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My First Spudgun

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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My First Spudgun

Unread postAuthor: strangers » Sun Sep 02, 2007 1:39 pm

Just a few pics and the specs of my first spudgun.
The attached barrel is 4' of 1.5" SCH 40 PVC dwv.
The chamber is 18" of 4" SCH 40 PVC dwv.
The is ignition is camera flash circuit charged with a 9V battery, the main capacitor is dumped into a little ball of steel wool.
The chamber fan is rotatable and wired in parralell(SP?) with the charging circuit, each one has it's own paddle switch.
The second barrel for my gun is 5' of 1.5" SCH 40 CPVC.
4' Barrel with ghetto handle
Chamber with ghetto handle, the top switch is the firing switch, the bottom one is for the fan
Chamber close-up, the mass of grey ductape is the charging circuit, the gold thing is the 9V, the red and black things in the duct tape are alligator clips
My rotatable chamber fan mounted on a piece of pvc with paper clips
Ball of steel wool in between the electrode/screws
5' CPVC ping-pong ball barrel, the pic looks wierd because i edited it in paint to make it smaller
Edit: I forgot to ask the questions I wanted ask :D , is there a better way I can secure my ghetto handles because with the hoseclamps they slide around alot. Does my fan look to small? I've seen a lot of people say CPVC is dangerous, it should be fine though on mine right?, I've already made several shots with it and it hasn't failed yet. EVBEC said that my cannon should only be able to get 200 fps with a 100g projectile, is that laughably weak or just weak?
My next cannon I want to build will be a propane hybrid pingpong ball launcher, probable just running a 2x mix with compressed air and propane at enough to fill 8" of 4" PVC to 35 psi with 5' of 1.5" for the barrel, does that sound safe?
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Unread postAuthor: f.c » Mon Sep 03, 2007 2:41 am

post the pictures next time not just links to pictures otherwise youve done a decent job.
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Unread postAuthor: boilingleadbath » Mon Sep 03, 2007 12:19 pm

I'm going to presume that:
1) You used 1.5" as the barrel diameter (instead of the 1.59" actual diameter of sch 40 PVC)
2) The "200 fps" is a typo (with the real value being 300 fps)

When I use 1.59" as the inside diameter and load it with a 100g slug, EVBEC predicts 302 fps. (1.59" yields 313 fps)

Either way, this is 600 foot-pounds of energy or so... which is a fairly good amount of energy. (about 1/4th of what a .308/30-06/similar rifle will generate; about 1/2 of what your typical (.223) AR-15 will give you)
**************************

Otherwise:
1) the DWV chamber and barrel really shouldn't be used.

2) CPVC is pressure rated, and so won't rupture, but I wouldn't trust the glue joint. It's not a big issue in the current system, though, because all that might happen is the barrel falling off.
It's embarrassing, but not a major issue.

3) A 3.3x mix (filling the chamber to +35psig, which is what you described) wants, at the minimum, a sch 80 PVC chamber (in 4"). Some here will advise you to use metal.
A 2x mix (filling the chamber to +15 psig) could be done in pressure rated 4" without exceeding the pressure rating... but I wouldn't advise it, unless you have a remote firing system. And a barricade.
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Unread postAuthor: jimmy101 » Mon Sep 03, 2007 12:31 pm

Your hose clamps won't slip if you connect the handle to the chamber where you have a much nicer surface to work, instead of the junction of various pieces.
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Unread postAuthor: jackssmirkingrevenge » Mon Sep 03, 2007 12:34 pm

boilingleadbath wrote:When I use 1.59" as the inside diameter and load it with a 100g slug, EVBEC predicts 302 fps. (1.59" yields 313 fps)

Either way, this is 600 foot-pounds of energy or so... which is a fairly good amount of energy.


I think anyone who's ever been shot with a Colt '45 (370 or so foot pounds) would suggest that's a bit of an understatement ;)

Oh, and this is by far the ghettoest wiring setup I've ever seen, congratulations!
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Unread postAuthor: spud yeti » Mon Sep 03, 2007 12:41 pm

f.c wrote:post the pictures next time not just links to pictures otherwise youve done a decent job.

