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Old 08-19-2014, 01:07 PM #1
sixfootsideburns
 
 
Join Date: Jul 2014
Location: New England
farting issues

I've been doing some work on my autococker that hadn't been used in probably 7 years and part of this process was to re-time the gun. During the re-timing process when I gassed up the gun and did the slow trigger pull I noticed that my cocker makes a farting like sounds during the firing. So I did some research and found several sites discussing the autococker farting issue and I believe that's what I'm experiencing.

What I'm confused about though is that every site I found on the topic was discussing pump cockers, and mine is a full mech gassed marker. If I manually cock the marker when it is not gassed it also makes a twanging sound when it's fired.

Is it likely that I'm experiencing the same issue? Or does anyone have any other thoughts on what may be happening with my gun? I can take a video it that helps.

Any insight/info would be awesome!
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Old 08-19-2014, 02:17 PM #2
Dk-79
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It's a pressure and spring imbalance.

If the main spring/valve spring is too light, the hammer assembly can be pushed back by the valve re-seating itself. Sort of like a bouncy ball on a hard surface.

Usually, I'll re-sweetspot and triple check the timing to make sure all the points are in the proper order. If the pull is too long, and the re-cocking point is too far back, it can lend itself to the farting issue.

What pressure is it running at? How far in is your IVG, and how old are the springs?
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Old 08-19-2014, 04:53 PM #3
sixfootsideburns
 
 
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Yeah I totally get why it's happening (ie valve bounce), I was just surprised to see that it was only talked about with pump cockers and not full mech pneumatics as well.

I have no idea what my reg is running at though because I don't have an inline gauge. I've considered putting one under the front block where the setscrew is but never really felt the need. Is there a simple/cheap way to check? My inline reg is stock so it's not easily adjustable either. I'm hoping to spend a day at the field this weekend sweet spotting my reg, but the paint they use at the field is not the greatest and I don't have a freak insert for re-balls so it seems like something of a moot point.

Originally I had my IVG about 1/4inch in, but if I screw it in far enough the bouncing does go away. It seems silly to sweet spot the reg that far in though because I will only have adjustment in one direction for velocity. Any thoughts on that?

My springs are probably original and it's an '03 Prostock. I bought the gun used years ago when I new very little about autocockers, played a little with it and then it sat in my closet for a long time. I hardly ever touched it during that time. I pulled the IVG last night to take a look at the hammer and hammer spring though and the spring looked OK. Definitely had some buildup on it but I didn't see any cracks. With that said, I have no way of knowing how it would compare to a new spring in terms of force applied. If I have to buy a spring set I will, but if I can avoid it I'd like to. I love playing with this gun and lately I haven't been able to because it's always in pieces at my house.

I read a fix a couple of days ago where someone suggested cutting a few coils off the hammer spring to make it shorter. The dead space helps keep the hammer from oscillating and bouncing off the valve pin more than once. That seems a little shady to me though...

Ultimately what I'd like to accomplish with all my tuning is to make my marker run smoother with a bit less recoil. I've read a bit about running really low pressures and it eating into your efficiency though and I'm not completely sold on the pros vs cons. So with that said I think I'd like to land somewhere in the middle. I don't mind a little recoil, but the smoother I can make my marker the better. From what I've read I'll probably end up wanting it to run somewhere in the 250-300 psi range depending on my springs?
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Old 08-20-2014, 01:37 AM #4
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I'd get a spring kit, and a gauge for the hole under the front block.

Maddman kits are cheap, and you get both valve and hammer springs. Fresh is best.

I'm running blue/blue in my STO and shooting 295+/-1 @ 285PSI with my IVG sitting just shy of flush. I get six pods and a hopper off a 68/4500 fill.

Personally, I'd also get a new reg. The stock one works great, but it's such a pain in the ***. I also wouldn't clip springs, I'm not sure who told you that, but you should karate chop them in the pinky toe. That is absurd advice.

Hate to say that a lot of autococker hiccups came from stock equipment, but a gauge and externally adjustable regs should have been factory equipment.
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Old 08-20-2014, 06:02 AM #5
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Alright I'll go for that. Any suggestions on regs and gauges? I've heard good things about sidewinders but I'm not sure I can spend the $80 on more parts right now

Also not sure who makes a decent gauge, or are they all pretty reliable?

