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Cannon #3 - 14mm Automatic Air Rifle

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Cannon #3 - 14mm Automatic Air Rifle

Unread postAuthor: PCGUY » Wed Sep 02, 2009 11:01 pm

Cannon #3

14mm Automatic Air Rifle

SFDBGOEPHP14ABAR (or the 14mm automatic air rifle)

"Select Fire Delayed Blowback Gas Operated Electro-Pneumatic High-Pressure 14mm Automatic Bullpup Air Rifle"

Final Judges Score Chart
-Idea 12.1/20
-Use of materials 2.7/5
-Creativeness 5.2/10
-Quality of build 1.4/5
-Function 1.8/10

This cannon is part of the SpudFiles Innovative Contest. For details see here...
http://www.spudfiles.com/forums/spudfil ... 19233.html

--Details and pictures from cannon builder--

Originally this design was meant to be built with a lot of care and precision.
It was meant to use a custom made high efficiency Quick Exhaust Valve machined from EN-AW 2014 T6 aluminum.
It was meant to run on 850psi dry air and be able to send various projectiles over 218yards (200m) down range in rapid succession.
Oh and it was meant to look good too.

However a lot of things went wrong and this project couldn't be built as planed, in time.

But this competition focuses on the innovation in the world of spudguns, so I decided to make it anyway from parts I had lying around and that would be available to most spudders.
This ghetto version, runs on high-ish pressure instead, is less compact, powerful, accurate and efficient, it also isn't very pretty.
However the ghetto version still uses the same principles.

Ghetto specs:

Overall length: 130cm
Bore size: 14mm (.55 cal)
Barrel length: 110cm
Rifling twist rate: 1:8inch
Main valve: Slightly modified 3/4" QEV for better flow.
Chamber volume: 160cc
450psi regulated air from HPA bottle.
Pilot valve: Modified electro-pneumatic 3/2 NC 1/8" solenoid valve (to work as NO)
Safety, semi-auto and full automatic fire modes.
Pump action manual reloading.
Gas piston controlled delayed blow back for auto-loading.
Electro-mechanical automatic trigger system.
Detachable 10 round magazine.
Bullpup configuration.
Rail mount for optics .

This is how it operates step by step:

1- The HPA is connected, flows through the 3/2 distributor and pressurizes the system (pushing the QEV piston forward and making a seal against the barrel port).
2- A loaded magazine is inserted
3-The first round must be loaded, the front grip is pulled back. This does two things: the bolt lock is pushed open and the bolt is pushed back. As the bolt moves back, a round from the magazine is pushed up by the magazine spring.
4- The grip slides back into initial position. The bolt is spring loaded and also returns to initial position, pushing the projectile past the main valve port and into the barrel. As the bolt moves forward, the bolt lock clicks back into place.
5-The fire mode switch is moved from Safe to Semi-auto.
6-The trigger is pressed and the 3/2 valve moves to firing position, the pilot volume is vented, the piston flies back and air from the chamber is dumped into the barrel exerting pressure on the projectile and on the bolt.
7-The projectile accelerates down the barrel following the rifling grooves. The bolt on the other hand cannot move back thanks to the bolt lock.
8-The projectile passes in front of the gas piston port, the air pressurizes the cylinder and pushes the gas piston back. The gas piston acts on the bolt lock rod, and opens the bolt lock.
9- With the bolt lock open, the bolt can recoil back using the pressure remaining in the barrel. The projectile is nearly up to speed and acceleration starts to drop as it is about to leave the barrel.
When the bolt recoils back, the front grip is not affected.
10- The bolt hits the spring in the buttstock, and its backward motion is absorbed. A new round is pushed up from the magazine. By this time the first projectile has left the barrel and is traveling down range, stabilized by its rotational movement along the firing axis.
11- Pressure in the barrel has now left, the bolt and projectile move forward, the gas piston returns to initial position and the bolt lock clips into place. The new round is now loaded.
12- The trigger is released and the 3/2 valve moves into filling position, air flow through it and resets the piston filling the chamber with 450psi regulated air.

