SpudFiles

if u try to fill at the same time they will not mix right. Just make a meter with a T after the reg... then just make double after that. get the 2 coaxial working, then work on what makes em look cool

thats the plan. I'm at work right now starting to get a hold on what i actually need to buy today to start the build. as for pneumatic + metal chamber...this is supposed to be shoulder mounted, and that will make it WAAAYYY to heavy. I'm not even going to keep the propane meter on the gun,it will be an external thing that fills through a fitting of sorts(haven't worked out details yet)

I'm still not sure what parts to use to mount the real barrel inside the chamber tube seamlessly. of someone can either show me an example,draw a picture,take a picture, just something to show me how its supposed to work, because honestly i have no idea how to make that coaxial. absolutely none.

but ya, thats the plan is to get the 2 cannons and the propane metering working, and then build the shell around it.

I've determined that the lower body will consist of a bike pump,a 1" square aluminum bar, and some other assorted stuff. The outer barrels of the gun will be bolted to the lower frame,and the "middle box" will have a hinge and open up to do maintenance(wow, what a weird word...maintenance). I considered making it breach loading under the middle shell thing, but thats not happening, at least not yet.

i plan on using something like http://www.advancedspuds.com/propane.htm this for fuel, and the back of the gun,while not completely built in, will be probably rather hard to access.


Could i use a bike pump mounted to the front and wired to the chambers somehow to keep fresh air in the chamber/clean it out after shots


I've decided that i am doing 2 triggers...or possibly one trigger with a barrel selecting switch.

I'm excited to get this project off the ground tonight! No promises but if it goes as plans, ill start posting construction pics as early as this afternoon

I just started figuring c:b ratios and now i understand why it needs to be a coaxial.

I'm going to try and figure out what the lengths need to be, but if someone knows what it needs to be for 2" barrel in 4" chamber, overall length is 60"....that would be great.

Also what fittings should i look for to modify to fit inside it?

I was thinking like 2 to 4 inch bushings(I'm sure thats not what its called,its like a thick disk 4in diameter with a 2in diameter hole in the middle) or a regular pipe reducer filed down on the outside....although i don't know if that will work. This is going to be a challenge, but i think its doable....

that and the more searching I've done, the more people i find that attempted this... i want to do it...i want to do it right



i also now understand why people are suggesting pneumatic because it needs a much smaller chamber ratio. I'm going to rule pneumatic out for this one, but i think the next one will be pneumatic


also ill post pix of my other spud guns in a bit

After researching Coax spud guns, I've now confused myself even further. I just need someone to clarify a couple things. Most coax spud guns are pneumatic and use some sort of a piston, right? To make a combustion coax i just make it how i would make a regular combustion except modify the bushing/reducer and put it inside the bigger pipe,no piston or anything fancy like that?

i also just had another idea while typing this. I haven't checked the math,and using my knowledge of geometry, I'm pretty sure its not right, but ill ask anyways. If i were to use...say 45 inches of the 4inch for the chamber, and the barrel equally as long, since the chamber pipe is 2x the diameter of the barrel, wouldn't that put close to 1:1? I'm guessing probably not,but i figured ill ask anyways

Damn, this double barrel rocket launcher idea was in my head last week!

They only problem is: How will i make a double barreled (coaxial) combustion.
My idea was to have one 110mm pipe as chamber with 2 40mm pipes in it as barrels. Here in the netherlands they have a REALLY nice adapter for that. (110mm -> 2x 40mm and its flat, not sloped down)

But now how would i do that?
Is it possible to fire 2 barrels with one chamber?
Or could i make something to divide the big chamber in 2 (in the length!)
i dont know it yet...

Edit: added design picture:

Well, just a little input, but if the two guns are the same size, you could make one propane meter for it, with a ball valve going to each gun.

noname wrote:Well, just a little input, but if the two guns are the same size, you could make one propane meter for it, with a ball valve going to each gun.

Noname has the right idea with the propane system.
You might be able to set it up like this: See picture

The slanted lines in the middle indicate male/female adapters and possible reducers

noname wrote:Well, just a little input, but if the two guns are the same size, you could make one propane meter for it, with a ball valve going to each gun.

Maybe it would be wise to change the ball valves into check valves.
They you wont need to keep turning them on and of AND can they be build somewhere inside.

