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Posted: Wed Mar 14, 2007 5:01 pm
by Hawkeye
I just did a test to find out the capabilities of my pump. It is based on a twenty inch cylinder of 3/4 inch copper. Thirty strokes filled the chamber of my sawed-off marble gun to 325 psi. The way the pump is screwed to the back of the gun makes it difficult to bear down with both hands evenly. Essentially I am pumping it with one hand. I am going to make a better balanced design to eliminate this problem.
I realize that I underestimated the capabilities. I would imagine that it could reach 400 plus psi with little additional effort. I was not even using my weight to bear down on it.

Posted: Wed Mar 14, 2007 5:31 pm
by chaos
pictures......i would like to see this as well as your gun Hawkeye.

Posted: Wed Mar 14, 2007 8:08 pm
by Hawkeye
I actually had a vague idea for entering the upgraded version in the contest. Can you wait? It's really nothing new or revolutionary.
The gun is just a run of the mill piston style with a brass tee on the back. There is an additional threaded street elbow at the back of the tee and the pump screws onto that via a 1/8-1/4 brass reducer. Inside the reducer is a lip of metal that provides a surface for the one way valve o-ring to seal against. A spring from a pen holds the tiny valve shut. The one way valve is simply a screw head and a short section of shank and a tiny o-ring.

Posted: Thu Mar 15, 2007 3:00 pm
by Brian the brain
You have a sawed-off?? You have a home made stirrup pump??
You made your own one way valve??

We seem to think very much alike..

Posted: Thu Mar 15, 2007 5:23 pm
by Hawkeye
Yes to all of the above. The best part is that the pump doesn't need a bleed valve to remove it as the one way fill valve is located within the gun rather than the pump system.
I really want to make a 3/8 ball bearing pistol that operates at 400psi. Now I know that those pressures will be easy to obtain.
I'm kind of surprised that pumps aren't high on the list of things to make considering the problems most people have obtaining a consistent source of pressure. Particularly high pressure.
So far my pump is the only one I've seen on any of these forums. Maybe I'll start a trend.
It literally only took about half an hour to put it together, with some additional time for the glue that holds the piston washers together to dry.

Posted: Thu Mar 15, 2007 10:13 pm
by chaos
well can we see it....

Posted: Fri Mar 16, 2007 6:20 pm
by Brian the brain
I would like to know how you made the pistonhead.
Half an hour seems to good to be true.Your idea seems simpler and the best thing..it's tested!

It would save me some time building and fiddling to get it right.

Posted: Sat Mar 17, 2007 12:35 am
by Hawkeye
Brian, The piston head is simply a stack of various tap washers and an o-ring that perfectly fits inside the copper pump tube. A small hole is drilled through a copper end cap and a small bolt is placed through from the inside out. I then placed a 1/2 inch washer, a 1/4 inch washer a 5/8 inch washer and then one more 1/4 inch washer. A rounded off bolt was then added and glued in place(threadlocker glue). Two deep grooves are made in the 5/8 inch washer. The o-ring is placed around the small washer in the center of the stack. The end cap and assembled piston head is attached to a half inch copper pipe which forms the pump rod.
When the pump rod is pulled out the o-ring moves forward and butts against the larger(5/8) grooved washer which allows air to leak past the piston. When the pump rod is pushed in, the o-ring moves back against the solid smaller washer(1/2 inch) and forms a seal.
So you can see the intake valve is located in the piston head which eliminates the need to build one in the end of the pump itself. The air comes in from the top where the pump rod slides.
I will be posting some pictures soon if this isn't very clear. Forget the contest ;)
PS In the second model of this pump I also added a washer to the bolt before I placed it through the inside of the end cap. That gives the bolt a better seal against the inside of the cap as well. I also glued all the washers together but it probably isn't really necessary if the bolt is tightened sufficiently.

Posted: Sat Mar 17, 2007 9:22 am
by jrrdw
I hope i didn't miss anything before saying this... if you used a cup shaped rubber so that it would exspand with the pressure, wouldn't that increase the effencie and pressure out put???

Posted: Sat Mar 17, 2007 10:12 am
by Hawkeye
I think a cup shaped rubber piston head is used for a regular low pressure bike pump.
The 0-ring functions the same way though. It is a perfect fit by itself and when the pump handle is pressed down it is forced back and seals 100%. It no doubt also expands slightly as the pressure builds in much the same way as a cup seal.
It really can't be more efficient than it is.

Posted: Sat Mar 17, 2007 1:23 pm
by risto
Brian the brain wrote:Oh..I have finished my competition gun.
It is not what you will expect...
Why ya gotta be like that Brian? This will keep me awake for weeks. :evil:

Posted: Wed Mar 21, 2007 3:09 pm
by Brian the brain
I reveiled it already..I couldn't wait.

The pirate IS the competition gun!!

I won't be here when the competition starts so I decided to post it regardless...

Posted: Sun Mar 16, 2008 5:19 pm
by Antonio
VH_man wrote:You could fill your own paintball tanks with these..... but with air.... so theres no friggin CO2 liquid to mess your gun up. LPNitro!!!!! I might have to make myself one of these........ i wont have to pay for CO2 anymore!
Thats what I was thinking of as well. Would be awesome!!

Posted: Sun Mar 16, 2008 6:17 pm
by VH_man
do you think you could get one of these up to about 2000 PSI?

My friend has come upon the realization his famlily owns almost 80 acres of unused property, and he got the go-ahead to make it into a private airsoft/paintball Field.

the only problem is, none of us want to hop in a car and drive to the paintball place 20 minutes down the road every time one of us runs low on air........

Posted: Sun Mar 16, 2008 6:21 pm
by Hawkeye
While you could fill a paintball tank to 800-1000 psi with a homemade pump it will fire more powerfully and give fewer shots due to the difference between air and CO2.
It would still be handy.