GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: UCChris on February 03, 2015, 04:54:24 PM
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Okay, I got some chrony work done on my Disco this morning and I'm getting 85 shots from 2000-750 psi. These 80 shots start at 642 fps, go up to 763 fps, and come back down to 670 fps. This is strictly a 30 yard gun for pest bird removal, so I chose 40 shots from 1500 psi down to 900 psi. This gives me a 40 fps spread (5.2%) which I figure is fine for pest removal.
HOWEVER, if I were to install a regulator set at, let's say, 1000 psi (750 fps) could I fill the gun to 2k and possibly get 60 shots at a relatively stable velocity? Currently I'm getting 65 shots before dipping below 1000 psi, and I figure the regulator takes a few cc's of capacity, so I'm thinking I could possibly get 60 good shots? That would make this a great gun for an entire day removing sparrows/starlings at the permission.
There was a member here selling custom regs for the Disco (and Mrod, I think) a few months back. If that is you, PLEASE PM me again. You PM'd me once about it, but I didn't want to go this route back then. Thank you.
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Look up member ( Milo74 ) he is your go-too guy ;)
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Okay, I got some chrony work done on my Disco this morning and I'm getting 85 shots from 2000-750 psi. These 80 shots start at 642 fps, go up to 763 fps, and come back down to 670 fps. This is strictly a 30 yard gun for pest bird removal, so I chose 40 shots from 1500 psi down to 900 psi. This gives me a 40 fps spread (5.2%) which I figure is fine for pest removal.
HOWEVER, if I were to install a regulator set at, let's say, 1000 psi (750 fps) could I fill the gun to 2k and possibly get 60 shots at a relatively stable velocity? Currently I'm getting 65 shots before dipping below 1000 psi, and I figure the regulator takes a few cc's of capacity, so I'm thinking I could possibly get 60 good shots? That would make this a great gun for an entire day removing sparrows/starlings at the permission.
There was a member here selling custom regs for the Disco (and Mrod, I think) a few months back. If that is you, PLEASE PM me again. You PM'd me once about it, but I didn't want to go this route back then. Thank you.
You're probably thinking of milo74. I had two of his regs installed in my dad's Marauders. Motorhead liked them and that was good enough for me. :D Edit: See above...
I just purchased a disco reg from him.... I got it last week and promptly misplaced it. :| Golly it's frustrating. I'm just hoping to find it before the new Rat Sniper valve comes in. These valves have stronger retaining screws and can standup to overfill. If the rest of the system is up for it, then you might get more shots that way. For me it's an extra layer of protection because my dad's eyes aren't that great.
Edit: I had milo74 preset mine to 1200psi, which I think will give me 12ft/lbs using an 18" barrel.
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You could also do a regulated bottle. I shot the one rdsail made...it was sweet.
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Chris, regulated is the sweetness for small caliber rifles.
Remember that revelation of accuracy you discovered when you switched from springers to PCP? Regulation is the next most significant step in my opinion.
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Chris, regulated is the sweetness for small caliber rifles.
Remember that revelation of accuracy you discovered when you switched from springers to PCP? Regulation is the next most significant step in my opinion.
Awesome to hear. I think I am going to get one of Milo's regulators with part of my next paycheck.
Will shot count be the same with a regulator? Or will shot count increase?
The way I see it, valve dwell time is the same since my hammer settings won't have changed. However, since the air going into the valve is at a lower pressure, less of it will come through during the time the valve is open. Meaning less air used?
If this is correct, then there might be the added benefit of the gun being quieter (assuming it uses a shroud or ldc) since there is less air, overall, escaping the valve.
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Tuning a regulated rifle for good efficiency is pretty easy compared to a conventional PCP. The air pressure seen by the valve is always the same so there is no magic balancing act between high pressure/low lift versus low pressure/high lift and dwell to deal with. Generally if you can trim hammer strike with an RVA, you won't have any trouble getting it tuned for good efficiency.
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Don't forget to allow some volume between the regulator and the valve or you will lose power compared to what you expect at the setpoint pressure you choose.... A plenum of 1 cc per FPE is recommended, and that assumes no restrictions on the inlet side of the valve.... You will have to reduce the preload from your current tune or you will end up with an air hog....
Bob
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Tuning a regulated rifle for good efficiency is pretty easy compared to a conventional PCP. The air pressure seen by the valve is always the same so there is no magic balancing act between high pressure/low lift versus low pressure/high lift and dwell to deal with. Generally if you can trim hammer strike with an RVA, you won't have any trouble getting it tuned for good efficiency.
