Taming the bark of an Avenger

[subscriber]

I just ordered a fat boy for the impact so I’ve got an extra moderator for the avenger.

For anyone who is interested, I have a fatboy inspired .22 Avenger LDC design.  It uses my two stage reflex air stripper, with a Maxim inspired 2" OD front section. 

I made this LDC "fat" so as to better accommodate a smoother spiral air path than the very cramped dimpled LDC version, that Matt and Chris have just printed and tested, above.  It also uses permanent thin support walls to enable printing the otherwise "floating" ceiling.

The STL for this LDC can be downloaded by anyone, until 17 April, from:  https://www.dropbox.com/s/t9fq48er6vpzrb3/.22%20Avenger%20Maxim%20Fatso%20LDC%205CH.STL?dl=0

[Outer_Rondacker]

Factory barrel mics at 25.10mm round. I would say best to not go past that in diameter. Your threads measure around 13.40mm and the factory one is 10mm the one from thingivers is 7.50mm. They all hold in fine just the barrel shroud of the gun only has 13mm of threads in it.

Factory diameter of pellet path is 9.10. Thingivers one is 7.75 on the back side and 8.00 on the front. Yours looks to mic at 7.10-7.15mm I will be honest with the crown it is hard to get a good reading. On your older model the one wit the holes on the front it comes in at 6.75mm.

You have my apologies as I dont have this one to measure as it is in Chris's gun. But so far this shape seams fit the gun best for size and filling.
https://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=196584.0;attach=397748;image

I am not really sure what you mean by  an envelope shape. Do you mean like a triangle? I think round is best. Once the world gets moving today I will beef up the reg pressure to 2400 and test some 18.13g pellets at 30-50 yards and give you the feedback on that.

TorqueMaster (Bob) I get it. I have jumped into a forum post many times to not read the entire thing and ask what was already stated or suggested it. Just incase you have not had time to go back and look at the posts I am testing with 1650-1750 on the reg with CPHP's 14.3g at 30-50 yrds and sound testing on 200yrd open range. Test is done at the muzzle not the ear. I know its acceptable to my ear I want to know what everyone else might hear down range or on the sides of me. In the firearm world I test at the ear since that is what I am looking to protect not in small bore air guns. Hope this catches you up to speed.

[subscriber]

Thanks for the info, Matt,

By envelope, I mean to map out a space that needs to be left open so that you can air fill the gun, without removing the LDC.   The sketch below shows the zone that must be left open to remove the air fill cap with XXXX. 

Generally cylindrical LDC is assumed, possibly with a long taper to clear air fill cap.

[Outer_Rondacker]

Thanks for the info, Matt,

By envelope, I mean to map out a space that needs to be left open so that you can air fill the gun, without removing the LDC.   The sketch below shows the zone that must be left open to remove the air fill cap with XXXX. 

Generally cylindrical LDC is assumed, possibly with a long taper to clear air fill cap.

I believe it would have to be 25.00 mm Peter. Not sure if that is worth it as the size keeps getting longer and longer. Ugg I am looking out the window to frost on the shooting bench. Sun do your thing.

I would also like to add I do not own a Chronograph that can register a 22 pellet at these speeds. If I had one I would gladly give you guys the fps maybe even fire up the  cameras.

[subscriber]

Matt,

I have incorporated all your feedback into a slim LDC that has tightly spaced BuckRail style conical baffles.  The bore has been scaled in diameter to print at 7 mm. 

The twin reflex air strippers remain, but the thread length has been reduced to 10 mm.

Anyone can download the STL for 7 days from: 
https://www.dropbox.com/s/rxwfg6w7eu8d8j8/.22%20Avenger%20LDC%20BuckRail%20baffle%20style%20with%20two%20stage%20reflex%20air%20strippers2.STL?dl=0

Or Wetransfer:  https://we.tl/t-ruKXucoLYC

[subscriber]

For anyone who is interested, I have a fatboy inspired .22 Avenger LDC design.  It uses my two stage reflex air stripper, with a Maxim inspired 2" OD front section.

Dropbox seems down, so I also downloaded this STL to Wetransfer: 
https://we.tl/t-xKOjo6EHmz

[subscriber]

This is perhaps the last spontaneous Avenger LDC design I will post.   If testing of my or other designs brings new insights and inspiration, then great - new motivation.

This design is based on the shape of the plume as pressure in the LDC decays, and the air in the bore tends to want to zip straight through down the hole due to its forwards momentum.  I posted a sketch of this plume in post #155:  https://www.gatewaytoairguns.org/GTA/index.php?topic=196584.msg156311883#msg156311883

The two stage reflex airstripper is retained, with the shorter thread, as requested by Matt.

