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Project - Silent Laminar Flow Fan

Silent Thunder Ordnance


I'm not the kind of guy to spend $500 on a blow job at Walmart..... even if it's from a guy named James Dyson.

The issue with the Dyson fans is that they’re pretty inefficient, loud, and not what you’d call cheap. So if you want to get blown in your sleep without disturbing your significant other, a better solution will be required. This project was embarked on with the explicit goals of being:

  • Silent (won’t bother you or your SO while sleeping)

  • Ultra-low energy consumption (remember ultimately the point of this is to cool you off, so a fan which eats a hundred watts or more may feel cool to sit in front of, but is ultimately generating a fair bit of heat)

  • Focused and smooth air (so it can blow on you, but not your SO who doesn’t like it, again minimal disruption. We’re going for a gentle Hawaiian breeze here.)

  • Inexpensive (it is a total experiment, so starting with a couple hundred dollars in parts just to see if something is viable stinks!)

  • Adjustable for all angles (so you can aim it EXACTLY where you want it)

So objectives set, how to go about it? To solve this, we’re going for a quick and dirty project here, completed in a day thanks to rapid prototyping. Best to start with a base. Designing impellers and fans is a bit of a process, so lets go with something off-the-shelf. Computer fans are notoriously inexpensive, efficient, reliable, and well documented regarding their performance and noise level. I went with a Thermaltake 200mm case fan, two of them actually, for all of the above reasons. The exact model number is CL-F015-PL20BL-A.

And if you wanted silent air at a cheap price alone, you could very easily just build a mount for these and call it good. But bladed fans deliver their air, not continuously, but in pulses. They also tend to spread their air out quite a lot, producing turbulent flow. The optimal would be, not turbulent, but laminar flow. So the next obvious step was to set about building an integrated laminar flow head w/ mount for the Thermaltake fan.

Thanks to the miracle of rapid-prototyping, this head was ripped out quickly and fit first try. Note the dovetail at the bottom. Tripod ball heads will point in all directions, and cheap ones are available for a song, so an Arca Swiss clamp seemed like an obvious choice rather than trying to fabricobble some sort of head. I should note though that, if you had one kicking around, one of those old school adjustable desk lamps with the coil springs on the side would also work well for this application, concealing the wires as well.

So at this point you might be saying something along the lines of “great, but that isn’t laminar flow, that is just some vague stumpy ducting. What gives?” Right you are, in the famous words of Brittney Spears though “I’ve got a plan.”


So you want a whole bunch of smooth parallel thin walled tubes. What better way to kill two birds with one stone than to use soda straws? I know I’m doing my part to help us use the 6 bajillion straws Americans allegedly consume per year. (it is approximately 500 straws per fan, if you were wondering)


Having shoved all the straws together, I encountered my first problem: the relatively short duct required the straws shoved in and compressed rather forcefully. This meant the friction fit holds them in place, just as I had intended, however it also means they have a certain flare outward at the top. Not good. The other problem, running the fan, is that apparently these Thermaltake fans are absolutely piss poor at positive pressure applications, even ones as mild as this.


The flare at the top was an easy fix, just a retaining ring can be press fit around the sraws and nicely constrains them. Problem solved.

The pricklier problem of the thermaltake fans has to do with blade velocity, blade geometry, and ductwork. I could run the fans harder, I could design new blades, but the low hanging fruit is to clear the MASSIVE almost 3mm gap between the blade tips and the fans. A surprising amount of air can be felt exiting the intake side of the fan through precisely this gap.

This one took me two tries to get toleranced correctly, and even still there is about 0.5mm of under-utilized space so I could hit it a third time for even more performance. Allegedly the increase in performance is exponential as the blade tips approach the ducting. This, for now though, mostly resolved the problem.


So how does it work you might be asking? Well, as far as flow goes an inexpensive (read as inaccurate) anemometer I had kicking around measures the output as about 3.5mph at the output (straw) side. Compare that to the 5mph one of these fans, unmodified, produces on the same (again, innacurate) anemometer. Perhaps more importantly is the subjective impression, which is that even 7 feet away there is still a distinct gentle and very smooth feeling breeze. The whole assembly runs in almost complete silence.


The other question is, of course, one of power consumption. Looks like two of these fans running together is 6.7 watts, or about half one of those crappy “save the world” LED lightbulbs which outputs an advertised 60 lumens and you almost believe them. So that is pretty good.

So there it is, cheap, quick, smooth air wafted silently from any angle all for less power than the vampire draw of all those phone chargers you have plugged in all around the house. In the immortal words of George Bush “mission accomplished!”


Project - Hasselblad XPan Body & Rear Lens Caps

Silent Thunder Ordnance


You may remember, around this time back in 2018, we built a replacement lens shade for the Hasselblad XPan. For those not already aware, Hasselblad are the makers of some of the finest film cameras ever made. The XPan is a discontinued panoramic 35mm film camera, which is to say it uses the archaic standard of 35mm film, however it takes non-standard exceptionally wide (panoramic) exposures with it. 35mm film cameras have overwhelmingly fallen by the wayside in favor of their digital counterparts. Take the Nikon F5, arguably the greatest 35mm SLR professional camera every built; in 1990 they were sold for 3,000$ each new. Now on Ebay such a legend can be had for a mere 300$. Unusual gems such as the Hasselblad XPan though are bucking this trend, and skyrocketing in price. Their accessories are too, as they’re being snapped up by collectors and users alike. So last year we made a replacement lens shade for a friend of the company, an otherwise expensive and somewhat fragile original component.


