off the seat longer and more total air exits
Im not sure if the effect does something but if do its definietly the opposite, the flowing gas between two surfaces creating lower pressure, blow air into the inside of paper V (between two pieces of paper)
@Stubbers Explain how the sail effect or drag on a poppet changes based on pellet weight?
As with pellet weight the flow is changing also the sail effect needs to change but as most probably this effect is not even noticable the change is also not doing a much.
Dry fire a gun that is typically 'mouse fart quiet' at 12 fpe shooting 10 gr for example, and it will be LOUD, why? If it shut faster it should be quieter?
I think too this one is because of the intensity of the air releasing gradient. If you release slowly the air from a baloon its not loud but if it blows its loud but the released energy is the same. Same stuff why the fast train tunnel exits are not straight vertical.
Anyways, unfortunately today i had no opportunity to try it but i really believe that in some cases (rifle/valve types) the dryfire is less air consuming than the fire with projectile. I have never tryied to measure but i have memories that a time ago on one of my rifles (there was some) during the de-gasing i experienced that the pressure was droping slower than with pellet. Remember this only because it was getting me annoyed. Maybe this one i think depends on the "balance" (design) ?

View attachment 377578

Feel free to test shot count within an identical pressure range and hammer strike with and without a pellet (heavier pellet is better to show the disparity in the test, ie: test with 14.3 gr or less in .22 would carry disparity than a 18.13 or 25.4 gr due to the pellet/air weight ratio). However I have no doubt the dry fire shot count will be less than the heavier pellet shot count, at least it was undoubtedly so in my tests with both a conventional (unbalanced) valve, and balanced valve.

-Matt

 

[explorer]

Feel free to test shot count within an identical pressure range and hammer strike with and without a pellet (heavier pellet is better to show the disparity in the test, ie: test with 14.3 gr or less in .22 would carry disparity than a 18.13 or 25.4 gr due to the pellet/air weight ratio). However I have no doubt the dry fire shot count will be less than the heavier pellet shot count, at least it was undoubtedly so in my tests with both a conventional (unbalanced) valve, and balanced valve.

-Matt

Im gonna definietly try it asap as i will have the opportunity. But what you mean with "balanced valve"? Just because till now i heard this expression only in marketing bullpoops and still have no idea what the balanced valve is.