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Getting the projectile to go further

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Getting the projectile to go further

Unread postAuthor: jrf155 » Mon Jan 01, 2007 2:38 pm

i just made my first mini. It uses harispray and is a pill bottle, pen tube, and grill starter.

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Igniton(2 nails)

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The gun does work, it fires a 6mm .2 gram plastic airsoft bb maybe 10 feet. My question is how do i get the bb to go farther? After the bb is fired if i click the starter again a second little combustion happens, i don't know if thats normal. The bb is held in place with a small nail hammered into the barrel. Any ideas on how to get the bb to fly farther?
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Unread postAuthor: Flying_Salt » Mon Jan 01, 2007 3:00 pm

If you put something that fits tighter in the barrel in, such as a Q-tip, it will build up more force and go farther. I don't think airsoft bb's fit very tight in a pen barrel. The result of that is too much of the explosion's force will escape around it. You may want to use aluminum foil or something like that as wadding.

Oh and the second ignition is probably from the residue left over from the hairspray. That sticky stuff it leaves behind can still be flammable.


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Unread postAuthor: Bluetooth » Mon Jan 01, 2007 3:20 pm

Yeah like Flying Salt said use some kinda wadding. Just take a small 1"x1" square of paper towel and put it on top of the barrel at the end and put a bb on top of that and use a ram rod to push it down.
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Unread postAuthor: CpTn_lAw » Mon Jan 01, 2007 3:45 pm

putting some wadding is the first improvement. The most important improvement is a longer barrel. you must have a 10:1 ratio.
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Unread postAuthor: jrf155 » Mon Jan 01, 2007 4:04 pm

i used some paper towel to wad it and then put in the bb. When i fired it went signifigantly farther than before. This is probably a very newbish question but what do you mean by a 10:1 ratio for the barrel?
Also i think alot of the force of the explosion is escaping out of the cap in the back, any ideas on how to hold the force in better, all i could think of was tape but then i would have to retape it every shot.
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Unread postAuthor: Insomniac » Mon Jan 01, 2007 5:05 pm

The ratio we are talking about is the C:B ratio (chamber to barrel ratio).

A 10:1 ratio means your chamber is 10 times larger than your barrel. This means that a lot of energy is wasted. IF you used a longer barrel to make the ratio a bit better it will shoot a LOT harder. My mini could put a sultana throgh both sides of an empty tissue box. (I can't remember what the correct one is, for minis it doesnt really matter if it is a little off)
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Unread postAuthor: medievalman » Mon Jan 01, 2007 5:28 pm

a good airsoft barrel is 3/16 inch brakeline(i think thats the right size) get like 2 ft of that.
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Unread postAuthor: Insomniac » Mon Jan 01, 2007 5:34 pm

Oh crap, I'll edit that, I meant that the chamber was larger.
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Unread postAuthor: jrf155 » Mon Jan 01, 2007 9:54 pm

so is doing something like adding an extra pen tube to the existing one enough?
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Unread postAuthor: Flying_Salt » Mon Jan 01, 2007 10:11 pm

That will help, but you'll need some sort of ramrod to shove the projectile all the way down the barrel. You should also be careful to keep it nice and smooth on the inside.
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Unread postAuthor: jrf155 » Tue Jan 02, 2007 9:10 pm

this is what i did
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Its pretty cold and its a poorly constructed barrel but even in the black of night i saw a signifigant increase in projectile range. The gun used to fly backwards and fire shot out of both ends, now i can see the inside of the gun illuminate for a short time and thats about it. The performance was much better and it will probably be very good with a nice straight barrel and good seals.
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Unread postAuthor: medievalman » Tue Jan 02, 2007 10:03 pm

Looks like that simple mod increased performance alot! Glad to see you using your "noggin"!

oh, i just noticed that in the pic of the inside of the chamber, in your first post, it is labeled "2 nails", when it is actually 2 screws...maybe you aint usin' that noggin after all... :lol:
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Unread postAuthor: killagorrila99 » Tue Jan 02, 2007 10:42 pm

If you want to go farther, use butane (or acetylene and oxygen)
If you wanna kick ass, Make a pneumatic. Even a crappy ball valve mini would kick this ones ass!
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Unread postAuthor: Insomniac » Mon Jan 15, 2007 12:11 am

How come no one does what I do and put the barrel in the lid????? That way you can breech load it, and its easier to use blu tac or teflon to make the barrel seal. Also, if the explosion pops the lid off, it doesn't fly back and hit you like it would on a normal pill bottle gun.
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Unread postAuthor: BL4K_}-{4WK » Fri Jan 19, 2007 6:45 am

i saw a video of a guy wit a launcher that was made to perfect specs and was running it on oxy/accedilene n it wne toff wit a big bang, what he did was get the oxy goin to the right mix of O/A the he would put it out n then open up his gun n put that mixture n the chamber, this gives a perfect mixture n accedilene is extremely flammeable so. knock yoursef out.


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