From: jdolske@magnus.acs.ohio-state.edu (Justin H Dolske)
Date: 26 Jul 93 19:26:06 GMT
--------------------------------
The Ancient Art of Cannonry v1.0
by
jdolske@andy.bgsu.edu
7/23/93
--------------------------------
===
0.0 Index
Section Title
0.0 Index
1.0 Introduction and Disclaimer
1.1 Equipment list
1.2 Credits
2.0 Tennis Ball Cannon v1.0
2.1 Tennis Ball Cannon v2.0
2.2 Tennis Ball Cannon v2.5
3.0 Other Designs and Ideas
3.1 Alternative Fuels
3.2 Alternative Designs
3.3 Assorted Ideas
===
1.0 Introduction and Disclaimer
So you wanna build a cannon? I think nearly everybody is familiar with the
basic idea of the Tennis Ball Cannon -- some type of device that, when
ignited, fires a tennis ball out one end. This sounds simple enough, but
making a cannon that can shoot long distances (E.g., 100+ yards) can be a bit
tricky. The purpose of this document is to guide the reader through the
production of a number of different types of cannons.
Section 2.0, 2.1, and 2.2 deal with the three types of cannons I've
built to date. If you just want to build a cannon, these are the sections
for you. These cannons are probably not the most powerful that can be made,
but they have all been built and tested. They're easy to build and easy to
fire, unlike some of the vague net-info I've seen floating around. Hopefully
I've been precise enough that anyone with some a little talent and time can
successfully build a cannon that can fire impressive distances. If you're
interested in theory or experimentation with unproven designs (by this
author, at least), check out later sections.
While I've never had any serious accidents with my cannons, I recognize
that this it *not* a harmless sport! I feel that although the simpler cannons
are fairly safe (assuming standard precautions are taken), the more advanced
models can generate TREMENDOUS pressures in the barrels. The power of such
simple devices still amazes me. With this said, keep these points in mind:
* Don't build and use any of these cannons if you're not willing to
take a risk. If you feel wary of setting off large fire crackers,
this sport isn't for you.
* I'm not perfect person, and this isn't a perfect guide. Just
because I don't mention something or I leave a point out doesn't mean
it isn't important. Use some common sense.
* Play it safe! Wear eye-protection (e.g., impact resistant goggles)
and ear-protection. These things can blow up and can make VERY loud
bangs. A sturdy pair of gloves is also a must. I'm not kidding -- I
wear all this stuff. A thick piece of PVC (I use 4" Schedule 40) pipe
is recommended also for use as a "blast shield" around the cannon.
If these cannons explode, you'll be glad for 1/4" or more of PVC
between it and you.
* Read through this entire document before building or buying
anything.
* I take no responsibility for your actions and/or stupidity. If you
get hurt, it's not my fault. Use this information at your own risk.
Please email me with any suggestions/ideas/experiences. The quest for the
bigger, better, farther, safer cannon never ends!
===
1.1 Equipment list
Here are some basic items you'll want to have on hand when building cannons.
Don't run out and buy everything at once -- Not all of it is used in every
cannon.
* Duct Tape -- Used to reinforce cannon. Plan to use at least 1/2
of a roll for every cannon.
* Glue -- Wood Glue (a.k.a. Carpenter's Glue) and Super Glue are handy
* Cardboard tubes -- About 2.5" diameter. Pringles cans are easiest.
For future reference, a Pringles can is 9.5"
long.
* Tennis Balls -- Your projectile!
* Pop Cans -- Can function as a both barrel components and as a tip
to firmly hold tennis ball.
* Lighter or Matches -- Used to ignite cannon. Long matches are a
good idea...
* Knives -- A good sharp knife for cutting cardboard/tape. A cheap
knife can be used to cut cans and other thin metal.
* Lighter Fluid -- Used as a fuel. Don't use butane! You want the
liquid stuff, also known as Naphtha. "Zippo" is
a common name brand.
