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Noob help

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Noob help

Unread postAuthor: alkapwn1 » Sun Oct 05, 2008 9:39 pm

Well I am new to spudguns and such and have decided to build my first.

I have perused the cannons sections and am collecting ideas

I plan to build a rifle type one, combustion, not massive (size of a real rifle, but bulkier) and just to fire small ammunition (about the size of marbles). I grasp the basic idea of how they work and the functionality of the parts but there are some questions I have.

1. Whats the importance of a fan in the combustion chamber, do I need it for this small a gun and wont it get blown up by the explosion?

2. Will high-temp hot glue and PVC cement work well for gluing and such?

3. Whats the minimum pressure rating I should be looking at when buying my PVC? I don't want to blow my face off.

4. For having a small chamber (compared to most) should I put two sparkers in the chamber? I know how to set it up.

5. The connection from the barrel to the chamber, is it just open? or some kind of inner tapering is required to make sure that the projectile doesn't fall into the combustion chamber?

6. Finally, to make a breech loader, would I just use a screw to connect the barrel and the rest of the gun together? or is there some kind of bolt type mechanism to load even faster? The bolt seems like it could have the risk of blowing apart or giving crappy performance.

I know its a lot of questions, but I would be very grateful for help with my first spud gun project. I will post my build also
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Unread postAuthor: CS » Sun Oct 05, 2008 11:27 pm

1 - A fan is used to both mix fuel and exhaust the chamber. I would recommend a fan in your cannon, and place the fan at the rear of the chamber.

2 - When combining PVC fittings and pipe use PVC primer and glue.

3 - Pressure ratings generally decrease with larger diameter pipe. Look for NSF-PW or NSF-61.

Before continuing I would suggest you read cannon construction and safety SpudFiles Wiki articles.

4 - Yes when your chamber becomes longer it is good practice to increase ignition points.

5 - Yes you probably want to implement something to stop your ammo from rolling back into the chamber. It can be as simple as a screw through the side of a fitting.

6 - You could just use a threaded connection for breach loading, or implement some type of bolt or similar mechanism. As to what type, well thats your choice. You need to read around and find out what will work for you.

As you noticed I already linked to the SpudFiles Wiki, but I would suggest you go through it when you get a chance. If you do you will be able to ask more specific questions and in return we can give you better answers. Best of luck.
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Unread postAuthor: starman » Mon Oct 06, 2008 11:00 am

Great questions alkapwn!! We want more like you. Welcome to Spudfiles.

Also, take a long look at the Burnt Latke site. It's the defacto reference for all things combustion gun....
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Unread postAuthor: alkapwn1 » Mon Oct 06, 2008 7:06 pm

Thanks! ill make a build on this because I have a neat idea for my breech loader. Im using a .5 inch PVC pipe for a barrel, Im not planning for big rounds. Ill make a potato cutter for perfect potato rounds
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Unread postAuthor: starman » Mon Oct 06, 2008 7:24 pm

alkapwn1 wrote:Thanks! ill make a build on this because I have a neat idea for my breech loader. Im using a .5 inch PVC pipe for a barrel, Im not planning for big rounds. Ill make a potato cutter for perfect potato rounds


Cool! Keep us posted on your progress.
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Unread postAuthor: alkapwn1 » Mon Oct 06, 2008 9:27 pm

for my size of gun, a section of 2" PVC pipe would be good with my small .5" barrel? (all the numbers are referring to diameter btw)

Nvm the 2" PVC, I have a new 80mm PC fan which i will trim to fit some (don't know how big yet) PVC pipe. Ill bring the fan with me while I shop so I can see how it would fit
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Unread postAuthor: alkapwn1 » Tue Oct 07, 2008 10:57 am

How do you get a pic on? Its saved on my comp do I have to put it on the net?
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