Hello from the UK

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ant3000
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Re: Hello from the UK

Post by ant3000 »

Thanks for the info on spacing.


BTW - Im going to pay out for a proper 60mm countersink so I can make the K-Baffle perfect for the new silencer. Im so shocked with K-Baffles performance, they are amazing.



New Question
The Silencer tube is 30mm but I've got a spare 40mm CF tube. Is their any way I could shroud the 30mm tube, put baffles parallel to each K-Baffle, a mouse hole or whatever you recon, and somehow increase the performance without increasing the silencers length?

This is my drawing for the double shroud idea and its not to scale or correct number of K-Baffles.
Ive seen small silencers use similar designs with sound foam etc, but I figure someone here would know if the idea is worth anything or if it will work with alterations.


Image
a_canadian
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Re: Hello from the UK

Post by a_canadian »

I'd expect something on the order of a 5% to 10% further reduction in noise with such an arrangement, provided you used a small number of fairly small (2mm to 3mm) holes in the inner CF tube to vent to the outer tube volume. You want to provide modest escape routes for the higher pressure air, while not making the holes so large or so many that the air has an easy time getting back into the main bore as it drops in pressure and bounces back. Some sort of baffling in the outer volume might be helpful, or not. Hard to say.

But if you were planning to use Scotchbrite pads or similar damping material in the outer tube volume, then I'd say drill much bigger holes to allow escape to that material. Unfortunately a normal optimised K baffle doesn't really allow for such holes. Unless you made extended skirts on the faces and then bored those out and somehow managed to align them with holes in the inner CF tube I'm not sure how you'd get the pressure to go out into the outer volume. Perhaps instead use the outer volume as an initial and final escape valve? What I mean by this is that if you made a blast chamber before the first K baffle and vented that with a few holes into the outer chamber, then left a simple volume between the last K baffle and the end cap with similar holes leading to the outer volume, perhaps the open air space outside the inner CF tube could absorb the impact of the pressure stream in a useful way. Hard to say, and a bit of a fussy experiment. But if you didn't mind potentially wasting the materials and effort to try, it could be worthwhile.

In my experience my most satisfyingly suppressed PCP airguns have resulted from a combination of factors. Careful tuning such that efficient use of air is optimised is paramount. Dumping extra air after the pellet is gone has no use except to get you back to the pump sooner. Once you've done a lot of subtle balancing of the hammer mass, hammer spring length, strength, and spring preload, valve stem length, valve spring strength, poppet seal shaping (a cone is much easier to knock open than a flat or formed seal), valve volume, transfer port size, and pellet probe flow, then a suppressor has much less work to do. With an ideally tuned PCP rifle a 1" OD x 7" long K baffle suppressor is more than sufficient to render a very small sound signature, certainly a small enough noise not to bother neighbours, and should you happen to miss a squirrel now and then the critter won't notice the shot, will keep nibbling walnuts until you reload and take another shot.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Dear a_canadian, you mention a possibility of venting from the blast chamber, I actually tested venting 4 tubes off the air stripper, it didn't give the results I hoped it would. I expected more after me firing into the 30ft garden hose pipe and it being totally silent, but the pellet didn't make it out.

Ive also tested with one way valves (Fish tank aerator) to stop the air returning, thats a feature I might try here by placing rubber bands over the inner tube holes 2-3mm holes.

Where I'm up to
K-Baffles have been the best by far so I've got my tube and built the shroud bit (threading bit in the tube then a 2" blast chamber; like Kalibrgun's design) now I've ordered the 60 degree countersink so I can make the K-Baffles perfect. Im just wondering if this outer chamber can be incorporated for extra effect because I've seen youtube vids of new silencers using outer chambers with damping material.


Question
Please can you explain more about extended skirts bit "Unless you made extended skirts on the faces and then bored those out and somehow managed to align them with holes in the inner CF tube I'm not sure how you'd get the pressure to go out into the outer volume." If I'm to use the outer chamber as a way to reduce pressure and help the K-Baffles then I will need to know exactly where and how to make sure I can vent the pressure without messing the K-Baffles design up.

