SpudChucker1

Post questions and info about pneumatic (compressed gas) powered launchers here. This includes discussion about valves, ratios, compressors, and anything else relevant to launchers powered by compressed gas.

Postby pcitizen » Thu Aug 14, 2003 11:21 pm

Greets,

I have just finished the first cut on my first spud laucher. I prototyped it, then built the model you can see at the links below. It has one mod left, but afterwards it will be done. This hummer really sounds off with a crack. It doesn't report with the obvious increase of your standard ballvalve cannon - quite the opposite. It lets go with a distict, high pitched bang... and really good after effects water vapor. The cannon consists of about 1274 cuin chambers feeding into a 2" barrel through a pneumatically operated 2" ball valve. The pneumatically operated ball valve is driven by a 2" id piston pushed by a about 20 psi from a secondary air chamber. The cannon is triggered through a sprinkler valve that lets go the 20 psi to push the piston that opens the valve (really fast) resulting it an impressive firing. It works great.

Since this is my first cannon, please provide ample comment and criticisms.

http://members.cox.net/spudwerx

I hope to post a little MPG this weekend - weather permitting.

Jeff
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Postby someguynamedchris » Thu Aug 14, 2003 11:47 pm

That looks nice. How fast does the ball valve opean?

Chris
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Postby pcitizen » Thu Aug 14, 2003 11:53 pm

I don't have a method to measure it speed but I would guess from 0 to 90 degrees (max) less than a 10th of a second. It snaps open. During testing, it makes quite a poping noise from the piston hitting home. It truly moves fast.

Don't get me wrong... it's no SUPAH valve, but it'll run a close 2nd or 3rd and is multitudes faster than opening it by hand or with a rubber mallet.

Jeff
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Postby pacogoatboy » Fri Aug 15, 2003 8:50 am

that is very cool. a great job, especially for your first! i love the idea of pneumatically actuating the 2" ball valve. the articulating arm on the piston is a particularly nice feature. is it a pvc valve that you are using, or brass? the only problem i can see is that the thing really isn't too scalable. this would be incredible for a platform gun, but i don't think it is too practical for the average backyard spudder.

just out of curiousity, how long is your barrel? also, why is there a tee on the end of it? (at least, that's what it looks like in the third picture.) is the bottom of the tee cut out, to give the barrel a tank cannon look, or are you planning on hooking it into multiple sub-barrels?

the only aesthetic problem i see is the piece of lumber holding the barrel up. you could replace that with a length of PVC and grind out an arc into the end of it so that it matches the rest of the gun. or maybe use two metal rods that lead down toward the ends of the chambers. it isn't a real problem, just a small incongruous part of a very nice looking gun.
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Postby FoxxLord » Fri Aug 15, 2003 9:09 am

I think it looks bad-ass man! Clever.
I wish all the newer spud gunners would be able to stuff like that instead of cheezy paintball sniper rifles...[:0]
Did I just say that out loud?

-FoxxLord
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Postby pcitizen » Fri Aug 15, 2003 10:06 am

That barrel in the picture is 72 inches long and 2" dia. The T on the end was mainly for looks as it impressed the pizz-whacky out of my son. The side affect is that it changed the resonance of the tube when it fires.... much better CRACK! The end is cut out to about the OD of the barrel.

As for the piece of lumber. Yes... it is getting replaced. I was working on the last night. The problem is that I have several barrels for this hummer so the prop has to be different for each. Here is the list.

84" x .75"
72" x 1"
84" x 1.25"
84" x 1.5"
72" x 2"
60" x 3"

I am testing each at similar pressures to see the effects of the different barrel and projectile weights.

jeff
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Postby Freefall » Fri Aug 15, 2003 11:51 am

That has got to be about the sweetest looking ball-valve gun I've ever seen! It's nice to see some craftsmanship go into a project.
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Postby pcitizen » Fri Aug 15, 2003 1:58 pm

Thanks for the comps.

More about SpudChucker1. It is a PVC ball valve. As you probably know, PVC valves are pretty tight and hard to turn fast - especially big ones. I tried soapy water and graphite lock lubicant to help loosen it up. Nothing really worked well.

The prototype (this basic cannon) was fired using a large rubber mallet by striking the paddle on the valve. It worked really good, but it was difficult to hit the thing squarely, hold the cannon, and watch the launch. The piston idea came to me and there you have it.

I spoke of a final mod previously. As you might be able to see in the pictures there are two compressor hose fittings and two guages. I have parts on order that will allow me to fit the cannon with a small regulator off the main tank that will be used to pressurize the small tank. I think it will work nicely. I will post pictures of that when it's done.
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Postby pacogoatboy » Fri Aug 15, 2003 3:36 pm

nice. i wish i had good enough build skills and discipline to create a gun that sweet. unfortunately i am easily distracted and tend to get impatient and just finish a project quickly instead.
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Postby dd13 » Fri Aug 15, 2003 4:24 pm

wat did u use as a piton to activate the ball vvalve?
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