Well said friend of the company has been greatly enjoying his XPan and lens shade, so much so he returned asking for two more exotic and discontinued XPan components: body and rear lens caps.


To my knowledge, both of these components were never sold as separates either. The rear lens caps in particular came as part of an unusual bubble-style container in which the lenses themselves were sold. The rear lens cap had an odd external locking system, which attached it to the container bubble. It is common to see container bubbles, SANS REAR LENS CAP, available for sale on Ebay as well. Apparently these are another functional collector’s item in short supply.


Thus we once again set out to replicate the form and function of said caps, which I think was a solid success. The body cap has an alignment notch, and functions much as one would expect. The rear lens cap though is more of a triumph, fitting to, not just the lens, but the original container bubble.

More functional replicas of irreplaceable parts for camera obscura? Done!

New Product Option - Bocote Scalpeldashi & Sheaths

Silent Thunder Ordnance

Scalpeldashi and sheath in bocote over phenolic

Scalpeldashi and sheath in bocote over phenolic

We take a break from our (apparently) regularly scheduled blog posts on airguns to introduce a new product option. Our popular and practical scalpeldashi now is available in bocote. Bocote is an exotic hardwood with an absolutely stunning yellow and black grain. This patterning is all natural, no stains or dyes of any sort are added, which makes it all the more spectacular. For this limited run, we’ve also done up a handful of sheaths to match. What a beautiful and exotic combo!

Scalpeldashi and sheath in bocote over phenolic

Scalpeldashi and sheath in bocote over phenolic

Airgun Moderator Design, Performance, and Development - The Final Mus Test+ (part 12)

Silent Thunder Ordnance


Catch the previous episode HERE.

So there are a couple things to wrap together into this test. The first is the highly anticipated tests of the DonnyFL Emperor and Ronin. I believe I'm correct in saying that the EMP is the largest commercially produced airgun moderator out there, being substantially larger than the Huggett Magna and heavier and larger diameter, although a smidge shorter, than the Clague .30 (previously the largest moderator tested) I've put these tests below, however I'm also going to insert them into the big test so anyone looking for more info can find them all in the same place. These tests were done on the Crown .22 running 32 foot pounds, just like all the others.

The second thing is to test the final Mus revisions. This is the culmination of months of trial and failure, but finally I have a design I'm happy with so this will be generating its “final” numbers. I mentioned this before, but I've abandoned optimizing it for .22 as I just don't know how I'll ever get it to beat the Pilum, but this rev. should work great on .30 and I'll also test it on the .22 just for fairness.

The third is addressing the complaints of unfairness regarding the Clague .30, and that it ought be tested on a .30 like it was intended. I don't think these claims have a great deal of merit, that it'll suddenly change directions and be an outstanding performer when dumping almost three times as much air down the bore, but I'm prepared to give it a fair shake and a chance to shine.

Donny Emperor

Donny EMP.png

Sound – 81.0
Mass (grams) – 436.6
Volume (mm^3) – 536,804
Length (mm) – 266
Diameter (mm) – 50.69
Exit OD (mm) – 8.55


The first thing that jumped out at me about this wasn't the size, it was the weight. In fact it was so heavy, I had to pull the core out and weigh it in parts as it was maxing out my scale. For those who don't speak metric, that is a whisker shy of a pound. It also is the only thing I've yet tested which is heavier than the Clague, and although it has a larger bounding volume it is a little shorter. Internally this, and the Ronin, differ from the other Donnys I've handled in that, instead of three chambers of varying sizes and two baffles, these have multiple chambers of identical size and far more of them. The Emperor also now has wire mesh around the outside of the felt as well, and it is held closed with zip-ties rather than the usual black masking tape. There also appears to now be not-insubstantial space between the outside of the core-wrap and the tube, effectively creating a permeable barrier between the inner core and an outer chamber of sorts. It may seem like a small detail, but this could have a substantial impact on ultimate performance, causing these designs to perform much better than their diameter would suggest. Fit and finish is otherwise identical to the other Donnys, as described above.

Before I leap into testing, I want to note that this Emperor was marketed and sold for .22/.25, but Donny said these came out a little on the snug side for .25 so really it is best as a .22 can. This is probably because, with a couple stacked tolerances and such a long mod to amplify any tolerance issues, you want that size exit hole to quite large to reliably clear a .22 pellet. The point I'm trying to get at though is that this was very much NOT made for .30.

My initial reaction to this design was surprise, and in a good way. Given all my testing with large diameter designs, I was expecting this to be much much louder than it actually sounded. Maybe it sounded a bit like a Huggett Belita but without the ring of the Huggett? What I'm getting at is, if you didn't know it was an enormous moderator, you'd never guess it by listening to it. It didn't seem to have that sound of very high peak and low subsequent sound you (or rather I) expect from a large diameter can. Another thing I want to note here is that the muzzle is substantially farther from the shooter's ear than with other designs, and the face is much wider, so it is possible some sound attenuation to the shooters ear occurs based simply on the form factor. Put another way, this can moves the “muzzle” of your gun almost a foot further away from your ear than no moderator, and then casts a significant shadow. Given that your muzzle may have only been two feet away from your ear to start with, this is likely not inconsequential.

So how did it actually do? Not bad really. Again I was expecting armageddon, something up in the Clague range of mid hundreds. To be below 100 was great, in fact this design was almost as good as normal sized moderators. Looking at the traces, there is clearly less residual sound than many other smaller designs, but it isn't dead silent either. It is enough that, if you were to measure with an unsuitable sound meter or a phone, you might get erroneous numbers suggesting it is quieter than say a 0dB. Given this design's length and weight I can't exactly call this result great, being almost as good as a design a quarter its mass, but it sure is a heck of a lot better than I'd have guessed.

Donny Ronin


Sound – 103.6
Mass (grams) – 267.7
Volume (mm^3) – 325,562
Length (mm) – 160.5
Diameter (mm) – 50.82
Exit OD (mm) – 8.11


I covered above, on the Emperor, the internal and aesthetic observations of these two. Beyond that, they are largely similar to the other Donny designs I've tested from an aesthetic perspective and are covered in greater detail above.

I also want to note that this design was sold for .22/.25, not .30. I too would expect this exit OD to be too tight for .30.

My subjective impression on how this design sounded was “peaky,” that is to say producing a peak which is much higher than you'd expect given its draining sound. That isn't to say it sounded quiet, because it really didn't, but having passed my initial surprise given the performance of the Emperor I guess this sounded neither luxuriously quiet nor ostentatiously loud. It definitely has the kind of sound delivery which would make it hard for an untrained ear to judge how loud it actually is, if that makes any kind of sense. I do worry I've listened to too many moderators at this point, and so my subjective impressions are starting to diverge substantially form what a lay-person would perceive, however this is why hard data exists.

Well, for those who say this sounded quieter than the Sumo, I believe them because it is..... barely. We're probably within margin of error here, but on a previous day the Sumo averaged 108 and the Ronin averaged 103.6. Of course both of these are substantially louder than smaller diameter designs, but there it is. I suspect, although could easily be wrong as I have been so many times before, the design alterations of the Ronin will give it a further edge over the Sumo on higher flow guns.

As a small aside to these two Donny tests, I expect someone will point out that, while these designs may have been bored for small-calibers, they were intended for higher power air handling. To this end I screwed them to my Crown .30 (80 foot pounds) and ran some dry-fire shots through them. The results were erratic, but far from flattering, producing the highest peak of the session at 220. I wouldn't read into that though, because I also ran a couple other designs dry for the purposes of comparison and discovered that dryfires cause moderators to behave very strangely. In short, a dryfire test of a given moderator may or may not be representative of its performance with projectile, and you'll have no way of knowing until you test it properly. :/


Mus on FX Crown .22 pushing 32 foot pounds

Mus on FX Crown .22 pushing 32 foot pounds

Mus on FX Crown .30 pushing 80 foot pounds

Mus on FX Crown .30 pushing 80 foot pounds

Sound – 78.8 (80 foot pound .30 cal Crown VP), 82.0 (32 foot pound .22 cal Crown)
Mass (grams) – 120
Volume (mm^3) – 333,794
Length (mm) – 170
Diameter (mm) – 50
Exit OD (mm) – 8.4

I just can't tell you how happy I am to have reached this point. I keep harping on it, but really this Mus design was one hell of a slog. From my original test back in March, I've been pounding my head on this wall trying to figure out why large diameter designs don't work well, and how to overcome it. I haven't figured out the former, but at least for higher power guns I've cracked the latter. Good riddance. :P As I noted in my penultimate Mus test, this winding path ultimately lead me to a concentric chamber design. A compound blast baffle deflects the majority of the initial flow and pressure to a pressure reservoir. This then slowly feeds the gas diodes which further delay the flow. Finally the dampers provide the final sound attenuation before exiting the muzzle. The only other thing I want to draw attention to about the design is that I took great pains to keep it light weight to maintain the rifle's balance and minimize POI shift. Physically it is very large, 170mm long and 50mm in diameter, but it only weighs 120 grams or 4.2 ounces. If you read my comments on the Trident and why I liked it so much, you'll notice I really put a premium on weight, especially when hung out there on the end of my barrel.

As far as performance goes, I think it performed well. It isn't quite as much of an advantage over the Pilum QD as I'd have liked on the .30, but it does sound noticeably better. Some of that is down to the quieter draining sound, there is just less noise post-peak going on here. In a weird way you can think of this design as basically a longer moderator which got smushed and so the initial sections were pushed to the outside which make room for more sound damping toward the muzzle end. It is rather giggle-worthy to shoot something this powerful and have it be this quiet. On the .22 it is noticeably louder than what I usually run, a Pilum DD, but not outrageously so. In both cases you can see the trace has a lot less going on after the peak than both Pilum designs it is “competing” with.

Beyond that I guess I don't know what to say other than that I'm just so relieved it is over. Somehow this one started losing some of the elements of fun and became a bit of a slog. So, for now anyway, I think I'm probably going to take some time to step back from airgun silencer design. After all the point of this is fun, and so when it stops being fun you ought take a break. At some point though, there is one more thing I want to specifically “debunk” which is the all-to-common-refrain of “loudest part of the gun is the hammer slap.” This might be true for the shooter, but if so it is only because your face is inches from the hammer and feet from the muzzle; measured at an equal distance the muzzle sound is definitively louder and I want to do some testing to, not just show it, but quantify it. Remember sound attenuates substantially with distance, doubling it will cut 6dB. It'd also be cool to see just how loud the target impacts are with various calibers and backstops as compared to the gun itself going off given, say, a range of 75 yards.

Performance summary for all moderator designs tested to date.