Thanks so much for your help man.
a_canadian
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Re: Hello from the UK

Post by a_canadian »

In isolation, I'd not expect much suppression if any from extending the airways from a stripper. The reason being that static air has a lot of friction against whatever surface (your 4 small diameter tubes), as well as inertia (the longer the tubes, the more pressure needed to move the air inside them) such that the easiest path for the high pressure air is straight down the bore. By adding tubes to an air stripper you are essentially partially plugging the stripper vents, rendering them less efficient at getting air away from the bore line. If instead you used the stripper to vent directly into an outer CF tube, then had your smaller CF tube with K baffles ahead of the stripper, it seems to me the comparatively vast volume of what is essentially an extended outer blast chamber would be quite useful in suppression. Provided of course your air stripper was bored small enough and designed efficiently enough that it stripped away are properly, without harming accuracy of course. The outer tube's static air volume would still increase resistance against added pressure coming from the stripper but not nearly so badly as when adding tubes to the stripper. Just keep the whole area open, plugging the large CF tube behind the stripper to align and seal to the barrel (snug-fitted delrin is great for this) and again using a plug ahead of the stripper to align on the front of that and to provide the backstop (with a turned step matching the ID of your smaller CF tube) for the baffled volume.

I doubt rubber bands would do anything more than add sound effects, perhaps a high pitched farting noise, before they blew out of the way after one or two shots. Perhaps a few more, hard to guess, as it'd depend on the bands and how well they were fitted/secured. In general I find the idea of one-way valves a bit silly. Over-complicating things, adding unwanted weight and the increased possibility of mechanical failure.

I referred to extended skirts on the K baffles as one possibility for making room to bore holes such that pressure could be allowed to escape to the outer tube volume. But extending a K baffle just for that is actually rather poor use of material, and the alignment issue (holes bored in the long hollow skirts - or perhaps I'm using the wrong term here, I am referring to the outer diameter of the face of the baffle being extended backwards towards the muzzle) with holes in the inner CF tube presents a problem. Better probably to use tubular spacers between the K baffles with a lot of large holes, not so large as to weaken them excessively though. Then drill holes at the matching locations in the inner CF tube such that at least some of the holes would line up, regardless of spacer rotation. But the above notion of getting the highest pressured air into the outer volume using an air stripper probably beats this idea. So I'd suggest staying with a traditional stack of K baffles with no spacers. The best place to vent to the outer volume is going to be the highest pressure part of the stream, which is just after the muzzle. Your stripper will provide a good drop in noise before the pellet even gets to the K's provided you leave the path as unobstructed as possible. The delrin spacer locating the inner and outer CF tubes at the front of your stripper will need to be milled out in a handful of places around its perimeter to vent forward, or bored out is great if your outer CF tube is large enough to make this practical.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Image

This pic shows how the tubes would go, I've superimposed the barrel over the silencer tube and the red tape shows where the air stripper is.

If I were to release pressure from the muzzle then the 40mm tube would need to be push fit on, it couldn't screw on. Im starting to think the outer tube is a looser. In all my tests the K-Baffles kicked ass, so I don't want to mess with them at the cost of it going wrong and loosing the CF tubes.

BTW I plan on this being a second silencer, so its ok being long.

So now you have seen what room we have to work with, do you think we can use the 40mm outer tube or will it be a useless add on?


Thanks for your continual help and advice
a_canadian
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Re: Hello from the UK

Post by a_canadian »

I wouldn't bother with the outer tube. It's awkward, bulky, won't look pretty, and there's so much room in front of that stripper for K baffles that the only trouble I can see is alignment and baffle clipping. I'd make it shorter frankly as a baffle strike at that length without absolutely perfect alignment to the bore is likely. There's a point of diminishing returns with any suppressor design. A couple of threads around here somewhere about that. I expect that around 8 or 9 K baffles with an airgun you'll hear very little improvement in suppression, where the risk to accuracy or even baffle damage is much reduced when the tube is shorter. As I've said, a stack of short K baffles of between 6" and 8" is a good idea. 9" maybe, if your alignment is very solid and your bore isn't too tight. You might consider opening out the K baffle bores to slightly wider diameter as you get to the last few baffles just in case. Same with the end cap, unless you want to machine more of those things after a pellet smashes them.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Yeah I recon your right, the only advantage I can think of is for stiffness, the OD tube would help stop me bending the tube by accident.

