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My Spring Chamber Modification


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#1 taiden

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Posted 06 January 2011 - 03:53 PM

Hey all, I apologize if this has already been talked about on here. Still, it may add some fuel to the fire in all of your minds for some modifications you are thinking about making to your NERF guns. I just want to point out that I have been waiting a few months to post this, due to the wait for new accounts. I just want to tell the moderators that I'm sure you have your reasons for this wait, but if I hadn't come across my notes today I wouldn't have bothered to post this because of that waiting period.

Here goes

This is my first post on Nerf Haven and I hope that someone will find it useful.

I stopped modding nerf guns in 2005, I just lost interest. I had a 4 barrel AT2k and a singled AT2k, that was all I needed. I am in college now, and a few of my friends decided to go buy nerf guns just for the heck of it. This sparked my interest in modded nerfs again, and I came on this forum to do some research. Of the current line of guns the Nite Finder seemed like a good starting point. I had never worked with a springer before, it was cheap, and it seemed easy enough to mod.

After performing a CPVC barrel mod, AR removal, double o ring mod and 7/8 x 4 x 0.080 cut spring swap, I was seeing good improvements. I especially loved how you can vacuum load a dart with a springer, while my old AT2k required a ramrod (I didn't have a pvc coupler on it).

I was finding however that if I vacuum loaded a dart and then shot it very soon after the range suffered significantly. I thought about this issue and found a solution.

Let's begin. I apologize in advance if I am too verbose.

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This is the basic dart, barrel, cylinder and plunger model. Note the double o ring mod. Without it, this writeup is completely irrelevant.

On the left is our stefan, which is loaded inside our barrel, which is eventually stopped from being sucked into the cylinder by some wire. Then we have the sealed plunger and cocking shaft inside the cylinder.

This is the way it was set up BEFORE I addressed the issue.


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When you vacuum load the dart, the dart will reach it's furthest point before the cocker is in the fully back position.


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This causes a significant vacuum inside the cylinder/chamber due to the fact that your stefan is well fit to your barrel and sealed, and your double o ring mod and lubrication choice is also sealed.

If you sit and wait half a minute (approx) all the air will be sucked around the dart and the pressure inside the chamber will reach equilibrium with atmospheric pressure. If you fire it before this half minute is over, your range will suffer.



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THE FIX:

I found the plungers position in the fully cocked state and drilled a very small hole right before it. It will be known in this writeup as the 'pressure release hole.'


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Here is a picture showing the pressure release hole.


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Your dart vacuum loads just like before because the system is completely sealed.


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Vacuum occurs for 90% of the plungers range of motion.


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Then as soon as your plunger is in the fully cocked back state, the hole is introduced to the system and the pressure inside is quickly back to atmospheric pressure. The vacuum is lost in a split second!


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When the gun is fired, the plunger passes over the pressure release hole before any significant pressure is built up. The system is quickly sealed and the dart fires just as if it has been loaded down the end with a ramrod.


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Finally, the dart is fired out the barrel, which is all we are aiming to do anyway. It is fired with consistency.

The time from vacuum to equilibrium within the chamber is reduced from 15-30 seconds to less than a second. I have found that this is extremely useful with tight fitting darts. I have increased my range with nerf micros by 10+ feet after this mod. The quicker you shoot after loading the more this will help you.

Edited by taiden, 06 January 2011 - 03:54 PM.

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#2 roboman

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Posted 06 January 2011 - 04:31 PM

Not a bad idea, but you could just cock your gun before you load a dart. This wouldn't allow you to vacuum-load, but couplers are more reliable, at least, in my experience.

Edited by roboman, 06 January 2011 - 04:37 PM.

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#3 utahnerf

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Posted 06 January 2011 - 06:43 PM

I feel that you may lose a few feet from your range because of the hole. Also, make sure that the hole's edges are sanded down, so the o-rings don't get caught on it and tear/fray.

Edited by utahnerf, 06 January 2011 - 06:43 PM.

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#4 roboman

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Posted 06 January 2011 - 06:59 PM

But (in my opinion anyway) doubling up the o-rings in a NF loses far more to friction than it gains from sealing.


I agree with Bob on this one. I've never had any luck with doubling the O-rings on NFs. I usually ended up decreasing the ranges, probably due to friction.
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#5 Blue

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Posted 06 January 2011 - 08:39 PM

But (in my opinion anyway) doubling up the o-rings in a NF loses far more to friction than it gains from sealing.


I agree with Bob on this one. I've never had any luck with doubling the O-rings on NFs. I usually ended up decreasing the ranges, probably due to friction.


