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Post questions and info about combustion (flammable vapor) powered launchers here. This includes discussion about fuels, ratios, ignition systems and anything else relevant to launchers powered by igniting things like hairspray or propane.

Postby boogieman » Mon Dec 08, 2003 1:53 pm

<h2><font face="tahoma,verdana,arial" color="#008000"><b>The SGTC Forum FAQ:</b></font></h2> <font face="tahoma,verdana,arial" size="1"> <p>The purpose of this FAQ is to limit some of the same questions. While every question is important, when one asks a question that has already been extensively covered, it becomes extremely annoying. Most of the members here are very helpful, and are willing to help solve any problem. Please take a moment of your time to read the FAQ and help alleviate the problem.<br><i>In no way is this FAQ meant to limit what you can post, it is just a guideline that will help reduce forum clutter.</i></p><p>The proper way to deal with any question is to do a search first. The search link is somewhat hidden, but it is in the top right corner of the screen. You can also access the search feature by clicking this link: <a href="http://forums.spudtech.com/search.asp">http://forums.spudtech.com/search.asp</a>. If you find a topic dealing with the same issues, reply to that post. Even if the topic seems dead, post there, as it is much less intrusive than making a new topic. For example, instead of making a new post to ask what type of barrel to use for a golf ball, do a search, find a topic to do with golf balls, and if appropriate, ask your question there.</p><p>Here are some posts/questions that come up way too often:</p><p>1. <i>Post your Pics/videos here:</i></p><blockquote> <p>This post, which comes up often is understandable. Many people, when first coming into spudgunning, want to see other peoples launchers, for ideas. <a href="http://www.spudfiles.com">http://www.spudfiles.com</a>, any member sites (click their signature pics or look at the profiles), or look at various sites on the spudtech link page: <a href="http://www.spudtech.com/content.asp?id=18">http://www.spudtech.com/content.asp?id=18</a>. If this doesn't help, try doing a search on Google, it's amazing how much stuff you can find!</p></blockquote><p>2. <i>I want spudgun plans/designs:</i></p><blockquote> <p>This question is considered by some, the most annoying question that could be asked. Again, do a search at Google, or go to the spudtech "build your own" page (<a href="http://www.spudtech.com/content.asp?id=5">http://www.spudtech.com/content.asp?id=5</a>). The consensus about this question is this: Look at a picture or a launcher you would like to duplicate. Honestly, you should be able to figure it out by looking, if you cant, you probably shouldn't be attempting to build it anyway. Read up on proper construction techniques and safety instead.</p> <p>If there is a particular launcher that you have a question about, post a picture of it, then ask what you want to know. If you cant post a pic, at least give us a link to the launcher.</p></blockquote><p>3.<i> The infamous "paintball gun or paintball sniper rifle" post:</i></p><blockquote><p>Paintball rifles are great, but don't ask the same thing everyone else does! This topic comes up usually one to four times a week. This causes much annoyance to regular/semi-regular members. I know of some people that actually leave the forum due to stuff like this! Do a search: <a href="http://forums.spudtech.com/search.asp">http://forums.spudtech.com/search.asp</a>. Don't ask for plans/pics/etc. The topic has been covered extensively!</p></blockquote><p>4. <i>"I want to test my paintball rifle on a friend." or "I want to make a paintball rifle that is safe to have a game of paintball with."</i></p><blockquote><p>While either question is understandable, the second is more admirable, at least it shows the person is safety conscious. A properly built paintball gun could be used on people, but before you do so, fully understand this: To make a paintball gun to compete in an actual paintball game would be suicide! Without spending much time and money to machine parts, there is no way you could compete. The loading/charging time would put you at a major disadvantage. You would be better off buying a cheap paintball gun.</p><p>Many of these guns are just not human safe! Lets look at a small gun with an air chamber built from 2" sch40 and a barrel of 3/4" CPVC. Our launcher will use a sprinkler valve that is pneumatically actuated. A tiny gun with a 3" long chamber (this is the pipe length, fittings are accounted for) and a 10" barrel will break 300fps at 100psi! It should do about 316 fps! This is barely human safe, most paintball fields would permanently ban you for speeds like this. Now lets keep that same 3" long chamber and add a 24" barrel (sniper rifles should have a long barrel after all!). The gun will now do 470 fps. NOT HUMAN SAFE!</p> <p>Believe me, these things are no joke, I made one which uses a coke bottle for a chamber, and at 160psi, I have chronied a paintball going 617 fps! The damage they cause is unreal. I was able to blow holes in a plastic 55 gal. drum with just paintballs. Look at the damage pics from my coke gun: <a href="http://www.advancedspuds.com/photo_020.jpg">http://www.advancedspuds.com/photo_020.jpg</a>.