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Still thinking of selling pumps..

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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Still thinking of selling pumps..

Unread postAuthor: Mitchza89 » Thu Sep 10, 2009 6:13 am

Hi guys,

I'm gonna get the materials for a high pressure pump tomorrow. This is going to be all epoxied brass and copper with a polished finish. If this thing turns out as good as I hope it will and I'm confident it won't break or cause problems, I'm going to sell it. If I get a buyer that is further then they are able to pick it up or me drop it off, I'll post it dismantled with instructions on how to assemble. Australia only though. Everything should just screw together anyway. To keep costs as low as possible I won't be adding a gauge to it.

I'll be sure to post it when I get it going. If you think you may be interested, by all means give me a post!

Thanks all!
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Unread postAuthor: jmadden91 » Thu Sep 10, 2009 6:15 am

Got a rough estimate mate? I would probably consider it for when I cant use the fridge compressor. Would be a good way to get my head around them so I can knock up my own next time
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Unread postAuthor: Mitchza89 » Thu Sep 10, 2009 6:16 am

I'm not too sure but maybe 50 or 60. I'll give everything a good price hunt tomorrow. Of course there will be mates rates! :D
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Unread postAuthor: jmadden91 » Thu Sep 10, 2009 6:21 am

haha love it. Hm so thats without the gauge? Considering I have got 80% of the parts already I should probably save my money. Would you consider selling parts? Say a piston for one that will fit in 3/4" Copper?
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Unread postAuthor: Mitchza89 » Thu Sep 10, 2009 6:26 am

I'd be more then happy to make the piston and check valve assembly for ya mate. Just give me a rough diagram on the set up you want and the layout of the pump and we should be good to go!
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Unread postAuthor: pizlo » Thu Sep 10, 2009 2:23 pm

If you have the guts a two stage pump like one member made would be an awesome next step, pity for me though being here in america!
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Unread postAuthor: Northir » Fri Sep 11, 2009 11:45 pm

id be willing to pay for a high pressure pump, and id be willing to pay to have it shipped, as well as piston valve assemblys, im in the US :(
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Unread postAuthor: Mitchza89 » Sat Sep 12, 2009 12:38 am

I reckon I may just come up with a very in depth guide to making a pump as Geppito did. I'll keep you posted guys!
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Unread postAuthor: Northir » Sat Sep 12, 2009 1:45 am

sounds awesome, would be nice to get a good guide for a high PSI pump, all though im still tryin to wrap my head around the piston valve thing
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Unread postAuthor: Technician1002 » Sat Sep 12, 2009 11:28 am

Northir wrote:sounds awesome, would be nice to get a good guide for a high PSI pump, all though im still tryin to wrap my head around the piston valve thing


Good luck with the understanding of how piston valves work. The thing to remember is there is no magic. It is a cylinder with two ends. Pressure pushes on both ends in a type of tug of war. When force on one end is greater than the force on the other end it moves in that direction until it can move no more.

When closed the pilot end has lots of pressure on a large area holding it closed.

On the other end is an area inside the barrel with no force because there is no pressure. There is another area exposed to the chamber pressure, but it is a small area, so the total force of pressure times area is less than the force in the pilot, so it remains tightly closed.

When fired the pilot pressure is released. The force on that side is reduced. The force in the chamber area is now able to win the tug of war and the piston starts to move. As it does, the chamber air is now able to push on the area that was exposed to the barrel. As this area now has pressure the force on the front side of the piston becomes great and the piston gets a huge push open, so they tend to open very quickly.

Without all the bends and sharp edges going through a sprinkler valve, when open they flow very well.

Due to the sudden rise in force opening a piston, they are much faster than you could possibly open a ball valve by hand. This is why they are the fastest most powerful valve most spudders can build.

Common mistakes building piston valves include having too large of leakage between the chamber area and pilot area, so the pilot can't be vented fast enough do drop the pilot pressure far enough to unbalance it. The chamber simply vents out the pilot trigger.

Not using enough bumper material. When the piston moves, it does it with high speed and force, often breaking the valve.

Not getting a good piston seal, air leaks out the barrel and you can't fill the spudgun.

For these reasons building a working piston valve is a real achievement. Many build, some work, some don't, some break. I've built all types.
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