GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Taso1000 on November 09, 2015, 02:34:17 AM
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Hello all,
I am looking for information on regulating a B51 in .177 caliber. I pretty much understand what a regulator does from reading a lot on this forum but I am confused with all the different models. I have seen mentioned regulators from Lane, Huma, Milo74 and others. What are the design differences? Is one design better or more efficient than another? Why do some need the air reservoir tube drilled? I'd rather not make permanent modifications because parts are limited for the B50.
I will either want the rifle detuned to ~6 fpe for quiet back yard target practice or at ~20 fpe with 10.5 grain pellets at ~900 fps. Almost forgot to mention, I am pumping. So keep that in mind.
I have also read about the valve poppet design flaw. I think Tim McMurray's take on lightening the springs and hammer/spring guide to make the gun last longer makes a lot of sense. How light of a hammer and spring guide is recommended?
Thanks to all in advance for your help.
Taso
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I have a Bam B-50 from Mike M. I have cut 2 coils off the stock hammer spring, and a custom made from Mike delrin top hat. Also have a delrin transfer port drilled at 1/16", rifle shoots AA 10.34's in high 700's and is very quiet with the fake LDC on the barrel. I say fake, but if you take it off it is much louder so it does do something. It is almost as quiet now as my 30 fp shrouded synrod 22. Am giving this rifle to my grandsons who are 11 and 16. I should mention that it charges to 1500 psi now so will be great for hand pumping.
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I have come to the conclusion with my B50 that a couple of delrin or similar material spring guides varying in size of the stop end to change spring pre-load and the substitution of the Mcmaster Carr spring and a couple extra transfer ports starting at 1/1 6" then midway to the stock size will give plenty of adjustment for what ever power level you wish I'd also include some shim material to fine tune. As far as the dependability of the factory valve; tapering the face end and reducing the thickness of the bearing washer on the valve stem will take a lot of the stress off.
My favourite post on this rifle is this one for tuning http://www.gatewaytoairguns.org/GTA/index.php?topic=79971.msg762282#msg762282 (http://www.gatewaytoairguns.org/GTA/index.php?topic=79971.msg762282#msg762282)
Also if it appears in my posts that I was grovelling then that is the case, I had my rifle for almost 2 years and read all the info I could find and tried to understand it the best I could but when Rstearne started this post, it showed probably the simplest way to achieve the performance I wanted with out being a machinist, what ever parts I needed were done with a table saw and drill press.
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tracker1955 and GarthThomas,
Thank you both for your responses. I appreciate them. Findings from people who have already experimented are awesome. The more I research how to achieve my goals the more questions I have. I believe it's the journey that is important. I have to read the link you provided more thoroughly GarthThomas. I've skimmed it twice since I've been on GTA.
I found some videos on Lane regulators that may provide me with some regulator information. I don't know if I will benefit from them at less than 2000 psi fill pressures since I am pumping. But we will see.
If anyone else has any tuning suggestions I'd appreciate you sharing them or pointing me to the information.
Thank you all in advance,
Taso
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At 63 y/o and short stature, I find it none too stressful to refill my 35fpe .22 B-51 to 3000psi with a Hill MkIV.
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Yes sir. I didn't say I "couldn't" do it. I had a marauder for a couple days and pumped it up to 3000 psi a couple times with a Xisico pump. I'd rather not on a regular basis as it wasn't enjoyable. ;) But I am cheap so I will pump.
Is the Hill pump easier or more efficient than the Xisico pump? I got the Xisico pump in the FDPCP deal.
Thank you Yrok,
Taso
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Comparing the Hill MkIII to the Xisico, the Xisico is indeed easier to pump but does not move as much air per stroke. Consider it a tradeoff.
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Have put HuMa universals custom sized to the tubes I.D. on 7-8 BAM 50/51 rifles to date.
You can use a Daystate Huntsman size regulator but it still required reducing body diameter slightly.
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Hey Taso,
When I tuned my B50/B51, I followed Motorhead's tuning methodology and The Book as my references.
Here is what I did: .177 caliber
1) Milo74 regulator - $80 > You must drill the air tube, but no problem. Why would you ever want to go back ;).
2) Delrin Hammer and Spring guide.
3) McMaster Carr hammer spring per the book.
4) All ports - Barrel, Transfer and valve =9/64" or .140625
5) Replaced heavy valve spring with conical spring.
6) widened valve intake a bit.
7) Tapered factory poppet at 30 to 35 degree angle >
8 ) Vented Hammer, Spring Guide and rear of action.
9) Regulator set-point 1500 psi, gets 890/900 fps using CPUM or JSB 10.34
There was more, but I never wrote it down other than my posts ...... it's been awhile.
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Hammer001_zps1d545311.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Hammer001_zps1d545311.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Hammer005_zps853ccefe.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Hammer005_zps853ccefe.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Tune12-21-2014009_zps9c7edaa1.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Tune12-21-2014009_zps9c7edaa1.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/spring%20003_zpsb9cab2p6.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/spring%20003_zpsb9cab2p6.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Tune12-21-2014008_zps916f7043.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Tune12-21-2014008_zps916f7043.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Valvespring-poppet_zps80232bd2.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Valvespring-poppet_zps80232bd2.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/ValveandAssembly_zpsf908c773.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/ValveandAssembly_zpsf908c773.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/ExactPlacementofValvePlenumandRegulator_zpsfe68b48a.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/ExactPlacementofValvePlenumandRegulator_zpsfe68b48a.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/BAM%2051%20Action%20014_zpsiwjzzwi9.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/BAM%2051%20Action%20014_zpsiwjzzwi9.jpg.html)
(http://i113.photobucket.com/albums/n227/kirk_schwarz/BAMB50-4_zps2f43e012.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/BAMB50-4_zps2f43e012.jpg.html)
It's truly amazing how much fiddling that needs to be done adjusting hammer spring tension etc. to get the most out of the gun. I only pump too, not a problem when you get 70 shots per fill. I would highly recommend making the RVA per Bob to get the gun shooting on the Knee of the velocity curve. All things being said, My first full tune almost killed me - But I did learn a lot ;D
Kirk
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Check the links in my sig for some additional B50 info.
On mine, the mcmaster spring and a lighter spring guide gets me 40 860fps or so shots with a .177 10.5g. I could and should do more to it, but for now, I am happy.
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Thanks for reposting that, Kirk.
Lately been pumping 2x 1701Ps, a 1720T, '90/'91 .177 Daystate MkI round bolt housing (heaviest of the bunch), mid '90s .22 Daystate MkII and the .22 B51 several days a week. Sometimes twice a day. Break a sweat sometimes and my elbow hurts after pumping up 2 or 3 in a row.
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Thanks for the responses gentlemen!
McMaster Carr 94125K125 springs arrived today.
I've contacted Milo74 about a regulator. How does the Huma differ from what Milo74 offers?
I will order the tapered poppet springs today. Edit: I haven't been able to source these yet. Where are you guys finding them? Is there a comparable McMaster Carr part? Something available through Amazon? What has been recommended is the #83 and #86. 86 is most likely what I will need.
I've got to look at Rsterne's RVA again. Where is the knee of the curve? Is that were the velocities drop more abruptly for the 4% plateau we tune for?
I'm having a problem finding Delrin hammers and spring guides. I have an email out to Mike Melick on parts availability. Would the original hammer be hard to remove metal from the sides like in "The Book"? I've only got a bench grinder, dremel, electric drill and table top belt/disc sander. How light does the hammer and spring guide have to be? Should I worry about irreversible mods since these rifles have little parts availability?
I think my first B51 will be setup like a 10 meter target rifle shooting 7.9 grain CPSM's at 500 fps. This rifle will be shot the most in the basement and in the back yard so it has to be quiet and accurate. I seriously considered an Air Arms T200 for this role. But I won't learn anything or have the same pride in knowing that I tuned my B51 myself.
The 2nd B51 I am considering on getting will be tuned for 10.5 grain CPH's at 900 fps. Hopefully quiet and accurate also. It will fill the pest eliminator role and Field target if I can find somewhere to shoot in Illinois. So training on the low power rifle will transfer to this one, except for the different ranges, hopefully.
I have a full tuned B26 in .177 and a full tuned B28 in .22 from Mike Melick but they're not quiet. The power plants make more noise when they cycle than the muzzle report.
Thank you everyone for your suggestions. I can't wait to get all the parts here so I can start modding the rifle. I'm positive I'll have more questions for you! ;D
Thank you all!
Taso
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Hey Taso,
The Huma regulator ($120+), regulates better than the Milo74 and doesn't require venting in most cases. However, Motorhead was using the Milo74 regs. in field target (IIRC), so for $80 they are fine. Also, I don't believe Huma makes the size needed for a B50/B51, they would need to be customized (I think).
I ended up using the lighter Hillman spring in my later B51 valve as opposed to the heavier one pictured.
Lastly, I think the Hillman #52 works as a hammer spring IIRC.
Kirk
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Kirk,
Are you still using the delrin hammer? How has it fared wear wise? Is it much lighter than a lightened stock hammer?
Thank you,
Taso
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Taso,
Made all my delrin hammers, spring guides, tapered poppets and other mods with my lathe. I don't have any idea where you would buy them?
If you planning on doing a lot of work tuning air guns, buy a cheap HF 7"x12" lathe for $450 or so on sale. Otherwise, the parts are going to cost you the price of the lathe after a couple guns. I wouldn't even attempt to tune any airguns unless I had a lathe :P
I don't know how some people on the GTA do a lot of tuning with much simpler tools ......... I'm not that good.
I also don't invent any mods, I just copy the ones that make sense.
see Bob's post on tuning PCP's, and Motorhead's / The Bman's on tuning the Bam's.
My last few cents .............. Kirk
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Kirk,
I'm sorry, I meant to ask, what are delrin's material properties? I don't know if I've ever handled delrin. I was more curious as to how it wears sliding in the receiver and engaging the sear. It seems as it would be lighter than iron or steel. Is it close to aluminum in weight and hardness? I was trying to weigh delrin's pro's and con's against a lightened stock steel hammer.
I don't think I'm going to look for a lathe. I could ask my brother to keep an eye out for one. He's an industrial engineer at a metal recycler. But in all honesty I did think about how to turn pieces with a drill the last couple days. ;-) I don't think I can pull it off. lol
Taso
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Yeah Taso,
I forgot to answer your 2nd to last question.
Delrin is pretty durable, but not good as 100% Nylon (this is what I believe Scott uses). I shot about 1,000 rounds out of one of mine, when I checked the hammer, and there was a few scratches in it. I'm sure it would last 5 to 6 times that or more, but I really don't know. You can make 2 hammers and spring guides from 12" of 1-1/8" diameter delrin rod stock costing about $12/$15 (found on Amazon). However, like many small parts, its all labor. I sold a hammer and spring guide to toine a few months ago for $30, maybe he no longer needs them?
If you see Marty B post on tuning the B/51, he did all the porting, changed the valve spring to the heavier conical spring, tapered a poppet (using a drill) and IIRC used the MC hammer spring. He kept the hammer/spring guide OEM. He got pretty much the same results as I did with no lathe. See his post from early 2015.
