Need someone more expierenced please

[grum7n7]

I am making my first propane gun...i made some rough plans for it...i know the chamber size and barrel length and the amount of propane but i dont know the meter pipe length yet because i need to figure out a pressure to run it at...

barrel = 40" x .5"
combustion = 8" x 1'
amount of propane in chamber = 4.12ml

questions

1) will this plan work? if not please give me some corrections or tips
2) will the bend going from the combustion to the barrel affect anything as opposed to it being just straight?
3)same for the propane steup? will the propane setup work?
4) what pressure should i run this at (at 90 psi the meter pipe would have to be .24 inches long lol)
5)please tell me anything you see wrong with and a solution

im not being demanding and i dont mean to sound it, but im somewhat of a noob when it comes to propane stuff...if you dont want to help me dont, but if you wish, help me please...it will be appreciated

thanks

nick

[Mihlrad]

http://burntlatke.com/ft_live.html

Use that to calculate the sizes.

[grum7n7]

if the pressure is at 21.5 psi with a 3/8 meter pipe it will give me a length of 1 inch...

will a 1 inch meter pipe be ok and will 21.5 psi be enough pressure to empty all the propane into the chamber?

[Mihlrad]

if the fuel tool says its ok, its ok... but 1 inch at 21.5 psi seems a bit low, how small was the chamber again?

[SpudStuff]

that won't be very powerful

[grum7n7]

yeah tahts what i was thinking that it wouldnt be very powerful...


the chamber volume is 6.28 cu. in....102.91ml

should it be bigger and mae the barrel bigger too to keep the .8:1 ratio

[SpudStuff]

um that would be like a mini.

look into using a pnumatic. the only modification to your current design is to add a valve to the barrel near the rear. it will be much more powerful

[Mihlrad]

If your going to use propane just use 4" or 3" pipe, it will cost you 3x as much though, i agree with spudstuff go pnuematic, same design with a valve in it. Far cheaper too.

[grum7n7]

aright ill go pnuematic then...should i keep the same ratio (.8:1) or is the ratio supposed to be different???

also the bend from the chamber to the barrel has no effect right??

[SpudStuff]

the bend will have an effect because air is a fluid and fluids loose speed each time they change direction. you couuld ude to make the chamber larger. tre 2" x 8" and for the barrel use 3/4 inch CPVC so you can shoot paint balls. when you install your valve put it between thebarrel and the bends at the rear. i would recoment using a modified sprinkler valve.

[Shrimphead]

The bend will have an effect, but it is pretty minimal. Over-unders are probably one of if not the most common pneumatic, so don't worry about it.

[grum7n7]

aright cool guys

thanks

[grum7n7]

what pressure would you run it at?

and how does it compare to a combustion