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hose connections

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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hose connections

Unread postAuthor: BCITRobotics » Thu Oct 09, 2008 9:09 am

Hello. I am part of a school project to build a pneumatic t-shirt launcher. We've been doing research on it for several weeks and have begun the building process. So far we have a 2 1/2 inch PVC barrel, at about two and a half feet long. However we have run into a problem. Once we get a cap for our PVC barrel, we will have no way to run a hose to it. The average PVC connectors are too large, because once we drill a hole for it, we will have no way to tap the hole in order to screw the connector in. Our main priority is safety, since this is a school project so we need a safe solution to our problem. Please Help!
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Unread postAuthor: jrrdw » Thu Oct 09, 2008 9:14 am

Post a diagram drawing from MSpaint or a picture of your hose connectors and hose. Also use the Wiki button up top and the showcase section for referance's.

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Unread postAuthor: mark.f » Thu Oct 09, 2008 9:26 am

So why do you want a flexible connection to the barrel?

If you are dead set on it, you could take a look at Sgort's proton pack.
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Unread postAuthor: BCITRobotics » Thu Oct 09, 2008 9:41 am

We have a surplus of flexible tubes
link to the connection we are using . . . top left and center left
http://www.global-b2b-network.com/direct/dbimage/50335196/Pneumatic_Fittings__Metric_Tube_with_BSPT_Thread_.jpg
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Unread postAuthor: psycix » Thu Oct 09, 2008 1:20 pm

You want to feed air to the barrel by the way of an hose?
You either need a large diameter hose or else you will have alot of flow restricion and your cannon will perform poorly.
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Unread postAuthor: BCITRobotics » Thu Oct 09, 2008 4:45 pm

This is true and will be taken into consideration. however, no matter what we use to supply air to the barrel, we dont know how to connect it to the barrel. We kind of figured that by loading our ammo (in this case t-shirts) close to the end of the barrel and by packing it tightly, pressure would build up behind the shirt and then fire it out when the pressure exceeded the frictional force needed to get the shirt out of the barrel. We have a smaller version built already in "gun" form. It consists of a modified pneumatic piston, about one and a half inches in diameter, connected to a small air tank, by way of our "small" tubes. It fires small towels about twenty feet. We have concluded that all we need to do is increase the size of everything (proportionately of course) and it would work the same, if not better hopefully.
So all I need to know right now is what I should connect to my barrel as a hose and how to connect it.
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Unread postAuthor: rp181 » Thu Oct 09, 2008 4:51 pm

use a threaded busing and a hose barb.
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Unread postAuthor: BCITRobotics » Mon Oct 13, 2008 10:03 am

Are there any ways of doing this without having to drill the PVC. we dont want to compromise the structural integrity of the PVC. we are considering using a female adapter. Is this a good choice and if so how could we secure it to the barrel.
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Unread postAuthor: starman » Mon Oct 13, 2008 10:26 am

I'm not sure why you're so intent on using that hose system. Just because you have a surplus of them is no reason to use them. I can't see lots of success using these.

There are many examples of sprinkler valve T-shirt cannons to be found in the cannon showcase. There will be plenty of flow and you'll have standard threaded connections to work with.

Also, it's perfectly ok to drill and tap a hole through 2 layers of PVC, usually where a fitting or coupler slides over pipe. Use a 7/16" drill bit and a 1/4" NPT tap available from any hardware store, about $10.

I know, you've probably never tapped a hole in your life....it's easy to do in PVC. You'll wonder why you haven't done it before. I would suggest a practice hole on some scrap material and because the tap is tapered, don't ream the whole distance of the tap, you'll make the hole too large. Stop about 2/3 - 3/4 (or so) up the length of the tap. Use a drill press if you have access to one to drill the 7/16" hole as cleanly as possible.

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Unread postAuthor: psycix » Mon Oct 13, 2008 1:20 pm

Usually you dont even need a tap to tap into PVC when using metal parts.
The threads of any metal adapter are strong enough to thread PVC.

But yes, using a REAL tap unit will yield higher quality threads with less chance of leak.
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Unread postAuthor: DYI » Mon Oct 13, 2008 2:22 pm

Now I'm not sure that I completely follow what you're trying to do here, but what kind of main firing valve are you using, and how much pressure?

Gort's Proton Pack, modified to pneumatic operation with a backpack tank and a barrel sealing piston valve should perform fairly well, as long as you use a large enough diameter hose.
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Unread postAuthor: BCITRobotics » Tue Oct 14, 2008 9:32 am

I am in an engineering class and we tap holes all the time. The problem was that we didnt have a tap large enough and not that we didnt know how to do it... we might consider using the threads from the adapter, now knowing that we can do it. I will also try to convince my teacher to use solid connections instead of flex tubes. my next question concerns the trigger. we have one of the ones on the front page... the one attatched to the modified sprinkler valve. we know that it has an adjustable restrictor on it but we dont know how to change it. (I'm just going by what I've been told about it.) What do we do to allow more air through and, is it even a good idea to use it
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Unread postAuthor: Carlman » Tue Oct 14, 2008 10:15 am

need a diagram to help further mate :wink:
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Unread postAuthor: EphOph » Tue Oct 14, 2008 11:48 am

You could use a couple of these:
<img src="http://www.flexpvc.com/cart/picserve.cgi?picserve=/672-4260.png">

Put one on the chamber and one on the barrel, and then connect them by using bushings and then threading your hose connectors in. This way, you'll maintain a flexible connection but have a higher rate of flow than a single length of hose can provide.

P.S. Don't take the pressure on those hose fittings too high. When I bought some to make a propane meter, I was told they are rated for 150psi.
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Unread postAuthor: BCITRobotics » Tue Oct 14, 2008 5:08 pm

will larger pneumatic hose still restrict airflow. if so we have another design that may replace our last. link http://toolmonger.com/wp-content/uploads/2007/11/post-cannon.jpg
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