Kirk
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Motorhead,
I ordered a regulator for my B51 from Milo74 today. I was reading your post "USA manufactured PCP Regulator ( testing and discussion ) * RESULTS POSTED" I'd like to tell Milo74 what pressure to set the regulator at. I intend to shoot 7.9 grain Crosman Super Match wadcutters between 500 - 550 fps.
I am getting all the parts together so I have not run the rifle in that setup to be able to read the beginning and end pressures of the velocity plateau. I am concerned that I won't have the pressure gauge setup to accurately change it from the setting Milo74 builds it at. He's thinking between 1200 - 1500 psi.
What do you suggest?
Thank you,
Taso
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Taso,
It seems you need to go as low (PSI) as Milo74 can make it - 800psi or so. If he needs to be higher, you'll just have to choke the transfer port so that less air gets to the pellet. This way velocity can be adjusted down that low.
See what Motorhead says ..................
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You can do a lot with just a regulator, springs and a little fiddling.
Regulating the B50/51s fit perfectly in the 90:10 rule. You will spend 90% of the work getting that last 10%.
Your FT goal is actually much easier than you think. Start with the regulator and springs and see where you get.
As Kirk said, I got real close to his performance with not much more than that. His ES and efficiency are a little better thanks to the lightweight setup.
But mine were good enough for my goals.
The 10m goal? Personally, I wouldn't have started with a B50/51. Too big and heavy unless you are looking to build muscle.
Dropping a Milo74 reg into a Disco is basically what I did. Lightweight and FUN!
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Just for some FYI ... here the .25 cal power / regulator conversion on a BAM 50.
http://www.gatewaytoairguns.org/GTA/index.php?topic=83857.msg804455#msg804455 (http://www.gatewaytoairguns.org/GTA/index.php?topic=83857.msg804455#msg804455)
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When I worked on my B50 it was with the thought of not permanently altering existing parts. Sorry if I made the spring guide sound like a simple task, it took a lot of planning and slow work with a file etc. the existing spring guide is quite heavy and in order to get down to 500fps I had to make the stop end about 1/4" thick on the lighter Delrin version.
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Thank you every one for your suggestions and help.
I received the MCMaster Carr hammer springs yesterday.
I ordered a regulator from Milo74.
Mike Melick is sending lightened hammers, delrin spring guides with a 1/4" face, lighter valve poppet springs, air tubes and some delrin for transfer port sizing.
I will try to carefully turn the valve poppet down in a drill being carfull to protect the shaft from the drill chuck pawls. I hope I don't mar the stem but I do have a replacement.
I can't wait to get all the parts and start putting the rifle together. I think this weekend I will dissassemble the rifle for the first time and clean and deburr it.
Taso
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Taso,
You're good to go 8) Have fun :D
Kirk
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Hello everyone,
Thank you for your all your help! I really appreciate it. I'm sure I will have more questions as my tune proceeds. ;)
Is there a correct order of complete tear down of the rifle? I know the first thing to do is relieve all the pressure in the reservoir. Are there any areas where a spring or a ball bearing will launch and get lost in the Bermuda triangle of my carpet for all eternity? I've been taking stuff apart from when I was able to hold a screwdriver. So I'm sure I'll find a Taso way but I know there may be a correct order or else there may be hidden fasteners.
As for lubricants I have silicone grease, moly paste, Crosman silicone oil, pellgunoil and super lube. I will only be using silicone oil and silicone grease in the air path.
I went and ordered replacement polyurethane O-rings. I figured since they may be better, I may avoid having phantom leaks and thus peace of mind. Are polyurethane o-rings overkill?
Since I took a couple days off for my brains to rest, I have been thinking of a plan of attack. I'm thinking I will install all the new parts except for the regulator. Shoot rifle over chronograph and tune the shot string as flat and long as possible. Once I have the settings I want then re shoot and take reservoir pressure readings to find the low pressure knee??? and use that for the regulator setting. Hopefully it is close to what I asked Milo74 to set it at.
MartyB, I did initially consider a Marauder. But since the B51's are $244 each shipped from Canada and I wanted to mod/tune the rifle myself I figured that was the way to go. I have not read a bad review of them. Only that the valve poppet may fail when pushed hard. Thus my plan to go with the lightened valve and hammer systems. I have read that the B51's are all steel, built like tanks and super accurate. I did plan on two rifles, 6 fpe and 20 fpe, so identical made sense in operation and weight.
Tracker1955 reported that his B50 is quiet with the stock brake so I was happy to hear that.
My B51 weighs 7.3 pounds unscoped on my digital scale. It seems slimmer than the marauder but I don't have one to compare. Does anyone have an actual measured weight of an unscoped Gen 2 wood Marauder in .177?
Thank you,
Taso
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if you find that your B51 is still a bit noisy, contact GTA member Rocker1.
he made a moderator for mine that made it almost silent.
bob
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Hey Taso,
The only two gotcha parts are the two springs and ball bearing behind the safety and bolt adjustment screw on rear/left side of bolt (held in by Allen screw).
My advice is to take as many pictures of the gun's disassembly as possible on cell phone. all the small Allen screws are generally a pain, but likely because my eyesight isn't what it used to be.
Where are you buying the gun in Canada?
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Hey Taso,
The only two gotcha parts are the two springs and ball bearing behind the safety and bolt adjustment screw on rear/left side of bolt (held in by Allen screw).
My advice is to take as many pictures of the gun's disassembly as possible on cell phone. all the small Allen screws are generally a pain, but likely because my eyesight isn't what it used to be.
Where are you buying the gun in Canada?
On the Canadian Airgun Forum we have a store,Canadian Airgun Forum Store,you can google it,Dan operates it.
He can give you a shipping quote ,he carries some factory seal and valves for the gun,or at least he did when I bought mine...kelly
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Kirk,
I've been buying them from the Canadian Airgun Forum Store. Here's a link for the B51:
http://www.airgunforum.ca/store/product_info.php?cPath=22&products_id=99 (http://www.airgunforum.ca/store/product_info.php?cPath=22&products_id=99)
The second one is on the way with an extra barreled receiver in .22 caliber. I'm tempted to get a third one but I "really" don't need it. ;)
I really don't have anywhere to shoot besides my back yard. I've got about 20 yards from my back porch to the neighbors fence. I'm sure a 20 fpe .177 is good enough for pesting. Thus I really have no need for a bigger caliber or long range gun.
Pictures is a good idea. Thank you!
Taso
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Hi all,
Just an update. I got the regulators from Milo74. They look nice and I can't wait to try them out.
I also received the spare parts from Mike Melick. 2 reservoir tubes, 2 complete valves, 2 hammers, 2 delrin spring guides, a light and a heavy hammer spring, and 2 end caps. One with fill valve one without.
I'm still waiting on O-rings to arrive.
I can't find the Hillman poppet springs. The Hillman company is based in Illinois and I can't find who carries their products. Maybe I'll put a WTB in the classifieds for them.
I didn't get to take apart the first rifle as I had hoped. Too much yard work and putting stuff away for winter to do. We're supposed to get snow this Saturday. Got to check the Toro snow blower so it's good to go.
Thank you everyone for your help,
Taso
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Hey Tasso,
Send $10 to my PayPal and I will ship (2) #83 and (2) #86 to you.
My local hardware store has them.
PM me your address and I will give you my PayPal #.
Just a thought to help,
Kirk
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I had trouble finding a pellet that would shoot right out of my B-50, was going broke trying different pellets. One day when playing around with pressure I noticed that the JSB 10.34 would stack, but only between two fps settings. That is what started my quest to retune my rifle for a specific velocity. Mike helped a lot over the phone, then made and sent me the delrin spring guides and shims. Im using the guide with the 1/4 inch end cap, no shims. He also sent a turned down piece of delrin rod to make transfer ports from. The factory hammer spring was still causing the hammer to hit the poppet to hard which is why I shortened it by two coils. Now velocity is wear it needs to be for the JSB's to group well at 30 yards. I now have a disco that is super accurate in 177 for plinking and pesting in the back yard, along with my marauder, and the disco is so much lighter than the Bam, which is why I decided to give the Bam to the grandsons. I'm not small, just getting old, and the 16 year old now towers over me like my brothers. I was the shortest of the boys at 6'1". They just got a farm with 91 acres so the gun will come in handy when not shooting their powder burners. Still plenty of power to pest with, or just shoot tin cans or targets.
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Thank you Kirk.
Thank you Tom.
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Hello All,
I took most of the first B51 apart Thanksgiving morning. I am stuck on how the valve comes out. I've unscrewed every thing I can and have also removed the trigger housing. Do I just push it out of the air tube? Or does it cinch down after installation like an FDPCP valve?
I tried pushing it out from the muzzle end towards the breech end with not too much force and it didn't budge. I don't want to break anything.
Today I lightened the first hammer Mike Melick sent me. Not machine shop quality but not too bad with a couple draw files and a rotary tool.
https://goo.gl/photos/xvrwYKsRUXfhaTsNA
https://goo.gl/photos/4mUwih38ErksEvnC9
Everything was going great with rotary cutting tool until the last cut:
https://goo.gl/photos/RQMUvhSHXujdx3j38
D'oh!!!! Hopefully I can have someone put a spot weld there. I didn't cut all the way through but at least 80% through the leg.
There wouldn't be a lot of stress there but it could crack and maybe hang up. I'm kind of a perfectionist.
Taso
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Wow, it looks like you've removed a lot of material there. Have you been reading the "Book" it shows how to make a tool to unscrew the valve and then push it out through the breech. There is also a pic. of a hammer with material removed.
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GarthThomas,
Yeah, I didn't realize how much metal was removed until I was editing the pictures. The hammer looks real spindly now.
I used the lightened hammer picture from the Book as a guide. I tried initially with a die grinder but I didn't feel I had the control I needed and the hammer was getting red hot as I ground on it. I didn't think that was desirable. So then I used the rotary tool and cutting discs to remove the majority of the metal. Then I tried to clean up and radius the sharp corners I made to eliminate stress cracks. Either I was pushing too hard or the grinding stones aren't up to this sort of task.
I was surprised at how well the draw files worked. I wouldn't have thought they would have worked so well on the metal.
I have read most of the Book and skimmed the rest. I saw the modified sockets but I didn't realize what they were for. I guess that was one part I skimmed.
I found my real long screwdriver and I got the valve cap off no problem.
Hopefully I can get it all together today and see where it shoots with an 1200 psi fill.
Thank you,
Taso
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When I removed my valve I pushed it out with a piece of cpvc pipe, and out through the fill nipple end pushing from breach side with the pipe. It came right out without a problem. If you try through the breach end it wants to hang on all the holes. I also suggest getting an extra long standard screwdriver from Harbor freight if you need to tighten the end plug on the front of the valve for good o-ring contact and pressure with the air tube. Use the same cpvc pipe to push the valve back down the air tube until you can pin it back in place.
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Tracker1955,
That's what I ended up doing. Once I got the valve end off I used a pvc pipe and pushed the rest of the valve out the front. The rifle isn't full of grease like I had anticipated.