Good info to know. How exactly does one go about tuning a regg'd gun? I get, roughly, 750 fps at 1000 psi right now. So I was going to have Milo set the reg to 1000 and then stick it in, fill up to 2000, and then shoot down to 1200, or so, expecting all shots to hover very close to, roughly, 750 fps?
Am I missing something?
Don't forget to allow some volume between the regulator and the valve or you will lose power compared to what you expect at the setpoint pressure you choose.... A plenum of 1 cc per FPE is recommended, and that assumes no restrictions on the inlet side of the valve.... You will have to reduce the preload from your current tune or you will end up with an air hog....
Bob
I'm not sure how Milo's regulator works. I'm assuming it butts up against the gauge cylinder when I pressurize the gun? How do I set plenum?
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Since you are targeting a velocity similar to what you are getting now at 1000psi, I expect all you'll need to do is tweak the hammer spring preload with an RVA.
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Since you are targeting a velocity similar to what you are getting now at 1000psi, I expect all you'll need to do is tweak the hammer spring preload with an RVA.
Sorry to keep bothering you, but tweak in or out? Currently, I can only add preload. In order to decrease preload, I'm going to have to clip the spring.
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I think Bob answered above...reduce the preload.
The average pressure throughout the shot cycle will be lower because of the reduced volume of the [regulated] plenum. If I'm thinking about this right, keeping the same preload would result in too much dwell and waste air.
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Makes sense now. Thanks Jason (and Bob!). I'm super excited to try this.
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Honestly ....
You going to want some Valve Mods, Lighter poppet spring, Opened up gauge manifold to get equal performance to what you have now.
When asking gun to perform at less pressure also having less "On Deck" air to launch the pellet, valve and related plumbing needs to breath better.
Sadly there's no free lunch here.
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Been reading this thread by Bob.
http://www.gatewaytoairguns.org/GTA/index.php?topic=74919.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=74919.0)
When I get the regulator in, I will shoot a string and adjust according to how it matches up with Bob's second graph.
From what I understand, one should follow the velocity with their hammer preload. If the velocity steadily rises followed by a sharp hump, increase the preload. If it steadily decreases followed by a sharp drop off, decrease hammer preload.
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Bob, what is the relationship between plenum volume and efficiency? I have been reading that a larger plenum is more efficient, but at some point it will just be taking up valuable cc for useful air? Do you say 1 cc per desired FPE? A 12 cc plenum is only the equivalentof 2 US teaspoons.
Also, what material should I use for the plenum spacer? And what is this I hear about a breath hole?
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Just to say.
Use "next step" as if there is a final goal you want to reach. If you let us in on that final goal, would be a lot easier to figure out if a regulator is the "next step" or a step backwards.
I really do try to keep some goal in mind when I set out to mod and airgun. Could be more shots per fill, could be more energy per shot, could be more accuracy, could be more stable POI, etc. Generally, will tgry to have something I'm trying to reach before I start twiddling around with the innards.
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A Disco tube is 0.436 CI (7.1 cc) per inch, but the valve is a couple of cc's, and you will want to drill out the gauge mount or use a PRod mount (my choice), which will be another couple of cc's, so if you do that a 1" long plenum (assuming full diameter) should be enough for a 12 FPE gun.... I would use a piece of thinwall aluminum tubing for the plenum spacer, and you will have to follow the instructions with the regulator for a bleed hole.... You may have to make the spacer longer than an inch if the wall is a significant thickness, but of course there may be a plenum space in the regulator.... You are pretty much going to have to wait until you have all the parts to decide how long to make the spacer....
You can get away with a plenum as small as 1/2 cc per FPE, but you will have to add about 100 psi to your setpoint to allow for the loss of power.... and you will still not get the efficiency you would get with a larger plenum.... On the other hand, going larger than 1cc per FPE will gain you so little in efficiency it is unlikely to make up for the decrease of reservoir volume....
Bob
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Just to say.
Use "next step" as if there is a final goal you want to reach. If you let us in on that final goal, would be a lot easier to figure out if a regulator is the "next step" or a step backwards.
I really do try to keep some goal in mind when I set out to mod and airgun. Could be more shots per fill, could be more energy per shot, could be more accuracy, could be more stable POI, etc. Generally, will try to have something I'm trying to reach before I start twiddling around with the innards.
My final product will be a Disco that has a shortened BNM kit (done) dropped into a Nutmeg Blaster stock (getting on that) that has as many shots as possible at a minimum of 10.5 fpe. It is a pesting gun, so that means my longest shots are 50 yards tops. However, my shots are at angles that range from flat to almost straight up. My gun currently shoots 40 shots in a 5% spread which is decent for 30 yards. But the SD is over 10 fps. I just want lots of consistent shots.