</p></blockquote><p>5. <i>What wadding can I use for a barrel with <b>x</b> diameter?</i></p><blockquote><p>There is a sticky in the ammo section dealing with this: <a href="http://localhost/forums/viewtopic.php?t=129">http://localhost/forums/viewtopic.php?t=129</a>.</p></blockquote><p>6. <i>What ammo can I use for a barrel with <b>x</b> diameter?</i></p><blockquote><p>Look at the ammo section: <a href="http://forums.spudtech.com/forum.asp?FORUM_ID=7">http://forums.spudtech.com/forum.asp?FORUM_ID=7</a>, do a search, or Google it! SpudFiles has one: <a href="http://www.spudfiles.com/Main/ammo.php">http://www.spudfiles.com/Main/ammo.php</a>, trust me, look around and you should be able to find ammo ideas relatively quickly! Note: there are many more sites dealing with ammo, those ones just came to mind.</p></blockquote><p>7. <i>How do I mod a sprinkler valve?</i></p><blockquote><p>Go to Tim B's how-to page: <a href="http://www.spudfiles.com/forums/viewtopic.php?t=305">http://www.spudfiles.com/forums/viewtopic.php?t=305</a>.</p></blockquote><p>8. <i>"Where do I find <b>x</b> material?" or "Where do I buy <b>x</b>?"</i></p><blockquote><p>This question is not too bad itself, but what is annoying is most of the time someone asks this in the wrong category. For example, don't ask where to buy propane cylinders in the combustion forum, ask in the construction material section: <a href="http://forums.spudtech.com/forum.asp?FORUM_ID=6">http://forums.spudtech.com/forum.asp?FORUM_ID=6</a>. Also note that most materials or parts can be purchased from spudtech, at <a href="http://www.plumbingsupplies.com">www.plumbingsupplies.com</a>, <a href="http://www.usplastics.com">www.usplastics.com</a>, or at <a href="http://www.mcmaster.com">www.mcmaster.com</a>.</p></blockquote><p>9. <i>What is C:B ratio, and how can I calculate it?</i></p><blockquote> <p>C:B ratio is the "chamber to barrel" ratio. It can be found simply by dividing the chamber volume by the barrel volume. For more info on C:B ratios, see latke's site at <a href="http://www.burntlatke.com">www.burntlatke.com</a>. He has extensive explanations of all things C:B ratio, and extensive testing dealing with C:B ratios.</p><p>If you don't have the time/patience/ability to manually calculate ratios, look at latke's calculator page for several calculation programs: <a href="http://www.burntlatke.com/calc.html">http://www.burntlatke.com/calc.html</a>, or I have one at <a href="http://www.advancedspuds.com/spudtool.htm">http://www.advancedspuds.com/spudtool.htm</a>.</p><p>With a combustion, anywhere from a .6:1 to .8:1 C:B ratio is ideal. This will get maximum performance/speed, but will make the gun quiet. Much of the noise of a combustion spudgun is from wasted energy. If you hear a boom, your gun is not performing to its fullest extent. The boom you hear is wasted energy, that could have been used to propel the projectile. C:B ratio can be fine balancing act. You must decide if you want noise (which IS a good thing!) or power, or a little of both. For a little of both, I would suggest a 1:1 ratio, or a .9:1 ratio.</p><p>The .6:1 and .8:1 ratio is a result of extensive testing by latke. What it means, is that with any gun, you will get the most performance out of a longer barrel. If you make a gun with a normal sized barrel, and a smaller chamber to get .8:1 ratio, you will have a very efficient spudgun, but probably not as powerful as a launcher with the same barrel and a 1.5:1 ratio.</p><p>For a <b>set barrel length</b>, the bigger chambered 1.5:1 ratio launcher would outperform a smaller chambered .8:1 ratio gun. In turn, if you took the same larger chambered gun and put a longer barrel on it (to make it a .8:1), it would shoot much faster than before. C:B ratios can be overwhelming at first, but give it time and they will make more sense.</p></blockquote><p>10. <i>"How long of a barrel should I make?" or "How big of a gun should I make?"</i></p><blockquote><p>If you are using combustion, look at the C:B stuff first. This will shed some light on the subject. Generally speaking with a combustion make the chamber good sized, and the barrel as long as you can handle.</p> <p>For a pneumatic, look at GGDT, A program made by thehalls: <a href="http://www1.iwvisp.com/thehalls/ggdt/">http://www1.iwvisp.com/thehalls/ggdt/</a>. This will help to answer your questions. </p></blockquote><p>11. <i>"How do I post pictures?"</i></p><blockquote><p>Go here: <a href="http://localhost/forums/viewtopic.php?t=999">http://localhost/forums/viewtopic.php?t=999</a>.</p></blockquote><p>12. <i>"The monthlyhow-to has been the same for a while."</i></p><blockquote> <p>Yes, it has, but Joel is a busy man. Tim B Has made 3 how-to pages. The first, on creating PVC Rockets can be found here: <a href="http://www.spudtech.com/content.asp?id=26">http://www.spudtech.com/content.asp?id=26</a>.
The second, on "souping up" sprinkler valves is here: <a href="http://www.spudfiles.com/forums/viewtopic.php?t=305">http://www.spudfiles.com/forums/viewtopic.php?t=305</a>.
The third, on creating a CO2 setup can be found here: <a href="http://www.spudfiles.com/forums/viewtopic.php?t=308">http://www.spudfiles.com/forums/viewtopic.php?t=308</a>. Thanks Tim, for creating these great how-to's.</p></blockquote>
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boogieman
 
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