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Please help a nube.

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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Please help a nube.

Unread postAuthor: om3n » Wed Jan 27, 2010 12:40 pm

Hi guys, I have built a couple air guns now using sprinkler valves, but now I'd like to move onto something that can take more pressure. I've put an ungodly amount of pressure into my current 1" rainbirds (in excess of 300psi) but I'd like to make my own piston valve that can take that much pressure without fear of blowing stuff up.

The problem is that I can't find a good solid tutorial on how to make these valves. Maybe I'm just an idiot and can't find one on here, but I'm seriously just having a difficult time finding the information I desire. If someone could point me to somewhere, that would be great.

Thanks guys.

Just for fun, here is one of my current guns shooting marbles. I want to move onto bigger and better :)

http://www.facebook.com/home.php?#/vide ... 1491420897

Let me know if you can't see the video... it's from facebook. I'll post onto youtube later if no one can see it.
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 27, 2010 12:54 pm

Read through this first then let us know what you didn't understand. Once you understand the concept adapting it to the materials you have at hand is relatively easy.
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Unread postAuthor: jrrdw » Wed Jan 27, 2010 1:16 pm

I'm sure there are some Facebook users here so I'll let the link stay. For in the future use Youtube for your video's, no log in or registration is required with Youtube.

Welcome to Spudfiles.
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Unread postAuthor: om3n » Wed Jan 27, 2010 3:43 pm

jrrdw wrote:I'm sure there are some Facebook users here so I'll let the link stay. For in the future use Youtube for your video's, no log in or registration is required with Youtube.

Welcome to Spudfiles.


Alright, I will post the video on youtube and replace the facebook link later on- I hadn't thought about it being an issue, but I can now see how it could be.

And thanks for the welcome :) I've been lurking on this forum for a while, and there is a ton of great information and great ideas. I feel a bit overwhelmed already.

I will definitely begin reading the above link when I have some time. Thanks for the quick replies!
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Unread postAuthor: Hubb » Wed Jan 27, 2010 3:46 pm

What gets better than a sprinkler valve?...

jk - but if you're interested in more detail for these valves, check out my library (in my sig).
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Unread postAuthor: om3n » Fri Jan 29, 2010 5:39 pm

Ok, so I have read through the piston valves explained visually thread, and I feel that I have a comfortable idea of how they work. Now after the pressure chamber is pressurized, the second valve that is opened- do most people simply use a blow gun to vent the pilot area?

Now, the problem is I don't know exactly what to buy to build this device. Is there a nice list of specific parts available for me to read somewhere? Do most people have to fabricate the piston themselves, or is something standard used as the piston?

****EDIT****

duh... the link in the post above me is exactly what I was looking for. Thanks so much :oops:

So with this piston, how much pressure could I put it under?
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Unread postAuthor: McCoytheGreater » Fri Jan 29, 2010 7:24 pm

How much pressure is the material you're using rated at? That would probably be the deciding factor on how much pressure you'll be able to shoot your gun at.
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Unread postAuthor: Crna Legija » Sat Jan 30, 2010 12:29 am

this video on youtube is the same valve i use but i make a piston out of teflon

http://www.youtube.com/watch?v=vmxaI3_S ... re=channel
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Unread postAuthor: om3n » Sat Jan 30, 2010 12:34 pm

Ok, I think I'm going to begin making a materials list now. I just want to make sure of one thing though: instead of using the ball valve to de-pressurize the pilot area, could I use a blow gun?
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 30, 2010 12:47 pm

om3n wrote:instead of using the ball valve to de-pressurize the pilot area, could I use a blow gun?


It depends on various factors, namely your piston has to be a very good fit in the tube it's travelling in and there was to be a significant difference between the diameter of your barrel and that of your piston.
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Unread postAuthor: om3n » Sat Jan 30, 2010 12:52 pm

jackssmirkingrevenge wrote:
om3n wrote:instead of using the ball valve to de-pressurize the pilot area, could I use a blow gun?


It depends on various factors, namely your piston has to be a very good fit in the tube it's travelling in and there was to be a significant difference between the diameter of your barrel and that of your piston.


Ok, but could you explain why is this important? I guess I don't understand what the difference these factors would make.... wouldn't it have more to do with how quickly the pilot area is emptied, like wouldn't the ball valve theoretically empty the pilot area faster than the blow gun?
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Unread postAuthor: om3n » Sat Jan 30, 2010 12:59 pm

Also, hub, if you could explain a little more about how your piston works, that would be great. I'm looking at your 2" piston .pdf and I don't quite understand what it is- that can't be the piston that actuates in the T fitting because it's not round, right? Or maybe i don't fully understand how that particular piston works :? That can't be the entire assembly...

Also, I was considering making a hot-glue piston because I understand how it works, would you guys recommend against it? I would actually like to make the piston I found in hubs library if I could figure it out..
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 30, 2010 1:13 pm

om3n wrote:Ok, but could you explain why is this important?


When you open your pilot valve, air will start leaking past the piston from the main chamber into the pilot chamber. If air is leaking past the piston at a faster rate than is escaping from the pilot valve, your piston will never move. If for example your piston has o-rings and is airtight, even a pin prick could theoretically pilot it.

In this example the piston is cast epoxy and very tight so I could pilot it with a schrader valve.

As to the difference between piston area and barrel area, the larger the piston compared to the barrel, then the less pressure difference there has to be for the piston to start moving, so you can get away with a "worse" pilot valve.
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Unread postAuthor: om3n » Sat Jan 30, 2010 3:12 pm

Ok I think I understand now. I am going to build a larger scale version of this below and see how it turns out. Thanks for the help guys, I'm sure I'll have more questions in the future

http://www.youtube.com/watch?v=vmxaI3_S ... o_response
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Unread postAuthor: Hubb » Mon Feb 01, 2010 10:20 am

The document shows how to make the actual piston that goes inside of a tee or whatever. It does not go into detail on how the piston is placed into a tee. It is made from a 1 1/4" coupling, which is cylindrical.
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