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[][][] A Step by Step Guide to Making a Dry Ice Gun [][][]
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[][][] By: The Voice Over [][][]
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[][][] A Metal Communications Presentation [][][]
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[][] /\/\etalland 1 10megs/AE/BBS/Cat-Fur [503]538-0761 [][]
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Introduction:
------------
In the past, many people have experimented with the power
generated by the conversion of dry ice into gaseous carbon
dioxide. The most common use that I have seen is the dry ice
bomb. The dry ice bomb is easily made by using a two liter
plastic bottle, some hot water and some crushed dry ice. To
make one, one simply puts about a cup and a half of crushed dry
ice into the bottle, adds hot water, caps the bottle and throws
it. These bombs are not a joke, and have been known to blow a
metal trash can fifteen feet into the air, as well as bursting
the bottom of the can. If you make a dry ice bomb, you had best
throw it before it explodes due to the enormous force generated
by the explosion of the bottle. A friend of mine waited a bit
too long on throwing one, and he jammed three of his fingers
badly, got a huge bruise on his left leg, and one of the plasic
fragments was propelled with enough force to puncture his tennis
shoes and cut his foot all to hell. In short, be careful with
these things.
One day in May of 1985, an idea was introduced to me by a
friend. His plan was to control the force of the expanding dry
ice and harness it to a useful end. The result was the dry ice
gun. In following these plans, please keep in mind that when dry
ice is finished expanding, it can generate pressures of up to
2400 PSI...for this reason, I recommend that when arming the gun
and when disarming it, you hold all valves OPEN, and that you
wear a pair of protective goggles at all times. I will take no
responsibility for injury that occurs because of the content of
this file, or through the use of this information. This
information is intended for educational purposes ONLY.
Materials needed:
----------------
The materials required will vary for each gun produced
because of the nature of the construction itself and the effect
produced by using different parts. The following parts, however,
are necessary for a gun with moderate power and range:
1- Standard valve. I recommend the kind that is just a
lever and turns 1/4 turn to open or close and has 3/4"
connectors.
1- Blow gun (These can be found at auto parts stores... shop
around a little and get one with the highest pressure
rating you can find (probably 150 PSI)). This will be
sometimes referred to as a valve also.
1- Length of hot water PVC piping...this will be used for
the barrel. I recommend that you use 3/4" piping,
because that is the kind that fits paint pellets of the
type used in KILLER best. Note, however, that it is
possible to launch anything up to the size of an egg with
pleasing results, provided that the barrel is large
enough in diameter.
You will also need various lengths of regular lead or steel
piping (to construct the actual gun), and adapters to get the
blow gun to fit the rest of the gun (blow guns usually have
connectors that are 1/4" in diameter, while the rest of the gun
(except the dry ice container) should be constructed with 3/4"
fittings). You will also need an end cap to go on the end of
your dry ice container and probably an elbow joint.
Optional parts:
--------------
1- Standard valve (same kind as above, but with a shorter
lever).
1- "T" joint with 3/4" connectors all around.
1- 6 or 7 inch length of 3/4" diameter pipe.
1- 3/4" end cap.
Form-a-gasket and pipe dope
Construction:
------------
Because of the nature of the gun, step-by-step plans are
not possible. However, a diagram of the gun will give you an
idea of what has to be done, and construction tips should prove
enough to allow successful completion of the project.
Diagram:
-------
trigger (part of the blow gun) standard
adaptor______________ : valve
\ : \
: : :
______________________ : _ ; _____:______
! !\__ __!__________________________________ /! ! \
! barrel ! __!__!__! ! O ! \
!______________________!/ joint B____________/ : : : I \ \
blow gun_____________/ : : I / \ \
pressure chamber________/ : I / !_____!<-joint A
adaptor____________________/ / ! !
elbow joint________________________/ /! !
dry ice container_____________________/ ! !
end cap_______________________________ _!_____!_
\!! !!
+-------+
NOTES:
1- The dry ice container can be any size...the one I use is
about 6 inches long by 2 inches in diameter. The larger
the chamber is, the more shots the gun will fire before
reloading is necessary.
2- The elbow joint can be left out...it will only make the
gun in the shape of a straight rod rather than a
"traditional" gun shape.
3- The barrel length can be any length you like, but very
long ones are cumbersome and very short ones don't allow
much accuracy. I recommend a length of about 2 1/2 to 3
feet.
