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Spud4

In this episode of weekend projects, I make a spud gun and teach you how to make one too. In the process, I get hit with a potato, shocked by a stun gun, caught by security, and attempt to obliderate a pumpkin. How can you resist?

This video podcast was inspired by William Gurstelle’s article in Make 03. You can go to this blogpost to download a pdf with all the instructions to make your own “Tazer-Totter.” [Update: Testing a Digg button - please click it - pt]

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Comments

  1. monkeybbusiness@msn.com says:

    BEWARE: ABS IS NOT PRESSURE RATED. It can and eventually will fail over time. stick with pressure rated PVC!

  2. monkeybbusiness@msn.com says:

    BEWARE: ABS IS NOT PRESSURE RATED. It can and eventually will fail over time. stick with pressure rated PVC!

  3. moolcool says:

    hint: sand the end of pipe before glueing. also, isnt a tazer a bit overkill?

  4. moolcool says:

    hint: sand the end of pipe before glueing. also, isnt a tazer a bit overkill? Also, thats just a lil’ tater tosser.

  5. o-tang says:

    Just wanted to point out that these might not be legal in all countries, like in Sweden where I live for example. :( Apparently someone got arrested a while ago for firing one from his balcony (maybe not the best idea anyway). Well, it does look fun though, just make sure you wont get arrested for making one :)

  6. trebuchet03 says:

    ABS can be certified for to hold a pressure (which is the stuff I use). I guess there’s a debate over which is better – PVC or ABS?

    On one hand – PVC is readily available and its rating is stamped on the side (so easy to classify). It has a high tensile strength and is hard (aka: brittle).

    On the other hand – ABS is slightly more expensive and will fail by stretching (I don’t think ductile is the right word here). The rating is usually within a certification number stamped on the side rather than the pressure rating explicitly stated.

    Why I prefer ABS: ABS is resistant to the elements. Over time, ABS does not become brittle like PVC from exposure (and degeneration). I have yet to see anything about ABS or PVC fatigue curves – so I’m personally not worried about failure in that manner for either plastic.

    All that said, I’ve never had a PVC OR an ABS cannon fail on me from firing. However, I did have a PVC failure from an impact – it cracked. It was a pain in the butt, but it was repaired. In the end, you must ask yourself…. When this “thing” fails, how do I want it to do so?

    —-
    Oh, I’ve seen a plastic called ABSi. And from what I’ve been told at the local plastics co. It is available in a semi transparent color (or lack of color :P) but is pretty expensive.

  7. Bre says:

    Good point o-tang, always make sure to check local laws before making projectile hobby apparatus!

  8. hairyconiption says:

    USE ABS, even if it isn’t pressure rated. When pvc bursts it shatters and sends chunks of Plastic all over the place, when abs bursts (highly unlikely) it just sorta rips, no shrapnel. Also use old apples, they go about twice as far as any potatoe will (any not rotten potatoe)

  9. mechanisma22 says:

    I wanted to see it with clear PVC. Its cool to see how it works on the inside.

  10. mechanisma22 says:

    I wanted to see it with clear PVC. Its cool to see how it works on the inside.

  11. samurai1200 says:

    I’d recommend against ABS. A description of the production of ABS versus PVC is that ABS is a “whipped” version of PVC (though they are different: styrene versus vinyl, respectively), which turned me off when building my first spun cannon. This whipping thins out the material making it weaker (which is why it is often not pressure-rated while PVC is). You can actually look at the end of a cut ABS pipe and see the small “pockets” of air formed by the thinning process.

    Anyway, PVC can be found to be pressure rated very high (I used 430+ psi [sch120] material, while i remember some forum posting that standard combustion potato launchers do not exceed ~60psi), and is (in my experience) cheaper. Besides, in a high pressure system like a combustion cannon, the first thing thats gonna blow is your endcap (i’ve had this happen many a time… too much hair spray! nailed my brother right in the kneecap. it didn’t do him any damage, though. okay, maybe psychological, considering he didnt stand directly behind me while launching anymore!). Spudtech has some more relevant pros and cons to PVC vs ABS:

    http://www.spudtech.com/content.asp?id=14

  12. svofski says:

    Excellent project! Nice presentation too ;) Thanks.