Thanks,
Taso
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Hi All,
Yesterday I took apart the two reservoir tubes I bought from Mr. Melick. One of the tubes had a valve that had a conical valve seat and poppet.
The other two valves I have the 90 degree valve seats and the concave seal valve poppets.
I am having a hard time understanding the relationship of why a smaller diameter poppet is easier to move off the seat.
Also I understand how a conical seat and valve will make a better seal because of the larger contact area plus be more efficient fluid dynamically.
My dilemma is that if there is more seal area then the pressure per square millimeter is lighter? I'm so confused :o
So I guess if someone can explain valve theory or point me to prior post to read that would be great. Also can someone explain which valve would be better for .177 air rifles at 5 fpe and at 20 fpe. While I can turn down a concave poppet for a perpendicular valve seat, I cannot cut an accurate conical valve seat and poppet.
Please take into account I have the desire to do the mods but by very crude means, i.e. no lathe, mill or friends with these tools. For reference, see my butchered hammers above. ;D
Thank you and it's always an adventure ;)
Taso
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The simplest way I can think to explain it is by thinking about one thousand pounds per square inch (1000psi) pressing against an object having an area of one square inch. That's easy, right? That means there is a force of 1000 pounds pushing on the object.
Now reduce the size of that object to 0.5 square inch. The pressure is acting on half the area so it sees only 500 pounds of force.
Same principle with the valve poppet. The pressure in the air tube pushes against the poppet, so the smaller it is, the less force acting on it and less force will be required by hammer to open the valve when it tries to drive it in the opposite direction.
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I think that is where my brain get confused. My thinking is that if I still have a thousand pounds per square inch, 1000 / 1 = 1000. If we reduce the area to .5 square inches the force becomes 2000 pounds per square inch. 1000 / .5 = 2000
See what I mean? So there is now more pressure on the seat. Or is air pressure applied in all directions versus one direction like a weight or spring? Sorry, I don't remember much from my physics class 30 years ago ;D
Taso
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The way I like to think about it is like this...
There's high pressure in the tube. There's low pressure in the outside world. The high pressure wants to escape to the low pressure side but the poppet is in the way. The pressure is acting on one end of the poppet. There's virtually no pressure on the other side of the poppet (only 1 bar / 1 atm). It's the difference in pressure between those two sides that establishes the direction the poppet "wants" to go.
To draw a comparison, an object placed inside the tube--say, a small steel mass the size and shape of a sugar cube--does indeed have pressure acting on it from all sides. If that object were compressible, it would shrink in size but it has no impetus to actually move within the tube because the pressure is acting on it equally in all directions. One side of it would have to be exposed to the atmosphere (or some lesser pressure) in order to make it want to move.
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I think that is where my brain get confused. My thinking is that if I still have a thousand pounds per square inch, 1000 / 1 = 1000. If we reduce the area to .5 square inches the force becomes 2000 pounds per square inch. 1000 / .5 = 2000
See what I mean? So there is now more pressure on the seat. Or is air pressure applied in all directions versus one direction like a weight or spring? Sorry, I don't remember much from my physics class 30 years ago ;D
Taso
Actually other way around.
If you have a vessel with 1000 PSI within it, and your poppet to release pressure had a surface area of 1 sq in, it would take a force of 1000 LBS to break it loose.
Reduce poppets area to 1/2 sq in it would take 500# to break it loose .... 1/4 sq in at 250# on down the effort falls as the area pressure is exerted against keeps getting reduced.
This is why we speak of reducing poppet diameter so it takes LESS hammer/spring energy to open it.
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Hey guys,
I got the poppet springs yesterday! ;D Hopefully I will be able to get the first B51 up and running with a goal of 500 - 525 fps in .177 this weekend.
I bought a little dc inverter stick welder, I've always wanted a welder ;D , to fix the hammer I cut too far.
I also found an 8" drill press for $60 shipped. I'm going to try drilling out the hammers from the side to lighten them. Hopefully that will work out better than the rotary tool.
What diameter do you recommend turning the poppet down to for the first rifle? Or should I use the spare conical valve as is?
Thank you all for your help! :D
Taso
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Hey Taso,
The taper on my B50 poppet is about 35 degrees.
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Tune12-21-2014008_zps916f7043.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Tune12-21-2014008_zps916f7043.jpg.html)
Hope the pic helps ............ Kirk
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Kirk,
So you recommend the conical valve, from your picture, sealing on the edge of the flat valve seat versus a slimmed down flat valve poppet on a flat seat like Garththomas posted?
This is for the low powered B51. I haven't started on the high powered rifle yet. ;)
Thanks,
Taso
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Hey Taso,
I chose to taper poppet's end. The (large) outside diameter of the whole poppet was not reduced.
My valve spring is conical; this is the heavier valve spring I sent you. In Later versions, I used the lighter spring.
IIRC, I drilled the throat of the valve slightly larger too.
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Regulator004_zpsfdd42c9c.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Regulator004_zpsfdd42c9c.jpg.html)
Garth Thomas's poppet looks to be a slightly smaller diameter, with a taper near the sealing surface of the poppet. Since the poppet is unused, it's hard to see if the poppet seals on the taper or with the flat end?
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Kirk,
From his post here:
http://www.gatewaytoairguns.org/GTA/index.php?topic=79971.80 (http://www.gatewaytoairguns.org/GTA/index.php?topic=79971.80)
It looks like he tapered the poppet to 5/16" but I haven't found if his valve seat is flat or angled.
The seat passage/area around the valve stem, in my valve seems to be around .236" with a slightly rounded edge. So .3125 - .236 = .0765 .0765 / 2 = .03825 sealing ring.
Will that be enough to seal? I guess if there's abrasion/wear, with the taper, it may wear to an equilibrium point where the spring/air pressure balances with the delrin physical support properties.
Kirk, do you remember what your delrin hammer weighed? I like your tapered poppet solution the best so far. How did your poppet wear?
OR, am I worrying about stuff that has minimal effect and I should stop worrying and just shoot the rifle? lol
Thanks,
Taso
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The seal is on the flat face, the reduced diameter allows for less force to open as discussed. That is a factory poppet by the way, I'm still waiting for it to fail.
This setup is for what ever power level you want as a matter of fact it suits higher power especially with the thinner washer which reduces spring preload in the valve.
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GarthThomas,
Thank you for the clarification! I'm off to go get welding rods. ;D
Taso
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Hey Taso,
The taper on my B50 poppet is about 35 degrees.
(http://i113.photobucket.com/albums/n227/kirk_schwarz/Tune12-21-2014008_zps916f7043.jpg) (http://s113.photobucket.com/user/kirk_schwarz/media/Tune12-21-2014008_zps916f7043.jpg.html)
Hope the pic helps ............ Kirk
If your going to go with a tapered contact seat configuration, Angle as shown ( Or flatter yet ) is going to be required IMO.
Using a shallow contact angle is kin to a cork in a bottle ... The poppet head as it gets hammered into the seat will start going down the throat effectively CORKING IT !
The lift of poppet required to clear throat will become higher as the portion of poppet within throat of valve increases in depth.
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Hey Taso,
So GT's poppet seals on the smaller flat surface of the original poppet, while my poppet taper has a higher pitch and seals on the taper (as can be seen in the pic).
I believe, sealing on the taper requires a lighter hammer strike than the flat, but obviously both methods work fine. I used the taper seal because a very light hammer was being used. I don't know the combined weight of my delrin hammer & spring guide - maybe in the 40+ gram range.
You can use the light or heavy conical springs I sent you to further lighten the force needed to break the poppet from the valve seat. The lighter valve spring just allows you to use a lighter hammer/spring guide set-up and or a lighter hammer spring.
The goal of using the lighter hammer/spring guide/valve spring/tapered poppet & lighter hammer spring was to reduce stress on the popper, which has been a known failure issue with the BAM B50/B51. I have never checked a poppet for wear, but assume it will last much longer than OEM.
This "lighter" tune process is the Motorhead method using some tweaks copied from others.
Taso, much like I "DO" you are beginning to ruminate too much about this and just need start working. However, you don't want to get so caught up in "process" that you forget to be present while your working (I do this :o).
Good Luck 8) 8)
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Thank you for the clarification! I'm off to go get welding rods. ;D
Don't get me wrong but you may want to trash that broken hammer, they are a precise fit and welding may distort it and without say a lathe or some tooling that could true things up it may not fit back in the tube or slide properly. Since it was a spare just move on to your next idea or try the less invasive steps and shoot it you may like where your at before doing all the other stuff. JMO
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Garth,
I tapered the poppet to about 5/16" like yours. I learned a lot about delrin last night lol. First, it takes a lot longer to remove material than I thought. Second, have to keep the drill at a slow speed so the friction doesn't create enough heat to melt the delrin. It created a warped lip, kinda like a candle. So I slowed down, kept going and it came out well.
As for the welding, it went ok. I was able to mend the gap. I cleaned it up with a file and put it in the rifle but I found out the hammer was doomed from the start. I don't know if you can tell but the tail end of the hammer I posted pictures of had material removed from the diameter in the center portion. This change in diameter, step, causes the hammer release to catch and the hammer can't be pulled back enough to set correctly. I tried to radius the forward edge of the hammer release so it could pass the step but it won't work. So I filed the step out of the hammer. Tried it out and now the material is too low to catch.
So I'm done with that hammer. As for the new hammer I think I can get away with just drilling one .8 hole all the way through the side. Will a regular high speed steel bit work or should I look for a carbide tipped one?
I also noticed that there are two different length hammers. The one that came out of the new rifle is shorter than the unmodified one Mike sent me.
Thanks,
Taso
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Yes there is not a lot of room for play with those hammers as far as drilling I wouldn't know, I've never tried cutting into the hammer. I put my valve stem in a drill press and set it for low rpm so that helps with the heat, then I set the table so I can hold the file or emery paper on a block to shape what ever I'm working on, its a poor mans lathe but I have had a lot of practice with it. Even shaping the poppet takes precision I don't know if I could do a good enough job like Motorhead's taper with my method.
Also if I might add, since doing the work shown by rsterne I have tuned my rifle to below 6fpe and right now I have it at 17fpe just using the stuff shown in his post so that was what I liked about that post, nothing radical or permanent. For the lowest power I used the MC spring, the Delrin guide with 1/4" stop and a 3/32 Transfer port and some shims for the hammer spring to fine adjust as well as the valve work and that put it just below 500fps.
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Hi All,
I apologize for not giving an update for a while but I haven't done anything with my project till today. Well today I tried to drill my 3/4 inch hole through the side of the hammer.
The Bosch high speed steel drill bit I bought only made it half the way through the one side and stopped. It was going good until then. I guess the interior is hardened or the bit wore out that quickly? I was using oil to help the drilling.
Oh well, I need to find a carbide drill bit now. I'm going to skip the cobalt drill bits unless anyone has had success.
Thanks,
Taso
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Hi All,
Tonight I was able to lighten the hammer with my drilling through the side idea. It honestly came out better than I expected. The final weight ended up being 93.63 grams.