My first DIY silencer attempt had a length about half way between the pic you see and the end of the scope, but I cut it down to match the length of the end of the scope so it would fit in the bag and it made a fairly big difference to the sound levels.

Im going to make this silencer properly/slowly, I've ordered the 60 degree countersink to make the K's perfect and I will be fitting one baffle at a time and testing for clipping and effectiveness before moving on. Im expecting better results this time round, if I can get my baffles to more like the spec of yours 'a_canadian' then I will get plenty of compact suppression and less chance of the tube bending and causing clipping.

"The main thing is to think about that cross-bore jet, how to very aggressively push part of the forward stream across the bore and out into the outer area without making that exit hole so large that pressure can get back into the bore easily."
I will come back to you with that when my countersink gets here :)

Cheers
a_canadian
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Re: Hello from the UK

Post by a_canadian »

It's actually quite remarkable how quiet it can be with a couple of K baffles, a long tubular spacer, then a couple more then the end cap. Not quite as quiet as a good string of K baffles with their jets aligned alternating by 180°, but close. I wouldn't worry about stiffness with CF tubing. That stuff is very stiff. Biggest worry is alignment. Ensure your outer tube is concentric to the bore and make your baffles well and clipping won't happen.
ant3000
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Re: Hello from the UK

Post by ant3000 »

^ I didn't know about rotating the jets 180, thanks.

Question:- my gun is .22 or 5.5mm, so is their a standard size for the mouse hole relating to the pellet size?
a_canadian
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Re: Hello from the UK

Post by a_canadian »

Terminology can be a beast when folks don't share the same terms. By mouse hole, do you mean the bore hole for the pellet to pass through? Because a mouse hole typically refers to a small drilled or milled vent somewhere on the face or on the cone. If the bore, then I'd say 0.25“ if you are very certain of alignment and the baffles total less than 8" overall from the muzzle. 0.28“ if not quite certain or if a bit longer. 0.30" if a lot longer and/or if machining isn't top notch.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Yes I did mean the mouse hole and I its a coincidence that I guessed that the mouse hole would be about the size of the bore hole.

I read an article in Airgun World and the new FX Wildcat (also a bullpup) has a large shroud/silencer and its empty, they described it as one large blast chamber. Amazed by this they filled it with baffles and they recon it got louder. Weird.

Im still waiting on the countersink, but thanks again for the info.
a_canadian
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Re: Hello from the UK

Post by a_canadian »

ant3000 wrote:Yes I did mean the mouse hole and I its a coincidence that I guessed that the mouse hole would be about the size of the bore hole.
Seems I'm still not following you. I've never tried an actual mouse hole as large as the bore hole. Seems altogether too easy for the lower pressure air to get back into the main chamber with such a large hole. One wants the pressure to be absorbed through work as much as possible, so small exits for high pressure air are better as the higher pressure air will push through, but lower pressure air will have a hard time getting back the same way especially while higher pressure is still in the bore and inner chambers. There have been attempts made now and then to standardize terminology. One such is here:
viewtopic.php?f=10&t=92684&p=832853
No mention of a mouse hole there though... what about here:
viewtopic.php?f=10&t=70335&p=673389
Pictures missing, but at least some discussion and clarification. A mouse hole is not a Dater hole, very different functions. A Dater hole is strictly in the initial baffle face and is to help diffuse pressure of the highest pressure gas in rimfire and perhaps centre fire cans on the first shot to reduce 'first round pop' or FRP, not really relevant in air rifles. As Capt. Link mentions in this thread, a mouse hole is typically a carved gap at the end of the cone which allows movement of reduced pressure gas back into the main bore area directly across the bore flow, further disrupting flow. This may not be relevant at all in an airgun as the pressures involved are an order or magnitude or so lower than with even .22LR. The area outside a K baffle is certainly relevant in suppressing a PCP, but not as much as with a firearm cartridge.
ant3000 wrote: I read an article in Airgun World and the new FX Wildcat (also a bullpup) has a large shroud/silencer and its empty, they described it as one large blast chamber. Amazed by this they filled it with baffles and they recon it got louder. Weird
No baffles at all was quieter than baffles? Sounds like the baffles were very badly designed. Did they mention the baffle type, or show them? Without that information such an anecdote is pretty much useless.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Seems I'm still not following you. I've never tried an actual mouse hole as large as the bore hole. Seems altogether too easy for the lower pressure air to get back into the main chamber with such a large hole
'Not to be a smart arse' but Kalibrgun bore holes are 6.5mm or 0.23" and thats what I used for my mouse hole, 0.23" is a bit smaller than any of the figures you mentioned. But I'm very happy for you to be sending me appropriate links to this topic. Oh, as my silencer got over 6-8" past the barrel end I opened the bore holes to 7.5 due to clipping, but kept the same mouse hole dia.