4- all joints except the two marked 'A' and 'B' should be
tightened as much as possible and sealed by coating the
threads with the form-a-gasket and then putting the two
pieces together and tightening them as much as possible.
If you like, you can also caulk around the finished and
tightened joint.
5- The joint marked 'B' should be tight, but DO NOT SEAL IT
unless you do not intend to ever use more than one kind
of barrel.
6- The joint marked 'A' should not be sealed with form-a-
gasket like the others because it is the one that you
will be filling the dry ice into the gun through. To
fill the gun with dry ice, detach the dry ice chamber
pipe from the elbow joint. Load the container with as
much crushed dry ice as it will hold. Then, coat the
threads of one of the pieces of the joint with pipe
dope. This will prevent leakage of the carbon dioxide
after it has changed into gaseous form.
7- The pressure chamber should be about 1 1/2 inches in
length for a fairly powerful gun. The longer the
pressure chamber is, the more powerful the gun. On
a gun with a three inch pressure chamber, we shot a
AA battery 500 (yes, hundred) feet across a parking
lot. Such high power, however, is dangerous, and is
not recommended for use in games such as Killer, but
rather for target practice (on INANIMATE objects).
How to operate the dry ice gun:
------------------------------
Once you have the dry ice gun built and loaded, the first
thing you must do is to open the standard valve and immerse the
gun in water. This is to check for leaks. If any leaks are
present, they will show up as streams of bubbles rising from the
gun. If any are found, tighten the offending joint and put the
gun back in the water. When all leaks are gone (if necessary,
take the whole thing apart and rebuild it from scratch to
eliminate leaks, especially on either end of the pressure
chamber), release the pressure built up so far by closing the
standard valve and then operating the trigger. You should hear
a 'woosh' sound, and the gun should kick slightly. This
indicates that all is working properly. When loading the dry ice
gun, it is important to keep both valves OPEN until the dry ice
container is secure, and then close both valves. Even after you
are sure that the gun has no leaks anywhere, it is good to
immerse the dry ice container (while it is attached to the gun)
in water. This warms the dry ice and causes it to change into
gaseous carbon dioxide.
After the dry ice container has been immersed for 5 minutes
or so, remove the gun from the water and dry it off. The gun is
now ready to be fired.
Firing the dry ice gun:
----------------------
This is the simplest step of all. To fire the gun simply
place the projectile (I recommend paint pellets) in the barrel
of the gun, open the standard valve for about a second and
then close it. You should hear a muffled rush of air as some
of the gaseous CO2 is bled into the pressure chamber. Aim the
gun at who/whatever you wish to hit, and squeeze the trigger.
For more power, you can leave the standard valve open and squeeze
the trigger.
Disarming the dry ice gun:
-------------------------
To disarm the gun, open both valves until you can no longer
hear the pressure escaping through the barrel of the gun. Then,
unscrew the dry ice container and place it in cold water for
about 3 to 4 minutes, or until all of the remaining dry ice has
evaporated. When all of the dry ice is gone, clean the threads on
the dry ice container and elbow joint, and store the gun in a
clean, dry area.
Suggested modifcations:
----------------------
The only really nice modification that I've discovered is
to replace the pressure chamber pipe with a "T" joint and valve
so as to make a gun with long, medium, and short range
capability. To do this, construct the pressure chamber section
of the gun like this:
___adaptor I
: ______________________________________ ________I___
_____ _ :/! ! I
___#__!o!/ ! ! I
! ! ! I
! ! "T" joint ! O
________! ! !
: \ ! !
: \!____________ _____________!___________
: ! ! ^
: !_____________! !
:__blow gun !______O______!<-standard standard
! I ! valve #2 valve #1
! I !
! I !<-short length
_!______I______!_ of piping
!! !!
+---------------+
end cap_______/
What this does is make a pressure chamber with a variable
length. The following chart shows the combinations in which the
valves may be used to create different ranges.
RANGE ! INSTRUCTIONS
--------+--------------------------------------------------------
short ! Open valve number 1, hold it open for about a second,
! close it, and then open valve #2.
--------+--------------------------------------------------------
medium ! Open valve number 1 for about a second and close it.
! Leave valve #2 closed.
--------+--------------------------------------------------------
long ! Open valve #2 before opening valve #1. Open valve #1
! for about a second, then close it.
--------+--------------------------------------------------------
The trigger can be squeezed at any time following any of the
above procedures. Have fun!
This file may be used on any system as long as all credits and
information remain intact.