Clague .30 on the Crown .30cal running 80 foot pounds – 115.6 – Note that this trace is on a different scale than the above. Color me surprised though, the Clague DID meter substantially better with a bigger slug running down its bore but....... there is a HUGE, round, face-swallowing but to that: it sounded like a cross between star wars blaster firing and high tension steel cable breaking. It'd be freaking awesome if it were intentional, and not trying to be quiet, but it is and so I'd call it flat out unacceptable. Appalling might be another word for it, it sounds like a bad silencer sound-effect from a Hollywood movie. The only other design which resonated this badly was the unbranded moderator which I believe was from Wolf. (the manufacturer was unclear, I don't want to throw Wolf under the bus here) I almost want to shoot a video of this to show to people, as it is so weird and distinctive. I did wonder if this sound might be caused by some sort of pellet-baffle interaction, and so I tried a few dryfires through it..... nope, still resonates. It is just so weird, I don't know what else to say. So for the people who thought the .22 test was not representative of the Clauge, I hope this addresses your complaints? :/

Airgun Moderator Design, Performance, and Development - The Semifinal Mus Test (part 11)

Silent Thunder Ordnance

Mus moderator on an FX Crown

Mus moderator on an FX Crown

Catch the previous episode HERE.

So I'm still blundering around with this Mus design. At the moment I've entirely given up trying to get a large diameter can to work well on my .22 Crown. I'm just not going to beat the Pilum, it isn't going to happen. The Pilum is too well optimized for what it is doing to overcome the large-diameter-can disadvantage. I've gotten close-ish, but I'm flat out of ideas and nothing has any promise in terms of beating it.

On my .30 Crown though is a bit of a different story. I've still tested what feels like endless designs that are louder, but I think I'm homing in on something that'll match or beat the high-power-optimized variant of the Pilum in, not one, but two critical respects. First is, obviously, cutting the peak. At this point I don't hold out hope for beating it by much, but beating it by a whisker is something I can live with. Why? Because the second factor in how quiet a moderator sounds is post-peak-noise level. This is where some of my better Mus designs look to have an advantage over the QD Pilum. There is no escaping it, the QD Pilum is amazing at cutting the peak given its diminutive size, but given how much air it eats it still has a bit of a “whoosh” to it. So even if I can just barely match or beat the peak with the Mus, using that extra bit of space to improve post-peak-damping might just be the key to getting a not-totally-worthless large diameter design.

There is something else I want to add here, and that is I've tried a LOT of different designs to get to this point. Large baffles, small baffles, near baffles, far baffles, baffles inside baffles, tubes inside tubes, complex flow paths and geometries the likes of which you can't imagine. All failures, in one way or another. So this test here represents just a teenie weenie tiny fraction of the number of designs I've tested to try and make a working Mus. There are vastly too many failed designs and bad ideas to write up and try to explain them all. Basically, what I'm trying to say, are two things:
1) Well meaning comments suggesting “you should try....” no, I've already tried it. Intelligent and well thought out suggestions are always welcome, but realize if you're about to suggest something based on conventional wisdom, CFD, acoustic flow analysis, or a vaguely conventional design please understand it has already been tried. There have simply been too many attempts to document, that doesn't mean I've been lazy in my designing, only in my expounding.

2) This test is meant to whittle down just the last few factors as the culmination of an immense amount of research. If this doesn't work, or at least if it doesn't point directly at the final solution, I'm going to give up on the large diameter concept entirely.

So far I have never tested a large diameter design, mine or anyone else's, which performed well. As we speak I have the final two pillars of “large diameter moderator performance,” at least as far as the general airgunning community is concerned, on their way to me: the DonnyFL Ronin and Emperor. If they perform well, I'll eat my shoe and bow to the master. If they don't perform well, or if they're actually tube-within-tube or another form of sub-tube design, then..... I told you so? I guess I'm not expecting them to perform well both given the performance of the Sumo, and the summation of all the other testing I've done, but I've also been so wrong about so many things at this point really I'm prepared for anything. Crow is pretty tasty when you've eaten it enough.

All three of these designs are some flavor of concentric chamber design. A blast baffle/s deflects the majority of the initial flow and pressure to a pressure reservoir. This then slowly feeds the gas diodes which further delay the flow. Finally the dampers provide the final sound attenuation before exiting the muzzle.

Mus SD – 137.6 – Clearly this didn't work. That single diode just needed backup on an 80 foot pound gun.

Mus SD AS – 86.4 – Just a single diode still, but now with a compound air stripper. This shows some real promise, but also shows room for improvement.

Mus TD – 93.6 – Three diodes standing alone. Again this shows some promise, but isn't good enough.

I chose to highlight these three tests because they really illustrate where I ultimately went with the design. I'm afraid I've been bad about posting, so I'm writing this conclusion and posting these tests “in the future” and am about to dig into writing up the next phase of..... well of everything. More commercial design tests as well as the final Mus test. I also have received some, well lets call it “feedback,” that I was unfair to the Clague .30 in my original test; the design was intended for a .30 cal FX, not a .22 cal FX, thus testing it so under-bored is akin to “dryfire testing it.” While I'm somewhat dubious of these claims that it'll magically become quiet when dumping several times as much air through it, if gas-seal with the pellet as it passes through each baffle is critical to the design, it may well perform more adequately given lower expectations for suppression with higher power rifles. And since I have said FX .30 cal, giving it the fairest possible shake by testing it as-intended is the least I can do.

Airgun Moderator Design, Performance, and Development - The Edgun Leshiy (part 10)

Silent Thunder Ordnance

Catch the previous episode HERE.

So this project had a bit of an up-and-down. As mentioned before, this Leshiy is here by the grace of a very generous AGN user who goes by Custard. These cores are 3D printed, prototypes are done in ABS simply because it is easy to use and inexpensive. They also don't have to print perfectly, because they're just tests after all, and on all our designs we use a series of precision reamers to ensure the bores are precise and consistent. For a finished version to put in Custard's gun and ship back to him, we want a perfect print to do it in 20% carbon fiber reinforced nylon. This material is, in our humble opinion, one of the best possible options for silencer cores as it is very strong, light weight, solvent resistant, and impact resistant. It really is fantastic stuff. I should add that Glock's “magical” polymer frames are also made of nylon, it really does have great material properties.

So what happened and why am I bringing up all this? Well as you'll recall the previous test results were excellent. The small wrinkle was that there were a few little print flaws here and there which ought to be resolved before moving to nylon and printing the “final” core. So I made a couple little tweaks to fix the print issues, and confidently printed out a carbon-nylon core. Putting it in the gun I was expecting quietness..... which is not what I got. By ear I could tell it just wasn't right, way too loud. I didn't even need to meter it. I was more than slightly disgusted that just a few minor design tweaks had caused such a performance shift, I mean really. We would later meter this core, just for giggles, and discover it was averaging 155. NFG.

So this launched a frenzied, and not well documented, series of design tweaks and tests to try and figure out where the magic went (the original test core worked just fine, and still metered in the mid-teens) and how to stuff it back into the design. Yes, silencer design can be just this annoying and fickle. This process resulted in a dozen small tweaks, and ultimately the loss of a baffle. This circles nicely back around to the original test which, turns out, also performed better with just 3 baffles. Go figure. So, below, is the final series of confirmation tests on this project. And the rifle is already on its way back to Custard.

Factory Leshiy Configuration – 260.3
It is loud. We've been here. It is also inconsistent, unusually so, sometimes throwing numbers down in the hundreds other times throwing numbers over 300. In all my testing the highest number it ever threw was 364, the lowest 196. The average from the entirety of testing was 256.8, and the standard deviation 41. If you're wondering though why some test are a little high and others are a little low, this is why. That inconsistency means if you're only pulling 3 shot averages one shot low or high can really skew things. I feel this total average is very representative of the gun's capabilities in the factory configuration.

Leshiy Final Rev.png

Final rev. core – 112.0
We lost a baffle here and also lost 3 points off the average of our previous best test. That is insignificant though because, even though this is an average of 8 samples, the standard deviation was 11. It is, to my ear anyway, a significant improvement in sound attenuation over the factory configuration so I'm happy with it. We didn't quite crack 100 (average) as I'd hoped, spending another two months trying to shave another 12 points off the average would be no fun so what is the point? There is also something else......

Leshiy 3baf shroud extension.png

Extended Shroud/350mmBBL – 87.0
We wanted to test this configuration, not just confirm assembly/fit. For those unaware, there is a popular kit out there which takes minutes to install that gives the Leshiy a longer barrel, longer shroud, and more power. Turns out our new core works very well with it, as it comfortably cracks the 100 mark. Standard deviation was even 6.8. Being slightly less volume constrained obviously helped, but the other thing we did was take a special cut piece of foam that fits inside the spacer/shroud and around the barrel, and shoved that all the way to the back of the shroud. This way, as we learned testing on the Crown, sound would be less apt to reflect up and down the tube. And, thanks to my core design, the damper is essentially “built in” as it comes in contact with an angled rather than flat face.

So there it is, the Leshiy and new core are on their way back to Custard as we speak, along with our sincere thanks for letting us have a play with this system..... and thats enough of highly eccentric volume constrained systems for a while now. :P


Airgun Moderator Design, Performance, and Development - Big(er) Bore Tests (part 9)

Silent Thunder Ordnance

Two FX Crowns, one in .22 and one in .30. The VP or Value Priced crown is, by my estimate, a screaming good deal on a fantastic gun. The aluminum tank really doesn’t add that much weight over the carbon one but cuts hundreds of dollars off the price.

Two FX Crowns, one in .22 and one in .30. The VP or Value Priced crown is, by my estimate, a screaming good deal on a fantastic gun. The aluminum tank really doesn’t add that much weight over the carbon one but cuts hundreds of dollars off the price.

Catch the previous episode HERE.

So enough people have picked up one of these moderators now that I figure I should probably test and design some at higher power outputs. To that end, I picked up a FX Crown VP in .30 cal to test with a little more go juice. The thing consumes about twice to 2.5 times as much air per shot as the .22 Crown, slinging a JSB 50.15 grain pellet at 850FPS for 80 footpounds of muzzle energy. Cool beans eh? I'm still less than entirely amused over the cost of ammo, which is more expensive than the match grade rimfire I use in my favorite PB, but I digress.

So the first and most obvious question is how do my designs which were optimized on the .22 perform on the .30? So far the feedback I've gotten from other people who've used them is “great,” but I'd bet 100$ they're not fully optimized for almost three times the kinetic energy. Hell the factory shroud extended on this thing, which was simply unpleasant on the .22, is now physically painfully loud when shot indoors. All that sound reflecting back off the walls of my indoor range leaves my ears ringing. So how does everything stack up?

