Full Automatic Single Barrel Spud Gun -F-A-K-K-

Hugeapnic · Mon Mar 11, 2013 2:14 pm

Hi,

i just wanted to share with you my first spudgun i have build.

I tried to do it "First Time Right", and not go with a simple kiddie-spudgun...

The idea was to have a full automated spudgun that is portable.

One major goal of the project was to achieve 1shot per second. Right now i achieve a cycle time of 1.2seconds, but there is room for improvement. The Loading and venting times can be reduced as is assume....

For ammunition i use golf balls. The power of the gun is, as i assume, average "low". High power was never o big goal for the project.

A typical problem found is the heat-up of the barrel. After each magazin (5shots) is empty, the temperature of the barrel is pretty high --> 50°C. The gun is constantly cooled, but this seems to be not enough for a longer fire sequences.

Overal weight is 2.5kg.
As propellant deodorant is used.
Venting system utilises a EDF.
All mechanical actions are done by Servos.

I try to upload a video of it in action later...

Fell free to tell me what you think of it....

http://youtu.be/cguRWX4IIyI

jackssmirkingrevenge · Mon Mar 11, 2013 3:07 pm

Fantastic!

[youtube][/youtube]

Some more details of the mechanism would be great

How are you venting the chamber between shots?

You should really consider propane or butane as a fuel source, a simple way to get more consistency and power.

Mon Mar 11, 2013 4:10 pm

Some more details of the mechanism would be great

I see a hybrid version appearing in the near future..

awesome job!
I assume it functions like a gaspowered nailer?

A "cool" solution to your heating problem may be to shroud the barrel and fill it with water like they did on the Maxim machineguns in WWI...

Without any means of circulating the coolant I reckon you could do 10 shots without any problems.

replacing the barrel by a copper one with a heatshield ( to protect your hands) would probably work aswell.

Hugeapnic · Tue Mar 12, 2013 10:40 am

Heer is a principle sketch i did today.
More details will follow later this evening...

POLAND_SPUD · Tue Mar 12, 2013 1:59 pm

that's impressive

I expected your gun to run on ethanol but you wrote it's deodorant
How do you meter fuel ??

Hugeapnic · Tue Mar 12, 2013 2:33 pm

Hi,

I try to answer questions and add information whenever I find time.

The deodorant is measured by an timer. I can select the injection time in 25ms steps.

The gun is controlled by an arduino micro controller.

I can contol the ESC that controls the EDF. On top the EDF I have a valve, that is closedd by a servo. Then I have the injection-servo, and the loader-servo.
The ignition module is controlled by a relais.

The EDF is always running at low speed.
When I start the fire-sequence the controller is doing the following:
1. Close the valve
2. Open the loader to load a golf ball in the barrel.
2.a start injecting
3. Wait the given injection time
4. Start ignition
5. Open valve
6. Wait for given time
--> the edf blows all used-air through the barrel out of the gun
-------> the gun is ready for the next shot

I now have to optimize the EDF speed and the venting time to allow more than 1 shot per second.

I doubt that I will more consistent inject times with butane/propane. Maybe the bang is better, but I need way more stuff to controlled it.

Even a nearly empty deodorant can needs little adjustments on inject time. I just go from 350 to 400ms, and I can continue to fire....
The adjust man can be made from the shooting menu, and permanently stored to the EEPROM later in the programming mode...

For cooling I have a special mode, that opens the valve and blows constant fresh air in the gun. After about 1min the gun is pretty cold again.

The most useful mode is the BBQ mode!! Very handy to fire up the coal on the summer BBQ.

jackssmirkingrevenge · Tue Mar 12, 2013 5:27 pm

Good stuff!

Maybe the solution is to replace the deodorant can with a pressure vessel filled with a stoichiometric fuel/air mix, that way you only have one valve to open and don't have to worry about ratios and mixing.

For example, a 2 litre soda bottle injected with half a litre of propane at atmospheric pressure, then pressurised to 5 bar with compressed air.

nickobelenus · Wed Mar 13, 2013 5:49 am

dang you beat me top building one with an arduino micro controller was gunna get some time and build one with an arduino or if i realy have the time a raspberry pi control

ramses · Wed Mar 13, 2013 10:52 am

jackssmirkingrevenge wrote:For example, a 2 litre soda bottle injected with half a litre of propane at atmospheric pressure, then pressurised to 5 bar with compressed air.

We call that a bomb. I have videos somewhere of igniting a hybrid mix in a 2 Liter and I can say that it leaves a small crater in the ground.

Hugeapnic · Wed Mar 13, 2013 11:47 am

so, some major step forward!

The current Cycle time is not 575ms per shot!!
That 1.7Hz (shots per second!!)

I had to change parts of the magazin to metallic, and add a end-stop to the spring-plate in it.

The limiting factor for the speed of the gun is now the injection with 375ms.
Means i can completely exchange the air in the gun in 150ms!!!! And the EDF is not even working on 50% power!!

So if i really want to go faster, i would need a second injection-source (2 deodorant-cans in parralel) to remove about 170ms. That would make it then 2Hz (shots per second)!!

Concept proven, targets exceeded!!!

jackssmirkingrevenge · Wed Mar 13, 2013 12:17 pm

ramses wrote:We call that a bomb.

Let's call it a bomb.

Bombs are designed to explode only under a very specific set of circumstances.

Everybody drives around frequently with a stoichiometric gasoline vapour/air mixture in their fuel tanks, without undue concern.

Sometimes it goes wrong, but the vast majority of occasions, it is not considered a significant risk.

Anyone who has ever made a hybrid knows that you need a well designed ignition system to make it go off, and this is not easy to achieve. It is also obvious that even the slightest leak will throw the mix off and make it impossible to ignite.

In my view, a pressures fuel/air tank fitted with a check valve should pose no significant risk of explosion.

Hugeapnic · Wed Mar 13, 2013 2:01 pm

That's the currcent status....
[youtube][/youtube]

If you look closely, you can even see the injection-valve opening an closing...

The magazine is 5 shots, but i forgot to remove the finger from the trigger, so the last "shot" is without ammo...

jackssmirkingrevenge · Wed Mar 13, 2013 2:34 pm

Really great work, what you've done is a bit of a holy grail for many spudders, kudos!

POLAND_SPUD · Wed Mar 13, 2013 11:32 pm

yup holy grail for many spudders

We call that a bomb. I have videos somewhere of igniting a hybrid mix in a 2 Liter and I can say that it leaves a small crater in the ground.

I agree with jsr on this - getting mix to ignite isn't easy... and it's not that difficult to source tanks that are rated to more than combustion pressure of say 20X mix

Not having to deal with fuel metering & stuff simplifies the process a lot -and that important because when a hybrid doesn't work you can never tell whether the mix is off or the ignition doesn't work

Hugeapnic · Wed Mar 13, 2013 11:55 pm

Thanks for the compliments.....

If this is (kind of) the holy grape, then the box of pandorra is now open.

There is nothing on the gun that is secret or that needs special tools or skills!

I have now opended my mind to give it a propper name:

-F-A-K-K-

Stands for
Fully
Automatic
Kartoffel (German for potatoes)
Kanone (German for canon)

Full Automatic Single Barrel Spud Gun -F-A-K-K-

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