So after my small victory I started searching for optimum hammer weight after I saw this recent post:
http://www.gatewaytoairguns.org/GTA/index.php?topic=101679.0;topicseen (http://www.gatewaytoairguns.org/GTA/index.php?topic=101679.0;topicseen)
So in my search I found this post:
http://www.gatewaytoairguns.org/GTA/index.php?topic=48892. (http://www.gatewaytoairguns.org/GTA/index.php?topic=48892.)
I have only read the first page but it seems I need a much lighter hammer. :( That or sorcery lol
Until any of those two things happens I'm going to put the rifle together and start shooting is and see what happens. ::)
Thanks,
Taso
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I shoot my .25 caliber regulated B50 at @ 45 to 50 ft lbs with a 100% nylon hammer with a steel screw contacting poppet stem weighting JUST 30 grams total weight. ( Reg set at 2000# )
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Wow, those hammers are hard, for sure something wore out doing that. David
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Rocker1,
I never would have thought they were that hard. I have read many times that these rifles are built like tanks and now I'm seeing why. :o I am so glad I picked this platform to tinker with.
My little, cheap drill press was chattering and groaning. I couldn't find a solid carbide drill bit in 3/4", that was budget friendly, but I did find a carbide tipped drill bit that's made to drill granite counter tops that had a sharpened edge versus concrete hammer drill bits that are pretty dull from the factory.
All in all it was $13.20 well spent.
Rocker1, are you still making B51 LDC's? I may need your services in the very near future. ;D
Thanks,
Taso
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Hi All,
I'm sorry I haven't updated you on my project in a while. I didn't realize I would have such a hard time locating parts. :o I did get very lucky though. Scott had time over the holidays and was gracious enough to make me 3 nylon hammers. Thanks Scott!
Kirk was also great in that he was able to locate and send me the conical valve springs. Thanks Kirk!
I was able to find a 1/2" od light hammer spring from Menards. Scott recommended the 10# Marauder hammer springs from WAR, so I've ordered 2 and waiting for them to arrive.
I had to open up the valve cap id to 1/2" as the conical springs were too tight and kept hanging up on the wall.
Scott recommended I also polish up the reservoir tube where the nylon hammer will slide with 600 grit. There are still factory machine grooves but Scott said not to worry about them.
I tapered the valve poppet to make it easier to lift off the seat.
Next I needed to vent the rear of the hammer chamber because vacuum is created when the hammer is released forward. I drilled a 3/8" hole but when I went to put it back on the air reservoir I noticed I made a mistake. I thought the end cap extended past the trigger frame. Oops! Then I figured I can file away some material from the end cap to allow the pressure to escape. It came out better than I thought. Good save Taso! ;)
The pictured spring is mostly temporary unless it works awesome. I cut it so it had about a half coil of preload per my measurements. I didn't have any 1/2" od washers to keep the spring pigtail from going into the air vent and changing spring rate. I will get some from Lowe's tonight.
Hopefully I can get the rest of the rifle together tonight, pump it up and shoot it! I will keep you updated!
Thanks for your patience and help!
Taso
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It's a BAM B51 air rifle again! It was apart way too long.
I hope there are no leaks and get some shots at different fill pressures to post.
Taso
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So I was able to shoot the rifle from 800 to 1500 psi to find the pressure to set the regulator. I don't remember which post Bob Sterne mentioned it but I'm glad I found it. Bob's way, pumping to 800 psi and taking a couple shots to see where you were velocity wise. Then pumping to 900 psi and recording your shot velocities. I used the gauge on my Xisico pump for the pressure readings.
I was going to pump up to 1500 psi and then shoot down from there. I planned to connect my pump after about 5 shots and pump till where the fill valve clicked open and record that pressure off the gauge. I like Bob's way better. Thanks Mr. Sterne!
So now for the issues. Remember this rifle was basically unfired. I probably put 10 pellets through it before I took it all apart to perform my lightweight plan. So it was never broken in. All the o-rings were replaced with polyurethane ones except for the transfer port o-rings which I used 70 durometer buna-n.
First issue: the valve poppet would not seal as I tried to pump up the rifle from empty. I tried to grab the poppet stem on the fully assembled rifle from the bolt probe notch on the left side but it was too narrow for my needle nose pliers. So I had to remove the stock, back cover and hammer to grab the poppet stem with the pliers while trying to pump. Yes, my feet came into play, almost like Twister but I got it done! ;) I will keep an eye on the poppet but hopefully it will break itself in and mate better with the valve seat.
Second issue: after I pumped the rifle to 1100 psi I heard air leaking from the foster fill fitting. I quickly shot my 3 shots before I lost too much air so maybe those shots are skewed and should be disregarded. While pumping to 1200 psi I was able to get a couple drops of silicone oil into the fill valve and the leak was almost gone. I put another 2 drops when pumping to 1300 psi. I will have to keep an eye on it too. If it doesn't go away I'll take it apart again. I'm almost positive there's a new poly o ring in there.
Now for the velocity results. I used Crosman .177 Domed 7.9gr Premier Pellets from the brown cardboard box. The end of the barrel was about 7 feet from the first chronograph sensor. I'm listing the velocities in the order they came out of the rifle.
800 psi 751, 761, 767
900 psi 740, 737, 735
1000 psi 672, 673, 677
1100 psi 621, 642, 655
1200 psi 571, 560, 569
1300 psi 507, 506, 505
1400 psi 455, 445, 440
1500 psi 398, 412, 417
It's obvious from my results that the higher the pressure goes the harder it is for the lighter springs and hammer to open the valve. Since my goal is around 550 fps as a regulated 10 meter target rifle I think I'm on the right path. Tomorrow I will take velocity readings starting at 400 psi.
If, for example, I hit my 550 fps goal at 400 psi Is it normal for a regulator to be set this low? Milo74 did say his regulators can be set as low as 100 psi. Or would it be better to shoot at the 1200 psi level?
I'm thinking the 400 psi level should be more efficient. More shooting and less pumping would be great. I don't plan on pumping to 3000 psi. I think 1500 or 2000 psi will suffice.
I have a feeling other issues may pop up running at so low a pressure. Would it be harder to keep the poppet sealed or under control if there is less seat pressure due to low psi and lighter poppet spring?
I remember reading the first page or two of Bob Sterne's SSG, maybe that can help, but I would have to re read it as I don't remember what I read back when he first posted it. Tomorrow is another day. :-) And besides, my brain is mush right now.
Thanks to everyone for your help,
Taso
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Actually the HIGHER pressure is more effecient. In a low power tune as you wanting experience tells me 1100-1500 psi range for reg set point will be where to start.
Also on the BAMs ... poppet diameter is WAY TOO LARGE and can be reduced to @ .320 or even a tad less. Poppet spring needs to be replaced as well with one much softer when utilizing those light hammers.
Burnishing in the poppet to body by spinning with an electric drill works quite well.
have fun !!
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Don't over power the poppit spring with to much hammer spring , it will make you dance. David
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Hi all,
First off I'm going to answer your questions.
Scott,
I did turn the poppet down a bit toward the sealing end. I initially removed material too fast and I think I heat warped it from too much friction on my files and sandpaper. So then I had to "true" the warped part. I cut a 3/8" strip of 600 or 800 grit sandpaper, poked a hole in it for the valve stem to pass through and put the poppet in the valve body. I figured it would keep my angles correct and only remove material from the mating surface. Then I connected my drill to the valve stem and held the sandpaper so it wouldn't turn in the valve body. I sanded the mating surface of the poppet slowly till all the warpage was gone. I am also using the #86 Hillman conical spring. It's much lighter than stock. There is a picture of both assembled together in my last set of pictures.
David,
Thanks for the heads up. :D I am using a 1/2" x 3.5" spring I found at Menards. It's much lighter than stock at about 6.5 pounds per inch of travel. I should test the force again as I basically cut the spring in half since then. I am not a very good dancer lol
So now for today's update:
This morning I checked the gun with my pump gauge to see if it leaked air overnight. It was down to around 950 psi from around 1400 psi from last night. So when I got home today I took the stock and the barrel off and checked the transfer port, valve body and fill fittings for leaks. The only place I saw leaking was the fill fitting out the foster end.
So I release all the pressure in the tube and remove the end cap. The little valve has a new polyurethane oring so I must have replaced it when I went through the gun initially. So I checked for burrs or junk that would interfere with the seal. I didn't find anything so I put some new silicone grease on the orings and put the gun together again. I start pumping and the poppet valve hisses. It's losing less air than I'm putting in and stops leaking after 2 or 3 more pumps.
So I stopped pumping around 400 psi so that I can start taking velocity readings up to 800 psi. I start releasing the pressure on the pump and all the air comes out of the rifle. I close the relief valve and figure 400 psi may not be enough to seal so I pump up too 800 psi, like I did yesterday and it held pressure. Upon opening the relief valve as quick as I can, all the air leaks out of the rifle again.
So I pull the endcap off and think there may be a thin casting line in the polyurethane oring. So I stretch it over a rod and I spun it about 10 times on some 800 sandpaper. I put it back together, pump up to 1000 psi and same thing. The valve won't seal. I got the same results with a buna-n oring too.
Am I doing something wrong? Is there a better foster fitting to use with a spring assisted valve like the FD PCP's have? I see the sintered filter is threaded and moves. Does that need to be a certain distance from the valve? I have the valve inserted so that the slot faces the rear of the gun also. Is that right?
As always, thanks in advance for your help! I am going to search the internet for possible solutions too.
Taso
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Yea the BAM oem Foster can be a MAJOR PITA !!!
many times had to polish the bore where sealing spud moves. Worst case manufactured another altogether changing it to a more conventional T stem and o-ring configuration.
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Okay, I'm a dummy lol. I found out what I was doing wrong with my fill valve. I, the genius (sarcasm), was pushing the little valve into the bore of the foster fitting. I "believed" that is how it was when I disassembled it. So tonight, as I thought about that design, I couldn't figure out how the valve was supposed to get back into the bore to seal.
So from searching the internet I read that the valve should rattle in the fitting and is designed to seal against the bevel on the end. I make the adjustments and now the rifle holds air after pumping.
Ta Da!
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Here are my velocities shooting from 400 to 800 psi:
400 psi 634, 616, 614
500 psi 701, 694, 690
600 psi 720, 724, 715
700 psi 755, 768, 761
800 psi 741, 753, 749
And a graph of the velocity averages versus psi below.
Taso
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Hi All,
I received the 10 pound Marauder hammer springs from Wicked Air Rifles on Monday and I had time to swap one in and shoot some pellets at rising pressures like my prior posts from 500 psi to 2500 psi. Everything is the same except for the new hammer spring. I only shot one pellet after 1500 psi because the rifle was so loud.
2500 psi 1138 fps
2400 psi 1124
2300 psi 1104
2200 psi 1101
2100 psi 1083
2000 psi 1066
1900 psi 1056
1800 psi 1044
1700 psi 1024
1600 psi 1008
1500 psi 984, 984, 970
1400 psi 973, 959, 951
1300 psi 955, 942, 933
1200 psi 924, 917, 907
1100 psi 905, 890, 878
1000 psi 870, 866, 851
900 psi 847, 838, 831
800 psi 812, 808, 802
700 psi 775, 760, 755
600 psi 726, 714, 710
500 psi 623, 619, 612 After this last shot the gun dumped the remaining pressure in the tube. The poppet spring couldn't keep the valve closed against the hammer spring.
