How does the RT/X-valve really work?

[TAC-ELF]

Many of you have seen I've been having problems with my Tac-One. Throughout all this, I've leared a great deal about how to tune the gun (despite the problems recurring) and I wanted to thank everyone for their kind assistance.

I've been going over years of posts and am still pretty fuzzy on how the valve does what it does. For general consumption I thought I'd ask the following question in a new thread for those seeking to know the following:

How does the RT/X-valve work mechanically in the several states it can be in. Think about it this way:

• What mechnically happens when you gas up the gun?
• What happens when you pull the trigger?
• What happens when you release the trigger?
• What is the path the air follows?
• What are the high-pressure areas versus low-pressure?

Valve diagrams:

• Blow-up diagrams with part names (not just numbers)
• Diagrams (GIF animations?) which show the mechanical motion

What is the function of the on/off assembly

• How does the RT on/off differ mechanically to the ULE on/off
• What are the functions of the ULE on/off shims
• What exactly does the on/off do? It isn't obvious just looking at it.

Cheers!

[Dayspring]

1) What happens when you gas up the gun-
Involved. Will type it in later.

2) Pull the trigger-
Push the trigger into the trigger rod. Sear pivots and pushes the on/off up into the valve, sealing the flow of air into the gun. As this is happening, the front of the sear drops and the bolt is pushed foward by the air in the dump chamber. Once the bolt stem clears the oring (either level 10 or 7) the gun fires.

3) Release the trigger-
Air pressure pushes down on the on/off pin, kicking the sear down and resetting the trigger, as well as locking the bolt in place. The bolt, has already traveled back and sealed against the oring in the power tube, bounced off the bumper and is ready to fire again.

4) Air Path-
To the dump chamber & to the reg (using the pressure feedback loop to keep the reg open until the proper pressure is reached, then snapped shut.)

5)HP vs. LP areas-
Top of the on/off pin is HP. Toward the reg is HP. Everything else is regulated to roughly 450psi.


Diagrams-
Look for them. They exist.


On/off function-

RT On/off vs. the ULT

RT pin is significantly thicker than the ULT pin. Pin heads are nearly identical. Functionally, however, they operate in the same fashion.

Shims-
They alter the sealing point of the top oring. The ULT pin is ~.770" or so. On/off pins vary in length from .712-.765". This is used to tailor the pin to the gun. In effect, it's like shortening your on/off pin because you are moving the distance from the head to the oring's sealing point. The rule of thumb for the normal RT on/offs was, the shorter the pin, the more reactive the gun. (To a point, too short and it would go full auto, bouncing from the oring to the sear and back uncontrollably.)

On/off function-
It seals off the incoming air from going into the dump chamber & to the reg. If you didn't, it would gush air the entire time the bolt is forward and returning. In fact, the flow of air might not let the bolt return, depending on pressure.

Many of you have seen I've been having problems with my Tac-One. Throughout all this, I've leared a great deal about how to tune the gun (despite the problems recurring) and I wanted to thank everyone for their kind assistance.

I've been going over years of posts and am still pretty fuzzy on how the valve does what it does. For general consumption I thought I'd ask the following question in a new thread for those seeking to know the following:

How does the RT/X-valve work mechanically in the several states it can be in. Think about it this way:

• What mechnically happens when you gas up the gun?
• What happens when you pull the trigger?
• What happens when you release the trigger?
• What is the path the air follows?
• What are the high-pressure areas versus low-pressure?

Valve diagrams:

• Blow-up diagrams with part names (not just numbers)
• Diagrams (GIF animations?) which show the mechanical motion

What is the function of the on/off assembly

• How does the RT on/off differ mechanically to the ULE on/off
• What are the functions of the ULE on/off shims
• What exactly does the on/off do? It isn't obvious just looking at it.

Cheers!

[TAC-ELF]

On/off function-
It seals off the incoming air from going into the dump chamber & to the reg. If you didn't, it would gush air the entire time the bolt is forward and returning. In fact, the flow of air might not let the bolt return, depending on pressure.

Thanks, but I'm still fuzzy on how this little metal pin seals anything or changes the dynamics when you add/remove shims. The pin is always the same length, afterall. Oh, and which direction does the air flow through the on/off?

Dump chamber: None of the diagrams indicate where that is, though conceptually I know what it is -- the resting place of the correctly pressured charge of air waiting to be released to the bolt when I pull the trigger (or is it already pushing against the bolt and waiting for the bolt to be released?).

Thanks for helping me learn a little more (than most people care to I suspect) about this gun.

Yes, I'm a newb but I'm trying to learn

[sumorai]

Ok, here's another question. Why do the shims go between the spacer and the Power Tube tip? According to the image below, the spacer doesn't seem to ever move. So what are the shims spacing? What does it affect?

[sumorai]

Thanks, but I'm still fuzzy on how this little metal pin seals anything or changes the dynamics when you add/remove shims. The pin is always the same length, afterall. Oh, and which direction does the air flow through the on/off?