  13. intheory says:

    As far as the pvc vs. abs debate, i’m uninformed, but i do know this. This project was made waaaaay more complicated by the use of a taser. A much easier (and cheaper) alternative is an igniter for a gas grill. They usually cost around $15 or less. This does require a slight modification to the overall design though.
    Instead of using a simple barrel for the combustion chamber, the piece which should be used has a small side inlet. Depending on the size of the inlet, the igniter can either be glued directly onto this inlet or a hole big enough to fit the igniter must be drilled into the endcap which the igniter would then be glued in to. Attaching the igniter on the side in this manner prevents potato debris from mucking up the workings. If anyone has any questions about this, let me know.

  14. trebuchet03 says:

    My problem with this page: http://www.spudtech.com/content.asp?id=14 is this:
    “If it [ABS] fails, it will fail. When it goes, it will turn into many little shards of sharp plastic that will invariably find you in some way.”

    That is exactly how PVC fails – ABS will stretch – PVC will crack into little shards. Here are two samples of PVC vs. ABS — notice the lack of sharp edges on the ABS sample.
    http://www.monarchplastic.com/QualityControl/qualitycontrol.htm

    —-
    “A description of the production of ABS versus PVC is that ABS is a “whipped” version of PVC…”

    ABS is a resin, just like PVC – I’ve never heard of it being whipped (say like cream to make whipped cream :P). I have also never seen pockets of air in my ABS (nor did I see anything in this video) – perhaps you got a bad batch? I have seen ABS extruded using power screws and molds (just like PVC :P). Processing is a big deal – but you really can’t compare how something looks to its strength properties. Margarine and plastic may be 1 molecule off (not sure – just an example) — but 1 molecule makes a huge difference :P

  15. Vrogy says:

    Good job Bre, after all these material-bashing comments, you’re obliged to make one from aluminum.

    Have fun with that :]

  16. sonicboy says:

    meth-elated spirits (100% alcohol) works much better and burns cleaner (no more sticky combsution chamber)

    put in a cap full and swirl it around to let it vaporize then BOOM!

    if the weather is too cold to vaporize, tip in a half cap, swirl it around and light it. this will burn for a few seconds and slightly heat the chamber ready for the first round.

    everyone uses CRC and spay can propellants, they are useless and messy.

    enjoy! and spread this info, I hate good spud cannons going to waste ;)

  17. Bre says:

    It turns out that you want 1.5x the volume for the firing chamber as you have in the barrell, so ya, it’s a tiny tosser… and it could have gotten more speed by having a longer barrell, but as it is there is a ton of muzzel flash and I like that!

  18. scottmclay says:

    I was inspired by the article in the magazine as well as your post, so I made one for my Thanksgiving project. I used a spare barbecue grill lighter for the igniter. Here’s a video of it:

    http://www.youtube.com/watch?v=B6906Be55Yo

    Here are few of my photos of it:

    http://www.flickr.com/photos/57023238@N00/

  19. Fergy says:

    Bit late on commenting on this, but we made one of these out of ABS in boy scouts a few years back, but it had a couple main differences. For one thing it was designed to launch tennis balls instead of vegetables, the biggest advantage of which is making the ammunition reusable. Also being tennis balls are rather flexible they can be loaded from the back hatch instead of needing to be stuffed down the barrel. Second like others we used an igniter from an old BBQ rather than a tazer and fashioned the button into a nice trigger to make it easy to fire. Our favorite propellant was starting fluid (ether), its a bit more expensive than hair spray, but it works really really well.

