Results 1 to 18 of 18

Thread: Why does an Emag require a shorter on/off pin?

  1. #1
    Join Date
    Jun 2006
    Location
    NE Ohio
    Posts
    3,489

    Why does an Emag require a shorter on/off pin?

    Is it because the quad-ring can seal sooner than a round o'ring?
    Does the Emag require more reactivity?

    What happens if a regular length RT pin (.750") is used.

    Can you use a .712" pin in a mech mag?
    Last edited by Pneumagger; 05-09-2015 at 04:28 PM.

  2. #2
    Join Date
    Oct 2001
    Location
    New Jersey
    Posts
    1,385
    I believe that a .750 pin is the only one NOT to work in an Emag. Think tuna said that, but it was a while ago.

    For a Emag/X/ReTro valves, it doesn't matter except for the minimum length. As i think you can go too short & the gun will just run away.

    As for the why, what you suggest could be it. The quad oring would seal earlier at the edges of it, instead of at the center or near the center of the oring.

  3. #3
    Join Date
    Feb 2005
    Location
    Nome Alaska
    Posts
    8,242
    Emag pin is SHORTER.. and that is to compensate for the quad oring which is supposed to make the pull easier for the solenoid to trip the gun.

    Longer pins will slow the cycle rate down or even stop it. Same with any mag if the pin is too long. A short pin in a non emag gun will increase the RT effect. How much is dependent on input pressure and the rest of the variables of the marker.
    [img]http://home.comcast.net/~ineedspeednow/BEOSig.jpg[/img] [QUOTE=Nobody;2878169]This is not me. I have nothing to do with this, but i aprove of it.[/QUOTE]

  4. #4
    aren't the emag pins .712 in length as standard?

  5. #5
    Join Date
    Dec 2000
    Location
    offshore
    Posts
    7,360
    Quote Originally Posted by vintage View Post
    aren't the emag pins .712 in length as standard?
    Yes. But the older emag valves below serial # 1000 were .728
    Email me for low prices on ALL AGD Products and more. tunaman5@verizon.net
    Tunamart

  6. #6
    Join Date
    Jun 2006
    Location
    NE Ohio
    Posts
    3,489
    EDIT: yeah, I mean SHORTER... not sure why I wrote "longer" - lol.

    I'm more interested in they 'why' though - so I can predict and understand changes I make to some (limited quantity) one-off parts I got. I've got a couple of my mega reactive on/off assemblies and I had a couple tests I want to try at different pressures (especially 1000+ psi). All my pins are .750ish but I think emag with hybrid would be pretty kickass on super RT so I might have to grind one down. I also want to try a spring-loaded sear rod idea in a mech mag (like a mini car strut). I'm thinking I can the mega RT to push back on the spring and bounce the trigger for you - just pull down and hold on tight, haha. It's got an extra-large pin head diameter and smaller lower pin diameter. It's like a ULT on/off and Chernobyl-RT on/off had a baby, LOL.

    It worked alright on a regular AM/MM valve 2 years ago but I never tried an RT/X valve, much less an emag.

    ULT assembly back-left, AM/MM assembly back-center, Super-RT back-right.
    Super RT pin lower-left, regular RT pin lower-right. (Mega RT pin required a single Quad ring... metric IIRC)


  7. #7
    Join Date
    Jan 2002
    Location
    Halifax, N.S., Canada
    Posts
    7,628
    I think your mega RT pin setup for the classic valve is a great idea. I was going to do that a while ago and just didn't have the time. In the retro/emag valve, I would think it would be hard to control, but fun to play with. It would be super reactive, thats for sure.

    Why do the different pin lengths have the effect they do? It has a lot to do with the mass of the sear assembly.

    The emag can't use a 0.750" pin because of the quad oring placing the sealing surface farther down in the assembly. With the full length pin and lower sealing surface, the pin never clears the oring to let air flow.

    It also has a harder time with longer pins that do allow the on-off to be opened when the sear is fully rotated forward. This is primarily due to the mass of the sear. The inertia is quite large because of the extra metal on the sear and the large plunger on the solenoid which is connected to the sear. It takes more time to accelerate it from a dead stop and move it any given distance. To shorten the time before air actually started to flow, AGD shortened the pin so that it opened sooner, even though the sear itself was rotated just far enough forward to reliably catch the bolt. The sear could continue its rotation while the chamber was filling. Under normal pressure conditions of 800 to 850 psi, most emags can only reliably shoot at about 20bps because of this slower on-off opening and recharge. The same emag valve with a retro sear assembly can reliably shoot 26bps. Using higher bottle regulator outputs, both bps rates can be increased because the acceleration on the on-off pin is increased, but the rate for the emag setup will always be less than that of the retro setup.