For reasons I don't yet understand, the dropbox links to download the STL for this LDC and the previous ones do not work for me.  In case dropbox does not work for you, the WeTransfer link for this file is also included:

WeTransfer:  https://we.tl/t-OApzOy8syo

https://www.dropbox.com/s/ej0g3dkwyqzx3j6/.22%20Avenger%20Plume%20Baffle%20LDC%20with%20two%20stage%20reflex%20air%20stripper.STL?dl=0

[Outer_Rondacker]

Thanks Peter,

The wind whipped and snow flew all day. Got to love living in the mountains. I was unable to do any testing other then getting the gun powered up and the new reg pressure set to what Air Venturi states in the manual. Weather man lies to me and is telling me today will be nice and sunny with a high of 45. I hope so. But for now I need another cup of coffee.

[TorqueMaster]

TorqueMaster (Bob) I get it. I have jumped into a forum post many times to not read the entire thing and ask what was already stated or suggested it. Just incase you have not had time to go back and look at the posts I am testing with 1650-1750 on the reg with CPHP's 14.3g at 30-50 yrds and sound testing on 200yrd open range. Test is done at the muzzle not the ear. I know its acceptable to my ear I want to know what everyone else might hear down range or on the sides of me. In the firearm world I test at the ear since that is what I am looking to protect not in small bore air guns. Hope this catches you up to speed.

Cool, thanks.  I'll use that pressure range and those pellets, and setup a bit downrange from the muzzle. 

I drew up an "envelope" for subscriber...attached.  Should be close.  I can't say if all pumps' fittings are exactly the same, though.

[subscriber]

Thanks, Bob

So, to avoid interference, the LDC radius should match the shroud for another 25 mm from the front of the shroud.  Then it may be increased by 8 mm further forwards.  At 100 mm from the front shroud face the LDC radius can be increased, with a curved path in between. 

Good to know, although a design that just clears the green line may look "funny".

So, what might look OK in that space?  Food for thought on that, attached below (dummy layout models without all of the internal details).  Obviously other diameter / length combinations would be possible:

[Outer_Rondacker]

Hey guys. Sorry for late post its that time of year when the work outlasts the hours of daylight. Anyway, I looked at the designs all look nice but we are getting very very long. We are getting upwards of a 9-10 inch print. I should of thought of this before. I have a suggestion to keep Chris on board printing. One I have to start paying him for his filament. Two I think a design like this would be a better Idea. When I say better idea I mean a 2 piece design. This will do two things I believe. First make it so we are just changing the out side the shroud part or testing just that. Since we know the inside fits and works well and are not really changing that to much. Second not so much to print to try new designs. Cuts down print time and on filament. I am going to post a picture of one from thingivers that we printed and tried but outer threads didnt work. Around that time you stepped in and we started trying your designs.

Just an idea to honestly cut back on some of these print times and materials.

Corn cob was all over the place with the heavier pellets and high pressure. Its so weird that it worked so well for accuracy at the lower speeds. The one with the wholes at the end at the higher pressure was not quiet at all. It did good for accuracy but not good for sound. So for me it was out. Not backyard friendly. I did not have the V4 with me as it is on Chris's gun. I will talk to Chris about printing the newer one. I like the one you posted yesterday. The internals look better to me.

[subscriber]

Matt,

I have also wondered about a two piece design.  Possibly with mating cones for best concentricity.  Else, in theory a single piece seems to offer better alignment.

If the first inch outside the shroud needs to keep its diameter down so that the air fill cap etc can be accessed, then perhaps that is where the split in the coupling can exist.

You sample part seems to have a 1/2 20 male thread on its end.  That suggest ability to add "standard" LDCs, and experimental ones that are handled the same way.

Any approach can be suggested.  Certainly, having a print take a day must be nerve wracking.   The risk of a print moving or breaking loose from the platen goes up as it gets taller.  Any way to reduce print time and increase the chance of success should be considered. 

Making the elements shorter is an obvious way to shorter print time.   Reusing some elements as you suggest is a good idea to save time, and conserve materials.  Speaking of filament; what is Chris using?  Where does he get it?  If it is on amazon, it may be possible to have it shipped to a preferred address.

Another idea I had is to print individual stackable baffles (or short combined groups).  Printing individually actually makes printing the toroidal spirals without support material possible (at least in designs I have not shared here).  Then, they can fit inside an outer sleeve, or each could have a male and female thread, so you can stack as many or as few as you like, in whatever order you want to try out.

I may have to finish some other projects before I can implement the above ideas, but feedback and preferred approaches would be appreciated.

[Outer_Rondacker]

Peter,
I like this idea of stackable baffles. I like the ideal of a tube with baffles inside also. Both ideas are moving in the direction with a good solutions that we have not brought up yet. Being able to clean them.

