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Homemade Pump


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#1 schoute1587

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Posted 10 May 2006 - 03:48 PM

While trying to build my new homemade gun I found out that my ball pump I bought won't be able to withstand all the pressure when pumped up to so many psi. So I was wondering how you guys make the pumps in your air powered homemades.
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#2 Dr Nerf

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Posted 10 May 2006 - 04:32 PM

I was able to quickly and easily build a pump when I was constructing my air pressure bolt action homemade. It was made out of 1/2" PVC, 1" PVC, 3 O-rings (5/8" ID and 15/16" OD I believe) and some duct tape. Basically, I made the piston by securing the O-rings with duct tape and duct taping the end. The piston was lubricated and put into the rest of the pump.

The pump is very easy to construct, but it lacks a major thing. It is missing check valves. A good pump should have two, one for input and one for output. An input check valve could be emulated by a hole that is drilled into the pump body at a point just before the end of the pump stroke (so that it can intake air when the pump is retracted). The output check valve would connect the pump to that gun. Its purpose is to keep the air inside of the pressure chamber.

While trying to build my new homemade gun I found out that my ball pump I bought won't be able to withstand all the pressure when pumped up to so many psi.

Does your gun have an "output" check valve as described above? If it does not, it may not keep pressure at all.
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#3 schoute1587

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Posted 10 May 2006 - 05:23 PM

Yes it does have an output valve. What i'm concerned with is that it won't be able to bond tight enough to the cpvc. Heres two pics.Posted ImagePosted Image As you can see the pump isn't pvc or cpvc so pvc cement wouldn't work. Also the pump is too long to be comfortable. Sorry pics got screwed up.

Edited by schoute1587, 10 May 2006 - 05:24 PM.

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#4 davidbowie

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Posted 10 May 2006 - 06:28 PM

2 suggestions:

1: Don't use a ball pump. Instead, buy a handheld bike pump from walgreens, the kind that has an extension hose that screws on to the end. Cut the end off this extension hose, and put in a hosebarb. Tap the hosebarb into your chamber wall, and you have a nice and sturdy pump connection.

2: Aren't the ends of ball pumps threaded? See if you can find a nipple that fits these these threads, and tap that into the chamber wall.

A homemade pump would probably be better, but I like storebought ones because of how slick, compact, and cheap they are.
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#5 schoute1587

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Posted 11 May 2006 - 05:28 PM

Okay, so i hooked up my ball valve and bonded my pump to my tank. I tried to pump it up but it was too hard and the air just came out the back of the pump. I thought it had an output check valve but i guess it didn't work. Can somebody please tell me the materials and how to build a home made pump?
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#6 m15399

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Posted 11 May 2006 - 07:07 PM

http://www.geocities...5399/pumps.html
http://www.sscentral...mades/pumps.php

1" Is a good size for a Nerf pump. You'll have to find an oring that will fit in 1" pipe, though.
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#7 Flaming Hilt

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Posted 11 May 2006 - 08:32 PM

That doesn't make sense to me. How does just having a shaft with an O-ring on one end constitute a pump? All you're doing is compressing the air and then allowing it to expand when you pull the "pump" back out. Unless you just push it in and keep it in to fire, in which case you couldn't prime it unless you kept the trigger valve open while resetting.

So, the thing I think I'm missing is: you use a one-way valve, right? Lets air in but not out? And even then: you shouldn't be able to draw out the pump shaft, because that would create a vacuum.

I'm so confused. Anyways, if there's something obvious I'm missing, then... well I guess I'm dumb. But I'd still like to know how it works. Thanks to anyone who helps.
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#8 m15399

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Posted 11 May 2006 - 10:22 PM

1 way valves are not part of the pump. The pump is just a piston. You would, however, need 1 way valves for a homemade like this.
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