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Magstrike Firing Mechanism Autopsy


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#1 Gas Mask Guy

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Posted 10 August 2008 - 10:28 PM

Alright, way back when I first tried to get in here, it was to ask if there was a good description of how the firing mechanism of the Magstrike (and powerclip, and wildfire, and rapidfire, etc.) worked. Now I bet a lot of you here have figured it out, but the few explanations I read didn't click with me. Luckily, my second Magstrike was a dud, so I got to rip it to shreds. So here's a writeup to clarify exactly how this works.

Just so you know exactly what you're seeing later, this is where I made the cut, at the back of the whole thing. Normally, all you see of this thing is the tube that it fits in, and I cut the back wall of this tube off to look inside here.
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This is the inside of the firing mech in a state of rest. Everything is all bunched together. Note, the back of the outer tube isn't normally shoved up against the disk that holds it all in place, but it has more room to expand now.
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Here is the firing mechanism with the front section extended. That front piece with the two holes in the side actually has a spring in there that tries to push back against the plunger.
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You know that air comes in the back, but the arrow points to where this air actually enters the mechanism: a tiny little hole in the central shaft just after the plunger.
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So, now that you've seen it, here's the explanation of the firing sequence. Pic first, then step by step. DL the pic and zoom in if it's still unclear: since these things are mostly cylinders, it's kinda hard to draw, so if it's a lighter version of the same color, that means there's a hole there on one or more sides, but not all the way around. Every color represents a different piece (i.e. everything in black is the "outer tube," everything in red is the "plunger," and everything in blue is the "stopper," and each of those is all one piece). This might not be actual size, but I was pretty meticulous about the scale.
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1. At Rest: The springs are spread as far as they can, there is no pressure in the chamber, and the stopper has sealed the front, so air in will not go directly out the barrel. The air starts filling into the middle (out of that little hole in the red piece). The blue piece is flush up against a wall, so the air can only push the red piece (compressing the both springs).

2. Filling: The air has filled as far as it thinks it can go. The smaller spring is compressed as tight as it can. This means if we push the plunger back any farther, it'll take the blue piece with it. But the blue piece is...

3. POP: ...the stopper. The rubber that was sealing the front off just got pulled off the exit. Now the air is free! So it goes rushing out, around the blue piece and out the black.

4. Push: The plunger is no longer held back by the pressure. As the last of it goes out the barrel, both springs extend as fully as possible, advancing the clip and pushing all these internals back into the original position, with the exit plugged, so it can happen again and again.

And that, ladies and gents, is the layman's explanation of the Nerf air-powered rapid-fire mechanism. First post (I've done plenty of mods, but nothing you guys haven't seen, so...).

[Edit: Title change, and reworded the Push phase as per imaseoulman's insights]

Edited by Gas Mask Guy, 12 August 2008 - 01:46 PM.

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#2 Guest_DarkInfection_*

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Posted 11 August 2008 - 12:11 AM


Edited by DarkInfection, 23 June 2010 - 09:23 PM.

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#3 BendyStraw

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Posted 11 August 2008 - 12:24 AM

Thank you for making this. I've always wondered how the magstrike plunger works, and despite the fact that I have one, I didn't want to gut it just to satisfy my curiosity.
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#4 CaptainSlug

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Posted 11 August 2008 - 02:48 AM

Wasn't sure what the part arrangement was, just understood that it was basically a spring-return air cylinder that was set to exhaust at a specific regulated pressure level.

Exemplary first post.

Edited by CaptainSlug, 11 August 2008 - 02:50 AM.

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#5 imaseoulman

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Posted 11 August 2008 - 05:41 AM

Thanks for posting this. And especially, thanks for posting it so clearly and articulately. A few times I tried to explain this on here without much success, but I also never created a thread for it complete with diagrams.

I just thought I would add a little to what you said that I found to be interesting. The "push" phase makes no significant difference in the performance of the NERF blaster (as far as dart range is concerned, it's an absolutely integral part of the clip advancing mechanism). I had done some experimenting with this piece last winter and had a lot of fun. I hooked it up to my electric inflator and the flow rate was just so, so that the piston would finish the filling cycle, but not pop. Air was leaking out exactly as fast as it was coming in. But, if I slightly pulled on the back piece (where the tubing connects) it would pop and the air would rush out the front. Using this method, I could measure range without allowing the plunger to return and it made no difference when compared to allowing the piston to return to "push the air out." Because of that, I think of it simpley as a return cycle and not a push cycle (though, obviously, it is pushing the clip/turret along).

All in all, an excellent first post. Keep doing the research and experimenting and sharring what you find. And above all, think of creative ways to implement the knowledge gained in modifying!

Welcome to the Haven.
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#6 Gas Mask Guy

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Posted 12 August 2008 - 01:42 PM

Thanks for the warm welcome everyone.

The "push" phase makes no significant difference in the performance of the NERF blaster (as far as dart range is concerned, it's an absolutely integral part of the clip advancing mechanism)... I think of it simply as a return cycle and not a push cycle (though, obviously, it is pushing the clip/turret along).


I thought so! I'm not as up on my physics as I should be, but does this mean that the pressure releases and pushes the dart out faster than the spring moves forward?