There are two things happening here. One we are centering the barrel with the shroud and using some of the internal space to dampen the burst of air. Two we have to look at the outer design as a separate entity. This is where we take it another step. I have noticed with an air rifle depending on the surroundings to the shooter is how much air is expelled is to how loud the shot sounds to the ear. In an open field its like a whisper but in a backyard the same whisper can be a bark with the air echoing off its surroundings. Reducing the force of the air expelling at high speed will hush an air rifle up in just about any environment.

We have Thursday and Friday to print if you do come up with anything. If you do not get to it there is always next Friday. Take your time. This has been enjoyable. You have no clue what its like trying to tell major manufacturers what you do and do not like about the item they just came up with. Even though they ask for you to give it the once over they refuse to listen. Its great that you understand the feedback is not negative but constative. 

[stylnchris]

Seems the Pablo "Thingiverse" designs were pulled from Thingiverse.   I find this to be a bit interesting -  Wonder why.

@subscriber -   Peter.  Have you ever considered posting your designs to Thingiverse?   

[avator]

Somehow I'm not surprised.

[WhatUPSbox?]

I like this idea of stackable baffles.

Well, There was an idea a while back to use something like this and just print an adapter and bore each section. https://www.amazon.com/s?k=B098DDQ2M1
Not sure if anyone actually made one.

[subscriber]

Have you ever considered posting your designs to Thingiverse?

I have contemplated it; yet the idea falls short of "taking".  First, a design needs to be proven good by a number of users.  Then, it will likely finds its way onto Thingyverse when someone who like the way it works, places it there.    I also have a gut sense that Thingyverse may not be the right place for me to place my designs.   Ditto for grab-cad.  Although it seems some of my designs may have inspired others at grab-cad.  For instance:  https://grabcad.com/library/air-gun-silencer-1 . That said, if I can think of something, so can anyone else.  Is the first LDC at this link a derivative of mine?  All I can say is that I have done dozens of designs for people on this forum behind the scenes, including ones that look a lot like that...

I would rather sell or gift some of the designs to Buck-Rail.  Then again, anything posted on a forum is public now belongs to everyone.  What is the point of giving these away?  I have more clever concepts that I am keeping to myself, with the hope of using the public ones as a sort of demo of what I can do.  It is hard to convince a company that your design is any good, without giving it to them to test.  The only way is to apply for a provisional patent.  Then try to sell the idea within the year that is valid.   What I am trying to do, is to identify people willing and able to make and test my ideas under NDA, without stealing them...

My problem is while my mind is still fast, my body no longer has the stamina to physically do the actual work.  Also, I lack an outdoor shooting area that I can access daily.

[subscriber]

FX has a stackable baffle product line.  It is close to what I have in mind, printed from plastic:  https://www.straightshooters.com/fx-25-stack-moderator-section-6.html

I am less bullish about making robust LDCs out of metal.  Sure, that is the way to get good alignment and robust connections.   You might say that if FX and JonnyFL can do it, then anyone can do it.  I prefer making these devices just strong enough for airgun use.  Or designing them that way.   How one of my designs may be adapted by someone else is then their business.

I like this idea of stackable baffles.

Well, There was an idea a while back to use something like this and just print an adapter and bore each section. https://www.amazon.com/s?k=B098DDQ2M1
Not sure if anyone actually made one.

[subscriber]

As a general remark about the Avenger (and all shrouded PCPs), I suspect that the shroud generates a pinging noise that will eventually make all in-shroud or external LDCs seem equal, and still noisy.  Simply wrapping the shroud in two or three layers of duct-tape should damp that ping very usefully.  This really is something that you guys should explore. 

It is really easy to ascribe the problem to the lack of good air flow management out of the barrel muzzle, when that is true only up to a point.  The principle of, "if all you have is a hammer, then all problems look like nails" can hijack broader systems thinking.

An analogy is suppressing a subsonic semi-auto firearm.  At some point "breech pop" becomes the dominant factor, and a manually operated system is required to be quieter.  Wrapping a shroud in tape seems too cheap and simple, so many people won't try it.  Yet this is like the first step into making your car handle better; increase the tire pressure (and experiment with a different front/rear tire pressure balance). 

[Some people would rather spend a lot of money to buy boasting rights, than manage tire pressure.   Stiffer antiroll bars with the right front/rear balance will make a huge difference in handling response and achieving the grip the tires are capable of.  Then invest in wheel rims that works with wider stiffer sidewall tires.  These work in conjunction with stiffer antiroll bars.  Starting with stiff springs and shocks is likely to instantly spoil the ride...   Ah, good times   ]

[WhatUPSbox?]

I am less bullish about making robust LDCs out of metal. 

Yep