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Old 11-30-2012, 12:04 PM #1
JoshC90
 
 
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PM8 lurker eigenring, metal top hat mod?

Ive heard that lurkers bolt ring is basically like a alloy version of the top hat mod. So ive got a few questions....

Has anyone actually installed this on there pm8?

What kind of efficiency increase can i expect/did you notice personally?

Will i need to re-tune after?


Thanks nation
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Old 11-30-2012, 12:33 PM #2
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I couldn't get mine to work properly for some reason, but I did end up selling my PM8 shortly after acquiring the Eigenring.

Many users report increases of several hundred shots in their Matrixes, including PbN's very own msonic.
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Old 11-30-2012, 02:29 PM #3
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Quote:
Originally Posted by JoshC90 View Post
Ive heard that lurkers bolt ring is basically a alloy version of the top hat mod. So ive got a few questions....

Has anyone actually installed this on there pm8?

What kind of efficiency increase can i expect/did you notice personally?

Will i need to re-tune after?


Thanks nation
It's not an alloy version of the top hat mod... basically, what it does is as the HP chamber is being dumped, the air between the e-ring and the top hat is pushing the e-ring towards the back of the bolt (because there is a pressure differential) and because of that pushing motion it keeps the dump chamber at a higher pressure longer.

It should allow you to turn down your dwell a bit, and it might allow you to turn down the HPR a bit.

The top hat mod fills volume in the bolt, so it holds less air, but you have to turn up the HPR to get the same shot speed. Because the higher pressure chamber puts out more force, faster then a non top hat modded bolt, it is able to speed up the paintball faster and use less air to do it... so you get a more efficient shot.
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Old 11-30-2012, 11:00 PM #4
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I understand the idea behind the eigenring, but I'm not really convinced by it's function. With no ring in place, the air volume that would normally be behind it still exists and still exerts a force on the air in front of it as it tries to expand. And in fact the air volume behind the ring is smaller than the volume occupied by the eigenring and spacer o-rings, and moving the ring itself slows the rate of expansion of this air. By the time the eigenring accelerates, the pressure would have already dropped significantly, so I don't see how the ring would maintain high chamber pressure. And because the eigenring doesn't seal against the tophat on the forward stroke, it can't really be called a variable volume chamber. Once the ring reaches the stop, whatever remaining pressure exists behind it would be capable of venting from under the ring. And as for the recoil cancelling, the momentum of the eigenring is insignificant compared to the momentum of the paintball and gas moving down the barrel or the bolt moving within the gun.

If someone would like to correct any of that please do. I've not tested one of Lurker's, and I don't want to discourage people from buying his products, but I made basically the same thing a while ago out of delrin and could not tell any difference in efficiency over a tophat mod of the same volume given proper tuning.
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Old 11-30-2012, 11:18 PM #5
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What is delaying the Eigenring from accelerating? It's low friction, and you have a huge impulse from the valve.

It is not supposed to seal, it works on restriction. SOME air blows under the ring, yes, but it's a lower flowrate than the valve, thus, actuation. The valve chamber is dumping much, much faster than the air escaping from behind the ring - that's where the net forces come from.

The air volume swept is larger than the static air volume - The 3 orings don't even have half the volume occupied per length they delimit.


Also, it doesn't work with no seal in delrin, and you have top pay close attention to the leakby area. I got very, very lucky to stumble on to the effect, thanks to msonic, really. But I'm quite sure at this point that it does work.
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Old 12-01-2012, 12:46 AM #6
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Quote:
Originally Posted by Lurker27 View Post
What is delaying the Eigenring from accelerating? It's low friction, and you have a huge impulse from the valve.

