Looking for some experts to chime in on regulating a big bore that doesn't have a balanced valve. The newer AEA Challenger's with their big poppets valves and air tubes is where I am going with this. To get four to six fairly consistent shots would be ideal. The pressure on the regulator would need to be about 2500psi and max fill on them is 3600psi. What do you think, is it doable?
Regulating a Big Bore..
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Please elaborate on your goal. Four to six consistent shots is most definitely doable, but what caliber and energy level?
The lack of a balanced valve isn't an issue because regulating it means the valve is easier to knock open. Granted if you plan to enlarge the throat, that will begin to offset the difference and perhaps at some point require some countermeasures to keep the cocking effort reasonable (heavier hammer, more stroke, or harder poppet).
The lack of a balanced valve isn't an issue because regulating it means the valve is easier to knock open. Granted if you plan to enlarge the throat, that will begin to offset the difference and perhaps at some point require some countermeasures to keep the cocking effort reasonable (heavier hammer, more stroke, or harder poppet).
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im not an expert but agree its what your goal is .. if its to have a grossly inefficient and expensive to shoot albeit powerful and impressive big bore target gun, its dooable .. for shootng large game you dont need 1/4" accuracy and 50 shot capacity .. you just got to broad side it with a big piece of lead then hit it with a possible follow up shot and then maybe a finishing off shot lol ...
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I am also curious. The reason for wanting a reg is this gun's 6 shot magazine. My understanding is that the tube can actually hold 4500 or maybe ever 5000 psi, although I havent tried. If that's true, then regulating it to 2500 should provide a full mag at least right? Would be kinda like a big bore huben k1. Well, in the sense that it can fill to 5000 and be regulated. My huben' is regulated at like 2900 psi, so in theory it should be possible. Maybe not idk. I get that big bores use up way more air per shot.
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Using the published energy figures as a starting point...
The manufacturer states 160fpe in .35 cal. The reservoir is 300cc. Allocate 80cc for the regulated plenum (using a 0.5cc per fpe guideline), leaving a 220cc reservoir. 6 shots at 160fpe, with 3600psi starting pressure and 2500psi end pressure, requires an efficiency of 0.94fpe/ci. An efficiency figure around 1.0fpe/ci is reasonable for a big bore with a 24" barrel.
I didn't deduct the volume occupied by the regulator itself or the plenum spacer but this was just to see if it's anywhere in the ballpark.
The manufacturer states 160fpe in .35 cal. The reservoir is 300cc. Allocate 80cc for the regulated plenum (using a 0.5cc per fpe guideline), leaving a 220cc reservoir. 6 shots at 160fpe, with 3600psi starting pressure and 2500psi end pressure, requires an efficiency of 0.94fpe/ci. An efficiency figure around 1.0fpe/ci is reasonable for a big bore with a 24" barrel.
I didn't deduct the volume occupied by the regulator itself or the plenum spacer but this was just to see if it's anywhere in the ballpark.
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It is a 45 caliber. Right now most of the Challenger Bullpup versions have a valve that knocks open fully around 3000 psi with no spring or weight mods. With washers for spring spacing and weight added to the hammer the valve opens up more at higher pressures but cocking lever goes up as well.
As far as energy levels go, the end user could determine what levels of power versus projectile they can tune for if it is regulated from 3000psi down to 2000psi. While the Challenger Bullpup is a decent platform for short range shots and high energy levels, when shooting longer distances because the FPS speeds are so far apart and only lasts for a few shots it is not a good long range shooter. Getting the shot string into a tighter more manageable spread is the goal, along with keeping the energy levels up.
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This Challenger Bullpup version is a 500cc tube with a 30" barrel. The current energy levels, with only some mild port work to the system, are up above 400 PFE at the muzzle and 300 PFE at 200 yards.
Is there a particular regulator design and or manufacturer that has a tried and true product to fit up that will work within the 2000-3200 psi pressure range? And is anything needed to be done to the air tube to get it installed?
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400fpe is more than double the energy of the .35 cal example, but a tube less than twice as big. Plus a larger portion of the tube would need to be commandeered for the plenum to support such high energy. The benefit of a longer barrel will not make up a gap that large.
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Just plugged some numbers in and it looks like it may be possible to get 3 regulated shots at 400fpe. Maybe. If the energy level can be obtained with a setpoint of 2500psi.
Six shots, no way.
Six shots, no way.
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Three consistent shots and a manageable descending shot string would be great. Where are you plugging in these numbers at? It sounds as though there is a formatted calculator online somewhere that I can figure out my power levels and ideal plenum space given the volume of air and pressure. Let us know where to go from here please.