* Tape Measure -- If you're interested in exactly how far your cannon
can *really* fire.
* SAFETY EQUIPMENT -- See Section 1.0!
===
1.2 Credits
This document was created as a summary and guide to cannonry after spending
the summer of 1993 building and improving cannons.
Ideas, suggestions, etc. were also contributed by the following people:
Kevin Parsley
brad@slammer.UUCP (Brad Isley)
dale@unislc.slc.unisys.com (Dale Clark)
david@baervan.nmt.edu (Davis Fritchman)
farb@ecr.mu.oz.au (William_Cuming FARROW)
gt5876b@prism.gatech.edu (Rick Farmer)
i919802@redgum.ucnv.edu.au (Douggie)
rhughes@mtgy.gtegsc.com (Ralph Hughes)
henlib@nevada.edu (Carroll Gardner)
Tidbits gathered from other UseNet rec.pyrotechnics readers
The Big Book of Mischief v1.3 (TBBOM13.TXT)
===
2.0 Tennis Ball Cannon v1.0
This is the first type of cannon I built, and it's also quite simple to
build. This design can fire a tennis ball about 45 feet. It's also quiet --
the "whoosh" sound of this cannon probably doesn't require hearing protection
unless you're sensitive to sound. I'd encourage anyone who's never built a
cannon before to build this one first; it can later be modified to a "v2.0"
cannon.
The design of this cannon is extremely simple. The barrel is made from
between 2-5 Pringles cans (I found that more that 5 has no effect). Just
empty the cans, and cut off the metal bottoms on all but 1 can. When you
cut off the bottoms, cut the cardboard sides as evenly as possible to ensure
a good fit. Tape/glue all the cans together as securely as possible. The one
can with the metal bottom intact should be the bottom can, everything else
goes on top. Make sure all joints and the bottom are reinforced especially
strong.
At the base of the bottom can, make a small hole. It should be no bigger
than 1/4 inch, and no smaller than 1/8 inch. A hole in the metal instead of
the cardboard should also work, but I found a hole in the side to be less
awkward to light.
All that needs to be done now is to make a fitting for the tennis ball to
sit in. The easiest fitting is to cut a circle out from the plastic Pringles
can lid so that a tennis ball can be snugly wedged into it. You may wish to
run a wire or string through the sides of the can near the top so your tennis
ball will not fall all the way into the cannon! An alternative to the lid is
to use a pop can with the top and curved-part of the bottom removed. The pop
can fitting may shorten the range of the cannon, however.
Now would be a good time to make sure your safety gear is on!
The cannon is now complete and ready to be fired. To fuel it, put a squirt
or two all the way down the *side* of the can. Don't just dump it all on the
bottom or it won't work! Do put a few drops on the bottom to make sure that
there is plenty of fuel by the ignition hole. It doesn't take very much
lighter fluid at all. Between 1/2 teaspoon and 1 teaspoon is PLENTY. We're
only interested in burning the *vapors* of the lighter fluid.
As soon as you've put in the fuel, stick the tennis ball in the top. Wait
5 to 10 seconds to be sure the lighter fluid has vaporized. Now point it in
a direction that won't injure anyone or anything, and ignite the cannon with
your lighter or match.
If all goes well, you will be rewarded with a "whump" and the tennis ball
will shoot out the top. At a 45-degree angle, the cannon should throw the
ball about 45 feet.
* If your cannon would not ignite:
- Your hole may be too small. Try making it a little bit bigger.
- Make sure the fuel was squirted evenly down the side, with a little
extra near the ignition hole.
- If you've fired it before, make sure you blow out the exhaust
gasses -- the lighter fluid must have fresh air in the cannon to
burn.
* If your cannon ignites but is very weak:
- Your hole may be too large. Use tape to shrink the size. A large
hole allows the pressure to vent through the hole instead of pushing
the tennis ball.
- The tennis ball may need to be wedged in firmer to allow pressure to
build up before launch. use a smaller circle in the Pringles lid or
push in the side of the cola can a bit.
- If you've fired it before, all of the exhaust fumes may not have
been blown out. A hairdryer can be used to quickly perform this.
- A 2 can cannon will not fire nearly as far a larger cannon. Roughly
expect about 20 feet for 2 cans, 30 for 3, 40 for 4, and 45 for 5.
===
2.1 Tennis Ball Cannon v2.0
Well, the first cannon was a good start, but it just wasn't impressive.
There was no real noise, and you could easily throw a tennis ball farther by
hand. Now enter the exciting world of the "baffle." By placing an obstruction
across half of the diameter of the cannon at regular intervals, the pressure
produced by the cannon is GREATLY increased. I suspect the baffles slow down
the combustion of the vapor, allowing for a more complete burn, but that may
not be correct. In any case, you can at least triple the range of a v1.0
cannon by just adding a few baffles.
WARNING! This is where these cannons become much more dangerous! The noise
produced is now much, much, MUCH louder -- ear protection is a MUST! I can't
stress this enough. I personally lost hearing for a few minutes after my first
shot -- stupid, but I'm much more careful now. The pressures involved are
also tremendous. The bottom end of a Pringles can is always dented and warped
after the first firing, and you'll always get seams blown out. The baffles,
which are made from metal, have the potential to produce shrapnel. And, of
course, the tennis ball has much more energy. I've heard these can cause welts
at close ranges.
I strongly suggest first building a cannon of no more than 2 cans. It's
fairly simple to add on one can at a time -- this will give you a feel for
just how much reinforcement to use when constructing cannons. Use of a PVC
"blast shield" is strongly encouraged!
The range on these cannons is impressive. A 3-can cannon can fire over
120 feet, and a 4-can cannon can reach 100 yards! Beware of blow-outs. The
first time a baffled cannon is fired, you will probably find areas around
seams where the cannon has split the duct tape. After securely taping these
up you can easily add 100 feet of range. Thus, the second shot is always more
impressive than the first.
A baffled cannon is also harder to fuel and ignite. Your first few attempts
may not work well at all, or may be very weak. Don't be fooled!
Construction of this type of cannon is similar to that of a v1.0, except
for the baffles. The best material for baffles I've found are the sides of
pop cans. Use some sort of cutting instrument to cut off the top and
bottom to a can, and slice down the side to create one sheet of metal.
Flatten this sheet out.
For baffles in the middle of a can, simply make a straight cut through
half of the can. Then insert the metal sheet, and cut so that it extends
about 1.5" from the side of the can. Baffles on a seam between cans just
need to be cut to shape.
Sheet of metal
(Top view) /
/
.----------------------------.
| |
| |
| |
| |
| __---__ |
| /' `\ |
| .' `. |
|______|_____________|_______|
`. .'
\ /
`--___--'
\
\
Pringles can
Using the extra metal on the sides, use a pair of old scissors to cut
flaps. These will be used to secure the baffle to the can to prevent them from
being blown out. The ASCII pic below shows 6 crude flaps. One-by-one, bend
the flaps down and tape them securely to the can. You may wish to use some
wood glue here to help get a tighter fit. The baffles should alternate sides
so that you cannon see more than 2 baffles as you look into the cannon.
.----------------------------.
| \ | / |
| \ | / |
| \ | / |
| \ | / |
| \ __---__ / |
| \/' `\/ |
|------.' `.-------|
|______|_____________|_______|
`. .'
\ /
`--___--'
Once all the cans are baffled, you'll have a cannon with a side view
something like this:
(Cutaway view)
__________________________________
| | |
|_____________|_____________|______
Make sure you use LOTS of tape to reinforce the cannon. On the last cannon
like this I made (4 cans), I used about 3/4 roll before the first shot, and
more afterwards to patch blow-outs. You can't use too much. Pay special
attention to the seams and cuts for the baffles. Make sure you've got plenty
holding on the back or it will blow off! If you've been firing from a hole on
the bottom instead of the side, consider putting the hole on the side so if
the back blows off it won't hit your hand.