Will 4" cell core ABS be ok for the chamber? I've read some about it, but i need a definitive answer.

thanks for the drawings. they help tons! i think i might just use that system. It will really depend on how heavy the whole setup is with or without the tank,and how easy it is to house the tank


I started buying the stuff on my lunch break. I got 2 60" 2in SCH40 PVC barrels, a hallow/square aluminum bar for the lower receiver, and the concrete filling tube for the round parts of the body. I'm going to use a bike pump for the front grip,and a paintball gun trigger frame backwards for the middle one, and some raw piece of metal or something for the shoulder rest.

I was going to get the 4" ABS outer barrels/chambers, but its all Cell Core ABS...even their 4" PVC is cell core. I know ABS isn't preferred, but that its generally accepted in combustion guns, but i hadn't learned anything about it. Is all ABS cell core? If so, is it alright to use for my chamber? I didn't get it because i wasn't sure it was what i needed, but as long as it will work, ill go get the outer barrels/chamber in a coulple hours. The last big struggle I'm having is trying to find a way to mount the 2 inch barrels inside of the 4 inch tubes. Depending on what does/doesn't work i may just make regular inline spuds that can slide into the 4 inch barrels. Ill start to assemble it when i get home

good luck! :iroc:

Psycix, you do know what a check valve is, right? They don't hold pressure on the side which would be connected to the meter. Therefore, the meter's pressure guage would never raise above 1 psi until the chamber was totally flooded, and wouldn't work.

Cell Core ABS is fine in my opinion for combustions, but don't get cell core PVC. If, that's IF, there's a failure, PVC explodes into very sharp fragments, while ABS tears down the side and doesn't blast shrapnel everywhere. Not all ABS is cell core, but it's hard to fnd ABS that's solid walled. If I were you, I'd get cell core ABS, but I wouldn't run it at the most efficient propane mix.
The "perfect" amount of propane is 4.03%, so I'd use that cannon at 3.8% so it wouldn't produce the maximum pressure.

alright. when i get done with work(hour and a half) ill go pick up the cell core abs 4" outer barrel/chamber

im still not sure how to mount it inside. i heard 3 inch caps fit inside 4 inch pipes. does anyone know of any other peices that are easily modifyable to fit inside this 4 inch pipe?
What i might do is have the front part of the outer barrel be seperate, with a reducing adapter, and a clamp inside the big box,so ill just slide it in place from the rear if that makes any sense? By the end of tonight you guys should be seeing a rough halo rocket launcher!

Kufive wrote:

noname wrote:Well, just a little input, but if the two guns are the same size, you could make one propane meter for it, with a ball valve going to each gun.

Noname has the right idea with the propane system.
You might be able to set it up like this: See picture

The slanted lines in the middle indicate male/female adapters and possible reducers

looking at this picture might have just let me figure it out....
do you think it would work if the 2 inch barrels were threaded onto the guns, and the 4 inch barrels(not chambers) dont actually even touch the inner ones? they just screw in and are chillin in the middle of the 4 inch?

EDIT: so im still confused as to what my CB ratio should be
if its coax do i have to take into acount the volume of hte barrel when calculating the chamber size? if i use a 5ft barrel,and a 2 ft chamber, with the barrel like 16 inches in the chamber, would that be a decent ratio? what if i didnt do coax and had the chambers be about 14 inches or so, and the barrel roughly 40 inches?

Well, 3" fittings fit inside 4" pipe, so you could probably cement the barrel into a 3" x 2" reducer, and put the whole thing in a 4" pipe.
If it's coaxial, you'll have to subtract the amount of space the barrel takes up from the chamber volume.

hmmm. even tho i said i was earlier, i don't think I'm going to do coaxial. First reason being that that makes it much harder to do chamber mods,specifically a fan. second reason being I'm more concerned with how it looks, and THAT it shoots, not necessarily that it has optimum performance. also if the barrel is too short, and the cb ratio was something like 2:1, the most noticeable difference i would notice is louder and more fire coming out of the barrel(nothing wrong with that,this IS a rocket launcher), as well as a slight reduction in velocity and range, right? ill be shooting nerf rockets, and I'm not really concerned if it doesn't shoot 200 yards. i just want to have that huge gun over my shoulder,and be able to shoot(more than like 50 ft,lol)