I have had great success doubling up the O-rings on my Nfs. Danco #14 or a smaller sized O-ring to push up the stock one works well.
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#6 shmmee

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Posted 06 January 2011 - 11:33 PM

I've noticed the same issue when i did a barrel replacement on my sharpshooter I pistol. It is a skirt seal, but i filled some of the inner void with toilet tank gasket foam to flare the edges out and regain some lost contact. I found a significant range drop with vacuum loaded darts fired quickly after loading (as much as 15+'). Though there may be some debate about single O rings vs double O rings, I think theirs validity in the theory being shared. I had considered adding a vent hole, but was scared to screw up the first pistol i ever owned. Is this a working, proven model or just a concept? I still worry about dragging a sealing edge across a gap and tearing. Granted skirt seals are less rugged than O rings (hornet trigger valves bridge 6 gaps as the trigger is pulled), they are also harder to replace.
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#7 Inferno Falcon

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Posted 07 January 2011 - 02:50 PM

I believe the u3 already does something similar to solve the "air gulp" issue.

I can't find a link right now, but they essentially did the same thing.
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#8 roboman

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Posted 07 January 2011 - 07:11 PM

I can't find a link right now, but they essentially did the same thing.


I can.
It's not a detailed writeup or anything, but it basically functions like a pump head, if you've ever seen one and thought about how they work.
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#9 Daniel Beaver

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Posted 07 January 2011 - 07:33 PM

OP: Should work, especially if the hole was small and right near the end of the plunger stroke. I can't imagine it would have a significant effect on ranges. This is a very simple solution to an annoying problem.

I would probably prefer an in-plungerhead check valve, since there is no vacuum effect during stroke.


But (in my opinion anyway) doubling up the o-rings in a NF loses far more to friction than it gains from sealing.

I will back up this statement. I spent the better part of a year doubling up the o-rings on nitefinders, only to realize the frictional losses were killing my ranges somewhat. A perfect seal is worth striving for, but never at the expense of frictional losses (which have a far greater effect than many give credit).

I have had great success doubling up the O-rings on my Nfs. Danco #14 or a smaller sized O-ring to push up the stock one works well.

I can't comment on that particular o-ring, but there certainly exists some sweet spot where you minimize friction while maintaining a seal.

Edited by Daniel Beaver, 07 January 2011 - 07:36 PM.

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#10 windtex1

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Posted 07 January 2011 - 07:52 PM

Taiden,that looks interesting and simple at the same time. However, having a hole that the o-ring "scratches" by would most likely tear up the o-ring. Especially if you have a tight-fitting o-ring for a good seal. Overall, I hope this works and I will most likely use it if it does. That is a good idea, but for now, the check-skirt by Kane is winning.
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#11 taiden

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Posted 11 January 2011 - 02:07 PM

Hey all,

I'm glad this has sparked some debate. Let me just say that this isn't a theory, this is a tested approach along with disassembly afterwards to check the condition of the o-rings. You will want to bevel the drilled hole somehow to stop the oring from being scratched. You will not lose range because if you place the hole in the correct place, the hole will be covered before any pressure builds up inside the chamber. On top of that, if you size the hole correctly (small guys, very small), the small cross section of the hole won't allow much air to escape at all when the chamber is being pressurized, yet it will allow for the vacuum to disappear.

I hope this clears it up. I suggest that you try this, but really think about the mod when you do it. If you place the hole too far forward in the barrel you will get a loss in distance for sure. You want it as close as possible to the plunger in the cocked position.

As for 1 vs 2 o-rings, I found that 1 o-ring was more consistent because it allowed the vacuum to bleed off. I found 2 o rings to fire further if the dart was loaded with a ramrod. With this mod you get the power and suction of the 2 orings without the consistency issues.

Loading with a ramrod for a weapon like the Nite Finder is in my opinion, not an option. Vacuum loading is fast, easy, and effective. With this modification it removes all the consistency and range problems.

Please understand, this method is useless if you don't vacuum load your darts.

Hope this helps,
Luke

Edited by taiden, 11 January 2011 - 02:09 PM.

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#12 taiden

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Posted 11 January 2011 - 02:15 PM

Also as far as doubling up the orings goes, I found that using a smaller oring to push the stock oring forward and hold it in place works best. You don't gain friction, and the seal begins sooner when you fire it. I'm not going to explain it, just look at the internals and imagine how everything moves and you'll see what I mean. Works better than single and double of the same size in my experience.

Also, I'm sure there's a huge lubricant debate and after trying all sorts of stuff I settled on a small packet of ID Glide. Yes, it does look like it has multiple uses! :P

Edited by taiden, 11 January 2011 - 02:15 PM.

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