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Combustion or Pneumatic

A place to ask general spud cannon related questions.
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Combustion or Pneumatic

Unread postAuthor: FeLeX » Tue Mar 13, 2007 9:00 am

I was browsing these forums the other day and I saw some ones picture, it has Linux holding Quake 3 rocket launcher. So I came up with an idea to make a replica of Quake 3 spudgun. I am planning on making the spud gun itself and then making a plywood casing that looks just like the rocket launcher and then putting the gun itself inside. Now I have some questions for you. Should tha barrel be diameter of golf balls or tennis balls and should I make it pneumatic or combustion. If its going to be combustion I am planning on making propane injection and having a fan, maybe stun gun too. I have about 80 dollars to spend on this thing and I think I am going to put it up for competition.
Sorry if its hard to understand my english is kind of crappy, I am from Russia. By the way, this is probably the best SpudGun website out there.


Heres the pic tell me that you think. Sorry it took me so long, I broke my foor on friday trying to do a 6 foot drop/gap on my BMX. Ive heard you can make a good piston for a 3" pipe if you find a cap that fits loosely in it and wrap it in duct tape and put neoprene on it for sealing.

http://www.putfile.com/slimak47
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Last edited by FeLeX on Mon Mar 19, 2007 5:57 pm, edited 1 time in total.
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Unread postAuthor: mega_swordman » Tue Mar 13, 2007 9:25 am

Your english is fine. Much better than some noobs on this site. It all depends on what you are most comfortable with in building. I personally would do a coaxial pneumatic cannon for a bazooka-like cannon.
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Unread postAuthor: joannaardway » Tue Mar 13, 2007 9:51 am

Your english easily beats some of the people on here who speak/write it as a first langauge (shame on them).

One thing that would improve your posting is line breaks, because solid text blocks are a little daunting to read.

It could be optimistic to expect a propane metered cannon with a reasonable set of extras to cost at $80 or less - but I have little idea of how Russian prices are at the moment. A simple pneumatic (with a piston valve perhaps) might hit that budget.

As a choice between combustion and pneumatic, it's all about the advantages of each. There are enough threads comparing the two, so just search a little, and I'm sure you'll be able to dig up some info on each to allow you to decide.

Your diameter depends on what ammo is available to you. But if both are equally available and similarly priced, then I'd choose golf balls, because golf ball diameter is also good for spuds as well, whereas tennis ball diameter is not hugely useful for other ammos.
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Unread postAuthor: FeLeX » Tue Mar 13, 2007 1:49 pm

^Hey I got the Idea from your Icon. Thanks!

Well the only major difference that I can see between Pneumatic and Combustion is that pneumatic is usualy much more powerful. But Burntlatke states that combustion can also be as powerful.

I am going with the golf ball diameter. I think it would be a litle more powerful than tennis ball. I live in America and the only thing that bothers me about combustion is the noise it makes. I got called cops on twice already, but lucklly I didnt get caught. I like combustion more because of the kick back and they for some reason look more powerful to me all though I know that they arent.

I also could go pneumatic as easily because I have a modified sprinler valve. I dont think I really understand how coaxile works and Ive looked at them many times, maybe Im just stupid and I dont think I am that good to make something like that work. I have tried making piston cannon a while ago and that never worked out. Are coaxiles easire to make?
The only thing is that I dont have a compressor I only have a regular bike pump, does that mean that my cannon wont be powerful at all?

Thank you very much for all your help.

PS: Where can I buy QEV, I am making a copper rifle. I tried looking at mcmaster.com and I never found anything. I am trying to get a valve like the one that Hotwired used on his awesome gun.
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Unread postAuthor: MrCrowley » Tue Mar 13, 2007 2:15 pm

I say go pneumatic.....But thats just me. If you want it to be really realistic go combustion but pneumatic should be more powerful.
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Unread postAuthor: FeLeX » Tue Mar 13, 2007 2:18 pm

Well I just watched a video at bcvids on how to make a barrel sealing valve and It looks reletively simple and its pretty cheap. The only proble is how am I going to fit all that in the case.
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Unread postAuthor: joannaardway » Tue Mar 13, 2007 3:45 pm

^Hey I got the Idea from your Icon. Thanks!

Glad to be of service.

Well the only major difference that I can see between Pneumatic and Combustion is that pneumatic is usualy much more powerful. But Burntlatke states that combustion can also be as powerful.

