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The Combustion Machine Gun

Posted: Tue Aug 11, 2009 6:13 pm
by NinjaFish
Hey guys,

I've recently made my first basic pneumatic spud gun and wanted to start moving towards a BBMG. But making the things mobile can be very dangerous and expensive with CO2. So after scrapping that idea i just continued to experiment and upgrade my basic pneumatic But after watching Starwars Episode 3 for the first time ever i noticed the mini jets R-2 uses to fly and searched Youtube to see if anybody had made such small jets.

After watching a few model jet planes, I came across the Pulse Jet Engine which is simple to make in both Tin Cans and Jam Jars. Below is a video of one in action.

[youtube][/youtube]

:idea:
By attaching some sort of Barrel and Breech loading magazine system would it be possible to make a Combustion Machine Gun? Im not sure however there would be many problems that would need to be addressed first below these have been listed;

1. The Pulse Engine generates alot of heat and so would need to be surrounded in a water container to help cool down the equipment. this would make it safe to handle as a spud gun but also maintain the cycle of the Engine for longer.

2. Secondly the engine both kind of Inhales and Exhales through the same hole. This maybe effected by the addition of a Barrel however this may be combated with a second inlet or a specific type of Breech loading magazine.

3. The final problem would be both starting and ending the cycle of the Pulse engine, I belive there could be simple solutions to this problems using a BBQ igniter for Ignition and a Valve to suffocate the Engine when finished.

I am going to begin basic research into Pulse jets and create a few basic ones to get to grips with the science. I plan on having some type of prototype for you guys before i run off to university and hopefully Combustion Machine Guns will Revolutionize Spudding for all :P

As a final note i would like to say that i do not belive this does not break forum rules as the Engine is able to run of Lighter fluid and Alcohol, which are as far as i know allowed on this forum.

Thanks Ninjafish.

-EDIT-

I Just thought Id add a video i found showing whats going on inside the container and what happens when there made from glass. :violent1:

[youtube][/youtube]

PLEASE FEEL FREE TO CRITICIZE AND POINT OUT OTHER PROBLEMS

Posted: Tue Aug 11, 2009 11:12 pm
by smiley_666
there would probably not really be enough pressure in a barrel to fire anything too far.

keeping it cool is a BIG problem, on some they glow white/clear.

the speed of the oscillations would need a bloody good magazine/delivery system to keep up.

they are extremely loud, as in even with ear muffs on they can be painful to listen to.

pulse jets are extremely temperamental when it comes to intake/exhaust lengths, so finding a barrel that shoots my cause the jet to not pulse, and if you get it pulsing (probably wont happen with an obstruction in the exhaust gasses) it may not fire a projectile at all.

a jam jar is an extremely basic design, and most do not work in the same way, ie they have both an intake and exhaust opening which complicates things even further

these are the problems i see with this idea, but if you figure out how to do it, good on you, but it will not be easy.

Posted: Wed Aug 12, 2009 1:45 am
by jackssmirkingrevenge
But making the things mobile can be very dangerous and expensive with CO<sub>2</sub>
Dealing with the above issues is much more complex and would probably amount to more than simply purchasing one of these and hooking it up to your BBMG.

Posted: Wed Aug 12, 2009 2:20 am
by qwerty
It's a bit expensive dont you think. $99!

i agree with smiley it would be hard to keep it going because it wouldn't get enough o2 with something in the way.

Posted: Wed Aug 12, 2009 2:22 am
by Moonbogg
I see a technology here that is super raw and crude. Harnessing that would take mountains of time and probably a bit of money here and there in R&D. I say go for it. Its a dare.

Posted: Wed Aug 12, 2009 2:26 am
by jackssmirkingrevenge
qwerty wrote:It's a bit expensive dont you think. $99!
If you're a student who has to live on $10 pocket money a week, I guess it would be expensive. When you have a reasonably nice paycheque at the end of every moneth, you tend to look at things differently.
Moonbogg wrote:I say go for it. Its a dare.
And who will foot the medical bill when he accidentally grabs the white hot BB chamber :roll:

Posted: Wed Aug 12, 2009 2:27 am
by spudtyrrant
qwerty wrote: i agree with smiley it would be hard to keep it going because it wouldn't get enough o2 with something in the way.
that could be fixed by adding small holes on the side of the top for intake and on larger hole for the output but i don't think it will reach significant pressures to send anything more than 100fps you would be better off making a lung powered bbmg in my opinion.

Posted: Wed Aug 12, 2009 2:29 am
by Willdebeers
You could put a check valve between the barrel and the pulse jet, sticking off to the side. then it could suck in air, and then when it exhaled, it would shut again. :)

Posted: Wed Aug 12, 2009 2:35 am
by jackssmirkingrevenge
Willdebeers wrote:You could put a check valve between the barrel and the pulse jet, sticking off to the side. then it could suck in air, and then when it exhaled, it would shut again. :)
Or you could just mount it on aFieseler Fi 103 and launch it at whatever it is you wanted to destroy in the first place :roll: :D

Posted: Wed Aug 12, 2009 3:21 am
by inonickname
I'm surprised nobody has realized this yet, but a pulse jet will never work for a spudgun unless it is feeding a very small vortex block. In that case, it would need reed valves.

Depending on the specific pulse jet, they often cycle at 50+ Hz. The issues in coming up with a feed mechanism that will supply 50 rounds into the barrel and fire every single second without a single jam is near on impossible.

The only thing that can possibly keep up with that demand for feeding is a vortex or cloud.

Edit: The pulsejet would not even run with a projectile in the "barrel".

Posted: Wed Aug 12, 2009 3:50 am
by jackssmirkingrevenge
inonickname wrote:I'm surprised nobody has realized this yet, but a pulse jet will never work for a spudgun unless it is feeding a very small vortex block. In that case, it would need reed valves.
I'm surprised it took someone who chooses to associate with the image of Pædobear to point it out :D

Posted: Wed Aug 12, 2009 3:58 am
by inonickname
jackssmirkingrevenge wrote:
inonickname wrote:I'm surprised nobody has realized this yet, but a pulse jet will never work for a spudgun unless it is feeding a very small vortex block. In that case, it would need reed valves.
I'm surprised it took someone who chooses to associate with the image of Pædobear to point it out :D
I don't get it.. :roll:

Posted: Wed Aug 12, 2009 4:05 am
by jackssmirkingrevenge
inonickname wrote:I don't get it.. :roll:
Your avatar ;)

Posted: Wed Aug 12, 2009 4:09 am
by inonickname
I know my avatar is pedobear, I'm just wondering why you brought it up.

Son, I am dissapoint. :lol:

Posted: Wed Aug 12, 2009 4:17 am
by smiley_666
i pointed it out in the second post of the thread :?
i didnt say it wasnt possible, just that it'd be hard to keep up? oh well *goes and sits in the corner* :P :lol: