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