  20. Laquisa says:

    This instructions are provided by UltimateSpudGun.com.
    Ultimate Spud Gun is an online store for the modular Spud gun component systems and parts for potato guns.
    general spud gun example
    SIK-20 Standard Igniter Instructions

    These instructions are intended to help you build an effective yet simple spud gun (potato gun).

    1. These instructions/procedures are provided as-is.
    No guarantee is made that this device will function as well or better as I have experienced, intend, or describe it to operate. In other words, your results may vary, and they may even be very undesirable results, possibly resulting in personal injury or property damage. Please review the site disclaimer for more information.

    2. The wording and statements/nomenclature pertaining to the construction and operation of this potato launcher are intended as such to help ensure one attempting to do this has a basic understanding of the equipment and materials involved. If some of the statements seem ‘Greek’ to you or you do not recognize some symbols or phrases, that is wholly my intent, and you should obtain assistance from a trusted source or not proceed at all.

    3. These instructions are intended for a beginner or someone that has never built a spudgun before. The procedure outlined below is not necessarily the method myself or another experienced spudgun builder uses. These instructions will help guide you in building a “sound” piece of launching hardware. As you gain experience, you may find that different things may work better for you…. but start simple. Thanks, and happy spudding!

    potato gun imageKeep in mind that PVC pipe/fittings are not approved by the manufacturer to be used for the purpose of constructing spudguns.

    Step 1: Getting stuff to build spud gun (potato gun)

    This materials list is to build a very simple starter model potato launcher, with the intent to get the most bang from your buck (so to speak). By no means is this the only way to build a launcher, or nearly the coolest, but still able to provide hours of fun. Also, make sure to obtain pressure rated parts for building your spud gun. We do not recommend ABS or cellular core type pipe and fittings, these are not pressure rated and unsafe.

    MATERIALS:

    Obtain the following items:

    1. 12″ of 4″ SCH40 PVC Pressure Rated water pipe (chamber body)

    2. 48″ of 2″ SCH40 PVC Pressure Rated water pipe (barrel stock)

    3. 4″ PVC coupler

    4. 4″ x 2″ PVC bushing (if not available combine two, like 4×3 and 3×2)

    5. 4″ PVC FPT adapter (clean-out adapter)

    6. 4″ PVC MPT threaded plug

    7. PVC primer, one with dye in it if possible (purple, blue)

    8. PVC pipe cement, medium body is best

    The rest is provided with our SIK-201 kit.

    EQUIPMENT/TOOLS:

    Suggested tools for building the potato launcher:

    1. Hand wood saw (or hacksaw, for cutting pipe, maybe you already got it cut at the store)

    2. Wire stripper

    3. Terminal ring crimper (pliers can work)

    4. 3/16” Allen wrench

    5. 7/16 wrench

    6. Drill and Ѕ” drill bit

    7. Medium half round file for shaping pipe (or a lathe if you got one)

    8. Rag for PVC cement clean up (disposable)

    Step 2: Preparing the materials for assembly

    To make sure everything goes together properly and smoothly, proper conditioning and sizing of the materials is necessary. Pay particular attention to the shaping of the pipe ends, as this is a major factor in proper solvent welding with the fittings.

    PVC PIPE SIZING

    Cut the two pipes to size, 4” dia cut 12 “length and 2” dia. Cut 48” length with the saw unless you already did so in the store. Using the file, take off the sharp corners on the inside AND outside of the pipe. Radiusing the inside helps reduce the amount of potato scud that can build up in the launcher, and breaking the outside corner ensures proper solvent welding, if this is not done leak paths may result. Cut ends should be as square as possible. To one end of the 1 1/2″ pipe it is suggested that the inside be chamfered about 0.020″ and the outside filed or turned down to almost meet the inner chamfer, creating a blunt knife to help size the potato.

    PVC FITTINGS

    Inspect the fitting for really bad weld lines or possible large dislocations that may result in premature failure. Remove all paper tags or labels by peeling, scraping, even using a bit of primer to clean off the last adhesive. File off any sharp spurs that may hamper your ability to grip the fittings firmly when assembling.

