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Is this concept printable?

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Mr.H said:
How hard would it be if you ghosted an image of my barrel and air tube, and then highlighted your moderator as it attaches to the barrel threads? If your OAL is approx. 10", I take that to mean that your design will extend past the air tube by about 4".
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I only bring that up as the 2" behind the barrel thread supply the needed anchor point for the factory shroud to align itself with the barrel.
How do we know that your design will line up correctly without that other anchor point?(or barrel band as you had previously said)?
 
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If I have an image of your airgun, taken from the side and some reference length to scale to, I can do it. The picture should be taken from far and zoomed in to avoid perspective distortion.

The line drawing around the moderator was my first layout. Some dimensions may have changed a little since.

1706103893817.png



Alignment is achieved via tight muffler shroud to insert; rear shroud to barrel plug; and muffler insert to barrel stud and shoulder. If you think we need to capture the barrel OD I might be able to do that. But, for the most part print length has been used up.

A barrel band could be a useful addition, regardless of any other considerations.

1706104243773.png






AZ
 
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Because the air tube and shroud only have a 0.5 mm gap between them, defining a barrel band that can clamp the moderator to the air tube by means of a cross screw, is a bit of a challenge.

By cutting a groove all the way around the moderator body (the section that is at shroud OD), the moderator can be rotated to screw it onto the barrel stud, and still accept a 3 mm cross screw. See images below.

I may thicken up the wall between internal cone and screw groove, because I am not generally in favor of weakening structures. The look of the M4 necked down barrel, for the launcher attachment does not appeal to me. So, consider this groove a thought exercise for now.

1706105645577.png

1706105738864.png
 
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The important thing about the appearance of this muffler is that you like it, Mr.H. Or at least, can tolerate it. To me, the head looks fat at 2" in diameter. So, I have shaved 10.8 mm off the diameter to see what a 40 mm OD version would look like - below.

How much would that loss in volume affect the sound? I think the smaller one would be very noticeably louder - but by how much?. If you are interested, you can have both versions, and then find out. I have the 40 mm head OD version saved as a separate file from the 2" OD version.

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A better section view than trying to capture both together:
1706110248790.png



1706109979098.png
 
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Correct.
subscriber said:
The air tank has a rotating collar at the front end, right? Any barrel clamp should avoid that collar, right? If so, the clamp would need to attach to the metal shroud tube, rather than the plastic muffler, ahead of the shroud tube. In other words, clamp over on the left of the threads, visible on the outside of the muffler.
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that is correct. The length of that rotating collar is 1 7/8 “
 
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subscriber said:
The important thing about the appearance of this muffler is that you like it, Mr.H. Or at least, can tolerate it. To me, the head looks fat at 2" in diameter. So, I have shaved 10.8 mm off the diameter to see what a 40 mm OD version would look like - below.

How much would that loss in volume affect the sound? I think the smaller one would be very noticeably louder - but by how much?. If you are interested, you can have both versions, and then find out. I have the 40 mm head OD version saved as a separate file from the 2" OD version.

View attachment 428451

View attachment 428457


A better section view than trying to capture both together:
View attachment 428461


View attachment 428459
Click to expand...
Visually speaking, I do prefer the smaller diameter look look of the 40 MM. Just as a reminder, I’m just trying to get a little bit of noise reduction at my ear, I don’t have any neighbors to worry about. In other words, it does not have to be silent, nor do I expect it to be silent.
 
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...YES! It is printable. It was the possibility of a tall print like this that led me to choose a "direct drive" modification for my Ender 3 that would not impede it's full 250mm print height. The final print critical dimensions measure up just as expected.

I had the big 50FPE 2"x6.5" sitting here, and some other test pieces, so I added them to the photo for a futuristic "cityscape."

1706297611519.jpeg
 
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Thanks, TorqueMaster, that does look good.

Mr.H, The installation of this insert is unconventional, and requires a little forethought: Essential to installation and removal is releasing the rear shroud to barrel plug attachments. That connection to the shroud has to float in order to pick up the barrel stud to insert threads.

I suggest you mate the shroud to insert threads first, out of the gun. They may be tight and you need to be careful the first time you screw them together. A little oil or grease on those threads may help. Before you attempt to mate those threads you need to verify the fit between shroud ID and insert OD. Based on TM's measurements there are a few small areas of interference on some of the ribs. When you insert the insert into the shroud and rotate it, the tight spots should change their appearance slightly. As we are talking a few thousands of an inch, a light dressing with a file or abrasive paper should relieve those areas fast. Then retry installation of the insert. It should go deeper into the shroud.