It can, but normally a pneumatic will beat combustions for power.

I am going with the golf ball diameter. I think it would be a litle more powerful than tennis ball. I live in America and the only thing that bothers me about combustion is the noise it makes. I got called cops on twice already, but lucklly I didnt get caught. I like combustion more because of the kick back and they for some reason look more powerful to me all though I know that they arent.

Noisy combustion cannons usually have an overly large chamber. Decreasing chamber size or increasing barrel length will dampen the sound.
Pneumatics can also be very noisy, but that really depends on the pressure that you use.

The sound is an important factor in how powerful a cannon is percieved to be. To use cars as an example:
You have two cars, which are identical in performance. However, one makes much more impressive engine rumbles. If you took someone out in each of them, and then asked them which was quicker, they'd almost certainly say the louder one.

Combustions are typically louder, so the mind percieves it as more powerful.

I also could go pneumatic as easily because I have a modified sprinler valve. I dont think I really understand how coaxile works and Ive looked at them many times, maybe Im just stupid and I dont think I am that good to make something like that work. I have tried making piston cannon a while ago and that never worked out. Are coaxiles easire to make?

Co-axials aren't that hard to make. When you're starting out, you'll need to be careful making it, but judging by your posting level (it is interesting to note that post quality and construction skill are very strongly linked) I reckon you could do it. They're pretty much modified barrel sealers.

The only thing is that I dont have a compressor I only have a regular bike pump, does that mean that my cannon wont be powerful at all?

Not at all. The pressure is the important factor, and normally similar pressures can be created from both methods. Actually, if you've got a track pump, you can usually get better pressures from it.
The only performance issue is how quickly you reach that pressure - but if you're not going for rate of fire.

Thank you very much for all your help.

PS: Where can I buy QEV, I am making a copper rifle. I tried looking at mcmaster.com and I never found anything. I am trying to get a valve like the one that Hotwired used on his awesome gun.

They can be found on Mcmaster. They are well hidden, but they are there. It's not possible to link to pages within Mcmaster, and I can never remember the part code, so someone else will need to enlighten you.
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Unread postAuthor: risto » Tue Mar 13, 2007 3:52 pm

i'd go combustion:

-recoil
-explosion
-looks more Quake-ish

i agree that pneumatic should be a first choice, but in my opinion, not for what he wants to do. He wants to replicate a Quake cannon, and there was never a Quake Air Compressor. I think the look of an explosion used for shooting a golf ball would be much more realistic in Quake-terms
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Unread postAuthor: FeLeX » Tue Mar 13, 2007 7:48 pm

joannaardway-Thank you alot for all the information. I am leaning more towards penumatics because of low cost. Ive found a portable 200 psi air compressor that runs off a motorcylcle battery and I could put all that into the cannon so it would be somewhat semi-auto.


risto-You do have a point there but the two reasons I am leaning towards Air cannon more is because combustion are mostly loud and it will probably cost me around $100 to build one.
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Unread postAuthor: risto » Tue Mar 13, 2007 7:53 pm

yeah, if you break it down, you're probably going to pay an extra 20-30 dollars for a muzzle flash, basically.
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Unread postAuthor: FeLeX » Tue Mar 13, 2007 8:02 pm

But still I think combustion would so much cooler, it would have a kick back and all that but yea I am making it air powered. Now I have to decide whether I am going to give piston a try again because if I do coaxile I wont be able to properly fit it.
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Unread postAuthor: kf4oij » Tue Mar 13, 2007 10:46 pm

Explosions are definatly cooler in my book, but a high tech looking pneumatic would be sweet too...
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Unread postAuthor: Recruit » Wed Mar 14, 2007 2:16 am

I know put an ignitor on the front so it stays lit and when you pump it up first put just a little fuel in the chamber or behind the ammo (if you have a burst disk) so when it fires the fuel hits the ignitor throwing or beltching (what ever the word is that you want to use) a fire ball.
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Unread postAuthor: FeLeX » Thu Mar 15, 2007 7:40 am

I decided I am going pneumatic. I have drawn a diagram on a piece of paper but I dont have a printer so as soon as I get to draw one in paint I will post it.
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Unread postAuthor: FeLeX » Mon Mar 19, 2007 6:03 pm

Ive put the link to my diagram up at the top.
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