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1st air gun, copper, 160 psi, boom.

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: air_dannon » Sat Jul 27, 2013 2:43 am

Ok, lesson learned with shock pumps... not fun.

I like the Giyo suggestion, JSM, but I'd rather it be higher than 260psi. Am I right in thinking pumps go up to around 260psi (because that's the top for bike tires) and then the next leap is air rifle pumps at 3000psi?

I'd like 400-500psi, and was wondering if there is a low-end air rifle floor pump that you guys have used that might be worth the extra dollar leap from the Giyo?

Do they even make Schrader valve connectors for those air rifle pumps?
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Unread postAuthor: jackssmirkingrevenge » Sat Jul 27, 2013 3:06 am

Do they even make Schrader valve connectors for those air rifle pumps?


Not quite, you'd need a series of adapters.

The cheapest option would be to build your own: http://www.spudfiles.com/forums/easy-st ... 13277.html

You might want to consider a fridge compressor though, potentially cheaper and much less effort ;)
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Unread postAuthor: air_dannon » Sun Jul 28, 2013 3:40 pm

Ok, I'm gonna try the stirrup pump suggested.

I'll probably have questions and I see that post is not for help-me's... Is there a help forum for it?

Initial question:
Do I need to use the Bondo Resin, or can I use some Loctite 5 min. epoxy to fill the copper mold?
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Unread postAuthor: jackssmirkingrevenge » Sun Jul 28, 2013 10:01 pm

air_dannon wrote:I'll probably have questions and I see that post is not for help-me's... Is there a help forum for it?


The forum is not for help-me threads, but you can certainly post questions within the threads if you have any difficulties.

Do I need to use the Bondo Resin, or can I use some Loctite 5 min. epoxy to fill the copper mold?


I doubt it will flow sufficiently to fill the mould, does it have liquid consistency? You could use something like epoxy putty though, push it in at this stage then add the second nut and washer to seal it in.
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Unread postAuthor: air_dannon » Tue Jul 30, 2013 6:20 pm

What's a descent 0-600 psi gauge for the stirrup pump? I see ones with glycerin and different stem mount sizes.

How's this one? http://www.northerntool.com/shop/tools/ ... 739_357739

Also, what is the variable that makes a pump be able to offer higher psi? Meaning, Gipetto said he feels his pump design is good-to-go at 400psi, but what would it take to offer 500 psi? Thicker tubing? Or is it all about the piston?

Thanks!!
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Unread postAuthor: Gun Freak » Tue Jul 30, 2013 8:23 pm

The smaller the piston, the higher the pressure you will be able to take it to. The limiting factor is your weight, so you can do some calculations to find out how high you will even be able to pump before designing your pump. As piston diameter increases, so does the force needed to pump. So as you can see, there is a negative trade-off either way you go with piston size, because a smaller diameter pump will take ages to reach its max pressure, while a larger diameter pump will quickly reach its max pressure but it will be low.
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Unread postAuthor: air_dannon » Tue Jul 30, 2013 11:11 pm

Thanks, Gun Freak. What is the equation to see how high I can pump?
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 31, 2013 12:43 am

pump tube radius (inches) x pump tube radius (inches) x 3.1415926535 x intended pressure (psi)

The result will the the weight in lbs you have to push on the pump to get the required pressure.

For example, say you have a 1 inch piston head and you want to get to 200 psi:

0.5 x 0.5 x 3.1415926535 x 200 = 157 lbs

Not really practical.

Scaling the piston head to half inch we get:

0.25 x 0.25 x 3.1415926535 x 200 = 39 lbs

By halving the diameter, we get a lot less effort to pump, only 25% of the original in fact. However, we are moving a lot less air too, so instead of one stroke it would take us four.

Basically, the smaller the diameter of the tube, the more pressure you can achieve with less effort per stroke, but you will have to use more strokes.

What's a descent 0-600 psi gauge for the stirrup pump? I see ones with glycerin and different stem mount sizes.


Consider getting yourself one of these little button gauges, very cheap on eBay and quite reliable in my experience.
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Unread postAuthor: air_dannon » Sat Aug 03, 2013 10:34 am

Hey Guys,

In the stirrup pump pic... what is the hose attaching setup there? I'm trying to figure out what kind of hose to buy for the pressure and how to attach it to the piping.

Thanks!
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Unread postAuthor: jackssmirkingrevenge » Sat Aug 03, 2013 10:41 am

http://www.ebay.com/itm/New-Paintball-C ... 5af1956ecd

For just over 20 bucks you get a hose, check valve and male/female quick connect, fittings are normally 1/8" NPT.
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Unread postAuthor: air_dannon » Sun Aug 04, 2013 10:20 pm

Thanks for the suggestion, JSR. I may go that route. Question about the DIY check valve in the stirrup... Do you think it can handle 500 psi?
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Unread postAuthor: jackssmirkingrevenge » Mon Aug 05, 2013 3:22 am

air_dannon wrote:Question about the DIY check valve in the stirrup... Do you think it can handle 500 psi?


A North African DIY check valve or a European DIY check valve? Since it's the pressure that holds it shut, I would say it can take 1000 psi easily.
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Unread postAuthor: air_dannon » Mon Aug 05, 2013 9:27 am

:D Come and see the pressure inherent in the check valve system! Help, help, I'm being compressed!
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Unread postAuthor: jackssmirkingrevenge » Mon Aug 05, 2013 10:04 am

hehe very droll :D
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Unread postAuthor: air_dannon » Mon Aug 05, 2013 11:53 am

Looking at this part of the check valve... The smooth part of the modified 3/8 bolt... when the cracking pressure is reached to push this down and compress the spring, is there any filing needed of the smooth walls on bolt to allow air to travel into manifold?
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