Factory Shroud Extended – 637.6, 617.2 – It is loud, what did you expect? Just for quick reference, the peak from the .22 with shroud extended is usually around 250. 250 is also about what a stock Edgun Leshiy meters at. So this is much much louder. I should note that I had to significantly adjust the scale on these captures so that they weren't, literally, OFF THE SCALE. :P So if you're wondering why they look about the same or lower than some of the above traces, that is why, the scale is different. ;) Why the two numbers and two traces? Because sound loves to resonate up and down hollow tubes, and what was a faint ping on the .22 is a very loud and annoying ping on the .30. So the higher one is before the shroud damper, and the lower one after. It wasn't supposed to cut the peak, but it did, so what can you do right? I made an entire post on just the shroud damping, so if you're curious check that out.

VP levitas.png

Levitas – 302 – my first design, small and light at just 35mm in diameter and 120mm long and just 50 grams. Pretty tiny for this kind of setup, and optimized for performance on the .22 obviously. Still, I think cutting the peak by more than half on a RETRACTED shroud (all the tests are with a retracted shroud except for the obvious extended shroud test) I'll call a win. I bet I can optimize this considerably for the shrouded .30 though, and my best guess is I can get it down to somewhere around 160-190ish. In the next couple Pilum tests you'll see why.

VP Pilum SD.png

Pilum SD – 278.6 – SD stands for Single Diode, as in it has a single gas diode for flow delaying and the rest is sound damping. I've had this Pilum kicking around for a while now, it and the DD variant are both comparable in terms of sound attenuation on the .22 Crown. Now that flow is a more significant issue though, the differences are more apparent.

VP Pilum DD.png

Pilum DD – 208.6 – DD obviously stands for Double Diode, and here we can see adding just one more diode took 70 points off the peak. Not too shabby.

Pilum QD Crown30.png

Pilum QD – 92.6 – QD stands for quad diode, four diodes and just a little sound damping material at the very end. This is staggeringly good performance. It has a little “whoosh” to it as the significant volume of air empties out, but after all my silencer testing I'd have never imagined I'd be able to get an 80 foot pound gun this quiet with this small a moderator. I almost can't believe shooting it just how well it muzzles the bark, you wouldn't guess it was a .30 if it weren't for the much louder “slap” of the pellet hitting the muddy backstop 100 yards down range. I'm happily confident this is actually optimized for this gun. Why? Two reasons. First, the trace shows the peak is about level with the protracted sound of the moderator draining, which can, but isn't necessarily, a good indicator of optimization. (it can be just an indicator of a very noisy design) The second reason is that, if you assume a roughly 70 point reduction per diode (it isn't linear, and doesn't work like that, but we're talking rough numbers here) that means the estimate is 68 with 4 diodes. 5 diodes wouldn't physically fit and would break the trend. 3 would be significantly louder than 4. Thus 4 with just a little bit of sound damping is almost certainly optimized for this size envelope. So yeah, pleasantly surprised and pleased with this one.

And now I want to take a brief pause to put a final nail in the “bigger diameter is better” hypothesis of moderator design. This is what me desperately throwing a bunch of spitballs at the wall and hoping something sticks. I tried conventional, I tried unconventional, I tried small diodes in large tubes, and of course I've tried the good old hair curlers and washer baffles, that is to say flat faced baffles with felt held around the perimeter. (I did put a few rounds through some famous manufacturers' big designs and they are VERY loud. I don't want to kick any brands here, but they do NOT get magically quieter with more air volume. So as counterintuitive as it is, and as much as I'm running over what is clearly airgun silencer dogma, currently the data is unequovical: a large diameter moderator of conventional design will not out-perform, and thus far will exclusively under-perform, its efficiently designed smaller diameter brethren. And this is to the extent that a Donny Sumo or Clague will be louder on a 32 foot pound Crown than the Pilum QD on an 80 foot pound Crown.

I am NOT giving up. Just because every single large-moderator-diameter test and experiment has resulted in abject failure doesn't mean it isn't possible to make a large diameter moderator perform well. What you're about to read below are more of my failures, but just a selection of the most interesting ones as there have been too many to recount at this point. As I think is pretty clearly demonstrated by said failures I don't understand the mechanism for why this occurs, why larger OD moderators are louder, however I am determined to make one which works well.

Mus Star – 172 – This design essentially incorporates traditional conical baffles of descending angle in what would be an otherwise fairly traditional design. Up front, as per usual, sound damping materials are incorporated into the skeletal area. And it didn't work, to be clear. This is still quite loud.

HBVF Star – 77 – So this was a bit of an odd duck, and you'll note it is marginally quieter than the Pilum QD. I'm still calling it a failure though. Why? Because with several times the volume to and a lot more mass to work with, I'd like to take more than a measly 14 points off the average. Basically, it worked, but isn't good enough. The basic premise of the design is a little hard to interpret from the picture, but basically it puts a conical baffle moderator of similar design to the Pilum inside a tube which is then incorporated into the tube. It is kind of like a russian nesting doll of silencers. The extra outside volume then becomes blast chamber volume. This thing was a pain to design and an even bigger pain to assemble. You might be asking why not gas diodes, and the answer is I made such a beast but on testing day it had assembly issues and so its performance was inconclusive.

Foamtastic – 262.6 – This was another shot in the dark. The dogma is sound damping, not baffles, and large volume are what creates quiet moderators.... okay, lets try that. So one gas diode, vented into damping material and the rest of the design also full of sound damping material. Take a wild guess how that went. Also note that it was about as loud as a Pilum with a single diode. So while I'm not sure this diode was working effectively, all this volume accomplished basically nothing.