This is what I've been taught a mouse hole is:
Image

Good news - My Countersink came today so ill be studying those links closely and getting ready to start.

When we were talking about adding the 40mm carbon tube as OD and spacing the K's forward, is this diagram the sort of thing you were thinking of?. If so I have 2 questions:
1) - I was going to ask if spacing the K's forward 3" and adding the OD tube, would it be better than just filling this space with K's, but I recon only a test will tell me that.
2) - porting the inner tube its advised to use 2-3mm holes to restrict air returning to easily, so what would be a good amount and pattern, example 'quarter the ports' one every 90 degrees to complete the ring or 1/8th? Then should I add ring's 1/2" apart?

Image


I just want to feel I'm 100% on the design before I go ahead, my work turns out better when I'm completely confident about the result I'm working towards. If I'm thinking about other options sloppiness creeps into my work.

Thanks for baring with me man :)
a_canadian
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Re: Hello from the UK

Post by a_canadian »

You're free to call whatever holes you like 'mouse holes,' I was only referring to the most popular usage of the term among suppressor makers. As for bore size, if you can get away with 0.23" for a .22" projectile over whatever length of baffle tube you're making congratulations, that's an extremely tight tolerance just leaving 0.005" on any side of the pellet as it screams past the plastic baffles. The slightest clip probably won't destroy your carefully made K baffles, but will certainly destroy any hope of accuracy. A more solid clipping will blast away much of the entry hole detail. I've seen several technical plastics come apart in this way due to misalignment, as I lack a large lathe, have only a tiny TAIG which can't cut threads, and so am at the mercy of a lot of wishful thinking and sweat when it comes to alignment. 0.25" has worked for a number of suppressors, but hasn't for a larger number when alignment just hasn't been perfect. I'd expect a Kalibrgun suppressor's alignment to be bordering on perfection because the tube starts back at the breech and so takes its alignment from the barrel. This alone wouldn't be good enough with some guns, but Kalibrgun bores are famously accurate and no doubt perfectly or near-perfectly concentric to the outside of their barrels. Much like FX barrels or LW barrels. Lesser barrels tend to have their bores somewhat randomly place near the centre of the steel... making suppressor alignment somewhat more of a challenge.

On the two questions, firstly I'd say that layout looks like it could make things usefully quieter than just K baffles, as it allows the highest pressure stream to escape into a large volume. I wouldn't fuss too much over what size and number of holes. Pressure will get out there and that will be useful. I'd be more concerned about weakening the inner CF tube excessively by drilling too many holes. You're going to want to keep that fairly strong so it'll last a long time. While an airgun's pressure in the initial blast chamber isn't anything near a firearm's, there's still enough there to tear apart a CF tube with thousands of shots if the thing is drilled to Swiss cheese. A few holes, say 3 or 4 should suffice. It's sort of like a ported barrel, except that it's a ported suppressor tube venting into another suppressor tube volume. That's a good thing and can be seen in a few high pressure firearm suppressors which implement a large outer volume fed from a blast chamber followed by a series of cones.

The other question about rings... I'm not sure what rings those might be. Rings of holes? Spacers of some sort? The air doesn't much care what pattern of holes you use. It just needs a way to get out of there.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Image

This is the spacer I've made. 9cm long with a 5 CM section for holes to let the pressure enter the outer tube. This was my third attempt at this space but now its made I wish id made the pellet bore more like an air stripper with a 7mm tube that lets the blast go around the tube, but never mind. Atleast the spacer doesn't clip, so after the silicone has dried the spacer in place I can drill the holes and test the air that escapes.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Image

That link you sent me to tech drawings of K Baffles didn't show these side holes, but they are appearing on some threads. Whisperfan's K Baffle building tutorial viewtopic.php?f=10&t=17116 shows him making them.