If the trigger is pressed again the process repeats from stage 6-11

If on stage 5 the switch is set to full auto (the alternative stages being called 5', 6', 7'... and so on), the trigger switch is no longer linked directly to the solenoid valve but is connected in series with another micro-switch.
This second micro-switch is activated by the bolt being in forward position.
This is the case following stage 5' so when the trigger is pressed on stage 6' the 3/2 valve fires.
Nothing changes until stage 9' when the bolt starts to recoil. As it moves back, it releases the micro-switch which breaks the circuit and allows the 3/2 valve to go back to filling position.
The chamber starts to repressurise. Once the projectile leaves the barrel and the bolt comes back loading a new round, it hits the micro-switch causing the 3/2 valve to fire once more and the process repeats until the trigger is released.
This also insures that if there is a jam and the bolt or round gets stuck the valve won't release the air.

The system is built so that the grip can act on the bolt and bolt lock rod, but the bolt and bolt lock can't act on the grip.
The gas piston can act on the bolt lock rod, but the bolt lock and grip do not act on the gas piston.

The delayed blow back means a lot less energy is wasted on the bolt and the shot is therefore more efficient.
This might not be crucial for smaller calibers but is a big advantage with larger bores.

A few problems I encountered building the ghetto version:
Lower operating pressure dramatically decreases the power and increases chamber filling time, thus reducing the rate of fire (with consistent full power shots).

The aluminum I used for the bolt lock isn't strong enough, after a few shots it bends back and doesn't open. Higher grade aluminum or steel should be used instead.

Some parts of the solenoid valve aren't designed to hold pressures that high and cause the valve to leak. I had to seal some parts together using epoxy glue and cast an epoxy block around it to reinforce it. The spring around the ferrous solenoid core had to be stretched and hardened as after multiple shots it would start to leak over 400psi.

I didn't have enough epoxy left and had to use hot melt glue and tape...
I had to rely on fridge compressors to fill my HPA bottles as I didn't get to finish my high pressure filling station setup and was limited to 650psi fills. That obliviously reduced the shot capacity compared to a 4500psi fill.
Knowing how far down the barrel to place the gas piston is quite tricky, I was lucky and it worked on the first try, I was expecting to have to experiment a lot more.

I still plan on making this design properly, I just don't have the time right now and still don't have the custom QEV I designed.
I haven't been able to do any nice videos, although I had a lot of good ideas to start off with, they will just have to wait for the final version.
I haven't even really had time to play around with this version, I fired only a few test shots, broke and bent a few parts, and didn't have time to improve.
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Overall View
Gas Piston
Trigger and fire mode selector switch
3/2 valve
Bolt lock
Pump action test version
Last edited by PCGUY on Fri Apr 16, 2010 1:07 am, edited 4 times in total.
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Unread postAuthor: Hubb » Thu Sep 03, 2009 8:07 am

Is there a way that the builder can produce a video of this in action. A select fire switch (if it functions) will probably make a huge difference in the judging (even if it is kind of ghetto).

I'm going to leave my vote open on this one until I can see a video of the select fire function as claimed. If it will function, I do think it will make a big difference in my vote.
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Unread postAuthor: PCGUY » Thu Sep 03, 2009 10:47 am

I haven't been able to do any nice videos, although I had a lot of good ideas to start off with, they will just have to wait for the final version.

I don't think he plans to provide any video, kinda sad :?
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Unread postAuthor: jrrdw » Thu Sep 03, 2009 8:06 pm

Idea 17 I like the idea of this cannon good thought went into it.

Use of materials 3 he used what he had all right.

Creativeness 6 because he was thinking what would be good.

Quality of build 0.5 this could have been built WAY BETTER tape to hold it together after all the design thinking that went into this, come on!

Function 0 if I can't see it shoot, I can't score here, (dam shame).
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Unread postAuthor: starman » Thu Sep 03, 2009 8:37 pm

Score Chart
-Idea (20 pts max) 13 - reasonably challenging idea in the spudding world
-Use of materials (5 pts max) 2
-Creativeness (10 pts max) 5
-Quality of build (5 pts max) 1
-Function (10 pts max) 1 - the functions that were described mostly failed...parts not properly specified, leaking, not strong enough, etc.
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Unread postAuthor: MrCrowley » Thu Sep 03, 2009 8:45 pm

Idea: 15
Pretty good idea, not something easily achievable.

Use of Materials: 2
Pretty shotty craftsmanship, but I guess time was against the builder and that made him improvise with other materials of poorer quality.

Creativeness: 5
Not a new idea, but well thought out and implemented.

