LDCs that screw directly into the Airacuda Standard shroud

[subscriber]

The Standard Airacuda did not come with a 1/2 20 thread adaptor to its shroud.  GTA user Robert 5 mm asked if it would be possible to design him an LDC with a M22 x 1 mm male thread, that would screw into his Airacuda shroud directly.  Along the way, four variants were designed, in three different outside diameters: 1", 1.25" and 1.5".  All are 6" long.

The better performing three of the four designs are shown below.  Their STL files are attached in one zip file, below.

You can see photos of the 3D prints that GTA member TorqueMaster produced for Robert 5 mm, here:  https://www.gatewaytoairguns.org/GTA/index.php?topic=209670.0

[oldpro]

 SLICK!!!!! Very nice work

[oldpro]

 can you do a short fat one? Maybe 3 baffles and 1.75 OD?

[subscriber]

Sure thing, Travis

How long would you like it?  3 or 4" ?

[subscriber]

Fat LDCs create an opportunity to wrap a large primary blast chamber around what amounts to a 1" OD LDC.  In this case the design also happens to have a fat last baffle chamber.  I may do a more conventional design after this one, but this is what I was inspired to come up with.  STL attached inside zip file below.

The rear mounting shoulder to front face length is exactly 3.5".

[subscriber]

The attached STL (zipped) is for a more conventional baffle version of the above short, fat Airacuda .22 LDC.

All other details are the same as the version in the above post, so there is no need to repeat all the images views:

[subscriber]

A third variant of the above short and fat LDCs, with the same external dimensions.  Version 2 of the Conventional baffle LDC has the same baffle shape design as the "conventional" design above, but the first and second baffles are shifted, to increase the open volume in the second and third chambers (relative to the now smaller first chamber).  Both baffle shifts were 4 mm, closer to the threaded end.

STL attached as a zip file, below.

[Tater]

Very nice! Great job on them.

[subscriber]

Thanks, Jerry

How they work matters much more than their look.  I hope someone is motivated to try all three and can report back if there is any perceivable difference in loudness, "snap", tone and grouping ability.

If I was going to recommend just one, it would be a 6" long version.    Else, the first or third short fat one.  I might change my mind after seeing results

[jackssmirkingrevenge]

Excellent work as always!

If I could make a small suggestion, I think the design would benefit from a fillet as indicated in red in the drawing below.  It takes up slightly more volume but should result in a more durable construction and more importantly should make it easier for the air to reverse direction and interfere more with the flow coming from the muzzle.

[oldpro]

  Ill print one out tomorrow when I get home. Thank You!!!  Looks prefect....

[oldpro]

Fat LDCs create an opportunity to wrap a large primary blast chamber around what amounts to a 1" OD LDC.  In this case the design also happens to have a fat last baffle chamber.  I may do a more conventional design after this one, but this is what I was inspired to come up with.  STL attached inside zip file below.

The rear mounting shoulder to front face length is exactly 3.5".

   This one has my attention!!!

[subscriber]

Jack,

What you suggested with larger corner radii has been added as alternative short fat "conventional" Airacuda LDC designs below.  STL files attached in zip file.  Go to bottom of this post to see images of new parts and download STLs.

There are at least two schools of though about air management:  Run the air into a wall and let it rebound, or direct the air to flow in an organized manner via larger corner radii.    An intermedia fillet causes the air to return flow with more friction and turbulence.  So, not as bouncy at a flat wall or square corner, and not a smooth return flow as with a large radius.

I have some designs that take the large corner radius idea to the extreme.  They work better the harder you drive them.  However the extra wall thickness makes for heavy parts, and steals considerable internal volume.  For instance; here are two Avenger inserts that have very organized air flow.  They require permanent printing supports that take up additional expansion volume:

https://www.gatewaytoairguns.org/GTA/index.php/topic,196584.msg156312899.html#msg156312899




https://www.gatewaytoairguns.org/GTA/index.php/topic,196584.msg156312899.html#msg156312899




It turns out that my "plume" Avenger insert work almost as well as the 2" external OD fatso Avenger insert.  So being much slimmer and lighter, my simple almost convention "plume" baffle style is what I go to now, most of the time.  Here is a version of my Avenger plume design that has a two stage reflex air stripper in the shroud.  According to those who have compared them to other options, these small Plume insert work rather well:

[jackssmirkingrevenge]

There are at least two schools of though about air management:  Run the air into a wall and let it rebound, or direct the air to flow in an organized manner via larger corner radii

In the latter case (that is very much in the spirit of Maxim's original design) it seems that the effect comes more from giving the air space to tire itself out spinning in toroidal circles as opposed to using it to actively block the flow from the muzzle so I imagine the extra volume is important and the limitations of 3D printing with PLA means it will always be a compromise.

