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3" pressure-rated PVC

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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3" pressure-rated PVC

Unread postAuthor: dimwell » Sun Sep 06, 2009 3:04 am

I can't find 3" pressure-rated PVC anywhere locally, so I used 2" PVC and extended the chamber by a third to maintain volume.

Where do you buy your 3" and 4" pressure-rated pipe and fittings?
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Unread postAuthor: jmadden91 » Sun Sep 06, 2009 3:24 am

Mate you need to state where you are from, otherwise none of us can help you. Generally hardware stores and the like will only stock up to 2", and you need to get larger diameter pipe from plumbing supply stores.
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Unread postAuthor: dimwell » Sun Sep 06, 2009 3:28 am

^ Huntsville, Alabama, USA. Sorry.

I can't find a local plumbing shop that'll sell to me as a consumer. They're all business-to-business dealers. It's pretty frustrating.
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Unread postAuthor: MrCrowley » Sun Sep 06, 2009 3:29 am

You can buy large diameter fittings on www.mcmaster.com, it's reasonably priced.

edit:

Sometimes Home Depot and Lowes will stock larger diameter pipe and fittings, it depends on the store entirely. Otherwise, buy online if you can't find a plumbing merchant who will sell to you.
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Unread postAuthor: jmadden91 » Sun Sep 06, 2009 3:32 am

dimwell wrote:^ Huntsville, Alabama, USA. Sorry.

I can't find a local plumbing shop that'll sell to me as a consumer. They're all business-to-business dealers. It's pretty frustrating.


Lol that sucks, well like McCrowley stated, there are a number of online American stores that would probably be your best bet. Just google them
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Unread postAuthor: MrCrowley » Sun Sep 06, 2009 3:37 am

Oh and model your cannon in GGDT, it will probably turn out you wont even have to extend your chamber. Most members will over estimate required chamber size.

If you don't know how to use GGDT, just post your cannon specs and we can do it for you.
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Unread postAuthor: dimwell » Sun Sep 06, 2009 3:45 am

A friend of mine bought the t-shirt cannon plans from American Air Cannons, then commissioned me to build the thing. This is my first cannon build, but it certainly won't be my list. :twisted:

The plans called for a 32" barrel and 16" tank from 3" PVC, but I couldn't find any pressure-rated PVC. I went instead for 2" SCH-40 pipe on the chamber and adjusted the length on the chamber to roughly 30" to maintain volume. I made the barrel longer, almost on a whim, so that the barrel is about 3" longer than the chamber + valve.

I used non-pressure-rated 3" PVC for the barrel. Is that okay? I thought about wrapping it in duct tape to catch the fragments in case of explosion. I also added a 115 PSI safety valve to the chamber so I can evacuate the pressure manually if I have to.

For an idea of what the given plan creates:

Image

I swapped the 3/4" sprinkler valve for a 1" sprinkler valve, assuming that a wider pipe would increase airflow and thus increase the muzzle velocity of the shirt. Based on some light reading here, it seems that I have a decent understanding of the basics. :)

I fired it a few times and I'm pretty happy with the results ... esp for my first gun. I just feel like there are a lot of little improvements that I can make, but I'm not sure where/how to start.

I also had a problem with the sprinkler valve leaking air into the barrel of the gun. I managed to fix it, but I'm not sure what the problem was or what I did to fix it. I'll have to search around here to figure out how exactly that valve works so I can better understand the physics and mechanics involved.

Unfortunately, this thing is almost 4' long and after a few test fires, I feel like the air chamber is a bit too long. After the shirt leaves the barrel, I can still feel/hear some gas behind it.

I need to launch a shirt anywhere from 50 to 150 feet with a pretty decent arc (45-60 degrees?). I want to lob shirts into the crowd, not give the audience black eyes!

I'd like to redesign this thing with easily-accessible components (2" pressure-rated PVC, 3" or 4" non-pressure-rated), shorten the design, and get rid of the over/under configuration. A bazooka-style t-shirt launcher would be great, but I've yet to find one that uses 2" PVC for the air chamber.

I don't have GGDT installed yet (I'm on a Mac), but I will as soon as I get Parallels updated and running. Feel free to load it up yourself and let me know what you think.