A Disco tube is 0.436 CI (7.1 cc) per inch, but the valve is a couple of cc's, and you will want to drill out the gauge mount or use a PRod mount (my choice), which will be another couple of cc's, so if you do that a 1" long plenum (assuming full diameter) should be enough for a 12 FPE gun.... I would use a piece of thinwall aluminum tubing for the plenum spacer, and you will have to follow the instructions with the regulator for a bleed hole.... You may have to make the spacer longer than an inch if the wall is a significant thickness, but of course there may be a plenum space in the regulator.... You are pretty much going to have to wait until you have all the parts to decide how long to make the spacer....
You can get away with a plenum as small as 1/2 cc per FPE, but you will have to add about 100 psi to your setpoint to allow for the loss of power.... and you will still not get the efficiency you would get with a larger plenum.... On the other hand, going larger than 1cc per FPE will gain you so little in efficiency it is unlikely to make up for the decrease of reservoir volume....
Bob
Excuse my ignorance, but why do I need to get a Prod gauge block? I'm ordering a plenum spacer from Milo74 at the same time I order the regulator. I'm thinking 1.5" just to be safe? I have to put in a parts order to Crosman tomorrow, so I can get a Prod gauge block then.
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Chris I have a couple of Milo's regs and they work great. Setting it up is pretty much a one shot deal as you need the correct length plenum the 1st time because you will need to drill the vent hole in the tube for the reg. Once the hole is drilled there is not much room to adjust the length of the plenum. A little extra length for the plenum is better than it being too short.
Norm
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The hole through the Disco gauge block is very small, and emphasizes the pressure drop in the plenum.... The one for the PRod has a much bigger hole, and not only adds volume, but allows better flow into the valve.... While you don't need huge flow for 12 FPE, that small hole MAY require you to need a bigger plenum....
Bob
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I told Milo74 that I'd like a 1.5" plenum spacer. I will check on the price of the Prod gauge block; hopefully it is only like $5.
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Chris, enlarging the hole through the Discovery gauge block should be fairly trivial. No need to buy a PRod gauge block.
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Not as trivial as you might think, as the gauge adapter seals into the block with an O-ring right next to the 1/8" center hole.... If you try and drill that hole out, you will run into the O-ring seat and ruin the Disco gauge block.... You have to mill it (or grind it out by hand with a Dremel) off center to enlarge the hole....
Bob
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Ah, I take it this pic from the Crosman EVP is not representative of the real thing? The hole is shown centered.
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Nevermind, I see the gauge adapter you are referring to. I was thinking the gauge threaded directly into the block with NPT threads.
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Can I screw my Disco gauge into the Prod block, or are they different threading?
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Should be the same thread, as the gauge on the Prod threads directly into the block. Also keep in mind that because of its location, your gauge will measure regulated air pressure.
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Nope, different threads, as the Disco gauge adapter is straight thread into the Disco block, and seals with an O-ring, while the PRod gauge block is 1/8"-NPT (tapered) pipe threads.... HOWEVER, the Disco gauge, without the adapter, will thread right into the PRod gauge block, although it will be quite deep in the stock.... If you want it lower, get a 1/8" NPT male to female adapter from a Hydraulics shop to extend it....
Another way to go would be to have a custom plenum chamber made to replace the gauge block altogether, eliminating the gauge, and with a large bore to get most of your plenum volume that way.... I don't know of anybody selling them, though....
Bob
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I don't mind it being deep into the stock, so I will just thread the regular Disco gauge into the Prod block. Does the Prod block use the same o-rings as the Disco? I'd assume it does since it seals in the Disco tube...
Milo74 notified me that my regulator shipped today, along with a 1.5" plenum spacer. Should be ready to assemble it by my next day off of work.
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I believe it does.... Oops, see Norm's post below....
Bob
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The Disco gauge block uses 016 O rings and the PRod gauge block uses 113 O rings
Anytime I have ordered either gauge block they have come with the O rings already installed
Norm
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Chris, I thought about this when I had a disco......regulator....use as much of the tube volume as you need then double tube it for max shot count..
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What do these regulators run price wise?
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What do these regulators run price wise?
$82.70 shipped as of February 2015.
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the robert lane reg i fitted to my disco fits in place of the gauge port so you don't have to drill the tube for the bleed hole as it vents through the gauge hole
only down side is getting enough pre chamber i took as much out of the valve as i could to enlarge it
ped
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Same here, but I want to put a gauge in to show the reg setting. I intend to use a Disco block with an Mrod adapter and gauge.
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I would strongly suggest the PRod gauge block instead of the Disco gauge block, unless you have the ability to enlarge it off-center, you can't just drill it out....