    Step 3: Assembling the spud gun launcher

    I Chamber Assembly:

    Prime both ends of the 4″ pipe, also priming the 4″ bushing, both 4″ coupler sockets, and 4″ slip fit female adapter. DO NOT get any primer on the adapter threads! Immediately apply pipe cement to the three primed 4″ fittings, then LIBERALLY to both ends of the 4″ pipe. Start both the coupler and adapter fittings on the pipe, start the bushing in the coupler, then right the assembly with the threads up, pressing it together with body weight while twisting about 1/2 turn. Hold this position for at least 30 seconds. The pipe ends should bottom each about 1 1/2″ inside the fitting socket. If they both do not bottom, either apply more force IMMEDIATELY somehow to get it to, or you are screwed and have to throw it out–start over with that. If the fittings and pipe are properly conditioned this should not be a problem. Wipe up any spilled glue with the rag, but leave a good bead at the external pipe/fittings line. If any glue got on the threads get it out of there as fast as possible! Any glue on your hands should just be left to dry and then peel it off. Using solvent to remove it will just increase your exposure to it.

    II Barrel Assembly:

    Prime one end of the barrel and the 2″ socket on the bushing. If one end of the barrel was chamfered to a knife, prime the square ‘regular’ end of the pipe. Apply glue, liberally to the pipe, and press together, again using a 1/4 turn motion to bottom. Hold for 30+ seconds. After releasing place the unit upright for several minutes, to let the glue set a little more. Solvent welding is more of a curing than a drying process. Solvent is lost, hence the term drying, but the action of the solvent effectively cures all those individual plastic parts into one continuous physically joined piece of plastic. Properly done, solvent welds are always stronger than bulk pipe.

    AT THIS POINT AND FOR SAFETY PLEASE WAIT AT LEAST 24 HOURS FOR THE GLUE TO FULLY CURE AND SOLVENT TO DISSIPATE.

    If you are planning to paint your spud gun cannon, now is a good time

    III installing the electrodes

    The SIK-20 kit includes 2 electrode assemblies sized to be used where the coupling fits over the pipe. The over lap of pipe and coupling is 2” and we recommend centering the electrodes within the overlap area, 180 degrees opposing. Once you have the electrode centers marked you will need to drill Ѕ” holes centered on the marks and exactly opposing each other. At this point the tips should be touching. (Once the terminals are attached and jam nuts tightened the well nuts will expand and electrode gap will increase… See section V)

    IV Handle Assembly

    Push the handle ends on the aluminum tube until its seats to the bottom. Connect the modular interface from the MRS-201 ring set and the handle assembly using the 4 ј-20 x 5/8” socket cap bolts. Check the alignment on a flat surface. Place the ring arches on the barrel near where the barrel and chamber meet. Attach with smooth top rings and (4) ј-20 x 7/8” Socket cap screws and square nuts

    TAKE TURNS TIGHTENING BOTH SIDES SO THE OPPOSING CLAMPS HAVE EQUAL SPACNG BETWEEN THEM. PLEASE DO NOT OVERTIGHTEN. OVER-TIGHTENING CAN FRACTURE THE PVC. TIGHTENING WITH THE SMALL SIDE OF THE ALLEN WRENCH WILL PROVIDE ADUEQATE TORQUE.

    V Igniter / lead / electrode connection

    Insert the electrode assembly through previously drilled Ѕ” holes. Insert red button igniter through handle hole guiding the wires through and out the side facing the chamber. Size wires, remove insulation, slide on heat shrink, crimp on terminals slide heat shrink to insulate terminal and wire connection. Heat shrink tubing using a lighter or hair dryer. Connect igniter terminals to threaded electrode assembly in this order: washer – terminal – nut and tighten. The electrode assembly well nuts will expand in the hole and provide an airtight seal, tighten until ј” threads are above the nut.