Quality of build: 1
Ghetto in most parts. Pity about the time restraints the builder had, would still love to see this fully completed after the competition though.

Function: 1
Sounds like a lot of things went wrong, maybe if the builder had more time it'd be a different story but it is what it is.
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Unread postAuthor: Hubb » Fri Sep 04, 2009 7:34 am

Idea - 5
The basic idea of this launcher is to make it function like a real semi-automatic rifle. This has been discussed and dismissed on several occasions.

Use of Materials - 4
While the launcher is ghetto, it does appear that the materials used seem to be used as they are intended to be.

Creativeness - 4
I do have to admit that it is a fairly creative, albeit ugly, launcher.

Quality of Build - 2
There is no reason for a competition launcher to be this ghetto. As I mentioned on The Challenger, I really like a nice rifle build and, although it does have a pleasant flow to it, it is just to ghetto for my tastes.

Function - 1
What function? All I see are pictures of the launcher. If the builder would provide proof that it actually worked as intended, it would be a different story.
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Unread postAuthor: clide » Fri Sep 04, 2009 12:43 pm

-Idea (20 pts max) 14
Many similar ideas have been proposed and built, but this idea does do a good job of implementing several ideas together. I like the electronic 3 way valve in conjunction with a pressure switch for semi/full auto capabilities. That is something I proposed way back when I made my first semi-auto and to my knowledge this is the first time it has been implemented.

-Use of materials (5 pts max) 3
He used what he had, which is what spudding is about, so I'm not going to dock him all the way down on this one.

-Creativeness (10 pts max) 6
While nothing new he does a good job of blending it all together

-Quality of build (5 pts max) 1
Duct tape :/

-Function (10 pts max) 2
It sounds like he might have got it to shoot a few times, so if he did I guess that is worth a couple points.
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 04, 2009 11:06 pm

-Idea (20 pts max) - 12
-Use of materials (5 pts max) - 3
-Creativeness (10 pts max) - 6
-Quality of build (5 pts max) - 1
-Function (10 pts max) - 0 (video or bust)
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Unread postAuthor: CS » Sat Sep 05, 2009 4:08 pm

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Unread postAuthor: jagerbond » Wed Sep 09, 2009 2:08 am

-Idea 10 can't tell if it works
-Use of materials 3
-Creativeness 7
-Quality of build 1
-Function 0
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Unread postAuthor: sgort87 » Fri Sep 11, 2009 4:30 pm


I've created a monster with that QCTBDC...

Idea: 13
Not really much new, but it took some thought to get this right.

Use of Materials: 2
There are a LOT of parts that could be made out of nicer things.

Creativeness: 3
Well, you used materials available creatively.

Quality of Build: 2
It's pretty sloppy.

Function: 10
I probably would give you a 7 or 8 if what you described in your step-by-step explanation is true, but I'm giving you a 10 because I believe you, and someone needs to offset all those terrible scores the other judges gave you. If it operates as described, I'd say the function is pretty much perfect.
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Unread postAuthor: Brian the brain » Sat Sep 12, 2009 5:30 pm

Whoever the builder is, I want him ( forget " her" ) to know I think this is the most innovating cannon.
Oh...make that the " only" ..

It's a shame so little is shown.Toggle switch has never been done..
The competition was aiming for innovation and the time to build something was too short for me to produce anything.
I was beaten to my own innovative idea, the onboard Benjamin pump.
My pretty radical valvemod did not give me the result I needed either..
No time to get it right. :(

So I can understand the duct tape...This one is purely about the idea.
Wich makes it the winner in my book.No matter how well made some of the others are.
They sure are beauties.

But what do I know..
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: POLAND_SPUD » Sat Sep 12, 2009 5:39 pm

I am surprised that it worked... it must have been a real PITA with so many things that could go wrong
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Unread postAuthor: THUNDERLORD » Sat Sep 12, 2009 6:49 pm

...This ghetto version, runs on high-ish pressure instead, is less compact, powerful, accurate and efficient, it also isn't very pretty.
However the ghetto version still uses the same principles. ..

Reminds me of an ex-girlfriend a while back. :D
(sin duct-tape of course).

Good job judges!!!
Dang this is getting exciting!!!
Man, I'd like to see moar of this one, gas assist, select- fire etc. etc.
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