Bob
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Here is a sketch of an insert that could be made to blank off the gauge port.... It slides in and sits against the front of the valve, sealed by two #016 O-rings....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Disco%20Gauge%20Blanking%20Insert_zpsjfun6vuv.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Disco%20Gauge%20Blanking%20Insert_zpsjfun6vuv.jpg.html)
It would add 3.2 cc of Plenum, and if you add the volume inside the valve, you will have about 6 cc total.... You can then use a piece of thinwall tubing between this and the regulator to increase the plenum to whatever you want.... It the tubing is 0.030" wall (any less and I would worry about it buckling), that works out to a 0.68" ID, which adds 5.9 cc per inch of length.... So, with a 1" spacer you would have about 12 cc total, and with a 2" spacer about 18 cc total.... You can see that you lose reservoir volume pretty quickly as you increase the FPE you expect to get on a regulated Disco....
Bob
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Okay, I finally got my Prod gauge block from Crosman. I will be working on regulating the Disco this week. A couple questions.
I ordered a regulated gun from a member here. It will do 50 shots at 25-30 fpe. So, I want to bring my Disco all the way down to 6 fpe (7.9 @ 600 fps or so). My goal is a &^^& ton of shots for sparrow popping and plinking. Do you guys think I will need to lighten the disco hammer? I realize that I'm probably going to have to turn the reg setpoint down from 1200 psi close to 800 or so.
Also, the Milo regulator needs a breathe hole drilled in the air tube. What will happen if I run the regulator without the breathe hole?
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To get the maximum number of 6 FPE shots you will have to do many changes.... First of all, the regulator setpoint will end up being less than 500 psi.... You will want the lightest hammer you can build.... and you will be running a 2240 spring with several coils cut off.... I made an HPA conversion of a .22 cal Disco running on a 13 CI tank, and it produced over 300 shots per fill at 7.7 FPE.... A Disco tube (8 CI) should deliver at least half that many, even with losing the volume for the regulator....
Bob
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Do you have a thread on that particular build Bob?
How would I go about making a lighter hammer? I have basic hand tools, a drill, and a dremel.
I already have a Disco hammer spring clipped down quite a bit. Can I just keep clipping it instead of ordering a 2240 spring?
Also, does anyone know how to change the setpoint on the Milo regulator? I know it is the little screw type thing in the middle, but is CW or CCW reducing the pressure?
Edit: Nevermind, I found a 2240 spring on Ebay for a decent price.
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http://www.airgunforum.ca/forums/topic43890.html (http://www.airgunforum.ca/forums/topic43890.html)
They are hardened, you have to grind them.... I managed to get rid of half the weight eventually, but you can start with a stock one.... I notice I didn't mention in that thread that I later lightened the hammer to gain even more shots, so it's not necessary....
You may be able to cut a stock spring enough, but it will end up rattling around loose.... I also note it was a 2289 spring, not a 2240.... The key is to get the pressure down under 500 psi....
Here is an alternate setup I made, with the regulator built into the valve for a Disco....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/RegulatedValve.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/RegulatedValve.jpg.html)
It uses a Ninja piston and spring, in a new valve front end....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/RegulatorParts.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/RegulatorParts.jpg.html)
As with most of my stuff, it never found anyone interested in making it....
Bob
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intresting thread. chris how's your reg going ?
@bob, looks like a real good idea.
peace
kj
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Chris if you need a 2289 spring, I can help you on that. PM me your address and I can get it out for you today or tomorrow.
Joe
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http://www.airgunforum.ca/forums/topic43890.html (http://www.airgunforum.ca/forums/topic43890.html)
They are hardened, you have to grind them.... I managed to get rid of half the weight eventually, but you can start with a stock one.... I notice I didn't mention in that thread that I later lightened the hammer to gain even more shots, so it's not necessary....
You may be able to cut a stock spring enough, but it will end up rattling around loose.... I also note it was a 2289 spring, not a 2240.... The key is to get the pressure down under 500 psi....
Here is an alternate setup I made, with the regulator built into the valve for a Disco....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/RegulatedValve.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/RegulatedValve.jpg.html)
It uses a Ninja piston and spring, in a new valve front end....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/RegulatorParts.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/RegulatorParts.jpg.html)
As with most of my stuff, it never found anyone interested in making it....
Bob
That looks very cool, Bob. How did it work and will it work with harder shooting setups?
Joe
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It worked well for non-PAL (<500 fps) stuff.... would be pretty much useless for big FPE because the only volume on tap is what is inside the valve.... maybe 3 cc.... If it had a larger plenum you could probably drop the pressure another 100 psi, but when it's only ~ 500, who cares.... Note Ninja piston, coil spring, and no shims....
Bob