You want to be able to rotate the insert in the shroud rather freely, so when the threads make contact, you can feel what is going on. Don't just sand everywhere aggressively, or the inert is likely to become sloppy in the shroud.

Once you are happy with the insert to shroud fit, the insert to barrel thread fit needs to be confirmed with the shroud off the insert. You can actually verify the barrel thread first, as it should fit just fine - TM chases 1/2-20 threads with a tap as standard practice.

For final assembly, screw the insert fully into the shroud, off the gun.
place the rear shroud support bushing over the barrel and slip it towards the receiver end.
offer the shroud and insert subassembly up to the rear support bushing. Mate rear support bushing with shroud, but do not tighten the screws that secure the bushing to the barrel.

Locate the barrel stud thread to the insert thread. Turning the shroud/insert CCW should result in a "click" when the thread starts slip off each other. Then rotate the shroud clock wise slowly to verify that the insert is screwing onto the barrel stud.

Keep the rear shroud support in the shroud to help guide the alignment process at the barrel stud.
Once the barrel stud is snug, verify the rear shroud support bushing is in the desired location relative with the shroud end; and snug the rear shroud support retention screws.

When tightening the rear support bushing retention screws, there are two choices:
Keep the airgun horizontal so whatever droop on the barrel system is relaxed with the retention screws tight. Or point the muzzle up when tightening the screws, so the barrel system is in tension when the airgun is horizontal.

The above may make no difference, or one of the two assembly states may result in more favorable barrel harmonics. Pick one and shoot with it. If you are less than satisfied with groups or POI, try the other assembly state to see if it is better.

If you want to remove the insert, the first step is to release the rear shroud support screws. (unless they do not grab the barrel, and the support is in fact free to float on the barrel). If the screws couple the shroud, support bushing and barrel, and you forget to release the support bushing screws, then unscrew the insert from the barrel, the system will go into tension, and potentially damage the threads. The fact that the barrel stud and shroud thread have a different pitch means any third constraint must be released before these threads are screwed in, or unscrewed.

I am thinking about a barrel band that would couple the shroud OD to the air tube OD. Due to their close spacing, finding a way to pull the band into firm contact around both parts seems tricky, so I am hoping that you won't need such a band, but can get the results you want from the above assembly sequence. The insert baffle bores are generous compared to the stock parts. So, I don't think you will see aerodynamic steering effects. Mostly just barrel system harmonics.

TorqueMaster, how much does the insert weigh? Mr.H, how does that compare to your more elaborate moderator installations? As the shroud is kept, its weight needs to be included with the printed insert.
 
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AlanMcD said:
Any results yet? Many of us would like to know how it turned out . . . .
Click to expand...
Your question was timed perfect, I got the printed unit yesterday.

Well, let me first say that this is the only thing I have ever had printed for me. The quality of the unit is top notch. Torque Mastert did an excellent job. And all of Subscriber's questions to me translated perfectly. I had to carefully sand the the insert with 240 grit so it would slide into the factory shroud.

The unit has two sets of threads, 1/2"-20 UNF for the barrel end, and M28X1.0 mm on the opposite end. The 1/2"-20 were printed perfectly. The M28 thread were printed pretty tight. I could get it threaded on, but it was so tight, I had a hard time getting it off. It looks like that section of threading was about 1/8" longer than the factory end cap.

The unit weighs in at 4.55 oz. The guts of my factory system weighs in at 2.54 oz. So, a net increase of 2 oz.

Now the moment of truth. I did 2 10 shot shot strings: 1 string factory system, 1 set using Subscriber's design.
I don't have a professional dB meter. I used the Niosh dB meter on my iPhone.

On average, 92 dB on both strings. So unfortunately, no benefit from the custom, printed unit. I didn't even shoot it yesterday, as it was pretty late in the afternoon. I probably shoot it today weather permitting, just to check for POI shift.

The unit probably needs to be longer and fatter to get the gun quiet. I'm not sure I want to do that at this point.

Spook at one point earlier in this thread suggested me getting a carbon fiber tube and fabricating a new shroud that would accommodate a couple more factory baffles. Sounded like a good idea at the time. Only one problem with that. I don't have the skill set or tools to pull that off. So I think I'm going to invest in a pair of Bluetooth ear buds.

I want to thank Subsciber and Torqueaster for all your time on this. And thanks to all the member of AGN for following along. Darn near 1K. views. Wow.
 
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