Last edited by sixfootsideburns : 08-20-2014 at 06:09 AM.
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Old 08-20-2014, 08:59 AM #6
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You can get a dye hyper2 or a Bob Long torpedo for $30 all day (Ideally you'd drill the later through the adjustment screw and spring washer), they're great regs but the hyper2 tops out around 400 PSI, which is still slightly more than what most 2k+ 'cockers run at.

As for gauges, you could get an ashcroft gauge or a liquid filled gauge; the later have less issues with rapid pressurization but are bulkier, they're better if you're just adjusting and then plugging the gauge hole.
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Old 08-20-2014, 12:32 PM #7
sixfootsideburns
 
 
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pardon the ignorance, but what exactly does drilling the regulator entail? And is it really necessary to get an expensive gauge from a company like ashcroft or swagelok? Can a reasonable result be achieved with a gauge meant to be used/mounted on a marker?

i.e. something like this
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Old 08-20-2014, 12:50 PM #8
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pardon the ignorance, but what exactly does drilling the regulator entail?
It entails putting the adjustment screw in a vise and drilling it with a 1/16" bit all the way through, and then doing the same to the spring washer in such a way that both holes are somewhat aligned. This is only for floating poppet style regulators with no relief hole in the spring section.

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And is it really necessary to get an expensive gauge from a company like ashcroft or swagelok? Can a reasonable result be achieved with a gauge meant to be used/mounted on a marker?

i.e. something like this
You could use that also, the more expensive gauges with a larger dial face will usually be more accurate though.
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Old 08-20-2014, 01:22 PM #9
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I use a 0-400 mini Dye gauge under my front block, I couldn't get the ashcroft to fit, and there's no port on my sidewinder. The big guys are better, but since I only use it as a ballparking tool to make sure my pressure isn't way over or way under, I'm more on the out of sight out of mind gig.

The sweetspot will always be its own thing, and you don't know where it is until you find it. Could be 250psi, could be 320psi.

Take a look in the B/S/T's on customcockers and McarterBrown. You might find a decent deal on an AKA reg. Even WGP regs are nice, the Karni reg being the least bulky. I've never had good luck with CP, but for the most part a reg is a reg.

Spend the money on a nice ram, three way, and delrin bolt.
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Old 08-20-2014, 01:25 PM #10
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It entails putting the adjustment screw in a vise and drilling it with a 1/16" bit all the way through, and then doing the same to the spring washer in such a way that both holes are somewhat aligned. This is only for floating poppet style regulators with no relief hole in the spring section.



You could use that also, the more expensive gauges with a larger dial face will usually be more accurate though.
Ahh, well that's not to bad. What's the point in drilling it? If it's required for floating poppet regulators why wouldn't it just come already done? I'm not doubting what your saying I'm just uneducated in this area of marker upgrades. I hadn't played paintball in probably 6 years until a few months ago when I picked up my gun again. So the past few months have been a process of re-educating myself.

Are high levels of accuracy really all that necessary? In the end any process of sweet spotting a reg is going to be based on paint velocity and feel of the marker, right? In theory you don't even need one to meet those requirements, it would just make it easier to baseline if you ever needed to make a change. Or am I missing something?
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Old 08-20-2014, 01:39 PM #11
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It's a great feeling to put one ball on top of another clear across a field.

Even the best paint to barrel match won't get rid of the velocity inconsistencies caused by the marker. Sweetspotting is a way to bring those FPS variations into the +/-2 range, and it's a damn good feeling when you know exactly where every paintball is going to go. It is also the point of maximum efficiency, which is nice if your field doesn't offer all day air or if you run off a scuba tank.

When you've got bigger jumps in velocity, you can't plan as well, and you shoot more in order to make up for it.