It'll come as a bit shock, but I have some ideas for where to go next with this. As far as I'm concerned, personally anyway, I've laid to rest the “bigger is always better” idea. Clearly design language which works on smaller silencers doesn't work on larger ones. And it isn't because the sound damping is innately ineffective, because if you look at the traces you can clearly see the post-peak-noise is effectively damped, but that initial spike is not. If you did your testing on a sound meter not capable of capturing that peak, which is the overwhelming majority of them, it'd be easy to fool yourself into thinking that bigger just works.

Airgun Moderator Design, Performance, and Development - The Edgun Leshiy (part 8)

Silent Thunder Ordnance

Edgun Leshiy with one of the experimental moderator cores. The finished versions of these should be matte black, but for the purposes of prototyping white is much much better at showing flaws/failures/problems.

Edgun Leshiy with one of the experimental moderator cores. The finished versions of these should be matte black, but for the purposes of prototyping white is much much better at showing flaws/failures/problems.

You can find PART 7 HERE.

So round one established primarily two things:
1) putting rubber in the shroud takes up precious volume and actually makes them considerably louder.

2) the general spacing and number of baffles, which is to say 3 or 4.

Given that the name of this game is testing baffle design, I opted for a 4 baffle design in the hopes I could improve baffle efficiency. Foam integration was done in between baffles, in the mostly “waste space” at the inside top of the shroud, rather than in a separate end-terminus section. This resulted in four simple designs. The idea here is that, once the basic baffle configuration has been affirmed, you want to play around with various little tweaks in an attempt to further optimize sound attenuation. And that is what is happening here. Some failures are expected, but this is a key part of the purpose of experimentation. Keep in mind the point here is to only introduce a single variable in each design, this way causality is obvious.

One other noteworthy thing here is that I messed up the captures for the long trace seen above the detailed trace. As a result you can see equidistant from before to after the trigger. The result shows something else very interesting: all the noise the gun makes BEFORE the pellet exits the front of the moderator. Cool huh?

Factory Leshy Moderator Core - 227.3

Factory Leshy Moderator Core - 227.3

Factory – 227.3 – This is the factory shroud insert, tested again as it is the perpetual benchmark. It makes both a high peak and sustained sound as loud as the uncorking sound. Sometimes this can be an indicator of optimization.

Control – 158.6 – Four baffles, flat faced, symmetric, the end. This is the vanilla designed to be a benchmark for what a more efficient eccentric conical design can/should be. And it performs okay, in that you can tell it is quieter than the factory insert.

Enhanced Blast Chamber – 172 – Four baffles but with the entire chamber separated into two sections. The bottom section houses the baffles. The top section is open and houses a little damping foam, but primarily is there to act as an expansion area/pressure reservoir for the muzzle blast. The idea was that maybe a large initial chamber would take some of the load off subsequent baffles and better attenuate sound. The baffle design is otherwise identical to the control. As you can see, it clearly didn't work. What is more interesting in its not-working is how it ramped up in sound. So the blast volume did work, capturing the air temporarily, it just made quite a lot of noise subsequently releasing it. (and all the traces look like this) It also looks like it made a pretty solid ~6kHz in doing so, which is well within human hearing range. As you might have guessed, that is annoying. Don't believe me? Have a listen to this:

Major asymmetry – 144 – Four baffles with an opening aggressively angled upward to induce the air to fill the top of the shroud. This design likely will introduce unacceptable turbulence, but is a worthwhile point of curiosity. It does perform better than the control, but not by a huge margin. I actually had higher expectations for this design. But this is why you test: you just don't know what is going to happen until you try it. It should be noted that this design was probably the quietest post-peak, however it just couldn't get that peak down.

Bilateral symmetry – 146.6 – Four baffles with a design loosely based off the old LIM moderator core from the earlier days of my airgun moderator experiments. The idea is that bilateral symmetry is maintained, however cross-flow may improve sound attenuation. Again it worked, beating the control, but audibly wasn't the best design here. Like the factory shroud it brings the uncorking sound down, but makes a fair bit of noise subsequent.

Tilted conical – 115 – Four conical baffles with the mouth ever so slightly angled upward. This should induce the air to fill the top of the shroud more efficiently, and indeed it appears to do exactly that. This design was noticeably quieter than all the others, it really worked a treat, it sounds great. So, much to my surprise, I think I have a winner here in this round. And looking at the trace, it really does look good.

So what is next? Well there are a couple little changes I want to make to optimize sound attenuation, improve printability, ensure compatibility with the 350mm extended barrel/shroud thingy, and of course I want to do a finished version in 20% carbon fiber reinforced nylon. It is much much more durable than PLA and much more solvent resistant than these ABS test cores. I also want to do some experiments with the endcap to make it a little more visually appealing. Once that is all done I'll do one final test check on accuracy and sound attenuation, and then I guess it is a wrap. I don't want to prematurely take a victory lap here, but my stretch-goal was to get the Leshiy down to 100 and it looks like I've essentially arrived. It is actually about the same peak as a DonnyFL Sumo on an FX Crown in .22 (which metered at 108 avg. in my test) so that is pretty good in my book. Now I just have to confirm compatibility and make it look pretty.

