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Unread postAuthor: silenttear » Sat Aug 05, 2006 7:55 pm

I just "attempted" my first gun today. My first test to make sure the gas transfer worked went well, and scared the crap out of me for its loudness. Sadly on my second attempt, i did the same thing and got nothing. i drew up a little picture of what i made (pretty standard)

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chamber is 2' at 4" the barrel 3' at 2". from the propane tank to the psi valve is 1/4 inch tubing. then 1/4 to 3/8 coupler. 3/8 ball valve. 3/8x12" nipple. 3/8 ball valve. then finally 3/8 street elbow into the chamber. My brother is a truck driver that used to haul hogs so he gladly gave me a cattle taser which it took apart and have wired to two old grill sparkers i had laying around. (the spark is REALLY strong and as long as i hold the button). I cant seem to get that damn thing to fire now to save my life. I figured propane, even a small amount would fire off... i am getting nothing. do i need to add more?

my filling procedure:
open first valve fill the 3/8x12" tube. shut first valve open second one to feed the chamber.
hold the taser button....... nothing.

i just am alittle reserved about filling more into the chamber without even getting one true test off. But that is the only thing i can thing of is not enough gas.

any thoughts?
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Unread postAuthor: CS » Sat Aug 05, 2006 8:37 pm

First off, if your not going to use a pressure regulator in your propane metering system, the pressure gauge should be in-between the set of valves. Since the pressure drop between the two shoots is so minimal I cant seeing that being a problem of the current you discuss of. Just a few questions-

-You hear the prod *sparking* right?
-Is there a projectile obstructing the barrel?
-Do you have a method to "vent" the shots?

Its very possible you dont have a way to exhaust the spent air. Answering the above questions would allow me to better answer your question.
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Unread postAuthor: silenttear » Sat Aug 05, 2006 8:42 pm

-You hear the prod *sparking* right? correct very strong sparking sound

-Is there a projectile obstructing the barrel? for testing i have a very tightly rolled ragthat sits very well in the barrel.

-Do you have a method to "vent" the shots? No what would be the best way to do that since i have it all sealed up already :/
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Unread postAuthor: djt » Sat Aug 05, 2006 8:47 pm

you could always cut off the end cap on the 4" and put on a threaded cleanout cap.
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Unread postAuthor: silenttear » Sat Aug 05, 2006 8:49 pm

so after you fire you just open the end for a few minutes to let the gun breath? i really dont know if i wanna put a fan in mine or not.. maybe its time to put my old computer crap to use.
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Unread postAuthor: CS » Sat Aug 05, 2006 9:10 pm

If you dont mind, you can use djt's method. Itll make you combustion chamber a few inches shorter, but its a fairly simple fix. You could blow it out with air, but that would get really annoying...

About venting... You dont need a chamber fan. I usally just blow it out, wave it around for a few seconds, or let it sit there for a few moments. I usally load - fuel - fire - remove cap - and repeat. By leaving the end cap off and loading the projectile, this will help exhaust.
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Unread postAuthor: MrCrowley » Sat Aug 05, 2006 9:14 pm

My old combustion took ages to vent i used to shoot frozen spuds and after i shoot them i used to walk 100m to pick them up for re-use and by then and only then my combustion would be vented.So thats like 2min
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Unread postAuthor: silenttear » Sat Aug 05, 2006 9:15 pm

thanks for the tips. looks like i have to go to the hardware store again bright and early. planned on firing it all day tomorrow at the lake for testing.
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Unread postAuthor: Velocity » Sat Aug 05, 2006 9:37 pm

To repeat what everyone else has said:

Just buy a female adapter and a cleanout cap. Cut off the cap, and solvent weld the female adapter on in its place. I doubt you will lose any chamber volume
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Unread postAuthor: MrCrowley » Sat Aug 05, 2006 10:31 pm

you might gain some if you cut right.my female adapter is huge at a bout 15cm long :D
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Unread postAuthor: silenttear » Sat Aug 05, 2006 10:45 pm

so to recap... you think that the only thing keeping my gun from firing is that screwoff cleanout? do you think i should do that then test and if nothing fires just keep adding propane until it does? n00b questions i admit.. but then again i am a n00b when it comes to this sort of stuff >.>
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Unread postAuthor: djt » Sat Aug 05, 2006 11:45 pm

not keep adding propane. if anything it would probably be not add as much propane. that could be part of your problem too. if you have too much fuel and not enough oxygen your gun wont fire.
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Unread postAuthor: CS » Sat Aug 05, 2006 11:52 pm

rmich732, why the echo? You dont have to post you know...

What is keeping you from shooting is the "air" in the combustion chamber is robbed of its oxygen during combustion. So you need a way to allow normal air in there with oxygen. Yes, this can be done with a cleanout adapter and cleanout.

Errr, how did you figure out the meter pipe volume in the first place? If you used a calculator, you shouldnt have to mess around with adding more amounts. Then again I might not be understanding you correctly, so feel free to correct me.

On a side note - You used "good" grammar in your original posts, then for this last post you like switched into "noob" grammar. Just in a hurry? Just wondering...
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Unread postAuthor: silenttear » Sun Aug 06, 2006 12:25 am

the later in the evening i get, the more alcohol is consumed. it is the weekend :P. Also, i knew when i was putting all of it together something didnt seem right about that psi gauge placement. i see now how it is wrong. Now it is all assembled i will just have to test and adjust the measurements.
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Unread postAuthor: sgort87 » Mon Aug 07, 2006 12:27 am

Your guage is fine where it is if you are using the twist valve on the propane tank to control the flow of propane. If you are leaving that open and using the first ball valve to control the flow only then you do need to move the guage.

With such a nice launcher you should try my favorite method of venting. You can see it used on my <a href="http://www.spudfiles.com/forums/viewtopic.php?t=2429&">Blue Flame II</a>. It works incredibly well but requires a chamber fan.
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