It is not supposed to seal, it works on restriction. SOME air blows under the ring, yes, but it's a lower flowrate than the valve, thus, actuation. The valve chamber is dumping much, much faster than the air escaping from behind the ring - that's where the net forces come from.
I know it's not supposed to seal, and the restriction will cause a pressure differential and move the ring. But the differential has to overcome friction and accelerate the ring's mass. Granted this is all occuring in a few milliseconds. In my mind though, by this point the air is moving through the bolt at a higher velocity than the ring travels and the rate of expansion of the gas in the chamber is higher than the rate of expansion behind the ring. (I haven't pulled out my fluid dynamics textbook for this, no equations or data so I could be wrong, just an educated guess.)

It's easier for air to push air than it is for air to push a metal ring. I feel like the work being done by the air behind the ring is simply to move the ring, and wouldn't really do much to maintain pressure on the rest of the air in the chamber.

Quote:
Originally Posted by Lurker27 View Post
The air volume swept is larger than the static air volume - The 3 orings don't even have half the volume occupied per length they delimit.
The o-rings themselves take up less volume, but the total volume of the o-rings and the eigenring look to be greater than the volume of air contained behind the ring. I will say that 3 spacer o-rings does seem to be an appropriate ratio of volume behind the ring compared to the stroke of the ring, given the pressure range you would be using. But this just means it will be efficient in cycling the ring, it doesn't prove or disprove anything of the ring's affect on the air used to propel the ball.

Quote:
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Also, it doesn't work with no seal in delrin, and you have top pay close attention to the leakby area. I got very, very lucky to stumble on to the effect, thanks to msonic, really. But I'm quite sure at this point that it does work.
Well I haven't tried one in aluminum, not sure what difference it would make other than delrin possibly creating a sort of light seal against the stop. I may pick up one of yours to play with one of these days. I'm sure you've spent more time thinking about it than I have. It's just that normally with paintball marker designs and upgrade/modification designs (including your other products) I can picture exactly how it works. The eigenring idea makes sense, but I can't quite picture it working in my mind, and haven't been able to replicate the results to prove it. Wish I had a lexan test tube and a super high speed camera.

I apologize if it seems like I'm calling you out and I apologize for paragraph bombing this thread. My brain is a little fried from navigating wiring diagrams all day. As always feel free to correct anything I said or PM me.
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Old 12-01-2012, 02:44 PM #7
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I don't mind, it's a very touchy thing. Trust me, I didn't trust what was going on - the original eigenring was fully sealed with a HEAVY spring behind it.

http://ogrestrength.com/EigenringMusings.pdf

Note here that the key is really the ratio of the 2 volumes (swept and contained). This defines how the ring will move.

The forces that would lag the ring (and it must lag a little for any work to be done).

I think the key sentence there was that you feel the air trapped behind the ball (assume on the timescale of a shot the flow under/past the ring is negligible) is doing no work on the chamber air - but how can this be? where else would the energy go?

I think of it as like a discrete time steps thing - the ring lags a little bit, then moves to equilibrate, then lags some more. At each catch up step it is imparting some energy back into the chamber. If you try to think of the whole translation as a single process it's hard to see how it would work.


You can do the math to see across what dP in the chamber you are distributing this energy "recovery". I do think there are secondary effects in valve opening and drop off based on fuse bolts being forward biased.
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Old 12-01-2012, 04:59 PM #8
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Quote:
Originally Posted by Lurker27 View Post
I think the key sentence there was that you feel the air trapped behind the ball (assume on the timescale of a shot the flow under/past the ring is negligible) is doing no work on the chamber air - but how can this be? where else would the energy go?
It's not really that it's doing no work, but assuming the ring was not there, that same volume of air would be pushing out in all directions (as any compressed fluid does.) Once the valve opens, would the air not be pushing the air in front of it in the same manner that the ring would be? Only the air would not have to also expend energy to move the ring. Because it must first move the ring, I would think the initial force it applies on the air in front of it would be reduced (though it would apply force over a longer period, since the air behind the ring would expand slower)

Strictly from a physics 101 energy perspective, you have X potential energy stored in a compressed gas of a pressure P and volume V, the volume of the air that would be contained behind the ring. Assume you have a tophat mod in an example without the ring, which occupies the same amount of chamber volume as the ring and spacer o-rings, so that P and V (and consequently X) values are equal for both examples.