So now I have to figure out what pressure to set the regulator. This is where Bob Sterne's "knee" comes into use. I need to read that post again. Milo set one of the regulators to 1200 psi and the other to 1500. Does anyone know what type of regulators they are so I can read up on them?
I also need to figure out how much plenum I need for the 10 meter setup shooting 7.9 grain wadcutters between 550 and 600 fps. I also need to know what to use as a plenum that won't crush. I also don't know which end is which on the Milo regulators. :o
But tomorrow is another day. :-) Thanks to all for your help!
Taso
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You're looking for about 6 fpe at that weight and velocity. plenum is normally 1cc per fpe so a 6 cc plenum. you'll have to do the math.
flat end of the milo regulator is the plenum end. I've got 4 from him now.
And I think I've got a length of the plenum spacer that he uses for the B50/51 that i can send you.
it is thick walled aluminum tubing its OD just smaller than the air tube ID.
use the 1200 set regulator. the plenum calculation is based on 1000psi.
tie a wire loop onto the stem end so you can pull it back out later if needed.
then play around with lighter/clipped hammer springs, striker adjustment and a restricted transfer port. 5/16 delrin rod makes easy transfer ports for these rifles.
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Marty,
Yes, that's my goal for this first rifle. I think my first spring, the cut down spring from Menards, may work. On that pressure/velocity graph, the first one I posted, the setup was hitting around 566 at 1200 psi.
Thank you for your offer on the plenum spacer! If it's something I can source locally I'd hate to inconvenience you. But if I can't get it from home depot etc. I will take you up on your offer. :-)
Do you have the ID of your thick walled aluminum tubing so I can calculate the 6cc's length?
Yes I agree, I will tweak preload, striker and transfer port one at a time to see what effect they have on my power and efficiency.
I am using the shortest of the three nylon hammers I have. The other two are longer so I can see how they affect power after I get the regulator installed.
Mike Melick sent me some delrin for transfer ports with the extra parts I ordered from him. I think I will play with that last.
I have attached a picture of my regulator. From your explanation, the side I labeled with "1" goes towards the muzzle and "2" towards the valve? The plenum will go between the regulator and the valve.
Do these regulators need to be vented to atmosphere? I'm assuming the vent needs to be placed between the two orings. Can you tell me what type these regulators are so I can read up on them and their design?
Thank you for your help!
Taso
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Direction is as stated, adjustment end towards muzzle.
Plenum between Valve and Reg.
YES needs a vent hole in main tube between o-rings. * Do so as far forward as you can once plenum size is known ... so if wanting more power later a longer plenum can be fitted and vent hole still falls between o-rings ( tho would be at other end of reg body )
That is a MILO74 regulator ... Excellent units made by a fellow GTA member " milo74"
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Forgot to add .... MAKE SURE the I.D. area of tube where regulator ends up is smooth and free of drawn tube marks. O-rings need a good surface to seal against. Using a 3 stone brake hone maybe required.
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Plenum spacer I've got is 0.895" ID.
Running through the math, a .75" spacer would give you a 7.7cc plenum.
You have a little more volume in the valve as well.
A little larger than needed, but a good spot for your goals.
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Thank you Marty! ;D
Scott,
What size does the vent hole need to be drilled? I can match it to the vent hole size on the regulator or does it have to be bigger?
I'm pretty sure it's not possible but I'm going to ask anyway. The hole cannot be sealed if drilled wrong correct? I'm thinking the heat created from an arc welder will change the tube properties and weaken it.
I think I'll measure 4 times and drill once lol.
Taso
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You are welcome!
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Thank you Marty! ;D
Scott,
What size does the vent hole need to be drilled? I can match it to the vent hole size on the regulator or does it have to be bigger?
I'm pretty sure it's not possible but I'm going to ask anyway. The hole cannot be sealed if drilled wrong correct? I'm thinking the heat created from an arc welder will change the tube properties and weaken it.
I think I'll measure 4 times and drill once lol.
Taso
I do mine with a 1/16" tip starter drill, stop short of breaking threw, finishing hole with a .040"
Run a hone within tube where reg will sit to BOTH deburr hole and make sure o-rings will seal.
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Hi All,
Sorry for the delay in my project to those that are following. I had time tonight to degas and disassemble my first B51 so that I could drill the vent hole for my Milo74 regulator. I used Motorhead's recommendation and it came out well. I started the hole with the 1/16 drill bit and completed with the .040 drill bit. I've never used a drill bit so thin and I broke it before the hole was all the way through. I was able to clamp the cutting end in my drill chuck and finish the hole.
I ran my 600 grill flex hone with 30 weight nd oil to remove any burrs from drilling. Surprisingly my tube had a mirror finish from the factory so I shouldn't have any problem with the regulator orings sealing. I rinsed the tube out with 91% alcohol to get the flex hone grit and oil out. I didn't remove the valve because I have a hard time removing the cross pin that holds it in. Maybe I'm doing something wrong. If there's a proper way to do it please let me know.
So I'm going to let the tube air out so I don't have a flame thrower and hopefully I can get it all back together tomorrow and start shooting it! ;D
Thank you to all who have helped. You know who you are!
Taso
UPDATE: I forgot the pictures!
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So I got the rifle all together and roughly adjusted to shoot around 550 fps with 7.9 grain Crosman Premiers. I have never had or shot a regulated rifle before and the prior configuration didn't have 50 pellets through it to break in.
Later I will try tuning it for better efficiency via striker length and maybe an ssg.
I know things should smooth up and settle down. My question is how is a regulator supposed to work? The reason I ask is right now the rifle with the regulator starts at a lower velocity, 490's, and then comes up to the 540's after 5 or 6 shots and pretty much stays there. I pumped it back up to about 2900 psi and it did the same thing.
I also think if I let it sit for an hour and then shoot it I get the same pattern. Is this normal? Does the regulator need to break in? I asked Milo74 to set at 1200 psi.
Thank you,
Taso
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So I got the rifle all together and roughly adjusted to shoot around 550 fps with 7.9 grain Crosman Premiers. I have never had or shot a regulated rifle before and the prior configuration didn't have 50 pellets through it to break in.
Later I will try tuning it for better efficiency via striker length and maybe an ssg.
I know things should smooth up and settle down. My question is how is a regulator supposed to work? The reason I ask is right now the rifle with the regulator starts at a lower velocity, 490's, and then comes up to the 540's after 5 or 6 shots and pretty much stays there. I pumped it back up to about 2900 psi and it did the same thing.
I also think if I let it sit for an hour and then shoot it I get the same pattern. Is this normal? Does the regulator need to break in? I asked Milo74 to set at 1200 psi.
Thank you,
Taso
The Up/Down velocity when starting out or stopping for a spell is SET POINT CREEP & not typical or wanted.
Pending hammer weight, spring rate, stroke in any combination etc ... has valves poppet react differently to the pressure within plenum changing.
What the specifics are in your case can't say other than this "general regulation profile" of operation ....
As a regulator creeps MORE air is put into plenum until reg stops finally resulting in HIGHER than set point pressure.
So generally this higher pressure makes the opening of poppet take more energy.
In this case I see this as hammer strike being too soft overall and when plenum pressure is up from the set point creep poppet is NOT opening sufficiently resulting in a lower velocity.
* It can also create a Spike in velocity in cases where hammer strike is on the heavy side and easily overcomes a rise in plenum pressure and releases the higher pressure to pellet resulting in a higher speed.
It is a dance of finding the balance .....
* Your regulator may be just fine being they ALL creep a little ... just in your case as set up the incremental change in plenum pressures messing with your velocity excessively.
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Scott,
"SET POINT CREEP"????? Is there a cream for that??? :o
All joking aside, I just did some educational reading on set point creep. The regulator was built by Milo74 and this is it's maiden voyage. I get what your saying that plenum pressure is increasing over the 1200 psi regulator set point over time and harder on the poppet opening thus reducing shot velocity until the plenum comes back down to 1200 psi.
Do you think the regulator is defective or maybe an oring in the regulator is leaking and could be replaced? There were extra orings in the zip lock with the regulator and they look like buna black orings. Would polyurethane work better?
Thanks,
Taso
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I degassed the gun and pulled the regulator out. I took the regulator apart and checked for any foreign objects or damaged orings. As far as I could tell I didn't see anything wrong.
Taso
-
I put the regulator back in the rifle and pumped it up to about 1525 psi, I think. I'm 95 percent sure but I could be wrong. Then I shot 50 7.9 Crosman Premier pellets. Velocities shown below:
1 550 26 568
2 569 27 563
3 595 28 564
4 601 29 566
5 580 30 566
6 569 31 568
7 567 32 579
8 574 33 580
9 563 34 575
10 573 35 561
11 583 36 578
12 580 37 579
13 568 38 582
14 575 39 579
15 581 40 586
16 575 41 557 first shot after 5 minute washroom break, sorry lol
17 570 42 574
18 553 43 601
19 577 44 586
20 574 45 586
21 572 46 598
22 562 47 593
23 575 48 594
24 564 49 599
25 567 50 605
Hi 605
Lo 550
Av 576
ES 55
SD 12
Ending pressure was around 1325 psi. Somehow that doesn't seem right that it only used 200 psi. I may be wrong about starting pressure.
I would have thought the regulator would give me a tighter ES. Do you think there is something wrong with the regulator or am I doing something wrong?
I'm going to pump the rifle to 2000 psi. Tomorrow morning I will check to see if the rifle held air and I will shoot 10 shots to see if above set point pressure crept into the plenum overnight. I'll report the results.
Thanks,
Taso
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You need to Reread my post and try & wrap your mind around hammer strike, pressure & variances in velocity.
Stated was regulator may be fine ... hammer strike is too light, heavy bias hammer strike with a plenum pressure change higher raises velocity.
as your currently set, way to define if reg is stable and/or other factors are at work ... is, raise hammer strike energy with a heavier spring
& go after a shot string ( At what ever energy it is stable at ) getting into the mid range of adjustments where slight differences in plenum pressure really have minimal effect on velocity. * as in the reg creep ( small if present ) really in not an issue.
Ideally even tho regulated, valve when getting more balanced should reflect attributes of a self regulated valve being pretty stable in output even tho digesting subtle changes in operating pressure.
If the tune at this juncture is stable, then more or less velocity is best controlled by transfer port size calibration.
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Scott,
My brain wants to think "if" the regulator is giving me a constant 1200 psi and my springs and hammers remain the same I "should" have a shot string that may vary + or - a couple feet per second due to variation in pellet weight and seal.
I get that in a non regulated gun, like an FDPCP for example, you fill to 1500 psi and say we have a goal of 900 fps with a rising and then decreasing velocity curve. At 1500 psi you are not in your hammer sweet spot and the valve is harder to open so you're only getting 800 fps. As you shoot and use air pressure, the valve becomes gradually easier to open, we get to our sweet spot pressure and the velocity climbs to our 900 fps goal. As we keep shooting valve is even easier to open but we're almost out of gas and velocities drop off.