The pin is always the same length, yes. BUT, when you add shims you increase the length of the on/off, so there's less of the pin sticking out at the top. Since less pin is sticking out at the top, you've got less pin that's blocking the airway and my guess is that makes it easier for the air to push the pin back down.

Dump chamber: None of the diagrams indicate where that is, though conceptually I know what it is -- the resting place of the correctly pressured charge of air waiting to be released to the bolt when I pull the trigger (or is it already pushing against the bolt and waiting for the bolt to be released?).

The dump chamber is literally the chamber of space behind the Power Tube. If you look down the Power Tube, you're looking into the dump chamber.

[Dayspring]

It actually will move. They will alter how far forward or back the level 10 carrier (or level 7 spacer length & oring) will sit on the bolt. Too far back (too many shims or too long a spacer) and it will leak. Too few (or too short a spacer) and the bolt shaft won't clear the oring and won't fire.

Ok, here's another question. Why do the shims go between the spacer and the Power Tube tip? According to the image below, the spacer doesn't seem to ever move. So what are the shims spacing? What does it affect?

[Dayspring]

Shims have no effect on how light or hard the pin is moved. Pin diameter does that. All adding shims does is alter where on the oring it will seat. Too many and it won't reach the oring. Too few and it won't clear the oring when the trigger is pulled.

The pin is always the same length, yes. BUT, when you add shims you increase the length of the on/off, so there's less of the pin sticking out at the top. Since less pin is sticking out at the top, you've got less pin that's blocking the airway and my guess is that makes it easier for the air to push the pin back down.



The dump chamber is literally the chamber of space behind the Power Tube. If you look down the Power Tube, you're looking into the dump chamber.

[Dayspring]

The sideways holes on the on/off assembly are where the air flows. Air comes down from over top of the on/off. When you pull the trigger, the pin moves up and seals in the oring, stopping the air from getting into the rest of the valve. Release the trigger and the air pressure pushes the pin down, unsealing the oring, letting the air flow and resetting the trigger.

On/Off pin length & Shims- you're not altering the length of the pin, you're altering the seating point of the oring in relation to the pin. See my comment about the spacer in the powertube, the same principle applies. Too long, it won't seal. Too short, it won't unseal.

Thanks, but I'm still fuzzy on how this little metal pin seals anything or changes the dynamics when you add/remove shims. The pin is always the same length, afterall. Oh, and which direction does the air flow through the on/off?

Dump chamber: None of the diagrams indicate where that is, though conceptually I know what it is -- the resting place of the correctly pressured charge of air waiting to be released to the bolt when I pull the trigger (or is it already pushing against the bolt and waiting for the bolt to be released?).

Thanks for helping me learn a little more (than most people care to I suspect) about this gun.

Yes, I'm a newb but I'm trying to learn

[TAC-ELF]

The sideways holes on the on/off assembly are where the air flows. Air comes down from over top of the on/off. When you pull the trigger, the pin moves up and seals in the oring, stopping the air from getting into the rest of the valve. Release the trigger and the air pressure pushes the pin down, unsealing the oring, letting the air flow and resetting the trigger.

On/Off pin length & Shims- you're not altering the length of the pin, you're altering the seating point of the oring in relation to the pin. See my comment about the spacer in the powertube, the same principle applies. Too long, it won't seal. Too short, it won't unseal.

Ok, I'm getting some feel for this. So why is there allowed to be movable space on the ULE trigger on/off. Even with 5 shims, I can still move the top-half and bottom half of the on/off vertically in relation to themselves -- not much with 5 shims, but it is there. The area where the shims go then have a gap. The less number of shims, the more gap you can create between the top and bottom halves of the on/off. While I can see how this is designed (threads on the botom don't go all the way down), wouldn't this add a great deal of unpredictability into the system?

Oh, I also noticed there is a little hole on one of the heads of the ULE trigger pin. The other head doesn't have a hole. Which direction should this hole be facing? Up towards the top of the gun, or down against the sear assembly. What is its function, if any?

[sumorai]

Ok, I'm getting some feel for this. So why is there allowed to be movable space on the ULE trigger on/off. Even with 5 shims, I can still move the top-half and bottom half of the on/off vertically in relation to themselves -- not much with 5 shims, but it is there. The area where the shims go then have a gap. The less number of shims, the more gap you can create between the top and bottom halves of the on/off. While I can see how this is designed (threads on the botom don't go all the way down), wouldn't this add a great deal of unpredictability into the system?

Well, I believe that there is enough pressure on the top of the on/off, that it just presses the top part into the bottom and it doesn't move around at all.

Oh, I also noticed there is a little hole on one of the heads of the ULE trigger pin. The other head doesn't have a hole. Which direction should this hole be facing? Up towards the top of the gun, or down against the sear assembly. What is its function, if any?

I don't think that hole does anything, and on mine, it is on the bottom.