X-valve reactive trigger technical question and idea…

[MoeMag]

Okay, in the past week or so I have noticed that some believe that there is a positive correlation between having a shorter on/off pin and having a lower P.S.I. input pressure to make the gun go reactive. My pin is a standard r/t .750-inch pin, and I require about 1100 P.S.I. to get around 20 cps reactive fire. Another guy “butterfingers” alluded to the fact that he is running a .712-inch on/off pin from an old e-mag, with a 650psi input to get his reactive fire.

Now my question…
Being that the longer pins do indeed fire the gun as effectively as the shorter ones in a normal input pressure range (850psi), that tells me that the actual length of the pin is not the factor contributing to this increased reactivity. Instead the decrease in the reciprocating mass of the pins seem to be the culprit. Is this correct?

To try and figure this out I went and found an approximate density for stainless steel (what I think the pin is made of, please correct me if I am wrong) that is about .286861 pounds per cubic inch. Well I figured the volumes of the .750 and .712 pins as being 0.004194 cu in, and 0.004003 cu in, respectively. From that and the density I figured the mass of the .750 and .712 pins as weighing .001203 pounds and .001148 pounds. This is only a change of .000055 pounds! Can this change really cause a decrease of necessary reactivity input pressure by 450psi!!!

And my idea...
If I am right so far (which I doubt), someone should make a .750-inch titanium on/off. The density of good tool grade titanium (6AL-4VELI) is about 56% of that of the stainless steel. Thus making a decrease in mass compared to that of the .712 pin of .000466 pounds! (I know pounds are not a unit of mass but g is constant everywhere paintball is played :D ). That would result in a very low minimum reactive input pressure, and with the added benefit of being the longer length would mean that it would have less distance to travel for each shot. In all I think that if this mod was made and used with my 1100 P.S.I. input the reactiveness could go really insane and maybe break the 60cps mark! Imagine a paintball gun that cycles as fast as a/c electricity. Unfortunately this would also mean that the trigger pull weight would possibly increase by 178.5%. I think I heard that the r/t trigger has a 5-pound pull weight; this would make it nearly 14 pounds!

Well what does anyone think?

[Coralis]

Ouch my head hurts

[MoeMag]

I said it was a “technical question” ;)

Edit:
besides I messed up on the #'s. will have fixed in a few mins.

Edit of the Edit:
...okay fixed now, perhaps it will make more sense now!

[Dayspring]

Length of the pin is important because it determines where the pin will seat against the on/off orings.

[SniperSmurf]

Dang Moe, got a little time on your hands? ;)

Less mass would certainly be nice, but as Dayspring said... length matters (no matter what the girls tell you) :D

Off topic, but I'll be moving back to Tempe in the near future. Maybe I'll see you around? I need to go catch up on the AZ AO posts...

[MoeMag]

Luckily as far as the ladies are concerned x-valve pins are not men, because shorter is better in their case. ;)
So does anyone have a good x-valve schematic I can look at? All I have is an old r/t schematic… I know everyone says the r/t is the same, well it isn’t… Enough so that I cannot make an intelligent inquiry or decision as to why the length matters. Does is there a better explanation than “where the pin will seat against the on/off orings” or is that it?

Check out my AZ-AO thread… but there isn’t too much interest so far.

[PumpPlayer]

Having a shorter on/off pin increases your "reactivity" because the on/off seals so close (in sear travel distance) to the point of bolt release. The reactive force isn't any greater, but the distance the sear assembly needs to move to fire off the next shot decreases.

As you pull the trigger, the the on/off is first sealed and then the bolt is released. As you release the trigger, the sear catches the bolt before it opens the on/off. The closer the two events are, the less the sear need to travel, the less the trigger needs to travel and, of course, the less your finger needs to travel. It doesn't change anything about the firing sequence except make it easier for you to achieve rapid-fire.


Jacking up the input pressure also makes it easier to achieve rapid-fire because it increases the reactive force. That means you have a wider window of trigger pull force that will give you rapid-fire. Even with ultra high input pressure, too little or too much squeeze on the trigger and it won't rapid-fire, will it?



The on/off pin length sets your trigger travel distance between shots in rapid-fire.
The input pressure determines the window of necessary maintained pull weight when in rapid-fire.

Either one can make it easier to achieve rapid-fire.