    The mass of the sear assembly is the same reason that the ULT doesn't work for the emag setup. The smaller head of the ULT reduces the amount of acceleration on the sear assembly so that it takes too long to reset. It also doesn't have enough momentum to properly finish resetting once the top of the on-off clears the oring. The smaller diameter of the lower part of the pin is too small to provide enough force to overcome the additional friction of the plunger to finish the job either. It might work in some setups, but not reliably enough in most.
    Except for the Automag in front, its usually the man behind the equipment that counts.

  8. #8
    Join Date
    Feb 2005
    Location
    Nome Alaska
    Posts
    8,242
    Paging Menace.....

  9. #9
    Join Date
    Jun 2006
    Location
    NE Ohio
    Posts
    3,489
    The Mega RT (MRT) on/off worked OK in the AM/MM setup.

    There is a reactivity increase you can feel, but it's not that significant like one would expect based on the math. Based on the pin diameter ratios alone, the numbers say the MRT + AM/MM valve should have nearly an 8X RT effect (which would be in the same ballpark of an X-Valve at 1200psi, lol) but it's not even close to that. It felt more like a regular X-Valve that was very underpressured. I think it's pretty much due to the flow limitations of the AIR regulator. If the AIR Reg could hit the on/off top with the full 425psi operating pressure, then you'd probably feel the expected RT ratio, but it just can't.

    Now, the Xvalve does have flow limitations too... so the forces and RT Ratios in this chart are more of theoretical maximums based off static pressures (ignoring dynamic flow losses). So will a MRT in an X-Valve have a 12:1 RT Ratio? No. But comparing the RT Ratios to each other should be very valid regardless of real world flow inefficiency. So it should be reasonable to expect the MRT to perform with about 3X more reactivity in any situation versus a standard RTP on/off. In fact, to equal the MRT @ 850psi reactivity ratio, an RTP would need about a 2000psi input.

    One interesting thing to note is that the ULT has an impressive RT Ratio, but the actual forces are so low that the quantitative increase in return force is still dwarfed by an RTP on/off. For example, at 850psi the ULT has about a 10.1 RT Ratio (compared t0 the RTP's 5.2) but the return force is only an increase of 50oz vs the RTP's 120oz increase in force. Again, the oz force figures are theoretical max, but whatever they actually are, the RTP's is well over 2X the real trigger return force.

    Needless to say, I'm super excited to try this in an X-Valve and get it working.

    Numbers:
    MRT Stuff.png

  10. #10
    Join Date
    Jan 2002
    Location
    Halifax, N.S., Canada
    Posts
    7,628

    Thumbs up

    Quote Originally Posted by Pneumagger View Post
    The Mega RT (MRT) on/off worked OK in the AM/MM setup.

    There is a reactivity increase you can feel, but it's not that significant like one would expect based on the math. Based on the pin diameter ratios alone, the numbers say the MRT + AM/MM valve should have nearly an 8X RT effect (which would be in the same ballpark of an X-Valve at 1200psi, lol) but it's not even close to that. It felt more like a regular X-Valve that was very underpressured. I think it's pretty much due to the flow limitations of the AIR regulator. If the AIR Reg could hit the on/off top with the full 425psi operating pressure, then you'd probably feel the expected RT ratio, but it just can't.
    I think you are right on the flow limitations of the AIR valve. If you could provide a reservoir of available air at the regulated pressure, I think you would see a result closer to your theoretical numbers.

    Quote Originally Posted by Pneumagger View Post
    Now, the Xvalve does have flow limitations too... so the forces and RT Ratios in this chart are more of theoretical maximums based off static pressures (ignoring dynamic flow losses). So will a MRT in an X-Valve have a 12:1 RT Ratio? No. But comparing the RT Ratios to each other should be very valid regardless of real world flow inefficiency. So it should be reasonable to expect the MRT to perform with about 3X more reactivity in any situation versus a standard RTP on/off. In fact, to equal the MRT @ 850psi reactivity ratio, an RTP would need about a 2000psi input.
    In all cases, the sear inertia has an effect on the overall reactive effect as well and has a significant effect on the force felt at the trigger. One can probably come up with a number that can be used in the calculation for its effect, though. We often ignore it, but for accuracy, it should be calculated and used for more accurate trigger force calculations.