Last edited by Dk-79 : 08-20-2014 at 01:42 PM.
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Old 08-20-2014, 02:51 PM #12
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Ahh, well that's not to bad. What's the point in drilling it? If it's required for floating poppet regulators why wouldn't it just come already done? I'm not doubting what your saying I'm just uneducated in this area of marker upgrades. I hadn't played paintball in probably 6 years until a few months ago when I picked up my gun again. So the past few months have been a process of re-educating myself.
The older floating poppet style regs' design didn't take into consideration that the piston moving in the regulator also creates back-pressure inside the spring side if there's no proper relief for said pressure, so you get a slower recharge and less consistent reg if it has no pressure relief in the spring section. Most 2k5+ regulators fixed this by drilling the hole on the side of the regulator (see Bob Long's 360 reg) or having a washer (rather than a coin) and a hollowed out adjustment screw (see Diablo FASOR line).

Come to think of it, your stock reg is one of the better regs of it's time, you can probably get by with rebuilding it and it should still work great (other than not being externally adjustable).

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Are high levels of accuracy really all that necessary? In the end any process of sweet spotting a reg is going to be based on paint velocity and feel of the marker, right? In theory you don't even need one to meet those requirements, it would just make it easier to baseline if you ever needed to make a change. Or am I missing something?
They're not necessary, but there's nothing more frustrating than missing that one shot because your marker isn't consistent enough for you to predict the paint's trajectory adequately even after the first shot. Usually a clean and properly lubed marker is a consistent marker; that coupled with a tight bore barrel and mid grade paint should have you in the +/-5 fps range easily.
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Old 08-20-2014, 09:45 PM #13
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Come to think of it, your stock reg is one of the better regs of it's time, you can probably get by with rebuilding it and it should still work great (other than not being externally adjustable).
By rebuilding do you just mean a clean, lube an oring replacement if necessary? Or are there modifications I ought to make? If so, any idea of a good guide to follow?

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They're not necessary, but there's nothing more frustrating than missing that one shot because your marker isn't consistent enough for you to predict the paint's trajectory adequately even after the first shot. Usually a clean and properly lubed marker is a consistent marker; that coupled with a tight bore barrel and mid grade paint should have you in the +/-5 fps range easily.
Yeah that totally makes sense, it just seems like that can be achieved with a decent chrono and no need for a gauge at all. I see the gauge providing value in that it would help me gather baseline data for future tweaks. i.e. I know what kind of spring balance and pressure provides me with a result that I like.
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Old 08-20-2014, 11:24 PM #14
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By rebuilding do you just mean a clean, lube an oring replacement if necessary? Or are there modifications I ought to make? If so, any idea of a good guide to follow?
Pretty much, the stock reg is a moving base type reg with the relief hole already drilled in the spring section. Clean, replace all dynamic o'rings and lube. The only downside is that it's not externally adjustable, so you have to degas and take it apart every time you want to make an adjustment.

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Yeah that totally makes sense, it just seems like that can be achieved with a decent chrono and no need for a gauge at all. I see the gauge providing value in that it would help me gather baseline data for future tweaks. i.e. I know what kind of spring balance and pressure provides me with a result that I like.
Yes, it's value is reference. Once you've sweetspotted your HPR, you just write the pressure down and next time you need to rebuild your reg, you just set it to the same pressure you got last time (provided the springs are also the same).
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Old 08-22-2014, 02:02 PM #15
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Well I love to tinker so I don't mind adjusting the stock reg at least for now, though in the future the value of an externally adjustable reg is pretty apparent.

The bit that I still don't understand is how come screwing the IVG in fixes the farting issue, but screwing it out doesn't? I would have thought both would, at some point, fix the issue.

Here's how I thought about it...

Screwing the IVG in increases the spring compression, which overcomes the valve springs ability to throw the hammer back and cause bounce off the hammer spring.

Screwing the IVG out decreases the spring tension, which (at some point) would stop providing enough rebound for the hammer to bounce off the valve more than once.

Can someone explain where the gap in my logic is? Because I didn't see these results in practice. The only logical thing I could come up with that would explain it would be if the hammer spring is so long that it never allows the 2nd fix to actually take effect.
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Old 08-23-2014, 02:02 AM #16
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If you're at field FPS and already at the HPR's sweetspot, turning the IVG out will decrease the FPS and leave you with nowhere to go but down (FPS-wise); turning it in, you could decrease the pressure and still be at the legal field FPS limit (although you loose some efficiency).
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Old 08-26-2014, 07:51 AM #17
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Yeah that makes perfect sense, but how come turning the screw out doesn't get rid of the farting? Turning it in does, which makes sense, but I would have though turning it out would at some point fix it as well (see logic above).