[MoeMag]

Ahhh, Thank you. “The on/off seals so close (in sear travel distance) to the point of bolt release” Makes sense now.

I figured it had to be something else because a 2% of a gram change in mass really could not make that much of a diffrence. But then again I am not used to calculating things operating at 4500psi, so I thought I would ask.

The Ti pin would make for a stronger reactive trigger still, and increase rapid fire performance a little bit but not as drastically as I had hoped.

Oooh… On the other hand increasing the mass of the pin would result in a decrease of trigger pull weight (Of course the pull weight could not be less than the weight of the pin).

Anyone have any thoughts (maybe even some math)about pin mass affecting the trigger pull weight?

What is the air pressure on the on/off pin?

[Dayspring]

In a classic valve- 450psi

In an Xvalve- whatever the tank output pressure is. So figure anywhere from 600-1200psi.

Classic valve- the on/off pin gets regulated air.
Xvalve- get un-regulated air.

[Butterfingers]

A titanium pin wont do squat. Just take some of your time and make your wallet lighter. The mass is insignificant. A lighter pin will do nothing to effect trigger pull weight.

Mathmatically the RT function can be broken down into this formula.

Where:

A1= Area of the On/off pin top
A2= Area of the On/off pin shaft
P1= input pressure (assuming constant supply)
P2= chamber pressure.
S1= Sear shear force
F1= A1 x P1
F2= A2 x P2

Pull force= A2 x P2 + S1
Return force= (A1 x P1) + (A2 x P2)

The differential force is the diffrence between the return force and the pull force= (A1 x P1) because the other factors (A2x P2) cancel. S1 is a one way force and must be overcome by A1 x P1 for reactivity to occour.

Your goal is to maximize either A1 or P1 to acheive reactivity. A1 is pretty much constant with the on off pin top diameter. P1 must be consistent. If your airsystem has a slow recovery time or drops off P1 will decrease dramatically thus reducing the RT effect.

Of course this is a very simplified formula. There are minute little details that also need to be accounted for. The second most important thing is sear realease and On/off top sealing points.

In the begining of your trigger pull you are overcoming S1 as well as on/off shaft pressure F2. When the sear relases you are now only overcoming F2. The on/off top then seals the pin and input pressure forces the pin back down (F1). On the return stroke, when the pin disengages the on/off top o-ring you loose F1 pressure and you revert to F2 pressure with a reduction in accompanying return force.

The goal of the shorter on/off pin is to make a sweetspot easy to acheive by reducing the distance between the release of the bolt and the On/off top sealing.



A third factor is on off pin shaft diameter. This factor does cancel out but it is more of a physyological factor. The smaller the shaft diameter the lower the inital pull force. However it cancels out mathmatically because that pull force also pushes back. So mechanically it has no effect. However physyologically it does. In the human body your musles are more sensitive to change and have more dexterity at lower forces and is better able to regulate lower pull forces than higher pull forces. Thus you will be able to acheive sweetspot easier.

This has to do with the combined muscular recruitment theory which I wont go into.


The most important thing that effects reactivity is your airsystem first and foremost. I have found AA systems to be THE best for acheiving reactivity.

Your gun wont work with a .712 pin unless you have an E-mag quad 0-ring like I do. The shortest you can go with the normal urethane 0-ring is about .740 +/- 0.005. Depending on your tolerances.

You also want to have Level 10 tuned correctly with the appropriate spring because that will take load off the initial shear action of the sear.

Shorter is not always better if you go too short your gun will just leak down the barrel and go nuts the first time you pull the trigger.

[FlawleZ]

A titanium pin wont do squat. Just take some of your time and make your wallet lighter. The mass is insignificant. A lighter pin will do nothing to effect trigger pull weight.

Mathmatically the RT function can be broken down into this formula.

Where:

A1= Area of the On/off pin top
A2= Area of the On/off pin shaft
P1= input pressure (assuming constant supply)
P2= chamber pressure.
S1= Sear shear force
F1= A1 x P1
F2= A2 x P2

Pull force= A2 x P2 + S1
Return force= (A1 x P1) + (A2 x P2)

The differential force is the diffrence between the return force and the pull force= (A1 x P1) because the other factors (A2x P2) cancel. S1 is a one way force and must be overcome by A1 x P1 for reactivity to occour.