On a tangential note there is one idea I would love to play with one day, that is to use the airflow to physically block off the muzzle, something like this:



Of course it would need to be tunable because a premature actuation that would make contact with the projectile would be potentially catastrophic, but if it does work then it could potentially be an effective and very compact way to attenuate muzzle blast.

[subscriber]

Jack, that shot activated air sluice gate is a brilliant concept. 

To ensure the gate does not start closing before the projectile has passed, place the gas taps directly after the gate, rather than before.

To ensure the air ahead of the projectile does not activate the gate, add a slight detent.  Besides, there is a large hole for the air ahead of the projectile to escape, so I don't think much pressure will build; but it will be above ambient.

Or you could make the gas taps slant such that the air rushing by in front of the projectile creates a suction at the port, like a spray painting gun not worthy paint from a bottle, despite the use of compressed air.  Basically, a venturi effect.  Once the projectile passes the slanting port, the much higher air pressure will overcome the dynamic partial vacuum, activating the sluice gates. 

How and when they open again is the next question.  They need to open fully for the next shot, but need to stay together until the pressure trapped behind them has had time to bleed off.

The two sluices will bang together hard, if the action is fast.  Needs to close in perhaps 0.01 second.  So, the materials must stand up to the task, and not make too much noise as the valve slams shut.

I have thought of a similar concept, but one that uses three rubber heart valve like sections that are blown closed; and held closed until a controlled leak vents the air pressure.    Somehow that seems like it would need help with timing, unless an air port system could be configured as for your system.

[subscriber]

Another idea I had some time ago is a simple rubber flap valve.  I have attached a very crude mouse driven sketch below to help visualize it.

The valve is opened by the high pressure air blast behind the pellet.  When the pressure in the casing is higher than at thee barrel muzzle, the flap slams shut and seals (well enough) against the tube ID.

The rubber could start as a flat disc, or is could have some shape; such as being conical or hemispherical.  The disc would be attached at its ID and free to move at its OD.

One might need to support the valve and limit how far it can open (and close) by means of a perforated backing disc of suitable shape.  The backing disc would have a smaller OD than the rubber disc to keep an annular channel of sufficient area open around the perimeter of the main tube ID.

Notation: 
Black lines = barrel and pellet
Blue = LDC
Red = rubber valve
Green = air flow

[jackssmirkingrevenge]

Another idea I had some time ago is a simple rubber flap valve.

It's a concept that has been around for some time, here are some proposed ideas using flaps and balls:





With the latter you want to be careful about not pointing your muzzle downwards 

One implementation that was apparently made to work is the Kitzmann "gas tong" type:



There is one moving part, and as it moves forward against the endcap, the two "tongs" are guided towards each other effectively blocking the muzzle.

Combining it with your idea using a flexible component (because we don't have concerns with hot gasses in airguns) it could look something roughly like this:



A soft rubber piston could be forced against a cone and constrict to effectively block the muzzle.

The crucial element for all of these is timing.  The Kitzmann for example would only work with a certain type of ammunition because the system would easily be thrown off balance with different gas pressures.

In a modern world of electronic sensors perhaps a system that doesn't rely on gasses and uses for example a capacitor discharging into a solenoid to block the flow once the projectile is detected as having cleared the device would be an interesting option.

 

[avator]

Maybe it's just me but that's some scary looking stuff right there.
I reckon I'm just more of a K.I.S.S kinda guy.

[jackssmirkingrevenge]

Maybe it's just me but that's some scary looking stuff right there.

I agree that it's a very good idea in principle but if done wrong then the consequences could be catastrophic.

[subscriber]

Clever ideas, Jack but blocking the actual muzzle of a centerfire would slam that valve closed so hard, something would deform or crack in no time.  Probably should distill that into PCP applications, or someone may take offense.

Back to airguns, I decided to model my crude sketch, as I seem better at that than driving a mouse in place of a pencil.  See this as a concept design, minus improvements required for a production version.  For instance, the long central tube needs supports near its free end.  If this were a 3D printed part, print direction has to be taken into account and "floating features" provided with support.

The concept seems simple enough.  Certainly, a 1 mm thick rubber sheet can stand repeated pounding, without cracking the parts it bangs into.