Nothing to do with the regs pressure because I can hear the hammer bounce even when I draw the hammer when the marker isn't gassed
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Old 08-26-2014, 09:32 AM #18
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Yeah that makes perfect sense, but how come turning the screw out doesn't get rid of the farting? Turning it in does, which makes sense, but I would have though turning it out would at some point fix it as well (see logic above).

Nothing to do with the regs pressure because I can hear the hammer bounce even when I draw the hammer when the marker isn't gassed
It will eventually, but you'll be nowhere near 295 FPS if it was farting at your sweetspot.

It does actually have to do with the pressure the HPR is set to; that pressure is also acting against the valve face (cup seal), so it adds to the force exerted on it by the spring. If the pressure is high enough, the hammer won't even open the valve at all.

Hearing your hammer bounce on the poppet while the marker is degassed is not an indicator of farting, I have the hammer bounce on the poppet while degassed on my SystemX vengeance 4.0, but there's no farting at around 250 PSI, which is where the marker sweetspots.

Farting is dependent on your spring combination and HPR pressure: if you use a hard valve spring and sweetspot at a low pressure (say 200 PSI), while using a soft mainspring, it'll be more likely to fart than a soft valve spring with a medium mainspring sweetspotting at medium pressure (say 275 PSI).

Why? 'cause the poppet in the first case acts like an underpowered short stroke gas piston, it'll impart enough momentum to overcome the spring's force for about 2-3mm and then the hammer will reset forward with less force, bouncing less every time until it settles on the poppet or gets cocked back. In the second case, the mainspring has enough resistance that the hammer is never separated from the poppet, but not enough to overcome the spring and pressure in the valve chamber while at rest, so it'll smack the valve open and stay in contact with the poppet always, eliminating farting,

YMMV on the pressures and spring combination required to achieve this.
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Old 08-26-2014, 10:36 AM #19
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I thought the reason that farting is more of an issue with pumps is because:
1. When you are shooting an autococker you're cocking it immediately after each shot. Unless your holding the trigger after each shot, but why would you do that?
2. Pumpers are always trying to sweet spot to get the lightest pump stroke.

The first thing I would try is shooting some paint through it and seeing what it sounds like with paint. I notice that some of my pumps sound a little farty dry firing, but sound fine with paint. If it still sounds farty, turn up the reg a bit. I don't think you're losing efficiency by going to a higher pressure, it just makes it a little harder to cock because you'd have to turn in your ivg to get the same velocities.

But take this with a grain of salt. I haven't owned a semi autococker in a while... they're all pumps now.
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Old 08-26-2014, 12:34 PM #20
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I thought the reason that farting is more of an issue with pumps is because:
1. When you are shooting an autococker you're cocking it immediately after each shot. Unless your holding the trigger after each shot, but why would you do that?
Even then, it'd already be cocked.

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2. Pumpers are always trying to sweet spot to get the lightest pump stroke.
Exactly, this means the manspring is sometimes too soft and won't keep the hammer on the poppet after it strikes, making it bounce in stead.

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The first thing I would try is shooting some paint through it and seeing what it sounds like with paint. I notice that some of my pumps sound a little farty dry firing, but sound fine with paint. If it still sounds farty, turn up the reg a bit. I don't think you're losing efficiency by going to a higher pressure, it just makes it a little harder to cock because you'd have to turn in your ivg to get the same velocities.

But take this with a grain of salt. I haven't owned a semi autococker in a while... they're all pumps now.
I agree with most of this, except higher pressure being less efficient; (In 'cockers) higher pressure (up to a point, usually under 400 PSI for 2k+ bodies and valves) will usually give you a faster valve resolution, making it more efficient (if it's properly tuned and sweetpsotted).
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Old 08-26-2014, 06:30 PM #21
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I see what I was missing now. Awesome info gentleman, I appreciate the insight!
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