Your goal is to maximize either A1 or P1 to acheive reactivity. A1 is pretty much constant with the on off pin top diameter. P1 must be consistent. If your airsystem has a slow recovery time or drops off P1 will decrease dramatically thus reducing the RT effect.

Of course this is a very simplified formula. There are minute little details that also need to be accounted for. The second most important thing is sear realease and On/off top sealing points.

In the begining of your trigger pull you are overcoming S1 as well as on/off shaft pressure F2. When the sear relases you are now only overcoming F2. The on/off top then seals the pin and input pressure forces the pin back down (F1). On the return stroke, when the pin disengages the on/off top o-ring you loose F1 pressure and you revert to F2 pressure with a reduction in accompanying return force.

The goal of the shorter on/off pin is to make a sweetspot easy to acheive by reducing the distance between the release of the bolt and the On/off top sealing.



A third factor is on off pin shaft diameter. This factor does cancel out but it is more of a physyological factor. The smaller the shaft diameter the lower the inital pull force. However it cancels out mathmatically because that pull force also pushes back. So mechanically it has no effect. However physyoloically it does. In the human body your musles are more sensitive to change and have more dexterity at lower forces and is better able to regulate lower pull forces than higher pull forces. Thus you will be able to acheive sweetspot easier.

This has to do with the combined muscular recruitment theory which I wont go into.


The most important thing that effects reactivity is your airsystem first and foremost. I have found AA systems to be THE best for acheiving reactivity.

Your gun wont work with a .712 pin unless you have an E-mag quad 0-ring like I do. The shortest you can go with the normal urethane 0-ring is about .740 +/- 0.005. Depending on your tolerances.

You also want to have Level 10 tuned correctly with the appropriate spring because that will take load off the initial shear action of the sear.

Shorter is not always better if you go too short your gun will just leak down the barrel and go nuts the first time you pull the trigger.

Very informative. Thanks!

[MoeMag]

Awesome,
I was hoping I would get your attention.
How did you learn all that!? You have to be an engineer or something.
Thanks for taking the time to set my mind to rest about this flight of fancy.

[REDRT]

Okay, in the past week or so I have noticed that some believe that there is a positive correlation between having a shorter on/off pin and having a lower P.S.I. input pressure to make the gun go reactive. My pin is a standard r/t .750-inch pin, and I require about 1100 P.S.I. to get around 20 cps reactive fire. Another guy “butterfingers” alluded to the fact that he is running a .712-inch on/off pin from an old e-mag, with a 650psi input to get his reactive fire.

Now my question…
Being that the longer pins do indeed fire the gun as effectively as the shorter ones in a normal input pressure range (850psi), that tells me that the actual length of the pin is not the factor contributing to this increased reactivity. Instead the decrease in the reciprocating mass of the pins seem to be the culprit. Is this correct?



Sound almost like the time the ULT idea was concieved. A much lighter pin in the ULT.

[SniperSmurf]

Sound almost like the time the ULT idea was concieved. A much lighter pin in the ULT.
Except the ULT kills reactivity, so there goes that theory!

[REDRT]

Except the ULT kills reactivity, so there goes that theory!

Well maybe not. The Ult has a diffent on/off housing/Oring set up. Put a light pin in a stock on?off housing/Oring set up and it might have better reactivity. After all, No shims in the ULT and it has more bounce than with them. I think the Idea has merit.

[athomas]

The problem the ULT has is the smaller top diameter lowers the return force too much. The mass of the sear assembly is a constant and is quite large on the mag. The smaller return force reduces the acceleration of the sear and the combined with the lower pull force required, minimises any differences between pull and return forces, which is what actually causes the rt effect. ( ie; the mass of the sear assembly has more of an effect on the rt effect as the forces acting on it become lower.)

You want to experiment, try making the sear lighter. That will give you more rt effect with any pin.

[Dayspring]

Actually, the oring setup isn't all that different at all. You have a top oring that it will seal against, and an oring within the assembly to seal the pin itself. No different.

The reason behind the lightned pull is the same principle behind the Level 10. Stepped piston. There's reduced force on the smaller diameter piston. That's why your pull weight is that light. The problem also is on the return force side, in that you have that smaller diameter pushing on the sear assembly.



Well maybe not. The Ult has a diffent on/off housing/Oring set up. Put a light pin in a stock on?off housing/Oring set up and it might have better reactivity. After all, No shims in the ULT and it has more bounce than with them. I think the Idea has merit.