Don't some of these laws of physics transfer to regulated rifles? I'm not being a smart aleck, I really do want to understand what is going on. I have no experience in tuning air rifles. That is why I am asking experts for help. Scott, are you saying to compensate for the regulators variance in pressure I should increase hammer spring force? When I increase hammer force velocity goes up. Then to decrease velocity you need to increase pressure or striker length or decrease transfer port.
Initially after I installed the regulator I started with a cut down Menards spring that had very little to no preload and the shortest nylon hammer I got from you. Velocities started at 136ish and went up to the 300's. This was probably the overnight creep you explained. I then removed that spring and installed the WAR 10# Marauder spring you suggested. The velocities were in the 900's and I could hear air screaming out of the barrel after each shot.
I then took another brand new Menards spring and cut coils till I was in the 700 fps range. Then I installed the middle length nylon hammer I got from you and velocities were in the 550 - 600 range. This is where I want to be velocity wise. I planned on fine tuning the striker length to find the knee eventually but my velocities were jumping around. Thus my present dilemma.
I guess there's more to learn and a regulator doesn't really eliminate the pressure variable in my equation like I thought. I am on here to learn, have fun and make friends. :D Can you help me understand?
Thank you Scott,
Taso
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Hello All,
This morning I checked the pressure in the rifle and it's at 2000 psi, according to my Xisico pump gauge, so it may be leak free. I'll have to watch it over a week or month.
So I shot another quick 20 shots this morning with no changes in the rifle from last night:
1 457
2 477
3 502
4 512
5 534
6 544
7 570
8 582
9 585
10 582
11 579
12 585
13 592
14 588
15 592
16 603
17 594
18 596
19 588
20 591
I'm probably premature but it looks like it's settling down. The last 13 shots are reassuring ;D I would like to get 50 or 100 more rounds through the rifle today. I will use cheap Crosman milk carton pellets just to break in the rifle and then shoot a 20 or 30 shot string with the Premier Lights to see the effects.
If you have any suggestions or comments please feel free to post.
Thanks to everyone for your help!
Taso
-
Tonight I put about 100 7.4 grain Crosman Hunting pellets, from the milk carton, through the rifle. I took a break for about an hour and then shot 30 7.9 grain Crosman Premier domes, from the cardboard box.
1 567 16 604
2 592 17 605
3 601 18 618
4 600 19 616
5 607 20 614
6 609 21 615
7 606 22 596
8 620 23 615
9 608 24 590
10 593 25 610
11 601 26 606
12 602 27 599
13 599 28 616
14 601 29 610
15 616 30 608
HI 620
LO 567
AV 604
ES 53
SD 10
If I remove the first shot, 567 fps:
HI 620
LO 590
AV 606
ES 30
SD 8
Does anyone have any thoughts or an explanation on what's going on? Average velocity crept up but that may be due to the breaking in.
Thanks,
Taso
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Most of your strings show an increase in velocity towards the end of the string.... That indicates that the hammer strike is too light for the regulator setpoint.... That setup typically causes a rise in velocity below the setpoint.... Increase the hammer strike (gives higher velocity) or reduce the setpoint....
Bob
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Bob,
Thank you for your input! My goal is right around 575 fps with 7.9 grain pellets. I just re read your post on tuning regulated pcp's and I finally understand what the knee is. I have not done the spring preload testing to find it yet. Should I do that first and see where my velocity ends up? Or should I reduce setpoint and then try to find the knee? It would not be terrible if my velocities are less than 575 as this is just going to be my offhand trainer. So accuracy is first, shot count a close second and velocity to maximize accuracy and shot count.
Thank you All for your help!
Taso
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Scott,
I found this picture when I re read Bob's post "Tuning a Regulated PCP" Is this behavior what you were talking about?
Disclaimer: This picture is Bob's, not mine.
Taso
-
While Bobs graph shows an upswing in velocity ... reason for, BOTH of us have elaborated on already.
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Hi All,
Just a little update. I went and lowered the regulator setpoint. It was initially set at 1200 by Milo. Half a turn only brought velocity from 920 to about 800 fps. Another 3/4 turn brought it down to 300 fps. So I went back and now I'm basically 3/4 turn CW from the original setting. I have no way to measure the output pressure to verify the setpoint.
Milo says a 1/4 turn is between 190 and 250 psi. So if I did 3/4 turn I should be between 630 and 450 psi. Does that sound right?
So now at this setpoint the rifle was shooting 630 on the plateau. I adjusted coils and shims to around 580 fps if I remember correctly. I wasn't able to shoot much yesterday. I will try again tonight.
So I have a question. In Rsterne's post on tuning regulated pcp's he explained that the knee velocity is around 3% lower than the plateau velocity. If my plateau is about 630 fps and with adjusted hammer stroke and spring tension I'm down to 580 fps goal which is 8% below plateau velocity. I think that puts me on the shin lol.
I will probably increase hammer stroke/spring tension to bring my velocity up to within 3% of plateau so I don't get the velocity spike when I come off the regulator.
I guess I'm at the 80% performance point with 20% effort lol. That was a lot of effort for that 80%. I have learned a whole lot though.
Do I need the last 20% performance? ;)
I still need to shoot a couple long strings to see ES but I think I'm close to having met my goal for this rifle.
Hopefully I can shoot some strings tonight.
Thank you to everyone that has helped!
Taso
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Hey Taso,
Do you have a RVA? Otherwise, shorten your striker (assuming adjustable on your set-up) to get velocity up to about 600/610 fps.
Good luck :D
-
No. I have the medium length nylon hammer Scott made me. I have so far been adjusting with shims in the endcap and spring length.
I could cut some off the front of the hammer or substitute the nylon hammer with the shorter nose. I don't recall how much shorter it is but I submitted pictures in this post earlier.
I had made a cheat sheet with what certain adjustments affected but that's at home and I'm at work. :( I didn't sleep well last night and I had plumbers come real early to fix a slow drain. So my brain is mush today. lol
What are the pros and cons of adjusting hammer stroke from the nose versus shimming at the endcap?
Thank you!
Taso
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Yeah Taso,
Don't cut the hammer; it would just add more shims to increase spring tension :D
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I was able to put some rounds through the rifle this morning. With the two washers installed in the end cap I got:
587 636
617 637
640 635
643 638
641 639
639 638
637 633
637 640
637 638
646 638
Which calculates to ave 634, es 59, sd 12. If I remove the first two shots it calculates to ave 638, es 13, and sd 2.
I also wanted to verify the plateau so I added more washers.
3 washers gave me:
677
665
659
668
664
ave 666.6
and 4 washers gave me:
672
663
663
663
665
ave 665.2
So with 3 and 4 washers installed the setup is on the plateau. With two washers installed the average velocity is 4.2% down.
I want to bring the velocity down another 80 or 90 fps hopefully to quiet report further for back yard use too.
What velocities are usually the quietest out of .177?
Should I try and 1/8 or 1/4 turn on the regulator set screw?
Thanks,
Taso
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Tighten up ( decrease ) the transfer port size now to get on the target velocity .... IMO.
You can screw with Reg output ... but lower the pressure within valve becomes, greater the dwell likely will be as well.
-
Scott,
Thank you for the guidance. I am currently using the original brass transfer port. Mike Melick had sent me two delrin rod pieces drilled with 3mm and 2mm holes respectively. I can try those but I'm gonna need to figure out how to "slice" them and keep them flat. Do you think they will be ok flat or do they need to be shaped like the original?
It may be easier for me to fill the original transfer port with JB Weld and drill the port out in increments and test in between.
Would that work Scott?
Thank you,
Taso
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Scott,
Thank you for the guidance. I am currently using the original brass transfer port. Mike Melick had sent me two delrin rod pieces drilled with 3mm and 2mm holes respectively. I can try those but I'm gonna need to figure out how to "slice" them and keep them flat. Do you think they will be ok flat or do they need to be shaped like the original?
It may be easier for me to fill the original transfer port with JB Weld and drill the port out in increments and test in between.
Would that work Scott?
Thank you,
Taso
In principal YES ... Sadly a 1000 PSI PULSE hitting a restriction is very similar to the resulting pellet being somewhat the same being it may blow the weaker JB right on out ... If not there ya go.
In brass, given the need to, personally would SOLDER it closed, drill it far under size and then open size till at wanted velocity.
Once done ... get one made of a billet material and be done.
JMO ...
PS,
This tune which is taking a platform typically making 3-4X the power is really non typical & readers need to understand how those of us helping the process may say things contradictory to common tuning practices.
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Scott,
Thank you for the guidance. I am currently using the original brass transfer port. Mike Melick had sent me two delrin rod pieces drilled with 3mm and 2mm holes respectively. I can try those but I'm gonna need to figure out how to "slice" them and keep them flat. Do you think they will be ok flat or do they need to be shaped like the original?
It may be easier for me to fill the original transfer port with JB Weld and drill the port out in increments and test in between.
Would that work Scott?
Thank you,
Taso
I use a flat delrin TP in my .22 B50 without issue.
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Hi All,
Sorry for the big gap since my last update. Life and work keeps on getting in the way. ;) I ended up lowering the regulator set point to get to the velocity I wanted. Next I want to fill to 2000 psi and shoot the rifle down to the set point or 100 shots, whichever comes first, and analyze the chronograph data.
I did try re crowning the barrel but am not getting nice lands and grooves on the crown. Has anyone else seen this? Could it be that the rifling is that shallow and not as noticeable or do I have a bad spot in my barrel?
So then I thought about choking the barrel.
http://www.gatewaytoairguns.org/GTA/index.php?topic=108629.msg1034807#msg1034807 (http://www.gatewaytoairguns.org/GTA/index.php?topic=108629.msg1034807#msg1034807)
I haven't decided on how to proceed. Maybe see how the rifle shoots before I worry about crowns and choking lol.
That's my update for now. Hopefully I can put some rounds through the rifle tonight.
Thanks,
taso
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Hello All,
After some issues with my chronograph not picking up my shots 10 feet away I setup 3 feet away. I pumped the B51 up to 3000 psi and shot it down to where the valve couldn't hold the remaining air in the tube and dumped. That last shot registered 462 fps
Initially I thought I would do a hundred or two hundred shots and be done. Nope. I got 378 shots! I never expected to get that many! The data shows 377 but after I had 99 shots in the first shot string I shot the 100'th shot but the chrono didn't count it. So after that I switched strings after the 99th shot.
I imported the data from the ProChrono Digital and made the attached graph. When I first saw the 4 shot string graphs separately I saw the velocity rising and dropping and I thought this isn't very good.
So when I got all the data together and made the complete shot group I though, "Hmm, that's not too bad." What should a regulated shot string look like?
Now I will have to ask the experts to give me their opinions as I'm not sure what I should do next? I know ruler flat probably isn't achievable. Could I restrict the transfer port to limit the flow to bring down the 580 fps shots down?
I can't find the post I read it in but I "thought" a transfer port restriction would not increase efficiency. The results from that post showed that efficiency and shot count does increase.
I have done nothing to the ports in this rifle. They are as they were born.