    CAUTION – BEFORE CHECKING ELECTRODE GAP MAKE SURE CHAMBER IS EMPTY OF GLUE/PRIMER VAPORS.

    With chamber open and from a distance, look to check for spark jumping electrode gap. Your gap should be around 1/8” to 3/16” and produce a bright spark. If the electrodes are too close pull them out and file/grind of tips slightly to widen the gap. Once you have consistent spark its time to add the electrode covers (plastic cover with metal insert). Align over the threaded electrode end and gently tap on.

    Step 4: Using the launcher

    1. Now that you spark is verified, test fit the threaded plug into the adapter. It should engage the threads at LEAST TWO TURNS. If not, check for crud in the threads, and if clear, obtain a 60deg triangle diamond file, and size down the plug threads a little. The threads are at a 60deg angle, so careful filing. Usually filing the first few threads is ok.

    2. With the cap off, load a potato! With the chamber on the ground, place a potato over the muzzle of the spud gun launcher, and press it down with your palm, shaving off the excess, creating a cylindrical potato plug. Make sure the potato contacts the wall firmly all around, or it will not fire or not that well. Loading the potato sideways is acceptable, as it creates a more stable projectile anyway. Ram the potato down to within 2″ of the breech of the barrel, using a smaller diameter PVC pipe or broomstick. Don’t push it too far or it will fall out into the chamber…and just be subject to a short baking cycle.

    3. With the spud firmly seated in the breech, pick up the launcher and holding with one hand, dispense 1-2 seconds of Static Guardâ„¢ (hairspray works too) directly into the chamber. Don’t use too much; it will just make a mess. Quickly close by screwing on the end cap hand tight, do not use a tool to tighten to two turns or you will likely never get it off again.

    4. Call out “Fire in the hole!”, point the launcher in a safe direction, and depress the igniter button. That potato you rammed down there should exit at a quite rapid rate with a sizable report, and depending on where you aimed and at what angle you pointed, it went anywhere from 6 inches to ~200 yards from the muzzle. Pretty cool. If you clicked the igniter a few times and it didn’t work, you are not alone, check out my next section.

    5. If spud gun worked, great! Remove the end cap (this may require a tool), vent the spent gasses getting a fresh load of air, and repeat as necessary!

    Trouble shooting your spud gun cannon

    There are a lot of reasons why your spud gun launcher may not be working. First and foremost NEVER take off the cap and start clicking away at the igniter. This again has led to human fires and that chemical thermal hair removal thing again….

    Hairspray in cold weather just does not go well. Too much of the burnable stuff in the spray condenses on the chamber walls, making it very difficult to burn. You might consider a lighter, hotter fuel (propane….)

    To ‘defuse’ a misfire you need to take off the cap, while pointing it in a safe direction. Allow the chamber to air out for several minutes, perhaps longer, to get the fuel load out. After you are certain the fuel has been vented, again verify the spark, just by turning the chamber enough so you can see where the spark should be. Never point the chamber bore directly at your face, or body, or anybody else. If it sparks then it is a fuel mixture problem.

    One of the most common fuel problems leading to misfire is too much fuel! Not usually a problem with hairspray, other richer fuels can be overloaded above their UEL value, and they won’t work. Always try less fuel rather than more fuel.

    If you still can’t get it to work I invite you to peruse the many other web sites that talk about how to troubleshoot your combustion launcher. Spudfiles.com is an excellent resource.

    1. Nataly says:

      Just to make it clear it is ½” drill bit and 4 ј-20 x 5/8” is 4 ¼-20 x 5/8”. There are furthur misprints in the text: j is ¼”. S is ½”in many places.
      did you know that this is actually by Sureshot Inc. / http://www.ultimatespudgun.com?

  21. rich westington says:

    found a cool looking animation of a spud gun at http://www.spudgundepot.com

  22. rich westington says:

    found a cool looking animation of a spud gun at http//www.spudgundepot.com/

  23. rich westington says:

    found a cool looking animation of a spud gun at http://www.spudgundepot.com/

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