SpudFiles

Hi everybody, I'm G-man, the administrator of patator.frbb.net, somewhat the "French spudfiles".
I'm here to show you my last creation, that's my first time here



So, this airgun is called PACa, wich mean in english something like "autonomous airgun". It's the second version, the first one was really basic, only working with a QEV.

It tooks me about 30 hours of work, and 130€ of materials.
Quite expensive because I didn't have any materials left in my garage, and because I first develloped a prototype.


Dimensions:

Total: 105cm
Barrel: 60cm
Weight: 3kg

Caractéristics:

General: The PACa is an autonomous airgun, equiped with an HP pump, wich allow you to shoot anywhere you want.

-HP pump, up to 28bar
-8mm copper barrel, reinforced (2mm thickness)
-large bolt, wich allows you to use various lengths of projectiles
-projectile lock inside the barrel
-a new sort of firing system (dunno how to call it in english lol)
-slight trigger
-adjustable chamber volume (2 possibilities)
-28bar manometer

Firing pressure: 20bar with full chamber, 28bar with reduced chamber (only brass parts)

Caliber: 8x1-100mm

Price: Approx. 130€

Firing system

The most important part in this launcher, is the firing system.
I call it "Auto-percusive valve".


I'm sorry for the french lines, but they are not really important so I won't translate

This system is based on the equilibrated pressure applied on the two pistons, diriged by the form F=PxS.
It works quite like a QEV, except it's a mecanichal trigger wich drives a pneumatic reaction.

The piston on the right is the seat, with the barrel behind.
The piston on the left helps you raising the first one.

It's quite dangerous because the system is on balance.
Only a slight pressure (I'd say 5kgs) suffice to break the balance, and shoot. You don't want to let the airgun fall on the floor.

But it's a very effective system, it has a large flow for a little size, and an interesting effect: the heaviest is the projectile, the stronger is the opening of the seat.
That's because of the traction piston, wich takes all pressure when the seat starts opening.

I hope that I'm clear enough, I have some problems translating the technical part...

Here's a picture of the real piston:



Performances:

Range: I don't really know, I'll go for 150m straight, then it can go further.

Damages: Pierce half of a 30mm piece of plywood, traverses an aluminum bottle without like butter

Firing sensations: The firing system is quite violent, the shot is powerful, real loud, and it produces a really nice recoil !

Pictures

Looks like there's hosting problems, some pictures are

General view:









Bolt:










Stock:



Central part:





Pump:



Projectiles:
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Vidéos

[youtube][/youtube]

As usual, the sound is not really persuasive, but in real, in really breaks your ears ! ^^
Maybe I'll traduce the video, but I think the general terms are understandable

I'm sorry for the many grammar faults I might have done, I read a lot of English, but I don't usually write it !
For the same reason I might have some problems to answer your replies, especially if there is technical questions !

Very nicely put together

The valve is similar in concept to Tech's Quick Dump Valve, kudos for implementing it with standard parts.

Wow this gun is amazing. adding its own mobile pump is Genius.
2 Thumbs up =-)

Very nice construction and features! Nice job on a great gun there.

Tiens je le connais ce pac , encore une fois bravo pour ton travail, j'aime particulièrement la culasse, ça me donne une idée .



Sorry I speak french because I know G-man, I'm also a member of "patator-forum" ,

thats the master desing

Hey its a QDV! This is a fantastique gun! I love it. Great job!

Nice looking gun! Very well integrated, and it look like it has some real power. Although, it looks like the trigger would be thrown back rather violently when the piston fires?

Thanks guys
Glad to see you like my airgun !


So, the english name is QDV.
Too bad, I thought I had invented a new firing system


Yes Daltonultra, the trigger is thrown really violently !
You don't want to left a finger behind....

If you watch closer, the trigger is a little bent.
Thats the very first shot: the copper part (dunno how you call this in english) wich I use as a grip, behind the trigger, was too close.


Put a nut behind the trigger: you got an awesome pneumatic nutcracker !

The trigger issue would be that hard to solve. All you need is to rig it so the trigger isn't directly attached to the piston.

I can see a way to do it with basically five pieces:

First, use a thin tube to cover the threads to nothing catches on them.

Next, attach a trigger lever to the stock with a pin so it can pivot. Attach an arm with a hook on the end to the trigger lever. The hook is to catch the nut on the end of the piston rod. You'd need a small spring to hold that hook-arm snug against the piston rod, or it would just fall and be useless. A slightly more powerful spring would hold the trigger forward, otherwise the hook-arm spring would cause it to pull against the piston rod.

G-man wrote:So, the english name is QDV.
Too bad, I thought I had invented a new firing system

Actually the spudfiles name is QDV, but really balanced spool valves like this one are not uncommon - for example, the Brocock air cartridge is based on a similar principle, only the valve is pushed forward instead of pulled back.

Love the built-in pump. Might be incorporating that into my recent creation because this pump design requires a pump to be upside-down from normal design, which would be rather awkward, but with the pump a part of the gun, with the check valve at the top, it could work. Thanks! Awesome build!

Thanks Daltonultra, that's a good idea, it could avoid some serious finger crush ^^
I guess I'll do something like this on a future one.
Maybe I'll do the same kind of rifle, but in the size of a handgun !

Woah, the Brocock air cartridge is really interesting !
I never heard of something like that !
I'll keep that scheme in mind, could be useful, thank you

I like your trident saefroch
Here's a picture of my piston:

It's kinda messy, but it works well.
It looks like your piston design.

Nice man. I like the design with the build in pump.

I love everything about this airgun, and is for sure THE airgun i love the most. The problem is, i don't really understand how it works and its really giving me a hard time.

I have tryed drawing stuff on paint and have got no-where. Could somone PLEASE explain in depth or draw a sketch for me how it works. I would love you for ever if you did.

Thanks in advance

EDIT:

Please explain the pump too

Im guessing its a sturrum (Spelling) pump that uses a bought check valve?


Thanks xD