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Propane Injected Spud Cannon. Are They Worth Building???

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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Propane Injected Spud Cannon. Are They Worth Building???

Unread postAuthor: hansom72 » Tue Apr 22, 2008 3:11 pm

I have heard many negative things about propane injected spud cannons usually to do with multiple misfires. I have already bought a lot of parts for the propane meter, but hearing all of the negatives, I'm having second thoughts of even building one. Has anyone built a really successful propane injected spud cannon and is completely satisfied with its performance???? If so, I could use any constructive ideas or tips please!! Are there any benifits of a propane injected cannon besides a general hairspray cannon??? Do they have more power??? Any info is greatly appreciated.

Thank You
Hans
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Unread postAuthor: pat123 » Tue Apr 22, 2008 3:16 pm

They are much more reliable then a "spray and pray" gun. they will also be much stronger. please search first and use the wiki.
welcome to spudfiles.
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Re: Propane Injected Spud Cannon. Are They Worth Building??

Unread postAuthor: psycix » Tue Apr 22, 2008 3:47 pm

hansom72 wrote:I have heard many negative things about propane injected spud cannons usually to do with multiple misfires. I have already bought a lot of parts for the propane meter, but hearing all of the negatives, I'm having second thoughts of even building one. Has anyone built a really successful propane injected spud cannon and is completely satisfied with its performance???? If so, I could use any constructive ideas or tips please!! Are there any benifits of a propane injected cannon besides a general hairspray cannon??? Do they have more power??? Any info is greatly appreciated.

Thank You
Hans



Hairspray cannons have almost always too much or too less fuel. This makes the cannon unreliable: a big chance of misfires, loss of power and its also not easy to use.
Propane injected cannons have the following benefits:
-Faster, just a few ball valves open/close and your set.
-Powerful, the right fuel/air mix makes the most powerful shot
-Good fuel, pure propane burns better then hairspray
-Clean, hairspray clogs your cannon (and the spark gap electrodes), propane does not.
-Best benefit: No misfires. (if tweaked the right way)
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Unread postAuthor: JDP12 » Tue Apr 22, 2008 3:57 pm

how does a propane metered cannon have multiple misfires? it shouldn't if you do the math right first..

second off, please don't make multiple posts about the same topic- you have one pretty similar to this in SB15's cannon thread/.
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Unread postAuthor: DYI » Tue Apr 22, 2008 4:05 pm

I have one propane injected cannon, and it's never had a misfire.
Here it is.

They're a worthwhile investment, but for your own good, be careful about using them in or near inhabited areas. I ended up in quite a fiasco during my testing of the gun in the link (but it's all better now).
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Unread postAuthor: pat123 » Tue Apr 22, 2008 4:08 pm

I ended up in quite a fiasco during my testing of the gun in the link (but it's all better now).


I want to here a story :D
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Unread postAuthor: Ragnarok » Tue Apr 22, 2008 4:10 pm

pat123 wrote:I want to hear a story

http://www.spudfiles.com/forums/viewtop ... tml#176239
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Unread postAuthor: hansom72 » Tue Apr 22, 2008 4:54 pm

I understand that you have to do the math right the first time, except that math is my worst subject. I found a formula for finding the correct propane meter, except that it is kind of over my head. Is there any way you could just use the same length chamber and same length metering pipe from a known successful gun? Is there any specs that someone could share with me? I plan on posting pictures of my two previous cannons on a weekend when i have more time. I also have some destruction pictures for everybody i will upload too. I think you will like it. My 2'' barrel cannon will put a dent in a tin shed from 50 yards away and go right through 3/4'' plywood from 15-20ft away. Anyways I am looking for length measurement for my chamber and a correct length metering pipe to go with it. If anyone is willing to help me, I would greatly appreciate it. Thanks.
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Unread postAuthor: DYI » Tue Apr 22, 2008 5:04 pm

Here's a simple method that only requires grade 7 level math skills:

Volume of chamber (length*pi*radius<sup>2</sup>)*0.042 = volume of propane needed. (V<sub>propane</sub>/V<sub>meter</sub>*14.7)+14.7=Required meter pressure in psig. This should be at least 30 psig, and no more than 90 or so.

We're not going to tell you exact measurements, as it isn't safe. Operating a potentially dangerous device that you don't understand isn't something we can allow you to do.
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Unread postAuthor: NECROMANCER » Tue Apr 22, 2008 5:09 pm

i have a propane injected cannon, it works fantastic
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Unread postAuthor: STHORNE » Tue Apr 22, 2008 5:38 pm

do you plan on making your cannon from a "Straight" design, or an "Over-Under" design?
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Unread postAuthor: starman » Tue Apr 22, 2008 6:13 pm

Are they worth it? In a word, yes. Once you get the hang of it, you won't ever go back to a spray and pray.

Come on now, the math isn't that difficult...challenging at first yes, but a worthy expenditure of effort. See if you can find a math whiz friend to help step you through it....in any case YOU should calculate your own meter. That way YOU get to take credit for YOUR achievement.

Edit: Oh and propane burns into CO2 and water [and a tad bit of CO (carbon monoxide) depending on conditions and mix] leaving no residue....extremely clean fuel for spudding...:)
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Unread postAuthor: hansom72 » Tue Apr 22, 2008 6:50 pm

I Planned on making a "Straight" design at first, then as i was surfing the internet, I kept seeing all of the "Over Under" designs and i really like those. What is the difference between the two??? I will probably end up making my first propane cannon a "Straight" cannon. Hopefully graduate up to my second with an "Over Under." Why do ya ask?
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Unread postAuthor: STHORNE » Tue Apr 22, 2008 6:58 pm

just wondering...and i suggest you stick with over under...its size is more compact and the difference it performance isn't really noticable without measuring...
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