The reason I tore this thing apart was for the daydream of scratchbuiling a larger version of the mechanism that would be long enough to operate a breach (such as the ones from my broken Recon and Longshot... actually, Slug was there when I broke my Longshot and the UMD indoor war) with its back-and-forth motion. When I did this Magstrike Autopsy (man, that's what I should've named this thread! I'll see if I can still edit that), I realized that the breach would not stay closed during firing, since the spring starts its backwards motion at the moment of firing. Was I right, or would the dart be out the barrel before it moves too far? A question that answers that question: is the clip barrel lined up with the mechanism's barrel before or during the clip advancement.
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#7 imaseoulman

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Posted 12 August 2008 - 02:23 PM

I thought so! I'm not as up on my physics as I should be, but does this mean that the pressure releases and pushes the dart out faster than the spring moves forward?

Yeah, the air has already left the tank/piston before the spring really gets moving, so it's moving through a near vacuum.

The reason I tore this thing apart was for the daydream of scratchbuiling a larger version of the mechanism that would be long enough to operate a breach (such as the ones from my broken Recon and Longshot... actually, Slug was there when I broke my Longshot and the UMD indoor war) with its back-and-forth motion. When I did this Magstrike Autopsy (man, that's what I should've named this thread! I'll see if I can still edit that), I realized that the breach would not stay closed during firing, since the spring starts its backwards motion at the moment of firing. Was I right, or would the dart be out the barrel before it moves too far? A question that answers that question: is the clip barrel lined up with the mechanism's barrel before or during the clip advancement.

Alright, you have to be careful with relative words like "forward" and "backward." When the MS piston/tank is fixed in the MagStrike, the piston is pushed FORWARD (relative to the MS orientation) flush with the clip. When it is flush with the clip, then it releases the air and fires the dart. (If this were not the case, air would never make it through the MS clip barrel).

However, while holding the piston in your hand, it is natural to hold to the piece that normally is pushed forward in the MS. This will make it look like the back part is being pushed backward. Keep that in mind while designing your version.

So, in your own design, there's no reason you couldn't have it set up so that when the piston is in the resting position, the breach is open and when it is pushed forward it is closed. Good luck. This will take some skilled craftmanship.
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#8 TheNerfLoki

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Posted 12 August 2008 - 05:14 PM

Nice First post!!! I have always wanted to Know how it worked, but never got around to finding out. Now I don't have to. Thanks
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#9 Draconis

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Posted 12 August 2008 - 08:28 PM

Interesting... So this explains why banding the cylinder increases range... The pressure must increase to overcome the added resistance from the bands, and when it does, all of that extra pressure exits in the same manner. I suppose the question is... How much is too much? We need to measure how much pressure is required to actuate the mechanism, then subtract a theoretical maximum safe pressure (such as the 60-70PSI the Captain Slug [also myself] runs his external tank system at), which gives us the extra amount of resistance we can add to the cylinder. I will check tonight and see if I can measure approximately how much pressure the stock mechanism requires.


UPDATE:

It appears that the cylinder requires approximately 24PSI to fully actuate. At least mine does. It does have a leaky trigger valve though, so the figure is probably not exact.

Edited by Draconis, 13 August 2008 - 03:04 PM.

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#10 Gas Mask Guy

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Posted 17 August 2008 - 09:31 PM

The sort of "cap" like part which your finger is pointing to, is that actually glued to the shaft (with the two holes in it)?

On the one I'm trying to fix, it sort of snaps on, very loosely, and it doesn't even look like there's glue residue inside. Yet I'm pretty sure it should be attached. It certainly would be easy to glue, I'd just like to confirm first.


I'm pretty sure I get what you're saying, so yes: the tube with the two holes on the side should be attached to the tip with the stopper. I can't look at the remains of the deceased right now, but it was all together when I opened the bugger up. Use something strong if you're gonna try to put it back together: everything in here looks like it gets slammed around a lot.
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#11 Lynx

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Posted 17 August 2008 - 10:07 PM

If the assembly is the same as the other automatic guns (like a WildFire) can I assume that the springs are the same?

And, if so, would it make sense to put that spring in a NiteFinder?
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#12 imaseoulman

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Posted 17 August 2008 - 10:41 PM

If the assembly is the same as the other automatic guns (like a WildFire) can I assume that the springs are the same?

And, if so, would it make sense to put that spring in a NiteFinder?

No, the springs aren't going to be the same; similar but not the same. That's like saying an AT2K and SM1.5K will have the same air tank. They're similar, but not the same. And I don't think it would make much sense to put it in a NF. It's not really the right size.
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#13 Gas Mask Guy

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Posted 18 August 2008 - 05:42 AM

If the assembly is the same as the other automatic guns (like a WildFire) can I assume that the springs are the same?

And, if so, would it make sense to put that spring in a NiteFinder?


I'm not entirely sure, as I don't have any of the other automatic guns (well, except for the Vulcan), but my gut says "probably, but why?" If you do have a spare Magstrike (which you might, since it seems they were designed to break), I say try it. I might look into this myself, since I do not plan on putting all that back together.
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#14 DflyDen

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Posted 18 August 2008 - 06:35 AM

Thanks for the excellent post. I was just wondering about the Magstrike firing mech. You must have read my mind.
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