    Quote Originally Posted by Pneumagger View Post
    One interesting thing to note is that the ULT has an impressive RT Ratio, but the actual forces are so low that the quantitative increase in return force is still dwarfed by an RTP on/off. For example, at 850psi the ULT has about a 10.1 RT Ratio (compared t0 the RTP's 5.2) but the return force is only an increase of 50oz vs the RTP's 120oz increase in force. Again, the oz force figures are theoretical max, but whatever they actually are, the RTP's is well over 2X the real trigger return force.
    The ULT forces are really affected by the sear inertia, even more than the retro on-offs because the sear inertia becomes a larger percentage of the system effecting the force. Even as the higher pressure hits the large part of the pin, a significantly larger percentage of the force is absorbed by the sear, which reduces the actual increase in force at the trigger even more.

    Keep it going. This is good stuff.

  11. #11
    Join Date
    Jun 2006
    Location
    NE Ohio
    Posts
    3,489
    Yeah, now that I think about it, the sear effect is probably a greater component than flow restrictions or even orings combined.

    It's pretty much going to be it's rotational moment of inertia (resistance to acceleration) integrated over the time/distance it takes to travel it's arc. Basically, calculate the acceleration happening and work out the MOI for the rotational mass and you've got the force it takes from the RT system (F=MA, although you probably want to use polar equations calculation... which I can't seem to remember off the top of my head at the moment). The emag sear not only has a bigger sear, but that big honkin magnet hanging as far as it possibly can from the sear... so even though it's not way heavier than a regular sear assembly, it's MOI is quite a bit higher because of the radial distance of that magnet thing.

  12. #12
    Pneumagger,

    We seem to have the AGD version of the Newton/Leibniz calculus thing going on, and there is much to discuss. I pmed you way back, but didn't hear back for ages. Here comes another.

    Stand by.

  13. #13
    Join Date
    Oct 2004
    Location
    Daniel Island, SC
    Posts
    1,613
    Quote Originally Posted by Pneumagger View Post
    It's pretty much going to be it's rotational moment of inertia (resistance to acceleration) integrated over the time/distance it takes to travel it's arc. Basically, calculate the acceleration happening and work out the MOI for the rotational mass and you've got the force it takes from the RT system (F=MA, although you probably want to use polar equations calculation... which I can't seem to remember off the top of my head at the moment). The emag sear not only has a bigger sear, but that big honkin magnet hanging as far as it possibly can from the sear... so even though it's not way heavier than a regular sear assembly, it's MOI is quite a bit higher because of the radial distance of that magnet thing.
    i absolutely hate rotational velocity and acceleration. but sounds like your on to something.

  14. #14
    Join Date
    Oct 2006
    Location
    Houston, TX
    Posts
    3,264
    There's probably a few new ways available to make a light weight custom sear now that were not practical for the original automag.

    If you really wanted to drop that weight, that is.

  15. #15
    Join Date
    Jan 2002
    Location
    Halifax, N.S., Canada
    Posts
    7,628
    Quote Originally Posted by Spider-TW View Post
    There's probably a few new ways available to make a light weight custom sear now that were not practical for the original automag.

    If you really wanted to drop that weight, that is.
    In a regular mag, you could cut a few holes in the sear itself, to reduce the metal. It wouldn't affect the strength of the sear. The emag sear could have the same metal removed, and you could change the solenoid to a lighter one if you used a ULT or ULT type on-off. With a lighter sear assembly, a ULT would probably work for the emag.

    In both cases, the sear and trigger would be much more responsive.

  16. #16
    Join Date
    Jun 2006
    Location
    NE Ohio
    Posts
    3,489
    Or you could use an on/off that pushes back with 3X more force
    My ghetto on/off be like, "what sear?"

  17. #17
    Join Date
    Sep 2004
    Location
    time to make a slurpee!
    Posts
    1,694
    My guess is to make the valve more reactive to aid in resetting the trigger due to the extra mass of the larger heaver sear and plunger. They do not automatically reset. The on/off does that task.
    ......You know you want one!!

  18. #18
    Join Date
    Oct 2006
    Location
    Houston, TX
    Posts
    3,264
    On the original topic, you just need the measurements. The stock pin was .750; the stock o-ring is right around 0.070. Instead of sealing at the middle, you are down about .035 to the lower lip, which would put you at .715. The main change is that it is about 0.008 shorter from the seal, if you give it a few in thickness on the contact area. Not much either way.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •