air gun (PCP pistol) baffle design idea (to 3D print)

[wasatch]

Here is a baffle idea for a low power PCP air pistol. It is a .177 (4.5mm) making about 5 fpe. The baffle OD is 27mm and the bore is 6.2mm. The two views show the baffle profile and the vanes. I want to redirect the air radially and use the curved vanes to slow the air, absorbing energy. There is a gap between the vanes and the OD to allow the air to circulate. The vanes have to be at least 0.7mm thick to 3D print well in nylon. I got my idea from turbo impellers.

I'd use 4 or 5 baffles with vanes printed inside the grey tube with 80mm in front of the muzzle in place of the red part (view3).

Would this likely make any improvement over simple baffles without the vanes?

View 1:

View 2:

View 3:

[Enfield577]

I tried one of my K baffle cans on a mates PCP rifle and you could only hear the mechanism operating.

Just make/print a K baffle can 6" long with 8 k's, it will be silent

Cheers

[wasatch]

How much FPE was the rifle producing?

I read either here on ST or maybe TalonTunes that M baffles are better than K for airguns. Is that accurate? I doubt my 5 fpe pistol needs 6" in front of the muzzle. Also, it is vented to an over barrel shroud. Here's a pic of the assembly. The blue piece is the mount with an integrated picatinny mount. The red is a removable baffle core. I'm thinking about making 3 different cores. The one shown below is so I can make something like the Weirauch/Hugett/Hogan core with 2 discs creating 3 chambers and some open cell type material wrapped around the vented central tube. Another core design has 4 conical M baffles. Guess I could try a core with some K baffles as well but maybe I'm over complicating it. The unit is for a Steyr LP which has 3 anti flip vents on the top of the barrel, behind the muzzle which is partly why I went with a shroud--to also capture the air from the vents.

Shroud assembly:

[T-Rex]

If I had your ability, in regard to multiple rev changes, I would try them all.
Record data
Determine which features held weight and revise.
You can become our own expert.
Make it modular and you can print various models for each section.
Real possibilities

[quietoldfart]

A couple of years back I made a 1" square aluminum tube suppressor for a Pardini K12, an air pistol with an un-shrouded barrel and a muzzle compensator and three ports in the top of the barrel just as your Steyr has. Placing a simpler mock-up suppressor around the compensator and in front of it didn't do much to damp the noise, when the pistol was adjusted to about 4.7fpe and somewhat louder than was comfortable, so I decided to make a full-length shroud for times when I wished to practice without disturbing others in my home. This simple sketch shows the basic operation:



It is a 1" square aluminum tube, the bottom face scraped and polished until it slips between the air cylinder and the compensator (thinning the approximately 1mm thick lower wall to about 0.3mm), with plastic plugs at the back end (split for insertion around the barrel then pushing into the back of the tube as the tube is pressed toward the frame), muzzle of the compensator (a 5mm deep hole shaped to centre on the front of that) and at the front to retain the baffle array. The front cap is shaped to act as a last baffle and is held in place by a pair of small grub screws, just as with the compensator locating block. The baffles themselves are formed from thin tin, pellet tins actually. They are bent into curving V shapes and soldered into place in a surround also made of this thin steel. This 'monocore' baffle array is open at the top and bottom, a near fit to the aluminum tube's upper and lower faces.

A hole was carefully bored through this assembly (very low down in the square as the upper part of the tube has to slide over the front sight blade and compensator) then a larger hole reamed until reaching a slightly messy bore of about 5.5mm diameter, giving 0.5mm clearance around the .177" (4.5mm) pellet. The baffle array is about 2.25" long. Adding the ~0.5" front plug the result is about 2.75" ahead of the muzzle on the compensator. The simple void around the barrel provides ample expansion volume for the barrel ports. Weight is about 145 grams, or 5 ounces. Which is significant... so I've abandoned using it simply because it adds too much to the pistol's weight to provide useful training time. So much about 10 metre ISSF pistol involves repeatability, muscle memory, and the added mass shifting the balance so far forward is like using a very different pistol. Still, shockingly quiet. Even when I adjusted the velocity upward to about 5.5fpe for close range use on grey squirrels it was an insignificant sound, bordering on the proverbial 'mouse fart.' The front plug upper set screw provides the front sight post, being vertically adjustable. But the changed front sight relationship meant making a shim to easily shift the rear sight blade up the equivalent of 45 clicks, to avoid unnecessary wear on the mechanism every time I wanted to go back and forth with the device.

Per your questions on baffle design, my take on the problem is that you may be over-thinking it. My other experimentation with baffles for various airguns has shown that even simple washers and spacers are rather effective, that a well fashioned delrin monocore is better still, cones are even better, and well made K baffles best of all. I've not tried K baffles on the Pardini as it's more a problem of air volume for the barrel ports and a short baffle set in front of the muzzle, not very difficult to suppress. For anything with muzzle-and-beyond suppressor tubes I've settled on K baffles as being the clear winner for quiet shooting, particularly made rather short, about 0.55" total length so as to get more of them into the tubes with well shaped cross-bore jetting hollows carved into the faces and waists. Longer K baffles (between 0.8" and 1.125" were tried) were less efficient, the longest being the loudest.

[wasatch]

If I had your ability, in regard to multiple rev changes, I would try them all.
Record data
Determine which features held weight and revise.
You can become our own expert.
Make it modular and you can print various models for each section.
Real possibilities

Thanks for your encouragement
I like the idea of experimenting but have read that good sound meters are quite spendy. Some other folks use computers and sound analysis software like Audacity.
Experimenting and drawing up the various baffle cores is fun but I really don't know much about the details of suppression (cone angle, baffle spacing, # baffles, overall volume, etc.) so I'm just guessing based on what I read of designs that were for other applications (most info available is for powder burners). And what I really need is something that is good enough, maybe not the best, so I'm tempted to just choose one design and incorporate it into the shroud body and print it as one piece. Although that would take away the coolness of being able to hold in my hand and see the part i drew up. In that sense I'm envious of the folks with lathes and mills and the skills/knowledge to use them.

[wasatch]

Per your questions on baffle design, my take on the problem is that you may be over-thinking it. My other experimentation with baffles for various airguns has shown that even simple washers and spacers are rather effective, that a well fashioned delrin monocore is better still, cones are even better, and well made K baffles best of all. I've not tried K baffles on the Pardini as it's more a problem of air volume for the barrel ports and a short baffle set in front of the muzzle, not very difficult to suppress. For anything with muzzle-and-beyond suppressor tubes I've settled on K baffles as being the clear winner for quiet shooting, particularly made rather short, about 0.55" total length so as to get more of them into the tubes with well shaped cross-bore jetting hollows carved into the faces and waists. Longer K baffles (between 0.8" and 1.125" were tried) were less efficient, the longest being the loudest.

The K12 has such a nice trigger! I have a MatchGuns MGH1 Hybrid for 10m match shooting. My Steyr is the LP50 5 shot for shooting silhouette. Want to keep the pop down in my backyard. I don't use the open sights for silhouette, instead a red-dot and the reason for the picatinny mount on the shroud mount.

Thanks for the design tips, I'll draw up some K baffles. The idea with my vanes is to absorb energy of the air by changing its direction which is what I think the K baffle accomplishes. I also like to take advantage of the manufacturing possibilities of 3D printing. Maybe (most likely I'm overthinking it or maybe have a design that couldn't be made easily without 3D printing?

[quietoldfart]

Indeed your design would likely help in suppression as regards energy absorption by redirection, but it lacks any sort of interference with the air stream at the bore. In my experience with various air rifles and pistols, incorporating cross-bore jetting does not interfere significantly with point of impact. Or rather it does so only when the bore hole is too small and there's some minor buffeting of the pellet though it doesn't quite touch a baffle edge. Keeping a 0.5mm minimum clearance all around is important, as is alignment with the bore. The lucky thing about suppressing such pistols as these is that most of the noise can be absorbed in the shroud, very little work left for the baffles themselves, so the baffle stack can be kept very short. Anything longer than about 3" ahead of the muzzle would seem excessive. As such, even if there is a slight misalignment the risk of a baffle strike or even a near miss is small, unless your machining (or printing) is flawed. Such things become more problematic when the suppressor baffle stack exceeds 6". At 10" I've had a lot of trouble. 8" seems a practical maximum for a small hobby lathe with careful work. Fortunately none of my airguns makes significant noise with the addition of suppressors between 6" and 8" length.

But to address your point more directly; why not keep the swirl fins but add a detail at the entry point of each baffle which can scoop part of the jet at the bore straight across the bore? Similar to a K baffle. Or if concerned about symmetry, use 2 or even 3 smaller scoops to generate turbulence, though these are less efficient owing to the collision of the streams at the bore centre. The asymmetrical scoop is most successful in knocking part of the main pressure stream out into the volume around it, where your fins would then have greater effect in conflating flow.

[wasatch]

How do these scoops look? I drew three but could easily make it one and could alter the angle of the scoop.

The bore is 6.2mm for a 4.5mm pellet so there is .85mm of clearance around the pellet. 80mm of space in front of the muzzle. Also what can't be seen is the blue shroud mount is vented with 4 small holes to the atmosphere. The mount is separate so some open cell material like used scotch brite pad can be fitted inside the grey shroud damping the flow of air coming back from the muzzle and out the anti-flip vents in the top of the barrel.

I'm wondering if the torque from the fins would be perceptible?

A disadvantage of 3D printing is the knife edges are delicate and need to be rounded.

[whiterussian1974]

How do these scoops look? I drew three but could easily make it one and could alter the angle of the scoop.

Those look more like notchs than scoops. You've drawn notched cones. Ks direct the gas using a flat surface to gather the gas by stopping the forward flow.
viewtopic.php?f=10&t=135930#p928365

[quietoldfart]

Sorry, but I must concur. Sharp edges aren't necessary anyway, nor even desirable, as obfuscation of flow is the aim not carving it. Slight flats around the entry points to your baffles actually assist in the scrambling of air flow, while the bulk of it gets scooped away by the face profile of the K baffle and the cross-bore scoop and in that face then largely released to the outer volume through the waist vent. Cones such as you've illustrated might be better applied to a .300blk or similar mid-powered firearm application, and with the three notches better for precision in such a cartridge than asymmetrical notches as recently shown by one builder in these pages. The vastly lower pressure of an air pistol makes the air stream vastly more manipulable. Much more opportunity for efficient suppression, less worry about hearing damage mitigation if any.

While cones such as you're showing will certainly suppress quite well for that pistol or even for a 20fpe+ air rifle, they'll not prove nearly so efficient as good K baffles. I've several times encountered shooters who thought their washer and spacer or conical baffle suppressors were doing virtually magical levels of sound suppression, claiming 'all I hear is the action' being the most common boast. Then they put on a well made K baffle suppressor... and they want one for themselves, realising how much they were actually hearing besides just the striker and spring. Actually hearing your trigger mechanism click during the shot, that's a sign of efficient suppression. That is something I hear when I shoot a squirrel with my 10fpe or 12fpe air rifles.

[wasatch]

Yes, it is a flat surface around the scoop or notch, not a ball end. But shouldn't it still cause cross flow? The surface of the scoop is about 60deg off bore.

Here's a revised drawing of the baffle and vanes. One scoop/notch that is wider with more surface. It doesn't open the bore any. The vanes turn the air more. Also the tips of the vanes and entry of the bore have been rounded for 3D print durability.

[whiterussian1974]

Quiet is more informed than myself about compressed air weapons. He'll give you the definitive answers.
For myself, I'll just say that they are very pretty and I'll love to learn how you like them.
If you look at the design and photo that I posted, you'll find what we mean by "flat" area around the mouth. The lips even have a collar around 270* of the mouth.
You've drawn a conical surface. Not quite the same as flat.
But try your design and report back to us. We'll be very interested in learning of your results.
---
Quiet: Are you British? Your speech patterns are highly refined. Something that seems difficult for a non-native speaker. Though, often Foreigners speak English better than we Yanks.
When I lived in Russia they were shocked at how many parts of speech I omitted as "contextually understood" and therefore unvoiced. Much like Russian itself.

[quietoldfart]

On the right track, but perhaps leave an area nearest the bore twice that thick or even a bit thicker and make your scoop more prominent using that material. You don't have a lot of pressure to work with at such low FPE, so grabbing as much of that flowing air as you can from near the bore and directing it across the stream is better.

Russian; transplanted British actually, retired. Something I must have mentioned early on in my participation in these forums. Got myself a shabby little place in a slightly less damp climate.

[whiterussian1974]

...and make your scoop more prominent using that material. You don't have a lot of pressure to work with at such low FPE, so grabbing as much of that flowing air as you can from near the bore and directing it across the stream is better.

Russian; transplanted British actually, retired. Something I must have mentioned early on in my participation in these forums. Got myself a shabby little place in a slightly less damp climate.

He could even build a slight "ramp" to direct the gas, and leave a 270* collar around the mouth to block any counter-flow.

Here's a design for a compressible wipe. It's even easier for you to try out since if doesn't work, just throw it away or try to modify it.

---
Quiet: I live on the outskirts of Houston, TX. So not quite as soggy as London, but still similar to a Louisiana swamp. In fact, Houston is built upon a series of Bayous/swamps. We have sinkhole problems where the ground collapses and sucks in whatever is near. Just like the homes in Florida that were pulled into the ground b/c of groundwater changes.
But we're so soggy that it keeps the groundwater pressure level fairly constant.
---
Your location says Fr. That's why I said, "Touche mon ami." in the other thread. I though perhaps you were gaulois Français.

[gunny50]

"wasatch"

I like your turbine design. Would not Scoop it in the blast baffle for accuracy.
Airguns are sensitive for this.
Check some of the airgun-splitters used in FT competition.
Integrate it in your Turbine design with 4 baffles.
Also make a good reflow curve on the blast baffle so that the air is split nice and directed back in your OTB portion.
For low velocity projectiles and airguns you do not want to much crosscutting as the air stream in front of the projectile will make it unstable when passing thru the baffle.
Most airgun pellets are not that stable in flight when flying three a heavily Cross jetted silencer.

Airstrippers
https://www.youtube.com/watch?v=GKyOa6Qx_ow
https://www.youtube.com/watch?v=GKyOa6Qx_ow
Gunny

[wasatch]

Gunny,
The blast baffle has a stripper cone, it is the first red baffle in the pic of the assembly above.

Quiet and White,
Thanks for your helpful advice. I got distracted from the cone & vanes by drawing a K. Thanks White for posting the pictures and link. The design pictured below is 14mm in depth, 27.5mm OD with 6mm bore.

[quietoldfart]

While I hold Gunny's work and his sharing of information in high esteem, my experience so far contradicts what Gunny is suggesting regarding airgun pellet sensitivity to asymmetrical baffles. Each of my PCP airguns has been suppressed at least for a time, the Pardini being the only one I'm not continuing to shoot that way. In the case of the Pardini it was a symmetrical baffle design and it did not suffer any group size enlargement when suppressed. I can't comment on point of impact shift in that case, as there was such a large rear sight elevation necessary in order to use the extended front grub screw (1/4"-20tpi) as a front sight post with the suppressor tube in place, the stock front blade being inside the square tube.

With my other suppressed airguns, ranging from about 8fpe to 20fpe and all in .22", I've seen less than a pellet diameter POI shift (about 4mm actually) at 10 metres with suppressors mounted. This greatest degree of POI shift was at the highest power level, 20fpe, when using a K baffle similar in design to what you're showing in this last post but with a deeper cross-bore scoop on the face, and a stack of 12 of these baffles plus profiled end cap and symmetrical blast baffle scooping air back into a 3" over-the-barrel reflex volume. That rifle is very quiet for its power level. A modern average car door being closed normally would adequately describe the noise. Wish such a long baffle array and alternating 180 degrees between K baffles I'd expect some slight POI shift, as the 18.13gr projectile moving at about 700fps is travelling in a more intense air stream than with lower powered airguns, generating a more severe cross-bore zig-zag effect. With the lower powered airguns I've seen zero or very close to zero shift with and without suppressors mounted. When I suppressed an old Baikal 46m pistol (single stroke pneumatic target pistol) which shot a 7gr wadcutter pellet at 460fps there was no POI difference between that and shooting with the suppressor off. My best scores of about 550/600 were identical at 10 metres whether using that ~3 ounce suppressor or not and the conical plastic baffles were asymmetrically clipped.

As I suggested with the cone type scoops I'll again suggest that the scoop dimension from bore outward is meagre. For better suppression I'd recommend a deeper, more aggressive cut. Here are my most successful K baffles, whether used for a .22lr pistol or on air rifles:

[wasatch]

Quiet, I think you and Gunny are on the same page... symmetrical blast baffle. The red disc is the blast baffle and has a symmetrical cone on the face.

Here's the K baffle core that will be inserted in the muzzle end of the shroud assembly pictured earlier. From the face of the red blast baffle to the shoulder of the cap is 70mm. I was drawing it before I saw your latest and will work on making the scoop larger. Might change the struts connecting the blast baffle to the 1st K into a tube... wasn't thinking about compression when I drew it. $15 to have it printed by Shapeways.

[wasatch]

Here's the face of the K with a larger scoop. Should the width of the scoop be the same as the bore?

Edit: I re-read your post... deeper not larger. To go deeper I'd need to change the two cones so the muzzle facing cone is deeper. Is there any recommendation on the sizing/angle of the two cones with respect to each other?

[whiterussian1974]

I looks like you are abandoning the vanes idea. A pity. It would resolve a long-standing debate. Your idea was even patented. (USPat 2375617 Whirl Vanes)
For a powder burning cartridge, the vanes would double as heatsinks and surfaces for ablative.
I would cant them more aggressively and leave more free volume along the outside for air to spin.

[quietoldfart]

Wasatch; sorry to have been less than clear regarding the scoop dimensions. You're on the right track with that last drawing. I meant 'deeper' in the sense of more deeply controlling the pressure stream, and your scoop going further out from the bore should do the trick. I also go somewhat deeper in terms of actual depth of cut away from the entry point, as you may be able to see in my photographed baffles above, by using something just a bit closer to an hourglass shape. Keeping the bore hole between face and open cone as short as possible is advantageous in terms of maintaining precision and for more efficient suppression. But the difference isn't great between yours and mine at this point. The ball end mill used is typically the same as the bore hole diameter.

[gunny50]

Gunny,
The blast baffle has a stripper cone, it is the first red baffle in the pic of the assembly above.

If you are going to print K's you can al least make them in a way you would not be able to machine them by making a bigger contact surface for your front scoop, Think like making a rain guard an a bicycle.
That way the air can still go around on the front-plate but is gets a bigger contact point so it will be guided down the crossflow passage. Resulting in a larger volume and higher pressure jetting over the mainstream flow.

Also the exit point for the gasflow to the skirt could be modified with a small flat area in the skirt

Gunny

Just to Give you some ideas

Proudly designed in Holland.

[wasatch]

Thanks for the suggestion. I can do the raised portion in the face in Solidworks but the small flat area in the skirt looks tricky to me. I've been off on a tangent figuring out how to fasten the different cores into the shroud and I think I've come up with the design i'll use. This pdf has design tips for SLS nylon printing and at the bottom is a suggestion for threaded assembly.
http://www.3dsystems.com/company/datafi ... eakpoint=1
I went with that idea and came up with the prototype pictured below. Might get just it printed first to make sure it works properly. The clearances are 0.2mm everywhere except the camfer at the flange of the male part. There is zero clearance there to center the male part in the female part. I might have to fiddle with the start of the threads on the female part to avoid having any really thin areas that might not print well. The hemispheres that are the positive part of the thread are 2mm dia. When printing I can select either .12 or 0.06mm layer thickness...

[quietoldfart]

The small shelf inside Gunny's cone seems a good idea, but perhaps difficult to clean regularly. Perhaps a specially shaped brass brush?