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Studying Baffle Designs

OldCrow - Many years ago, a company named Acerbis (sp?) made polymer, plastic, silencer/spark arresters for the off-road, 2-stroke motorcycle industry. These silencers were very effective at reducing noise, far better than anything available at the time. 
I would think the application would be very similar to that of an air rifle, when considering sub-turbulent air velocities. May be worth looking into. 
 
OldCrow - Many years ago, a company named Acerbis (sp?) made polymer, plastic, silencer/spark arresters for the off-road, 2-stroke motorcycle industry. These silencers were very effective at reducing noise, far better than anything available at the time. 
I would think the application would be very similar to that of an air rifle, when considering sub-turbulent air velocities. May be worth looking into.

Thanks for the heads up! I'll have a look at their stuff.
 
I’m nearly certain Acerbis stopped making silencers years ago, but the significance is; plastic-housed silencers did a superior job over aluminum housing for quieting dirt bikes back then, and quieting a 2-stroke engine is not that unlike an air rifle. So the perforated core-tube and packing used then and still used now, may work well. 
 
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I’m nearly certain Acerbis stopped making silencers years ago, but the significance is; plastic-housed silencers did a superior job over aluminum housing for quieting dirt bikes back then, and quieting a 2-stroke engine is not that unlike an air rifle. So the perforated core-tube and packing used then and still used now, may work well.

Yes, I think it would make a good basis for a "hair curler" design. I just haven't felt good about any of those I have drawn yet. Here is a picture of the parts I am working with now.

Left to right, a baffle, a muzzle cap, and a base cap. The base cap contains a 1/2 x 20 UNF nut. I'll west system epoxy that in place during the print process for that part.

Baffles stack. They are epoxied to the sides of the tube and to each other at the four "redirectors". The code supports a one line change for diameter of the "can". I'm going to use PVC water pressure pipe to finish the prototyping and testing and then probably deliver using carbon fiber as the tube. Depends upon cost and weight. Even if I go with CF tube, I think I can deliver at below $50 US, free shipping to CONUS. PVC tube would cut that by about $10 so weight/cost are the deciding criteria.

The design is modular and I can replace/redesign any component independently. So 'bout done with development. On to testing ;) I am actually thinking about making the parts available individually. Maybe a DIY kit. 

muh-mod-design.1652498184.jpg

 
Nice design , i to have been working on these with a friend , made a larger one , and it really had no difference in sound than a smaller one? We asked ourselves why ???? Well , we started to add a special sound deadening fiber material in between the baffles and the outer shell. We drilled holes to slow air yo leak into this fibrous chamber and you now what ??? It worked fantastic . The plastic as is was just making a sound chamber that transferred the sound outside , the material now deadens this and the bigger can we make , now the more quiet the outcome !!!! Hope this helps !
 
Nice design , i to have been working on these with a friend , made a larger one , and it really had no difference in sound than a smaller one? We asked ourselves why ???? Well , we started to add a special sound deadening fiber material in between the baffles and the outer shell. We drilled holes to slow air yo leak into this fibrous chamber and you now what ??? It worked fantastic . The plastic as is was just making a sound chamber that transferred the sound outside , the material now deadens this and the bigger can we make , now the more quiet the outcome !!!! Hope this helps !

Yes the burst of air pressure slaps against the inside of the moderator and transfers the sound through it. A small diffusing baffle near the muzzle of the rifle would probably have a large effect on that problem.
 
What is that?

That is a baffle I printed on my 3D printer, steel wool rusts, bronze, brass, and copper corrode. I am wanting something which can be cleaned by dunking in a bucket of warm soapy water.

Wow! That is way cool…that reminds me of biological construction, like an organ or sponge or perhaps insect nest. 
 
What is that?

That is a baffle I printed on my 3D printer, steel wool rusts, bronze, brass, and copper corrode. I am wanting something which can be cleaned by dunking in a bucket of warm soapy water.

Wow! That is way cool…that reminds me of biological construction, like an organ or sponge or perhaps insect nest.

I have to be honest with you, I did not design that. The program I use (called a slicer) which takes the CAD file and converts it into a file the printer can use uses that pattern to fill in parts which are not configured to print as solid. I just tricked the program into believing the object it was printing had "invisible" walls and was hollow. The slicer then built the part out of that support filling. It didn't work particularly well as a baffle but was useful as a diffuser.
 
I'm LATE to this conversation and after a skim read, thought I would just add one thing I've discovered in 10+ years of making LDC's.



Supersonic speed air leaving barrel behind the pellet or slug that is going slower ... Can and will overtake said projectile and when this air gets ahead of said projectile the disturbance created within the LDC is great & having the projectile pass threw this turbulence will destabilize it !!! Isolating levels that somewhat keep the air from overtaking the projectile as it passes down the LDC's length work best IMO.
 
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I'm LATE to this conversation and after a skim read, thought I would just add one thing I've discovered in 10+ years of making LDC's.



Supersonic speed air leaving barrel behind the pellet or slug that is going slower ... Can and will overtake said projectile and when this air gets ahead of said projectile the disturbance created within the LDC is great & having the projectile pass threw this turbulence will destabilize it !!! Isolating levels that somewhat keep the air from overtaking the projectile as it passes down the LDC's length work best IMO.

I think you're right about that. I tried a bunch of K baffles and one thing and another and sent them to a another member who has far more ability than I do to shoot tiny little bitty groups. And that seems to be what he found out. So I made some changes and sent him the moderators with the changes. And at this point he is saying that we may have addressed that problem. He is of a mind to say that air strippers are far less disturbing than baffles. And to add to that it seems that my tests are showing that a really sophisticated baffle system isn't necessary at pressure levels that we see in air rifles. Now that's just a feeling that I have and I couldn't prove it.

I don't even have a good quality microphone I just use my cell phone. I do ensure that I use the same moderator as my standard and I test it every time that I test anything. Apples to apples.

My standard is a Donnie FL TANTO. Which is exceptionally efficient for its volume.

Thanks for the advice. 🙏
 
I'm going to assume you're talking about the basket weave baffle in the picture above? Unfortunately I cannot upload a file to confirm that... File uploads were working this morning and they are broken again.

Anyway it doesn't matter because I don't use a CAD program. I do have one but I prefer to make objects in OpenSCAD.

https://openscad.org/downloads.html

That particular pattern isn't something that I draw at all. That pattern is an infill pattern that is created by the slicer program I use to convert an STL file into a printable file.

You would have to ask the developer of the PRUSA slicer for the code that generates that infill pattern. I suspect it looks like a sine wave gradually rotated along one axis through about 180°.