------------------------------------------------------------------------------------------------------------------ From: agbrooks@teaching.cs.adelaide.edu.au (Zoz) Newsgroups: rec.pyrotechnics Subject: FAQ - Fuel-Powered Cannons? Date: 2 Jun 92 00:13:57 GMT Sender: daemon@ucbvax.BERKELEY.EDU Lines: 673 I have several sets of instructions for the construction of fuel-powered cannons, and was wondering if anyone had any comments on which, if any, of them would be suitable for inclusion in the FAQ. Thanks! >>>>> From: brad@slammer.UUCP (Brad Isley) Subject: Tin can cannon that works (repost) Date: 18 Dec 91 13:31:05 GMT After 20 requests for mail I decided to post this a third time... Here's one I posted a while back. I've seen a LOT of tennis ball cannons, but this design gives by far the best and most consistent performance. Touch holes are inherently unreliable, because evaporation of the naphtha produces a net outflow of gas from the touch hole. Piezo electric units are great. No PVC shrapnel here. And remember - the seemingly insignificant details related to loading are quite important. My cannon can consistently shoot a ball straight up so high it stays airborne for 8 seconds. If that's the kind of performance you want, read on... First off, a jointless barrel is best. Any joint will produce much friction. 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. Some will warn of explosions and stupidity like that, but if you relieve the pressure and empty the contents, there will be no explosion. (You might get a WHOOF in certain circumstances, but no KABOOM). 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 useable - 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 naptha 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 naptha. 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 naptha. If you get reliable performance from alcohol, I'd love to know how you did it! More fun: Use aerosol caps for projectiles instead of tennis balls. Makes a LOUD bang and moves like a bat out of hell. (These will injure you). Some caps have a lip that goes outside the crimp ring. These won't work. Even more fun (use caution - wear safety glasses): Place a tennis ball can (plastic) over the barrel for a projectile. Stay the hell out of it's way. The entire gun is now a chamber. Some other people mentioned putting aluminium dust in the end of the barrel and firing without a ball for a flash of light. I never tried this. And no, I'm not responsible for your foolishness if you get hurt doing this. >>>>> Date: Thu, 6 Feb 92 12:29:13 EST Subject: liquid fuel cannon To: agbrooks@teaching.cs.adelaide.edu.au X-Vms-Mail-To: uucp::"agbrooks@teaching.cs.adelaide.edu.au" Did I mention in the post that it was made of PVC? It's actually made from ABS (at least I think it is...... its that black plumbing stuff). I'm not really a plumber or anything....Hope there's no confusion as to the material here. Well, here goes... The Blooper Gun lighter |---|_|----------------------|_|-|- | | | | | | | | | |---------------------------------------| | | | | | -| V | | | | | | | |--- | screw-----> O | | | | | | | | | | | | | | | |--- |---------------------------------------| | | | | | _| ^ | |_| |_| | | | |---| |----------------------| |-|- | ^ ^ ^ ^ ^^^ | | | | | ||| Black ABS piping Adaptor (1 1/2" | straight sleeve | ||| (1 1/2" I think so that to 3 1/2") | connector | ||| a pingpong ball barely fits) | |Threaded | |end & cap 3 1/2" pipe 3 1/2" pipe Notes: The most difficult part will be trying to find all the various connectors to fit together. I hope that my piping diameters are correct, but I have no working model to go by anymore. The screw is used to block the ping-pong ball from falling into the combustion chamber (the gun is front-loaded) The rear of the gun is threaded to allow refueling the chamber (both with gasline antifreeze (which I should have stated as being methyl alcohol as opposed to methyl hydrate) and with oxygen (ie ventillation after a shot has been fired. I am working on a motorized version of the blooper so that ventillation occurs with the flick of a switch. The lighter used is one of those electric ones. They contain a small battery that induce a spark (rather than flint). This lighter was chosen because it activates a flame by pressing a button, and not rolling a wheel over flint. The lighter is mounted in the rear of the screw-on cap so that it is activated by depressing the bottom of the lighter, with the button secured on the cap. Securing the lighter in the chamber is the part of the gun which needs customization. I created a sleeve out of ABS piping by heating it around a lighter so that it was enveloped on all four sides. Then, a screw was secured through the sleeve so that it fit across the lighter button. This mechanism was then glued