Thanks. I have a feeling that I'm going to learn a lot from this place.
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Unread postAuthor: Willdebeers » Sun Sep 06, 2009 4:17 am

dimwell wrote:Thanks. I have a feeling that I'm going to learn a lot from this place.


I'm sure you will. :D

I frown apon AAC, with their overpricing and cheap ways of doing things, but you got the plans now, so here we go.

I am from the UK (as I brag about way to much :)) and here I get all of my PVC from either http://www.hendersons.co.uk or http://www.pipestock.co.uk. These are metric but I am proving that you can still get any pipe if you just look in the right place. For americans (lucky f**ks) you have a wide variety of suppliers, but http://www.mcmaster.com/# seems to be the most popular.

WDB
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Unread postAuthor: Technician1002 » Sun Sep 06, 2009 5:32 am

When designing t shirt launchers, It's OK to design for black eyes and then lower the pressure. I started with a 400 foot goal.. It's really hard to reach by the way. Got solid performance in the 325 - 350 range and then lowered the pressure. I didn't use a sprinkler valve. A sprinkler valve will be hard pressed to make the 150 foot range.

I just visited the American Air Cannons site to see what range they claim their launcher will shoot shirts. They only claim "into the crowd" for their MBTS-30. I'm not sure if that will reach 150 feet. For over 200 feet you will want a larger piston.

What range are you getting with t shirts and the 1 inch valve? A 1 inch piston valve cannon is able to reach about 200 feet at 90 PSI.
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Unread postAuthor: dimwell » Sun Sep 06, 2009 5:40 am

I was able to fire 2 shirts about 140 ft (150 ft after bouncing and rolling) at roughly 80psi and a firing angle of approx 40 degrees. I double checked the distance with Google Earth (we used a parking lot for that specific purpose).

I'm happy with the gun as it is. I'm just trying to make it more compact and would really like to replace the barrel with something that is rated for pressure.
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Unread postAuthor: spudamine » Sun Sep 06, 2009 5:42 am

I am from the UK (as I brag about way to much ) and here I get all of my PVC from either www.hendersons.co.uk or www.pipestock.co.uk. These are metric but I am proving that you can still get any pipe if you just look in the right place. For americans (lucky f**ks) you have a wide variety of suppliers, but www.mcmaster.com/# seems to be the most popular.


being in the uk does have it's advantages, for instance pipestock sell upto 4" pressure rated ABS, I'd like to see you get hold of that in the USA. :)
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Unread postAuthor: Willdebeers » Sun Sep 06, 2009 6:10 am

^ :D Yeah, the UK does have it's advantages.
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Unread postAuthor: c11man » Sun Sep 06, 2009 10:19 am

lol you bought the plans? how much did you pay for that? its a OK desighn i guess, to make it better move the sprinker to right behind the barrel, get a way bigger chamber ( same volume as barrel or slightly bigger, and dont guess, do the math).

in my opinion plans for spudguns are genarly worthless
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Unread postAuthor: Technician1002 » Sun Sep 06, 2009 11:18 am

c11man wrote:lol you bought the plans? how much did you pay for that? its a OK design i guess, to make it better move the sprinkler to right behind the barrel, get a way bigger chamber ( same volume as barrel or slightly bigger, and don't guess, do the math).

in my opinion plans for spudguns are generally worthless


Depending on the efficiency and power desired, it is perfectly permissible to operate a launcher that is stingy on air consumption. I lent my little launcher out to shoot t shirts at a benefit concert. It does just fine with a 200 foot range with about a 0.3 : 1 C/B ratio. It has a 54 cu in chamber with a barrel 2.7 inches ID 36 inches long. It did fine with the limited air supply they used. A larger chamber would only consume more precious air per shot and increase the cycle time. Small chambers charge fast.

:oops: Psst.. use spell check.
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Unread postAuthor: c11man » Sun Sep 06, 2009 11:51 am

for the chamber size i was going on more power. and are you sure that your barrel isnt slowing the shirt at the very end of the barrel? i dont doubt that your using at least 3/4 of the barrel but it seems just a bit too long.

and with a sprinkler vavle i dont think a .3:1 ratio would be very good. a sprinkler valve just isnt crazy efficent like the QDV
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