Now would be a good time to put on your safety gear!!!
Fueling baffled cannons is a bit trickier because you don't have a clear
route down the side. Get the lighter fluid as far down as you can by
squirting down the top, then flip the cannon over and squirt some through the
ignition hole. Rotating and tilting the cannon will help the fluid get to the
middle. Stick in the tennis ball, and let the fuel evaporate for about 20
seconds. Make sure you're wearing a glove when you ignite this! You'll burn
any fingers near the ignition hole if you're not wearing gloves...
Hopefully you'll hear a loud boom (muffled, of course, through your ear
protectors) and the tennis ball will shoot about between 100 feet and
100 yards. Now take a look at your cannon. Patch any blowouts with plenty
of tape. Observe the denting done to the bottom of the Pringles can and
damage done to the baffles. These cannons are good for about 5 shots before
the baffles are completely destroyed. Now go find your tennis ball. :-)
* If your cannon would not ignite:
- Check fixes listed under Cannon v1.0
- Baffled cannons take much longer to vent exhaust fumes from
previous firings. Always blow through the ignition hole to push
out the exhaust.
- Did you put fuel through the ignition hole to ensure fumes in that
area?
* If you cannon performed weakly:
- Did you allow the lighter fluid to evaporate?
- See caution above about exhaust fumes.
- On larger cannons, vapors may not be reaching the middle of the
cannon. Try putting fluid in the bottom first, and blowing though
the ignition hole to force vapors into the middle.
- Check your baffles. After 4 or 5 shots they are badly damaged or
destroyed.
- Refuel and try again. Sometimes they seem to fix themselves. :-)
===
2.2 Tennis Ball Cannon v2.5
This section is still "under construction." As of this writing, I have not
completed or tested this cannon, but I will describe it's construction. This
cannon is basically the same as v2.0, but is designed with strength and
durability in mind.
The barrel of this cannon is no longer made from Pringles cans -- an
important benefit to those of you sick of eating Pringles by this point!
Instead, use a thick cardboard tube of about the same diameter. These are
the kinds of tubes used for mailing things, storing blueprints/drafting plans
in, etc. A good art store, mailing store, or office supply store should have
something like this in stock. I'm using the shipping tube from 1960's vintage
M518 (?) 2.5" rockets, but other cardboard tubes will work just as well. I've
seen cardboard tubes with walls in the 1/4" range, so these should hold up
much longer than a Pringles can.
The tube I'm using already has a metal end on it, but most others don't.
I should think a PVC end-cap or tin-can of the appropriate diameter would
work well. Be sure to use extra tape to hold the end on and to help prevent
shrapnel!
Unfortunately, these cardboard tubes lack the smooth foil/plastic coating
that the Pringles can had. I plan to use a polyurethane (The type in a
spray-paint type can) to coat the inside to prevent the fuel from soaking
into the cardboard.
The baffles are made from sheet metal, the type used in air duct work is
ideal. These are cut with a metal saw in the same shape as before, and bent
with pliers.
===
3.0 Other Designs and Ideas
The following sub-sections are, unless noted, untested by this author. Some
designs/ideas were submitted by other "cannonists," some are just theories
or thoughts. I'll try to note which the case is. Experiment at your own risk!
===
3.1 Alternative Fuels
The fuel used by most cannons is just lighter fluid (naphtha), but other
fuels are available -- some are reported to be much more powerful.
* Fuels that don't work: (experience)
-Gasoline: I thought this would be great, but I just wasn't
able to get the cannon to light. This may just
be tricky to use properly.
-White Gas, a.k.a. Coleman Fuel: Same thing, wouldn't ignite.