to the threaded cap. A hole was drilled and filed out of the cap so that the butt of the lighter would poke through. When the lighter is depressed, it ignites a flame inside the chamber as the screw presses on the button. The fit of the lighter has to be just so! This way, the lighter will not fall out when in "action", and the lighter can be replaced when out of butane. Also, the tighter the fit, the less blow-by occurs when the gasses combust. Note, the head of the lighter had to be stripped down somewhat, to be able to fit into the sleeve. See diagram of chamber below for details. The Chamber /\-----\ /\----------------\ /\-----\ | | | /\---\ | | | /\---\ |//| | ///\ | | | | | | | | | | | | |//| --- | |// | | | | | | | | | | | | | |//| | ---|// | |/\| | | | | | | | | | | |//| --- | |__+// +---+___ |||| | | | | | | | | | | |//| | |+ |// | + |||| | | | | | | | | | | |//| --- | |=_|// |___+ |\/| | | | | | | | | | | |//| | | +// +---+ ^ | | | | | | | | | | | | |//| --- | ---|// | | | | | \/--- / | | | \/---/ |//| | |// / | | | | \/-----------------/ \/-----/ lighter \/-----/ ^ ^ ^ ^ ^ ^ | | | | | | ABS pipe straight sleeve ABS pipe Threaded modified small to segment segment end threaded large cap ABS adaptor I hope this is detailed enough. If not, ask for further explanations. Thanks. Mark Kosir >>>>> Return-Path: Date: Mon, 25 May 92 14:28:13 PDT To: agbrooks@teaching.cs.adelaide.edu.au Subject: item for rec.pyro FAQ /* Written 2:09 am Sep 27, 1991 by chroma in rec.pyrotechnics */ The following posting is a design for a hydrogen/oxygen fueled tennis ball cannon. The posting is 14K characters long. Dr. Explodo regrets having to publish under an alias; he does so in order to avoid difficulties with University and other authorities who might not share his view of tennis ball cannons as marvelous and society-enriching devices. Dr. Guy F. Explodo Ph D, FRS, emeritus professor at the Yeovil Academy of Theological Detonations A SERIOUS TENNIS BALL CANNON Version 1.2 9/21/91 Dr. Guy F. Explodo 1.0 Introduction This hydrogen/oxygen fueled tennis ball cannon was designed with 3 goals in mind: 1.1 Safety If used correctly and with proper respect, this cannon should not be a danger to those who stand other than in front of the muzzle. 1.2 Use of Commonly Available Materials The cannon, its projectiles, and its propellant should be easily obtainable and reasonably inexpensive. 1.3 Reliability and Ease of Use The cannon should perform reliably and be easy to load and fire. 2.0 THE CANNON 2.1 Bill of materials A 18" of 2.5" diam sched 40 PVC pipe (a tennis ball is a press fit into this pipe) B 2.5" PVC slip fitting connector, female slip fit both ends C PVC bushing; 2" internal pipe thread one end, male slip fit other end D 6" of 2" steel pipe, external thread both ends E Steel T; 2", 2", 1.25" F 2" external thread 1/2" internal thread steel bushing G 9/16" fine thread steel jam nut H 1.25" external thread ~1" internal thread brass bushing J a 1/32" copper sheet, about 2" x 2" K brass tubing - 1/16" OD, 1/32" ID L brass tubing - 1/8" OD M clear vinyl tubing - 1/4" N spark plug P Scripto Tokai Electra electric cigarette lighter 2.2 Supplier Suggestions A - J: any large hardware or do-it-yourself store with a reasonable plumbing supply department. K - M: available at a model-airplane-type hobby store. N: auto supply store P: drug/supermarket/hardware store 2.3 Useful tools and Supplies Acetone Blowtorch Electric drill Epoxy cement, high-strength filled Hot glue gun Pipe wrench Pliers PVC pipe cement Sand paper, coarse Soft solder Tin snips 2.4 Fabrication Instructions Exploded views of the cannon are shown in Figures 1 and 2. ---- J +--+ ( ) H +--+ A B C D +--+ E F +----------------+ +---+ +---][ +=====+ +==| |==+ +==+ G, M, N | | | | | ][ | | | | | > +----------------+ +---+ +---][ +=====+ +========+ +==+ Figure 1 Exploded View of Cannon (small scale) +---------+ | | | | | | | | | | | | | | | | A | | | | | | | | | | | | | | | | | | | | | | |/////////| <- PVC cement +---------+ +-----------+ | | | | |- - - - - -| B | | | | +-----------+ +---------+ |/////////| <- PVC cement | | | | C | | _| |_ | XXXXXXXXX | <- internal 2" thread ------------- +=====+ XXXXXXX <- external 2" thread I I I I D I I XXXXXXX <- external 2" thread +=====+ internal +=======+ 2" thread -> IXXXXXXXI H J I I I +==+ I=I [ I XI +X=+ I [ E I XI IX I I [ I XI IX I I [ I XI +X=+ I [ I +==+ \ I=I [ internal I I \ \ 2" thread -> IXXXXXXXI \ \---- external 1.25" thread +=======+ \ \------- internal 1.25" thread external 2" thread -> IXXXXXXXI I I F, G, N +- -+ \ / \ / U Figure 2 Exploded View of Cannon (large scale) 2.4.1 Barrel Assembly Using PVC cement, attach A and B. Then attach B and C. Wait for 24 hours for cement to come to full strength, then screw D into C. 2.4.2 Combustion Chamber