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I’m using a spreadsheet that I made for common airgun calculations, however Lloyd’s efficiency calculator can give you what you need.
http://calc.sikes.us/1/
http://calc.sikes.us/1/
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Regarding plenum size, a guideline of 0.5cc per fpe works well for in-tube regulators. More is better for efficiency, up to 1.0cc per fpe, but you’re trading off a portion of the reservoir volume for plenum with in-tube setups so the 0.5cc per fpe will produce a better shot count.
By that I mean contrasted against something like a bottle conversion where the whole air tube is available to act as the plenum.
By that I mean contrasted against something like a bottle conversion where the whole air tube is available to act as the plenum.
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Okay thanks for bringing that to our attention. In that case a 5000psi fill and 3000psi setpoint could yield 6 shots at 400fpe with an efficiency of about 1.0fpe/ci. However bear in mind I don’t know the minimum pressure the Challenger bullpup needs to reach the 400fpe level, and it can vary considerably depending on the degree of porting and valve work done, so I went with 3000psi since the OP mentioned the OEM hammer and hammer spring are capable of knocking the valve open at that pressure. However if the desired energy level can be reached with a lower setpoint, the shot count will likely increase…or vise versa.
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Thanks for posting this link. I will be able to play with the numbers now.
Can an internal regulator assembly, with the required plenum space be added to the existing air tube and being sealed by o-rings to separate the high and low side pressures, without any further modification to the tube? It seems like I saw somewhere that someone had to drill a tube to install one on another air gun.
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Yes a regulator needs an atmospheric pressure reference to work properly. Without it, air that permeates slowly through the O-rings will pressurize the middle chamber and cause the setpoint to climb.
In the vast majority of cases, this atmospheric reference is a tiny hole in the tube like you described. However some regulators are designed to vent along the outside of the plenum spacer and through the threaded endcap of the air tube. An example of this second type can be seen in the Huma document linked below (see p8 where it shows a trench filed across the threads to allow venting).
http://foto.huma-air.com/foto/installation%20guide%20Hatsan%20Flash.pdf
In the vast majority of cases, this atmospheric reference is a tiny hole in the tube like you described. However some regulators are designed to vent along the outside of the plenum spacer and through the threaded endcap of the air tube. An example of this second type can be seen in the Huma document linked below (see p8 where it shows a trench filed across the threads to allow venting).
http://foto.huma-air.com/foto/installation%20guide%20Hatsan%20Flash.pdf
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This is a great topic, I'll share a bit of what I've experienced in playing with many, many different configurations of the Bulldog and Extreme .457 platforms .....I'll assume we are talking within the confines of an un-tethered gun. If tethering, there is nothing to discuss YES, regulate if you have the ability!!!!
After regulating, if high pressure capacity isn't enough to yield more than 3 or so shots, then I'm not sure how much you are gaining by going regulated. Even with wide open, >or = to bore sized porting, one should be able to achieve 3 or so shots across a tight ES with most big bores.
it all boils down to available high pressure storage after creating your plenum. I'm sure there is a rule of thumb that could be developed. Just shooting from the hip her if you will--- If you want 5+ flat shots in the upper end of the energy spectrum on a given platform, IMO you will need 3x plenum capacity or greater ratio of high pressure storage to plenum to make regulating worthwhile..
Again, great topic. My $.02 isn't intended to discourage anyone from going down this path, just adding some anecdotal information obtained by burning through a bunch of nitrogen and lead experimenting in this area.......
After regulating, if high pressure capacity isn't enough to yield more than 3 or so shots, then I'm not sure how much you are gaining by going regulated. Even with wide open, >or = to bore sized porting, one should be able to achieve 3 or so shots across a tight ES with most big bores.
it all boils down to available high pressure storage after creating your plenum. I'm sure there is a rule of thumb that could be developed. Just shooting from the hip her if you will--- If you want 5+ flat shots in the upper end of the energy spectrum on a given platform, IMO you will need 3x plenum capacity or greater ratio of high pressure storage to plenum to make regulating worthwhile..
Again, great topic. My $.02 isn't intended to discourage anyone from going down this path, just adding some anecdotal information obtained by burning through a bunch of nitrogen and lead experimenting in this area.......
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Thanks for posting your experience. If I can get three to four consistent shots then I'll be happier. Right now it is way to extreme of spread for my liking, though it is cool seeing the chrony hit 980+ FPS.
There is about 550 cc's of air space available in the tube to work with, but sealing the regulator is going to be tricky. The way it is machined now, only 4 mm of space is available for sealing next to the valve body, and I don't know how it will be referencing atmosphere like that.
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