Thank you all for hanging around and helping!
Taso
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I haven't been following this thread, but that string certainly doesn't look like one from a regulated PCP.... You have nearly a 10% ES.... What is your setpoint pressure?....
Bob
-
Bob,
I have no way to tell what the set point is exactly as I have no way to measure. Milo set the regulator at 1200 psi originally but I've reduced it since then. I got the regulator set to where my setup would no longer produce a rise in velocity when I increased hammer spring preload. Then I backed the regulator down to where I felt the knee would be. I'd have to check my notes on how much.
The valve and hammer springs are very light and the hammer is a nylon one Motorhead made for me.
Taso
-
No idea what's happening there.... Sorry.... The only thing that comes to mind is that the regulator output pressure is falling as the reservoir pressure drops.... ie you have it set for, say, 1000 psi, and it's starting at 1000 when the reservoir is at 3000 and drops to, say, 600 by the time the reservoir is at 600.... It may be that you are way outside the parameters of the regulator's ability to regulate.... The only way to know for sure is with a gauge on the output side, IMO....
Bob
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Bob,
Milo had said the regulator was "adustable from 100 to 2100 psi". I don't know what to make of the curve. I thought it should average out to be ruler flat.
I mean I could live with it, as I'm tickled pink at the 378 shots.
I always thought restricting the transfer port did not help efficiency but a couple months ago I found out that it did actually help. I can't find the post now.
Bob, do you think a little transfer port restriction will squash the higher velocities? Does 378 shots sound right? I don't think I will always fill to 3000 psi. I can do some strings from 1500 and 2000 psi to see what the curve and shot count looks like.
Thank you,
Taso
-
Bob,
Milo had said the regulator was "adustable from 100 to 2100 psi". I don't know what to make of the curve. I thought it should average out to be ruler flat.
I mean I could live with it, as I'm tickled pink at the 378 shots.
I always thought restricting the transfer port did not help efficiency but a couple months ago I found out that it did actually help. I can't find the post now.
Bob, do you think a little transfer port restriction will squash the higher velocities? Does 378 shots sound right? I don't think I will always fill to 3000 psi. I can do some strings from 1500 and 2000 psi to see what the curve and shot count looks like.
Thank you,
Taso
Before the restrict the port you need to get the regulator working right.
-
Regulator most definitely IS NOT doing its job well as it could.
Have to agree with Bob that the Reg is operating OUTSIDE its range and is indeed changing output pressure with changes in storage pressure.
As good of luck as i have had with Milo's Regs ... seen 2 later versions / revisions that frankly though were a step backwards.
Personally have a 1st get that has HP intake down the adjuster cap direct to seat ... this style Has next to no changes in output as tank pressure rises / falls.
Milos later versions used a SIDE INTAKE for HP which placed HP on the HP end of spool outside of the seats diameter. This style the pressure exerted on the end of spool directly changed with tank pressure & regulator was less stable to set point as tanks pressure rose & fell.
Scott
-
A side intake regulator should be less stable, and could very well be causing the exact problem you are having.... I don't think choking up the transfer port is the answer....
Bob
-
I will check and take pictures when I get home from work. Is the side intake visible externally or should I take the regulator apart?
Thank you all for your help! ☺
Taso
-
I would doubt you can tell without disassembly, but Scott would know for sure....
Bob
-
I have the 2nd regulator still new in the bag, never installed. I can take pictures of that one easily.
Taso
-
Side intake has the HP bleed hole into the side of the regulators body upper reduced diameter end.
End HP intake has a bleed hole dead center of the adjustment bonnets screw.
-
Scott,
Do these pictures show the ports you are referencing?
Thank you,
Taso
-
Scott,
Do these pictures show the ports you are referencing?
Thank you,
Taso
No, Spool pictures don't tell what we trying to ascertain.
need to see the assembled regulators Adjuster bonnet / reg body at HP tank end
-
Scott,
Here are the external pictures. Aside from the vent hole that vents to atmosphere there aren't any other holes around the circumference of the regulator. If you need more pictures please let me know.
Thank you All,
Taso
-
Looks to be a center intake ? ... DOES the aluminum housing have a hole in the side of it in the upper reduced diameter adjustment nose area ?
-
Scott,
I'm 99.9% sure it does not. I didn't see one but I will verify when I get home from work.
Taso
-
If the case it DOES NOT ... then that is indeed a center intake and would honestly say with the profile of strings shown using it, it is operating OUTSIDE of an optimum bevel spring configuration internally.
It would be an educated guess that to operate at such a low pressure and have accurate metering the bevels would do better being in opposing singles such as ()()()()() ... which maybe how oriented, tho the pic would look the same if 5 sets of doubles like (())(())((
JMO ....
Scott
-
Thanks Scott,
I will try to pull it out of the rifle tonight to verify.
Dumb question, do the internals of the regulator need to be lubricated? I recently bought some Ultimox and can use that if applicable. Besides obvious damage in the regulator, is there anything else I should look for?
Thank you,
Taso
-
Thanks Scott,
I will try to pull it out of the rifle tonight to verify.
Dumb question, do the internals of the regulator need to be lubricated? I recently bought some Ultimox and can use that if applicable. Besides obvious damage in the regulator, is there anything else I should look for?
Thank you,
Taso
You can use ultimox IF YOU THOROUGHLY DEGREASE all the parts first. Krytox based lubricants DO NOT PLAY WELL when mixed or in contact with petroleum or silicone lubricants.
-
I have been following this thread on and off for a while now... I have a gut feeling that reducing your reg pressure that far is causing you more trouble then its worth..... I would be willing to bet that with the lightweight hammer and such that you have in it now you should keep the reg set around 12-1400 psi and use a severely restricted transfer port.... if I had to guess somewhere in the .07-.08 area (heck maybe smaller) and removing any plenum you may have in the setup because there is plenty of room in the valve itself to supply enough air..... heck in the 500 fps range you may even think about stuffing the valve a touch to remove even more space so that there is enough pressure drop for the reg to work effectively between shots....
I know if I was going to build a low fps all week on a single fill shooter thats probably where I would start.....
light weight hammer
fully internal through hammer SSG setup
regulator around 1200 psi
restricted transfer port around .07 (drill#50)
start from there and see where it needs to go......
-
Michael,
To be honest, Scott said the rifle would be more efficient running at a higher pressure way early when I was planning the project out.
I did a lot of reading and weighed pros and cons. I decided to go low pressure. I wanted low fill pressure since I pump. I wanted lighter hammer cocking because I don't think the hammer cocking lever screwed into the bolt is a strong design.
I was also inexperienced. I thought strangling the transfer port did not increase efficiency or shot count compared to less air from the get go.
If it doesn't work in the end many will still benefit. I have with all the experience I have since aquired. People can point to my thread and say, "Taso tried this and this and it didn't work."
Or it may not be the perfect setup but good enough for 10 meter practice.
We will find out eventually. ;)
Thanks,
Taso
-
Zooming in on this pic sure makes those bellvilles look like they have very little bevel, almost like they have collapsed.
(http://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=99648.0;attach=158878;image)
-
Rob,
Thank you. I will check that the washers are still convex/concave. It may be the angle of the picture because those washers are from the brand new in bag, never been installed regulator.
Taso
-
I found the transfer port thread I keep referring to:
http://www.gatewaytoairguns.org/GTA/index.php?topic=105564.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=105564.0)
They are Bob's, RSTERNE'S, reply's numbered 11 and 19
Taso
-
Hi All,
I didn't get a chance to pull the rifle apart tonight but the never installed regulator does not have any holes around the smaller diameter intake side. Since they both came together I am 99.99% confident they are identical. ;D
As soon as I get the rifle apart I will update the thread as to the condition of the regulator in question. I'm gonna contact milo to see if he has any suggestions.
Thank you,
Taso
-
Hello All,
I was able to swap out the first "Taso adjusted" regulator with the second unmodified regulator that was pre set with a 1500 psi set point. I also installed a delrin transfer port with a 2.5mm opening. This is the graph of the merged strings in order.
-
The huge bump in velocity at the right hand end indicates insufficient hammer strike for the setpoint pressure.... Either reduce the setpoint pressure until that bump disappears.... or increase the hammer strike to bring the velocity up on the plateau to the left.... Ideally, a bump of less than 1% of the velocity will give you a good balance between velocity and efficiency (shot count)....
Bob
-
I know the big spike at the end is because I have too much hammer tension so I need to adjust that out. I am impressed that my thinking was wrong and Motorhead was right. The setup was more efficient at the higher set point pressure because of the more shots it produced.
I shot a string last night with one preload washer removed but it wasn't enough to remove the spike. I'll post that graph when I get home tonight.
Once I get rid of the spike I will work on a smaller transfer port size. I soldered the stock brass transfer port and will try opening up the port size and see how it works to trim down the high points.
I still don't understand why I'm getting the velocity dips and rises. I wanted to think the regulator was not reacting quick enough to the small sips of air per shot. But from the last graph the dips are around 100 shots peak to peak.
I am puzzled as to what's going on.
These are the first 400 shots on a brand new regulator.
Taso
-
You have insufficient hammer strike, not too much, for the setpoint pressure.... That is what is causing the spike....
I have no idea why you are getting the large ES on the part of the curve above the setpoint.... I have never seen that before....
Bob
-
Thanks Bob. For some reason I thought I had to reduce hammer spring energy. I'll have to re read my notes.
It's seems we were both replying at the same time to my post. :-)
Taso
-
My guess is the high ES is precisely because the hammer strike is too weak. It's barely enough to knock the poppet off its seat so minor variations appear amplified.
-
I suppose that is possible.... The big spike does mean that the hammer strike is very light for the setpoint pressure, and any slight irregularities would therefore be emphacized, resulting in varying velocity.... You see the same thing sometimes in unregulated PCPs, with a zig-zag string on the initial upslope part of the bell-curve, which then settles down across the top, and nice and smooth on the downslope.... Quite common, actually, although only in guns tuned for high shot count, where the pressure drop per shot is tiny.... or tuned for a very wide ES.... That would be the case here, of course.... the ES of the spike is over 30%....
Yeah Jason, I think you nailed it.... I learned something new today.... 8)
Bob
-
You know what?.... I actually HAVE seen this before, but didn't recognize it.... Here is a low-powered setup I had on a regulated QB.... High setpoint pressure, very light hammer strike....
(http://i378.photobucket.com/albums/oo221/rsterne/QB%20on%20HPA/QBLowPower.jpg) (http://s378.photobucket.com/user/rsterne/media/QB%20on%20HPA/QBLowPower.jpg.html)
The green line is the AVERAGE velocity, the red line the maximum, and the blue line the minimum.... Note that for shots 1-30, the ES was very large, nearly 40 fps, which dropped for shots 31-60 to about 30 fps, and for shots 61-70 (near the setpoint) to less than 15 fps.... Once below the setpoint, the ES was only about 1%, shot to shot.... The maximum velocity stayed a constant from shots 1-70, but there was a bigger ES when the tank had more pressure in it, just like taso is seeing.... The differential across the regulator is larger, and the downstream pressure probably varies just a whisker, and when it's higher, the very light hammer strike doesn't open the valve as far, resulting in a lower velocity....