Assembly 2.4.2.1 Safety Diaphragm and Gas Inlet Cut a 3 " piece of tubing K. Drill a clearance hole for this tubing into copper sheet J. Insert the tubing about 1/2" into the hole, and bend it at a right angle so that the long section of the tubing is parallel to and in contact with the copper sheet. Make sure the bore of the tube is not pinched closed. Soft solder the tube to the copper sheet so that hole is sealed. Cut a 1" piece of tubing L. Slip this piece on the end of the smaller tube, crimp it with the pliers (again, make sure the bore of either tube is not pinched closed), and soft solder it in place. This tube should be a press fit into the 1/4" clear vinyl tubing M. 2.4.2.2 Safety Bushing Soft solder the assembly of 2.4.2.1 to the end of H without external threads. Do this so there are no voids. Trim the edges of J as close to the edges of H as possible. Screw H tightly into the 1.25" port of E; the only passage for gas into E should be through the brass tube. The idea of the safety bushing is the same as that of a boiler safety valve; it is designed to be the weakest part of the cannon combustion chamber. If for any reason the pressure in the combustion chamber rises to a point where it might rupture explosively, one of two things will happen: the safety diaphragm will rupture or the soft solder joint will fail. In either case combustion chamber pressure will be safely vented. 2.4.2.3 Screw D tightly into E, then screw the other end of D tightly into C. 2.4.3 Igniter Assembly 2.4.3.1 Roughen the inside surface of F and the outside surface of G with coarse sand paper. Clean the inside surface of F and G with acetone. Using high-strength filled epoxy cement, attach G to the inside of F so that the centers of the 1/2" hole in the bushing and the hole in G are coincident. Allow cement to set until it reaches full strength. Screw N tightly into G; the threads will not match exactly, but it should be possible to engage enough threads so that N is secure. 2.4.3.2 Disassemble P, carefully removing the piezo electric spark device. Soft solder a 3" insulated wire to each of the piezo device electrodes; one is on the bottom and one on the side. Use high voltage insulation wire if possible. Care must be taken in this operation; the electrodes on the piezo device are made of a low-temperature alloy, and the plastic body must not be melted. Attach the piezo device firmly to the outside of F in such a way that it will not interfere with screwing F into E. The best technique for doing this is left as an exercise for the builder; when the prototype was built acrylic tubing and hot glue was used. Soft solder the ends of the wires to the base and tip of the spark plug. When the igniter is taken into a dark room and the plunger of the piezo device pressed, a spark should appear at the electrodes of N. Screw the igniter tightly into E. The cannon is now complete. A mount or carriage for the cannon is left as an exercise for the builder. 3.0 THE PROPELLANT GENERATOR The recommended propellant for the cannon is a mixture of hydrogen and oxygen; this can be produced by the electrolytic dissolution of tap water. Other mixtures such as oxygen or air and acetylene could be used but are not recommended because no experiments were done with them and cannon safety properties are unknown if they are used. A generator for the recommended propellant can be built as follows: 3.1 Bill of materials A 4 carbon blocks 4.5" x 1" x 0.25" * B An automobile battery, or: C A transformer with a 120 VAC primary and a secondary whose voltage will produce a DC voltage in the range of 12 - 15 when applied to D. The secondary should be capable of supplying 2 amps without undue heating. D 2 amp bridge rectifier. E A plastic bucket of about 4 liter capacity F A large funnel whose small end fits inside the neck of a 2 liter soda bottle. G Several 2 liter soda bottles H Several 2 liter soda bottle caps * - this is the one item that does not meet the "easily obtainable" criterion of 1.2 above. The carbon blocks used in the Model 2.0 prototype generator were obtained from a metals-and-materials surplus yard. Large carbon electric motor brushes probably could be used. A Model 1.0 prototype was built with brass electrodes, but the atomic oxygen produced by the electrolysis corroded them very quickly. 