Without the ring in place, 100% of that X value is expended to accelerate the air and paintball, increasing the kinetic energy (not actually 100%, there is still friction applied to air etc, but an insignificant amount for this example.)

With the ring in place, some amount of that X value is transformed to heat energy in the form of friction on the ring (still not a lot, but much higher than the friction of the air) and a portion of the X value is also converted to kinetic energy of the ring, which is then transferred to the marker when the ring hits the stop, etc. So given a constant pressure and volume, less total energy is delivered to the paintball.

Now all of this energy loss may be insignificant, but I'm still lost as to how exactly the process benefits from the ring. I admit that I haven't considered the forward bias of the bolt, or really the bolt motion in general, I've just looked at it as opening and closing of a valve.

Last edited by speedy2k4 : 12-01-2012 at 05:06 PM.
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Old 12-01-2012, 05:40 PM #9
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I have msonic's Minion7 that Castro mentioned. I've since put the DM11 Billy wing kit in it, but I kept the Eigenring. My dwell has been lowered a little bit, and the marker has always been quite air efficient for Matrix.


If you want to re-tune, http://www.lurkerpb.com/manuals/dmmanual.pdf
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Old 12-01-2012, 06:05 PM #10
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I totally agree with you, there will be some SMALL energy loss, and the area under the energy curve is actually a bit less.

However, the expansion is chasing the ball, and so the shape of the discharge curve is going to be different - the main chamber of air will get some of the energy from behind the ring back as keeping the pressure higher than it would otherwise be. (Agreed?)

This changes the shape of the pulse and, because the valve is of a given geometry, the mass flow through the valve is higher while the chamber pressure is higher. In addition, there's more force on the front of the bolt fighting the residual pressure in front of the bolt sail. This is why less dwell is required, which allows the bolt to retract quicker.


Once the ring stops moving, the chamber is the same size as a full tophat mod, but the valve is still fully open. This means at any given pressure level the chamber pressure and therefore bolt forward force is dropping faster, which also allows faster bolt reset. The amount of "dead volume" venting to the barrel volume after the ball has left is in this way reduced.

I hope this paints a cogent picture.
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Old 12-01-2012, 07:48 PM #11
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I agree with a lot of that, still unsure of other parts. But they are hard to prove or disprove without high speed recordings, precise measurements or some levels of math/dynamics that are beyond what I know now. So I guess I'll take your word for it.

And I had to google what "cogent" means.
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Old 12-01-2012, 09:08 PM #12
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I agree, I could be wrong on HOW it works, but this explanation seems to fit all the data. I have enough customer testimonials to be quite sure that it produces efficiency increases far in excess of anything else offered for the DM.
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Old 12-01-2012, 10:31 PM #13
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So really, how much gnome blood is used to lubricate as these rings are being CNCed?
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Old 12-01-2012, 10:51 PM #14
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So really, how much gnome blood is used to lubricate as these rings are being CNCed?
Gnome blood, you say? I've always used gypsy tears for cutting fluid. I guess I've been doing it wrong.
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Old 12-01-2012, 11:06 PM #15
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Gypsies hate paintball. You'd just be cursing yourself.
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Old 12-02-2012, 12:08 AM #16
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So really, how much gnome blood is used to lubricate as these rings are being CNCed?
Just enough to thin out the eye of newt.

Seriously though, I lucked into this.
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Old 12-02-2012, 12:09 AM #17
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Gypsies hate paintball. You'd just be cursing yourself.
Must be why I spend so much time in the dead box. Damn gypsies.
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Old 03-01-2013, 02:37 AM #18
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i know, dead thread revival but josh, did you ever get the ring? worth it from a perspective that isn't 3 quarter of physics ahead of me?
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