Noise - when 90 fpe doesn't sound like 90 fpe

[MrP]

Thanks Knife maker - have you found any pages that show actual designs or strategies for effective 3d prints? Those pages are amazing on one level but more like product comparisons and (at STO) I might not have scrolled quite long enough... It's a lot of verbal description of commercial ldc's and was thinking think there must be images of baffle design somewhere, but I couldn't find them. Doesn't look like they're so much trying to teach you how to build things as how to figure out what to spend money on.

if I am ever in the market for a commercial LDC I'll DEFINITELY use these to compare - great resources. There's also a thread over at GTA where some guy has been testing lots of different ldcs and sharing the results. Once again a little frustrating because few useful details are shared, just brand comparisons.

 

[MrP]

here's what one of the prototypes looks like. Fins are for centering purposes. 

 

[Arash]

here's what one of the prototypes looks like. Fins are for centering purposes.

Nice, could you take pic inside of it? what about the result?

 

[MrP]

Arash - added a pic. Those little modules that I showed an image of in a previous post I decided were not the way I wanted to go... they were effective but I put them in the can in the wrong order and the one that I printed with lower print density which was supposed to be the last one in the stack ended up taking the brunt of the air and it knocked loose the little part on the inside and now it's like a rattle. I reinforced that but haven't reprinted. Tried something else...

Here are pics of some thing that I designed and printed yesterday. I want to have a single core which I think allows me to do tighter tolerances but still use the Tesla design. I modeled this in a very basic way in a fluid flow simulator before designing this and In the simulation this design was much better than models with only solid baffles.

This starts with an air stripper and vents to send air backwards, and then has 2 T diode modules, each with a pair of solid and perforated baffles Sound suppression is better than my last stack of the same dimensions (solid baffles only) especially at higher fpe. The core is 155 mm tall and 40.6 diameter and quiets 120 fpe very nicely.

 

[DavyBoone]

Thanks davyboone. Can you share that hammer setup that you use? Can anybody elaborate under what particular conditions hammer bounce is most likely?

I'll pull the hammer Arrangement sometime this week and take you a pic.

You want the breach very lightly resting on the valve head /top hat. Too much preload on the spring will cause more hammer bounce, waste a lot of hair and mess with your accuracy.

Three-piece anti- bounce Hammer arrangement for Airforce guns. Requires a 4in hammer spring in order to achieve no preload On Hammer.

 

[MrP]

Nice!!! Where'd you get that?

Here's what I'm printing now. That last core was AMAZING compared to previous iterations especially at 120 fpe. This one pictured here is the same principle but with curved surfaces to guide air inwards. 

 

[Arash]

You have solid tube. why wont use it as wall? I made it and use silencer wall to keep everything intact. less material = more area to expand the air.

 

[Arash]

Check this idea:

It has 5 baffle part and the main tube is the silencer.

That one upside down part has holes in it so when air want to compress, will leak through the holes and make more turbulence.

I choose 1mm thickness for baffles and 2mm for the walls.

 

[MrP]

That is nice and simple although I think those holes should be bigger and located closer to the walls. I modeled all kinds of configurations in a fluid flow simulator and I think you're better off with the cups are facing the same direction alternating solid and perforated that's by far the best speed and pressure changes that I see from any arrangement. I tested some designs like you have here and in the simulation they did not block the air as well. This was very surprising to me. Adding additional baffles or vents in every case I tested resulted in more high velocity air coming out compare to the simplest Tesla diode design. This was totally surprising. That alternation of solid with perforated baffles is incredibly effective.

Why I print a monocore and not loose baffles: I want everything absolutely centered on the barrel - I don't like to use loose baffles in a tube in the past I found that clipping is more likely and tolerances have to be worse. Also with this design you have to have some kind of a spacer anyway - something that occupies the space of the walls of a tube to keep one baffle separate from the other (a cylinder in your models) so why not just have them all print as a single core and all stay tight and aligned? Probably the same amount of material.

In fact the design started as a series of separate baffles in the modeling app but then I decided just to fuse them together. I think I will do what you suggest though and try to create some separate baffles with the same contours to stack into a tube. 

Also I am losing a lot of air space due to thick baffles but I need things to be thick - this is being hit by air up to 130 FPE so I need thicker walls. Looking at my model, the walls could be thinner...

 

[Guest]

You could use thicker walls on first and second chambers after muzzle and make them thinner towards end. Force inside drops really rapidly when volume increases. 

 

[DanWho]

any chance I could get a copy of the stl ?

 

[MrP]

You bet. Send me a private message and I will send it along. 

 

[JungleShooter]

You guys are AWESOME! Cool airgun engineering!!



I just realized that my Skyhawk/ P15 has NO baffles in the shroud, only one lousy washer...! 

Anyone have any remedy for this?

Matthias