3.2 Fabrication Instructions 3.2.1 Electrode Array Wire the carbon blocks as shown in Figures 3 and 4. Wires can be attached to the blocks by drilling holes in them and holding the stripped ends of the wires in place with 6-32 nuts and screws. Coat the parts of the screws protruding aboce the carbon with hot glue or epoxy to protect them from corrosion. Assemble the carbon blocks into the array shown in Figures 3 and 4; note that the blocks are staggered to provide clearance for the nuts and screws. Assembly can be done by using short sections of tubing E as spacers between blocks, and holding the blocks together with rubber bands. (+)-------+-----------+ | | >| |<- - - -0.25" +-|-+ +---+ +-|-+ +---+ --- | | | | | | | | | | ^ | | | | | | | | | | | | o | | | | o | | | 1.0" | | | | | | | | | | | | | | | | | V +---+ +---+ +---+ +---+ --- | | (-)-------------+-----------+ Electrode Array - Side View Figure 3 (+)-------+-----------+ | | >| |<- - - -0.25" +-o-+ +-o-+ --- | | | | ^ | | +---+ | | +---+ | | | | | | | | | 0.125"- - - ->| |< | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 4.5" | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +---+ | | +---+ | | | | | | V +-o-+ +-o-+ --- | | (-)-------------+-----------+ Electrode Array - Top View Figure 4 3.2.3 Gas Collection 3.2.3.1 Cut a 2" piece of brass tubing L (see 2.1 above). Drill a press fit hole for this tubing into the center of one of the bottle caps of H. Press the tubing into the hole so that 1.5" projects from the top of the hole; secure the tubing in the hole with hot glue to seal the joint between tubing and cap. 3.2.3.2 Put the electrode assembly into the bottom of E with F arranged over it so that any gas bubbles rising from the electrode assembly will be caught by F. Fill E with tap water so that the level is slightly above the top (small end) of F. Fill a 2 liter soda bottle with water, and holding your thumb over the neck to prevent leakage, invert it into the water in E. Maneuver it so that the neck is under water and over the small end of F. 3.2.3.3 Electrical Connection Either the battery B or the transformer C and rectifier D can be used as the power source. Connect the (+) and (-) leads from the electrode array to the appropriate DC outputs of the power source. When the power is applied as shown in Figures 3 and 4 bubbles should form on the electrodes, rising through F into the bottle. 14.5 VDC across (-) and (+) should put about 2 A through the circuit and produce 0.5 to 1 liter of H2, O2 mixture per hour, using tap water with a resistance of approximately 15 K ohms. If water resistance is larger than this, add a small quantity (approximately 0.1 gm/liter) of NaOH to the water to increase conductivity. The two liter bottle of 3.2.3.2 should fill with the gas mixture in 2 - 4 hours, displacing the water in the bottle. It may be necessary to siphon water out of the bucket to prevent over-flow. When all the water is out of the bottle, put an unmodified cap H on it to retain the gas mixture. Place the bottle vertically for at least 1 hour, so the hydrogen will rise to the top. A bottle of gas should not be stored for more than about 72 hours; with time the hydrogen can and will diffuse through the walls of the bottle, lowering the power of the propellant. 4.0 LOADING AND FIRING THE CANNON It is recommended that eye protection by worn by the operator and by observers of the cannon. No open flames or other sources of ignition should be within 50' of the cannon during steps 4.4 to 4.7. Have a tennis ball and a 24" ram rod ready (a piece of 1.5" schedule 40 PVC pipe makes a good ram rod). 4.1 Make sure the safety bushing of 2.4.2.2 faces away from the operator and any observers. 4.2 Crumple a paper towel into a roughly tennis-ball-size spherical wad, and push it into the muzzle of the cannon to PVC bushing C. This wad will prevent the gas from dissipating through the wad and out the barrel of the cannon in step 4.5. All people except the operator firing the cannon should be at least 20' from the cannon, on the opposite side from the safety bushing of 2.4.2.2. 4.4 Losing as little gas as possible, rapidly replace the cap H on the mixture-filled bottle from 3.2.3.3 with the cap of 3.2.3.1. 4.5 Connect the brass tube on the cap of 3.2.3.1 to the brass tube on the soldered to the safety diaphragm of 2.4.2.1 with an 8 - 10" length of tubing F. Holding the bottle vertically with neck up, squeeze it to force the gas mixture into the cannon. When as much as possible of the gas mixture has been squeezed out of the bottle, remove the bottle and plastic tube and push the tennis ball into the muzzle of the cannon. Use the ram rod to push it down the barrel until it seats against PVC bushing C. 4.6 All the operations of 4.5 must be done without delays or pauses so that a minimum amount of propellant gas is lost through the wad and out the barrel of the cannon. 4.7 Aim the cannon; press the plunger of the piezo device on the igniter to fire it. -- ______ _____________ ______________________ ______ /\####/\ / / / / /\####/\ / \##/ \ /_______ / / _ ______ / / \##/ \ /____\/____\ / / / / \ \ / / /____\/____\ \####/\####/ / /____\ \_/ / / /_______ \####/\####/ \##/ \##/ / / / / \##/ \##/ \/____\/ /_____________________/ /____________/ \/____\/ agbrooks@teaching.cs.adelaide.edu.au