So there you go, it DOES happen when you have way too light a hammer strike for the setpoint pressure.... Thanks Jason, for the solution, and to taso for bringing this to light....
Bob
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Well, Bob, it is truly reason for celebration to contribute a little brain dropping to you today. In fact, I think I'll have some ice cream tonight ;D
Actually I thought this was something that had come up at least a couple of times in past threads we were replying to. I too had noticed it on detuned regulated rifles. The extraordinarily small lift and dwell makes for both great efficiency and sometimes giggle-worthy report but at the expense of a higher ES. But the cool thing is if you're taking, say, a 30+ fpe .22 cal 70 yard rifle down to 10fpe for all-day discreet backyard plinking at 25 yards, a 10% ES isn't really a problem.
Same thing applies to suburban pesting at modest ranges. I once took a 30fpe rifle dialed down to 13fpe over to a buddy's house to thin out his gray squirrels and it went 6 for 6 that morning at distances out to 30 yards. And nobody in the neighborhood even knew I was there :)
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Hi All,
Here is the chart for the string I took last night. I've tried to scale the second graph to approximate the first graphs x axis scale. The first graph was shot from 3000 psi down to where the poppet dumped the remaining air. In this this graph I started at 2000 psi and removed one washer I used to increase preload. They are .5" in diameter and about .04" in thickness. So 2000 psi to poppet dump.
Taso
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Gentlemen,
I am glad to be able to bring things to light. ;D I don't expect to shoot it further than the 17 yards. That's the difference from the back porch to the fence in my back yard.
So my ES doesn't need to be that tight as long as it doesn't really affect my groups. It would be nice from a perfection standpoint but maybe not necessary if the difference isn't apparent in shot grouping. My goal was to build an accurate and quiet regulated paper puncher to hone my skills with.
It looks to me that last night's string may be a little flatter and the right hand peak wasn't as high. It is very similar to the first graph in this area. But it seems the wider velocity swings happen from 3000 to 2000 psi as shown in the first graph.
So what do you gentlemen think I should try tonight? At this time I'd like to leave the regulator alone to see how it compares to the first one and to remove one variable from the tuning, for now. ;)
Do you think if I tune the spring rate and preload I can flatten out the velocity curve? I could then use a transfer port restriction to lower the velocity average?
As always, thank you all for all the help and insight you have offered!
Taso
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When you say you reduced the preload, I assume you are talking about the hammer spring?.... To me, that is going the wrong way.... Are you trying to tune for ~ 600 fps or more like ~ 800 fps?....
Bob
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Bob,
I was looking for 500 - 550 fps with 7.9 grain pellets. I have been tuning with spring length and washers. Clipping portions of coils and adding washers to the side of the spring opposite of the hammer.
Taso
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Bob,
I was looking for 500 - 550 fps with 7.9 grain pellets. I have been tuning with spring length and washers. Clipping portions of coils and adding washers to the side of the spring opposite of the hammer.
Taso
If you want 500-550 you should lower the regulator pressure
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I pulled apart the original regulator. It looks like brand new. I checked that the bevel washers were oriented like this ()()()()() and they were.
While I didn't initially see it I did find that the top small oring was not in it's groove but jammed in the top of the adjuster. I have included pictures. All the times I had inspected the regulator the small oring was in it's groove. What would cause the oring to pop out of place and how would the regulator function if the small oring was out of place?
When I removed the regulator 5 or 6 times to adjust it I didn't have a way to pull it out of the air tube so I would put pressure with my air compressor on the valve output to push the regulator out. Could this 100 psi of pressure move the oring out of place?
Taso
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Rob,
It was suggested I try the unmolested 2nd regulator I had with a setpoint of 1500 psi because it was thought the first regulator may be wonky. I just inspected the first regulator and found the upper oring was not where it was supposed to be. I don't know what effect this would have. So I will try the first low setpoint regulator again when I've tested out the high pressure setup.
In reply #102 I have a graph of the low setpoint shot string. I don't know what pressure it is currently set at as I lowered it to tune velocity and I have no way to see the output pressure. I also don't know at what point in time the oring came out of place.
So I'm still collecting data and troubleshooting.
Thank you Sir,
Taso
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I would expect that with the small O-ring out of place, the regulator would not regulate, merely bypass the full tank pressure to the outlet, or leak, if the tube is vented between the two O-rings....
If you want 500-550 fps, I would lower the regulator setpoint to less than 1000 psi and see what you get for a shot string.... I'm guessing you may need even less than that, probably less than 850 psi, and maybe as low as 400-500 psi.... I set up one gun for under 500 fps, and it was only 400 psi....
Bob
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Sorry for the belated reply, I had the following typed up and then our internet connection went down and I've been on the phone with Comcast trying to get it working again. So anyway here goes...
A few options to tighten the ES:
Approach 1
Goal: Keep velocity at ~550fps without monkeying with the regulator setpoint
Approach: Increase hammer strike and try a very small transfer port (wild guess: 1.0 - 1.2mm). Adjust the aperture as needed until you hit the desired velocity.
Approach 2
Goal: Keep velocity at ~550fps
Approach: Reduce the regulator setpoint to, say, 600 - 700psi. Then adjust the hammer spring preload until you find the max velocity. If that happens to be pretty close to your 550fps goal, enjoy. If it's too slow, increase the setpoint and/or enlarge the porting if that is feasible. If it's too fast, reduce the setpoint further and/or choke off the transfer port as in Approach 1.
Approach 3
Goal: Higher velocity (800fps), lower shot count, louder report
Approach: increase hammer strike (more preload, stronger spring, heavier hammer or some combination thereof)
In my opinion, #2 is the right way to do it but #1 can work well and may in fact have the softest report because of how we perceive loud sounds. A loud, quick burst isn't as obtrusive as a softer but longer burst.
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Bob,
I think the first regulator is set around that setpoint more or less. I have no way to test the output pressure of the regulator. In reply 102 I have a shot string with that regulator but I don't know if the oring was out of position at that time. I will replace the orings and try it out again after I'm done testing the current 1500 psi regulator. Would polyurethane regulator orings provide any benefit over the buna orings? I have to check the sizes I currently have. Or I can order some. Poly comes in 70 and 90 durometer. What durometer would be best for the regulator?
Jason,
I think I'm going to try approach 1 at this point in time and collect the data from the shots since the 1500 psi regulator is in the gun. Then I can compare high and low setpoint shot graphs, pick the best one and start shooting the rifle for accuracy, finally lol!
All,
So the consensus to flatten the shot curve of the current setup is to add hammer spring rate/pre load?
Thank you,
Taso
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So the consensus to flatten the shot curve of the current setup is to add hammer spring rate/pre load?
I would say so, yes. For better consistency (low ES), you need to knock open the valve with a little more authority. You have a rifle operating at a pressure and with porting sufficient for much more energy than you want to use. You'd rather not reduce the regulator setpoint right now so it looks like your best option is to give the valve a good whack and choke off air flow to keep the muzzle velocity down.
Regarding the type and durometer of O-ring, polyurethane will have a slight edge in longevity because of its improved abrasion resistance. There isn't much movement of the regulator spool but there is some. Polyurethane's weakness is with high temperature and compression set leading to extrusion failure, neither of which should be a concern here. Also, a higher durometer will tend to wear better provided you can reassemble the reg without damaging the O-ring and I suspect that won't be a problem either. With that said, I would not hesitate to use a Buna-N. Either type will last a long, long time.
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I'm not an O-ring expert.... I would ask Tim @ Mac1 Airguns what he recommends.... I think he supplies MilSpec. 90D Urethane with all his Ninja regs, but I'm not sure....
Bob
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Hello All,
I have an update on my project.
Number 1, I calculated the plenum area wrong. My spacer is 1.425 inches long and the air tube internal diameter is 2.65 cm. When I convert all to centimeters a calculate the volume of a cylinder I get 19.96 cubic centimeters. Way bigger than needed for a 5 fpe gun. I know I need to deduct the volume of the spacer and add the volume inside the valve to have the exact plenum volume but I think they even each other out. I can calculate the spacer volume but does anyone know the volume of the rear chamber of the valve where the poppet and light Hillman spring are?
Could this be causing the regulator weirdness where the plenum is too big and the regulator is not getting enough drop in pressure to react/regulate? I could try to take up 15 cc's of space in the plenum to see if it makes a difference.
Number 2, I filled the brass transfer port with molten silver solder and drilled a .075 hole. Velocity was throttled to around 580 fps if I recall correctly. I'm going to verify the numbers by shooting and then try a .070 hole and see what that does. The next smaller drill bit I have is .0585 which may be too small. Hopefully I will do a lot of shooting over the holiday and record the results for all three.
After that I am torn on whether to retain and research this configuration further because I recently got a good deal on an FWB 601 match rifle.
I definitely know that at this moment I don't want to drill an air tube for a 5 cc plenum.
Thanks,
Taso
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Last night I put the low, unknown Taso lowered, setpoint regulator and spring setup back in the rifle. I pumped the rifle up to 1600 psi and shot down to where it dumped all pressure. I am using the same pellets, Crosman Premier Lights from the brown cardboard box.
It will be the first graph I post. My chronograph did not record about 25 shots for some reason. No errors were displayed, just no speed was reported.
The arch I had in reply # 102 seems to be gone. Second attached graph. NOTE: This graph started at 3000 psi. So figure for comparison the last 200 shots.
It seems the regulator is working better now except for the larger jumps in the first 99 shots. The remaining shots in the second string are closer together.
The third attachment will be the first 99 shots and the forth will be the remaining shots.
I reshot a 99 shot string from 1600 psi down this morning to see if the regulator settled down. The velocities seen more erratic at the higher pressure in the first half of the string compared to the end. I hope that makes sense.
I have two more things to try unless anyone has any suggestions. First, I'd like to try a restricted transfer port to squash the peak velocities and see how that works. Second, I'd like to reduce the plenum volume to see what effect it has. I'll have to hunt for smaller diameter tubing to fit inside each other like the wooden Russian dolls. lol
Thank you All for your help and patience!
Taso
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I had an idea. I think I may be able to kinda figure out what my regulator setpoint is. I was thinking I could remove the check valve out of the foster fill fitting. I could pump the rifle to a pressure above the setpoint and monitor the shot velocities on my chronograph while the pump is still attached.
I could then see the tank pressure drop as I shoot. When the shot velocity starts falling I can see the current tank pressure on the pump gauge.
Does anyone see any problems with this?
Thanks,
Taso
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No need to remove the check valve. Simply shoot until the velocity begins to fall off, then attach the pump and pump it until you hear the check valve open and look at the pressure on the gauge. That will give you the same result.
It won't be exact (you did say "kinda figure out..."). For example, if it is tuned to the knee, the actual setpoint will be somewhat higher than what you read on the gauge.
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Thanks Jason! I don't have a rise in velocities when it comes of the regulator so I think I'm on the knee or shin lol. I ended up concurring pretty much on your Approach 2 you suggested a while back.
Less hammer spring so lighter cocking effort.
Taso
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great info here.. thank you all. cheers