* Propane: (experience)
This worked quite well, it's as good or slightly better than
naphtha. Propane is certainly worthy of further study...
* Alcohol: (submission)
Also known as denatured ethyl alcohol. This is supposed to be
more powerful than naphtha, but is also supposed to be much harder
to reliably measure/ignite.
* Engine starting fluid: (submission)
Also known as ether (one brand is diethyl ether), this seems to
be second in popularity. One drawback is it's higher cost. Be sure
to only use with STURDY cannons! This is supposed to be quite
powerful.
* Acetylene: (submission)
Also known as welding gas. Acetylene/air mixtures can be
*extremely* powerful, and have the potential to be ignited from
even tiny amounts of static electricity. Use caution with this!
* Calcium Carbide: (submission)
When mixed with water, this produces a gas closely related to
Acetylene -- follow similar precautions.
* Hair spray: (submission)
Commonly available, but I would imagine that other fuels would
produce better results. I would also think this would leave a
sticky residue in the cannon.
* Hydrogen/Oxygen: (untested)
This should produce some impressive results, but has the potential
to be dangerous. A hydrogen/oxygen mix (66%/33%) will produce the
best results, but a hydrogen/air mix should also work (air is 20%
oxygen). A cannon filled with pure hydrogen will not work.
A fairly simple way to produce a hydrogen/oxygen mix is by
electrolysis of water. This has the advantage of producing the
gasses in the exact ratio.
Hydrogen alone can be collected as the byproduct of dissolving a
metal in an acid. Aluminum foil in muratic acid (usually about
9M HCl) works fine.
* Acetone: (untested)
Acetone evaporates quickly, but I'm not sure how explosive the
vapors are.
* Propylene Oxide: (untested)
This is what the military uses in Fuel-Air Explosives. I bet this
stuff would be great to use, but I have no idea on where to get
some, and it's probably highly toxic.
===
3.2 Alternative Designs
* A cannon made from pop cans: (submission)
This design is basically a cannon using 1 can as a combustion
chamber, and 4-5 cans as a barrel. This design may not be practical
today due to pop cans being pressed/molded rather than rolled steel
with ends put on. In any case, the tops and bottoms of 4-5 cans are
removed and the cans are taped together. I suggest using plenty of
tape on the sides to prevent blowouts and (especially) shrapnel.
The "chamber" can has holes punched on top -- a LOT of holes -- and
a small hole at the bottom to ignite the cannon.
With a few drops of lighter fluid in the combustion chamber, shake
the cannon to help the fuel vaporize. This cannon is supposed to
fire about 100 yards.
* Another pop can cannon: (submission)
This is similar to a v2.0 cannon. Cut the tops off of 4 cans, and
1/2 the bottom on 3 of those cans. Securely glue and tape these
cans together, using the can with only the top removed as the base
for the cannon. Again, use plenty of tape on the sides.
Use a few drops of lighter fluid for fuel. No ranges given, but
it is claimed to have a "significant" kick.
* Yet another pop can cannon: (submission)
Same as "Another pop can cannon" but a soup can was used for the
base. With ether as a fuel, this cannon is said to fire 200 yards.
* Juice can cannon: (submission)
Simple construction. A 3-liter metal juice can with a 2-foot
length of natural gas pipe stuck in the top. A weighted 35mm film
canister was used as a projectile instead of a tennis ball.
* Propane cylinder cannon: (submission)
This one certainly sounds sturdy! Cut the top off of two empty
propane cylinders, and the bottom off from one of them. These are
the thinner kind used for handheld torches, not the squat/fat ones
used for camping. Weld the two cylinders together, and weld a nut
over the ignition hole for a spark plug to screw into for remote
ignition. This cannon was used with acetylene gas.