Should I build them into my K's???
a_canadian
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Re: Hello from the UK

Post by a_canadian »

Those are what I was referring to as 'mouse holes', being the most commonly used application of that term from what I've seen here and on NFAtalk and on other forums where suppressor making is discussed. And it is those exact holes which I was saying had proven useless in my own experiments. Not bad exactly, just no improvement noticeable so a waste of time making the cuts and a waste of integrity in the cone.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Im glad you said that because I guessed that they would let the pressure pass too easily through the sections, reducing the benefit of the design for air guns. They may work for a powder bullet gun but id expect overkill for the airgun.
ant3000
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Re: Hello from the UK

Post by ant3000 »

Well I think I've made a big mistake by epoxying the ends onto the new silencer, it started off brilliant, Just BRILLIANT!, then the next day I went for a test at 50 yards it was 20cm diameter groups, So I drilled it out with a bigger 300mm long drill and now their is bits in it. I'm wondering if I should try and fix or make it with alloy K's.

Beginner's error. and a wast of £70 of material, about.
a_canadian
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Re: Hello from the UK

Post by a_canadian »

Well there are bits in it... so what? Go to any garage and use an air hose to blast it out for a few seconds, give it a shake, blast it again if needed until it's not rattling any more. If it suppresses well with the larger bore hole then no harm done! Bits in a suppressor should never be cause for throwing the thing away in an age (the past 100 years or so) when pressurized air is readily available. Heck, most stuff should just shake out. Did you epoxy the tubes to the airgun? Seems unlikely. So just pull the thing off and clean it. But drilling finished K baffles like that, wow, seems almost as careless as chopping up your original factory suppressor because of loose bits inside. The waist on each K can't have much material left with a larger hole drilled. Seems more likely to fracture in use.

As for it shooting fine one day and not the next, could it be epoxy sag? Did you leave it to cure vertically or at an angle? Epoxy can be a beast for keeping things lined up while it cures. Tends to flow a lot under even slight pressure when runny, and still moves a bit even when cured in stressed applications. Don't like the stuff myself except as a filler in low-stress situations and even then it's better filled with glass fibre. I can't think why else it would group well one day then badly the next. Unless there was an asymmetrical aspect to the assembled parts and you assembled it one way to test, a different way to glue?
ant3000
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Re: Hello from the UK

Post by ant3000 »

I bought a Casio Exilim EX_F1 which is a slow motion video, I could see the pellets were still clipping and on the video I saw one pellet enter the target sideways.
Next I opened the silencer and drilled the holes larger for the pellet which fixed it but I just wasn't happy with the 1mm wall thickness on the Carbon Fibre silencer tube so I ordered another CF tube but its got 2mm wall, this new tube is So much stiffer than the last one. Im half way through its build and I'm making this one disasembleable and I'm thinking of trying to turn some K baffles out of alloy this time, fitting more in too.

The design of the last silencer made a nice sound, slow blowing sound probably due to the expansion chamber you helped me design. But this time I've built the baffles to accept an expansion chamber but I'm going to test it without first.

Oh, the store that sold me my Cricket, who are now the main Kalibrgun supplier for the UK, they still didn't manage to even get a price of a silencer from Kalibrgun 2 months. I hope nothing ever goes wrong with my cricket because ill have to get it repaired by a gunsmith.
a_canadian
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Re: Hello from the UK

Post by a_canadian »

Unless the bore of your Cricket is severely off-centre from the outside of the barrel I'm having trouble understanding how you're getting baffle strikes. The suppressor is indexed off the barrel, right? Over several inches of barrel at least? Looks like about 6" from the picture. With a snug fitting and well centred spacer at each end of the supportive part of the barrel, centering should take care of itself. I rather doubt 1mm wall CF tubing has any sag in it over the length of baffles you're using. That stuff is seriously stiff, and so light it couldn't possibly sag enough to cause baffle strikes. My best guess is inaccurate boring of the barrel holes in your locating plugs.
ant3000
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Re: Hello from the UK

Post by ant3000 »

It baffles me too but all my work is done on a lathe, I've no answers, only to try a thicker tube.
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