Airgun Moderator Design, Performance, and Development - Shroud Dampers (part 7)

Silent Thunder Ordnance

FX Crown VP w/ shroud damper

FX Crown VP w/ shroud damper

In case you missed it, here is a link to PART 6. Fear not, we haven’t forgotten the Leshiy, or any of the other projects, this is just a quick hit for a little thing we discovered while doing testing. Then we’ll be back to, what is now apparently the regularly scheduled programming on this blog….. how the heck did that happen anyway?

So this is an oddball little project, however while testing all of these moderators I noticed there is a bit of a ringing sound with each shot which really sounds like it is coming from the shroud. On the .22 caliber Crown you can barely hear it. On the .30 caliber VP Crown it is very noticeable.

Let me rewind for a second. Normally you would assume this would be coming from your air tube, however there are two notable things about that, the first is that the FX Crown doesn't have an air tube it runs a carbon or aluminum bottle, and the second is that it is regulated, so there is no major air-shock to the tank anyway. The plenum should also be fairly well damped given its location and elements of its installation, so color me skeptical that it is coming from there because there are all kinds of factors going on which would impede resonance in this case. Obviously ruling it out though would be something you'd have to do experimentally, hence this mini-project.

I'm also not a big fan of the look of my crown when it has an erection. Color me weird, but I'd rather put a small light weight moderator of equivalent length on my crown's muzzle than extend the shroud which I think looks goofy and does a lousy job at sound mitigation anyway. On the .30 Crown it is actually earsplittingly loud if you shoot it indoors. If you pull your shroud off, you'll also notice that the shroud stop is part way up the tube, which essentially reduces the shroud's volume when it is retracted. So step one was loosening that shroud stop and gently moving it rearward so that it pins the shroud in its fully retracted position. This is necessary for silencer testing on the .30 as it blows itself open with each shot otherwise. Also it will stop the POI shift caused by rotating the shroud to different positions, another annoying “feature” from the floating shroud.

So back to the main story, sound loves to run up and down tubes. It really really does, particularly if the tubes have flat faces at the end. And guess what the Crown has? A nice long tube which is basically flat at both ends. So after finding this extra shroud volume, why not eat up a little bit of it with some damping material? Thankfully I have plenty of options kicking around, so I took some quick measurements and zipped out a little disc of rubber and some foam to, hopefully, damp the sound which is inevitably running up and down my shroud.

FX Crown .22 w/ shroud damper

FX Crown .22 w/ shroud damper

Having done this, to both Crowns, audibly the ringing is gone. But I’d like some sort of data to back it up. I should note here that this damper is NOT meant to reduce peak sound signature, just clean up the noise which follows.

This is the Pilum design on the .22 before any modification to the shroud retainer or damper. Note this was done on a different day from the rest of these tests. This moderator on this day metered an average of 57 (peak).

This is the Pilum design on the .22 before any modification to the shroud retainer or damper. Note this was done on a different day from the rest of these tests. This moderator on this day metered an average of 57 (peak).

So this is the exact same moderator, same gun, same everything except on a different day and now with the shroud stopper moved rearward and with the damper installed. The average for this moderator on this day day metered 51.8 (peak). 

So this is the exact same moderator, same gun, same everything except on a different day and now with the shroud stopper moved rearward and with the damper installed. The average for this moderator on this day day metered 51.8 (peak). 

So these two different peaks are outside their respective standard deviations, however they don't exceed what is POSSIBLE day to day variation. My experience, and looking at other tests between the two days, suggests that it is unlikely the peak difference was solely random and atmospheric differences. I can't explain fully why the peak is lower, but that doesn't mean it is the shroud damper. That said, after the peak, to my eyes the traces look much quieter. The damper appears to be working. Further, that faint ring is now audibly gone. 

Now on the .30 Crown things are a little different. First the ringing is much much more obvious and obtrusive. Second though is that, for a true apples to apples comparison, I tested with just the shroud extended, no moderator, and changing nothing between the two tests other than the damper. These were tested back to back.

This is the .30 with just the shroud extended. The scales are different between this and the above traces by the way. This thing is earsplittingly  loud in factory form. If you think you're going to shoot it inside, think again, any sound-reflective surface or room causes my ears physical pain anyway and leaves my ears ringing. It metered an average peak of 637.6, and the ringing is very very noticeable. (to the subjective ear anyway) 

This is the .30 with just the shroud extended. The scales are different between this and the above traces by the way. This thing is earsplittingly  loud in factory form. If you think you're going to shoot it inside, think again, any sound-reflective surface or room causes my ears physical pain anyway and leaves my ears ringing. It metered an average peak of 637.6, and the ringing is very very noticeable. (to the subjective ear anyway) 

This is the .30 with the shroud extended still, but now with the damping material added. Note that adding a damper without moving the shroud stopper rearward eats up reflex volume. It metered an average of 617, however that is not statistically significant as the two are within less than a standard deviation of each other. When airguns are this loud and messy, things are just a lot less consistent. Subjectively, this also seems to have done away with the ring. 

This is the .30 with the shroud extended still, but now with the damping material added. Note that adding a damper without moving the shroud stopper rearward eats up reflex volume. It metered an average of 617, however that is not statistically significant as the two are within less than a standard deviation of each other. When airguns are this loud and messy, things are just a lot less consistent. Subjectively, this also seems to have done away with the ring. 

Both looking at the traces, and to my subjective ear, this really appears to work. I’m happy with the project’s outcome, and for once something worked as intended on the first try.

Stay tuned for more on the Leshiy. There have been some very exciting developments, and the Leshiy is now considerably quieter than before.