* Aerosol can cannon: (submission)
Barrel:
Take a tall aerosol can of correct diameter. Most paint cans are
just right. The large Gunk engine cleaner cans are great. Make
sure the can is EMPTY. This means punch a hole in it in a
location that is to be discarded. This is to be sure there is no
pressure remaining. With a dremel tool or other grinder, cut off
the top completely. This includes removing the crimp. Leave a
smooth end. Then take a can opener and remove the bottom. Leave
the crimp ring on the bottom of the can.
Chamber:
Smaller aerosol can of same diameter. Large WD40, etc. With same
dremel tool or similar cut off the very top of the dome. The hole
you cut will need to be about 1/3 to 1/2 the diameter of the can.
This will form a stop for the ball as it is loaded. Punch a small
hole in the side near the bottom. If you want more power, use a
tall can for the chamber. I'm quite pleased with the medium sized
can for a chamber.
Ignition source and handle:
Get one of those trigger operated butane lighters that has a piezo
electric trigger. Zippo makes the one I use. The lighters I use
are red and white with a long chrome-plated steel extension for
lighting fireplace starters. Remove the coil thingie behind the
trigger. Unfortunately the coil thingie will vary quite a bit.
Some are not usable - they have a brass cap on the end. I was
unable to solder a wire to the brass cap. Solder a wire to each
post on this piezo thingie and insert it in a handle of sorts.
I made a pistol-shaped handle attached to a flat board like so:
Crimp Rings
\
-------------------------------=------------------
| /| |
| Dome -> | | |
barrel -> | \| | <- chamber
-------------------------------=------------------
================== <- flat board
\ \
piezo thingie trigger -> [####]=\== <- wires
\ \
\ \ <- handle
-----
Construction:
Using duct tape, tape the ringed end of the barrel to the dome
end of the chamber. Be sure the fit is tight. Drill a hole in the
handle where you want the trigger. Arrange for the wires to go in
first and allow for an exit where you want it. Attach the handle
to the flat board with screws. Duct tape the handle to the
chamber. Run the wires around to the hole you punched. Twist the
ends of the wires together for about an inch so they will stay in
close proximity. Strip the ends about 1/8" and make a gap about
1/8". Test the spark by pulling the trigger. Get as long a spark
as the piezo will make. Insert the wires into the hole such that
the gap is close to the center of the rear of the chamber. Test
spark with no fuel to make sure you get good ignition. If you
can, weld the cans together. The tape is slowly dissolved by
fuel.
Use:
Denatured alcohol is difficult to measure into a proper combustible
mixture. It is also much more powerful than naphtha and caused the
handle to be ripped off the chamber in our tests. Two layers of
duct tape solved this. We have had excellent repeatability with
the following fueling method with naphtha. If recently fired you
should sling the gun around in large arcs to get a fresh charge of
O2. Holding the barrel upright using a standard lighter filler
squirt for 1 second or a little less straight through the hole in
the dome of the chamber. Make sure that approximately 1 second's
worth goes through the hole in the dome. Fuel in the barrel is
useless. IMMEDIATELY insert a tennis ball into the barrel ALL THE
WAY to the dome. Wait about 5 seconds and pull the trigger.
Don't get in the way of the ball. I have a hole in the ceiling of
my garage from a shot. If you use alcohol, I'd stick to the
smaller chambers because it's a lot more powerful than naphtha.
===
3.3 Assorted Ideas
* Try a nighttime firing. These cannons, especially with starting
fluid for a fuel, as supposed to produce a decent sized flame/flash.
* Aluminum powder sprinkled in the end of the barrel is supposed to
produce a bright flash. (Probably best viewed at night)
* Try using one of the infamous dry-ice bombs in the bottom of a
larger chamber instead of a fuel that is ignited.
* I'd really like to make a reliable system for remote ignition. Any
ideas on this? I've had no success using model-rocket igniters or
steel wool. (Steel wool will sortof burn when a current is passed
through it) A spark plug may work well...
* If you get a reliable remote ignition system, sealing off both ends
of the cannon would probably produce a rather loud bang. (And
probably shrapnel)