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Homemade HPA pump questions

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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Homemade HPA pump questions

Unread postAuthor: saefroch » Tue May 11, 2010 9:57 am

I am constructing a homemade HPA pump myself since the desire for MOAR PRESSURE is greater than 200 psi allows. So... the questions are: Is the McMaster-Carr item #56145K116 overkill to use for a hose? It will need to handle a minimum of 600 psi. The second question: Is it possible to connect NPT threads to a schrader connection? Or does that require a specific tool or a rubber-based clamping mechanism?

I will probably be using this thread to post later questions if any arise.
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Last edited by saefroch on Tue May 11, 2010 10:06 am, edited 1 time in total.
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Unread postAuthor: Big-E » Tue May 11, 2010 10:03 am

Yes, a schraeder will fit 1/8" NPT threads, but you need to get the correct part. You need a schraeder for a compressed air tank. You can find these at the local hardware or auto parts store, by the air compressors, accessories and fittings. It will thread in to any 1/8" NPT fitting. they are mainly used to fill portable air tanks.

As for air line, buy some 1/8" threaded air line from a paintball equipment supplier, it's way overkill, but will not fail. That's what I use.

The shorter the air line, the better; Less dead space and wasted effort.
You could always just use quick connects, no air lines at all. just put the female connector on your gun; you won't need to add a ballvalve, as it will seal when disconnected from the probe.
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Last edited by Big-E on Tue May 11, 2010 10:06 am, edited 1 time in total.
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Unread postAuthor: saefroch » Tue May 11, 2010 10:04 am

Oh sweet, so all I need is a female 1/8" NPT connection to screw on to the input side of a schrader then?

I plan to use the schrader as a check valve, and less dead volume would be nice. I need some sort of flexible connection or it is going to be really awkward to pressurize the gun... so I guess I'll be looking into quick disconnects again.
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Last edited by saefroch on Tue May 11, 2010 10:09 am, edited 1 time in total.
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Unread postAuthor: Big-E » Tue May 11, 2010 10:08 am

Actually, if you use one from a tire, that's been shaved, it won't work. you need to buy one for a portable air tank (it's sometimes called a tank valve). it's a schraeder that screws into a 1/8" bung. The thread on connection to fill it is a bit harder to find either scavenge one off of a shock pump, or off of fill adapter.

I've seen 1/4" HANDS FREE TIRE CHUCKS in the air tool section of the hardware store before; that could work too. The key is the pressure it can handle.

someone had posted a source for one of those fill connectors; I'll need to find it.
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Last edited by Big-E on Tue May 11, 2010 10:13 am, edited 1 time in total.
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Unread postAuthor: saefroch » Tue May 11, 2010 10:11 am

I am going to buy a schrader valve with male threads on the out end... I need it to act as a check valve so I can't risk frying it with my soldering methods. And I am avoiding rubber as much as possible in all builds now. I tried to work with it before... don't work so good.
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Unread postAuthor: Big-E » Tue May 11, 2010 10:18 am

Just make a checkvalve yourself; it's easier, and flows better.

Check the thread on my build for ideas; soldering heat is not an issue if you build it like I did.

http://www.spudfiles.com/forums/my-first-stirrup-pump-build-t20370.html
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Unread postAuthor: saefroch » Tue May 11, 2010 10:22 am

Oh soldering heat is an issue if you are vaporizing copper like I did.
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Unread postAuthor: Big-E » Tue May 11, 2010 10:28 am

A propane torch will work fine; no need to go all oxy/acetelyne on it!

Seriously, you put flux on your cleaned fittings; heat with a torch, when the flux starts to bubble and flow, touch your solder to the joint; it'll wick into the gap, and you're all set. If you're vaporizing the copper; you're doing something incorrectly.

No, it's not an issue, because my checkvalve threads in; and isn't soldered. all the soldered components are assembled seperately, and everything is then threaded together. so, no, no melted o-rings or hoses.

BTW: it's possible to melt a schraeder as well; if you forget to remove the valve core before soldering.
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Unread postAuthor: saefroch » Tue May 11, 2010 2:17 pm

And I'm pretty sure I did not remove the valve core, I'll have to find out how to do that... if I ever need to again. Gonna have a look at your checkvalve and keep working on the vortex.
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Unread postAuthor: theBOOM » Tue May 11, 2010 3:15 pm

Hey, sorry about the chat yesterday I forgot about it and left my laptop unattended.

I didn't read through the comments but if you live in the U.S go to your nearest Harbor Freight and look in the hydrauilic section. I got a 10000 psi hydrauilic hose, 6 feet long for only 13 bucks, (they're usually up to 50 bucks). They also sell some hoses rated to 400 psi or something like that, and yes their hoses have NPT male threads on most of them so you can just add a threaded adapter.

If you want a short hose (10 inches long) I also saw some 3000 psi rated hoses at harbor freight, they where made of some type of plastic, flexible, and had npt female threads on both ends. It was about 1/8" in diameter, so really small.

If you want to use the schrader as a checkvale you're gonna need to find yourself an adapter that goes from NPT to the threads on the schrader, also if you use this method your either gonna have mod the adapter or use 70 psi or more on everything, beacause I believe that's the pressure at which schraders "open".

EDIT: A solution to this problem would be to buy a schrader tool that allows you to thread into a schrader and at the same time it depresses the pin. I'll post a pic once I'm done eating.
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Unread postAuthor: saefroch » Tue May 11, 2010 3:28 pm

I am planning on operating at about 600 psi with the schrader checkvalve system. So if I just connect the schrader valve through the pump system without a pin, I will just get a pressure differential of +70 psi on the input side?
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Unread postAuthor: theBOOM » Tue May 11, 2010 3:32 pm

No no no, if you don't have a way of depressing the pin on the schrader, you're gonna have to pump to 70 psi or so (I think that's what it is) before you get air into your chamber. What I'm suggesting is buying a schrader tool that threads into your schrader head AND depresses the pin on it to allow air to go in automatically.

I'll post a pic in a minute.
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Attachments
Schrader pic 1.JPG
Here is the schrader tool, on this side the tool threads onto the schrader and depresses the pin, on the other you have a valve core removal tool. You're only intrested in this side though.
Schrader pic 1.JPG (19.07 KiB) Viewed 1616 times
Schrader pic 2.JPG
Here it is threaded onto a schrader I'll be epoxying tonight (thus, the roughened up surface)
Schrader pic 2.JPG (30.11 KiB) Viewed 1616 times
Last edited by theBOOM on Tue May 11, 2010 3:46 pm, edited 1 time in total.
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Unread postAuthor: Gun Freak » Tue May 11, 2010 3:37 pm

Then it wouldn't be a check valve though, it would let air in both ways.
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Unread postAuthor: clemsonguy1125 » Tue May 11, 2010 3:39 pm

The other way would be to remove the spring from the schrader
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Unread postAuthor: saefroch » Tue May 11, 2010 3:43 pm

But I've still got the minor issue of attaching a female NPT connection to the input side of a schrader valve... solder? Not incredibly keen on it, but maybe if I take the core out of the valve I won't fry it this time...

EDIT: And when I vaporized the copper I didn't go all oxy-acetylene on it... I just have a beast propane torch and know how to use a two-cone flame from chem... was rather freaky to see the flame go green on me. Been a while since I seen that.
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