Please don't, it wastes my ADSL. Perhaps post one good picture, and have link to the rest.
Otherwise it looks like a pretty cool cannon.
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really good quote/phrase here
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Unread postAuthor: strangers » Mon Sep 03, 2007 2:42 pm

jackssmirkingrevenge wrote:Oh, and this is by far the ghettoest wiring setup I've ever seen, congratulations!

I'm shooting for the ghetto award.

@jimmy101: I can't put the hoseclamps their, they're too small.
@boilingleadbath: On the five-foot barrel, their is no glue joint, the barrel fits so tightly in the reducer and the MPT adapter, I couldn't pull it apart to actually glue it. And using SpudTool and EVBEC I figured that the real diameter is around 1.5922".

Did I mention it weighs 13 lb. and the recoil from a pvc rocket almost knocked me down? Does a 1.89:1 C:B ratio sound bad, I figured on my next one I should shoot for .89:1 ratio.
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Unread postAuthor: Blackett » Wed Sep 12, 2007 6:14 pm

1:1.5 is ideal.

anyhow, you definitely earned your ghetto award. seriously, project boxes,

if you used a high voltage ignition I am wondering how many times you would zap yourself
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Unread postAuthor: iknowmy3tables » Wed Sep 12, 2007 7:43 pm

yeah but the most ghetto ignition I have ever seen was a stick lighter pushed in a tight fitting hole and held by friction

and for that handle you should really cut the tee in half so you have a crescent shape resting on the barrel and not a circle that way it won't tilt
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Unread postAuthor: sgort87 » Wed Sep 12, 2007 8:04 pm

Oh wow, you are definitely deserving of a Ghetto Award. Here ya go man, it's all yours. http://www.launchpotatoes.com/images/ghettoaward.JPG

I'm sure it's a great launcher, but it can go for some cleaning up. :wink:
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<a href="http://www.launchpotatoes.com"><img src="http://www.launchpotatoes.com/images/uploads/logo2.PNG"></a>
http://www.LaunchPotatoes.com
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Unread postAuthor: singularity » Wed Sep 12, 2007 8:06 pm

about the barrel not being glued don't worry it will eventually come apart when your firing it one time. i built a cannon for my friend and forgot the glue the barrel (this was literally the second cannon i made and it was way before i found this site) anyway like the 20th time it was fired the barrel went flying removing the piezo from the rest of the cannon (it was housed in a handle connected to the barrel) so just expect your hand to be ripped from the front grip some time soon.
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be sure to check out my <a href="http://www.spudfiles.com/forums/ak-style-airsoft-vortex-gun-t10959.html">AK Styled Vortex Gun</a> and my <a href="http://www.spudfiles.com/forums/at-4-t9627.html">AT-4 Rocket</a>

upcoming projects... finalized clip fed BBMG and ball point pen sniper
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Unread postAuthor: strangers » Thu Sep 13, 2007 4:54 am

I need to find my camera so can post damage pics, and should I post this in the combustion showcase area?
I fixed my handle problem a generous helping of ducttape :D
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Unread postAuthor: Redcoat » Thu Sep 13, 2007 4:58 am

Can you please post a full pic of your gun?

-Thanks,

.
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Unread postAuthor: strangers » Thu Sep 13, 2007 8:36 pm

My camera sucks too much, see I'd have to get really far away to take a picture, then it would be very blurry, so just use you "imagination" to see what the whole thing would look like until I get my camcorder for my birthday, next year. Plus my camera circuit got fried so I have to get a new one this weekend, then solder wires to it, and I'm working on like three gluestick minis (is it bad to sell them for profit? or is it just the capitalist in me?), plus I've been drawing plans for friend for a basic breech loader, plus drawing plans for my pnuematic, and my hybrid. So there's a lot I've been working on.
That was a looooong post.
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Unread postAuthor: Blackett » Thu Sep 13, 2007 11:00 pm

yeah this should be in showcase.

on the good side, your fried camera could probably be used to make a flash ignition.
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