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Homemade high pressure pump

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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Unread postAuthor: Hawkeye » Sat Aug 25, 2007 6:16 am

You should just swallow your pride and do what I suggested. At least temporarily, by having it thread to your favorite gun for now. Nice work. I like how the whole top portion and the piston head is virtually identical to the one I made although I'm sure you didn't actually read my how-to.
I think I managed to eliminate a bit more dead space by filing the nut (rounding it)holding the piston together so that it fit perfectly into the bushing at the bottom. I also added a beveled washer in the washers making up the piston head that followed the taper of the reducer I put on the bottom.
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Unread postAuthor: noname » Sat Aug 25, 2007 12:10 pm

JB Weld a couple inches of brakeline into the hose barb and add more hose clamps.

I ruined the 0-100 psi guage on my hybrid and I'm lucky I didn't get plastic shards in my face. :P
If you look at the pictures, the clear plastic is facing up, which is where I usually am, ready to shoot. I left the ball valve open, shot, and heard a loud splitting-ish sound (very hard to describe), accompanied by the sound of the gun firing. I looked down, and the plastic face had split in half, both halves being bulged outwards. The tiny hole that allows air into the guage had been completely blasted out and was rolling around inside the guage. I junked it and slapped myself for wasting $12. Apparently a 6x/ 6atm mixture creates a bit more pressure than 100 psi. :lol:
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Unread postAuthor: SpudBlaster15 » Sat Aug 25, 2007 12:43 pm

Hawkeye wrote:You should just swallow your pride and do what I suggested. At least temporarily, by having it thread to your favorite gun for now. Nice work. I like how the whole top portion and the piston head is virtually identical to the one I made although I'm sure you didn't actually read my how-to.
I think I managed to eliminate a bit more dead space by filing the nut (rounding it)holding the piston together so that it fit perfectly into the bushing at the bottom. I also added a beveled washer in the washers making up the piston head that followed the taper of the reducer I put on the bottom.


I suppose I could remove the hose barb and use the 1/2" NPT threads to connect it to the launcher, while keeping the one way valve within the pump. I am also wondering about the pressure threshold of a standard air compressor quick connect coupling...

Where is your How-to? All I read was the first post in Brian's stirrup pump thread, which gave me the idea of using a sideways T as the pump bottom, and the spring and rubber check valve. I took apart my deceased bike pump and looked at the intake one way valve setup, which I figured would be easy to scale down.

I originally intended to use the threaded pump rod from another bike pump that failed last year, but the threads were 3/8" UNF, and I couldn't find any washers that would work properly with such a large shaft diameter. Having lots of 1/2" copper pipe laying around, I figured that + an endcap with a hole drilled in it, and a 1/4" bolt ran through it would work better. That also made it easy to find a pump rod guide.

It took me ages to find suitable washers at my crappy hardware store, and in the end I ended up going with slightly smaller steel washers sandwiched with rubber washers. The rubber washers didn't have the rigidity to hold the pump head together properly, and the steel washers would have likely gouged the inner surface of the pump cylinder if left on their own.

I was thinking about casting epoxy around the nut holding the pump head together to eliminate even more dead space. Think it would work well?
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Unread postAuthor: mike1010 » Sat Aug 25, 2007 2:10 pm

what about using a threaded hose for an air compressor and just use quick disconects instead of bike valves?
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Unread postAuthor: frankrede » Sat Aug 25, 2007 2:38 pm

mike1010 wrote:what about using a threaded hose for an air compressor and just use quick disconects instead of bike valves?
Indeed, I think thats a great idea
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Unread postAuthor: Hawkeye » Sat Aug 25, 2007 2:52 pm

My How- to is on one of those pump threads.
You will need a bleed if you go the compressor connections route. It would be too difficult to disconnect when it is pressurized.
I used the copper end cap with just rubber washers and a smaller spacer as the piston head. A 5/8 tap washer should work fine with a half inch as the one the o-ring seals against on the downstroke.
It could work using Epoxy to fill out the nut but it might suffer from the heat build up.
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Unread postAuthor: joannaardway » Sat Aug 25, 2007 3:55 pm

frankrede wrote:
mike1010 wrote:what about using a threaded hose for an air compressor and just use quick disconects instead of bike valves?
Indeed, I think thats a great idea

Oddly enough, that's exactly what Ragnarok's done, and it works great.

@Hawkeye: I don't know why people say they are hard to disconnect at high pressures. Hard to connect maybe, but it comes apart very easily.

Heat build-up is not a major concern in a copper pump - it's such a good thermal conductor that it will bleed heat off very quickly.
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Unread postAuthor: Gepard » Sat Aug 25, 2007 4:04 pm

joannaardway wrote:<snip>@Hawkeye: I don't know why people say they are hard to disconnect at high pressures. Hard to connect maybe, but it comes apart very easily.
<snip>


Some hoses are hard to disconnect when they have high pressures in them due to the increase in friction. I believe some companies also build it into their hoses as a safety feature as the HP causes a whipping effect that can be potentially lethal. For those you push the sleeve up/in to vent the air and then the other way to remove it.
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Unread postAuthor: joannaardway » Sat Aug 25, 2007 4:26 pm

It really doesn't seem that way.

It's a series 21 connector (the cheapest available from Airlines - I suspect penny pinching), and even at over 300 psi, it uncouples easily, with no more than a firm crack of pressure as the valve inside reseals.

It doesn't seem to be at any chance of accidental disconnection, or whipping. But it is designed to work up to 500 psi, so it may have a clever design feature to solve these problems.
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Unread postAuthor: Gepard » Sat Aug 25, 2007 4:40 pm

I thought we're just talking generally? I didn't see anyone specifically mentioning a quick release coupling.....

The whipping occurs on the side with the male coupler as you said the female side has a valve that reseats but the male one doesn't. This is the one I was referring to: http://www.airlines-pneumatics.co.uk/we ... de=S010162 where you vent it before disconnection.

On mine there are two bars that hold the two together. If you increase the pressure then surely the friction between the male coupler and the bars are increased? I know that mine is certainly more difficult to disconnect when it contains pressurised air - might just be the nature of the coupler though. Mine doesn't use a standard coupler (that said I'd imagine them to all operate the same way just with different plug/socket profiles) as I've tried to find an extension hose for it before.
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Unread postAuthor: joannaardway » Sat Aug 25, 2007 4:57 pm

Gepard wrote:I thought we're just talking generally? I didn't see anyone specifically mentioning a quick release coupling.....

We were talking fairly generally, I just mentioned the model I've been studying.

Ah, I was a bit confused about hose whip then - I somehow thought the danger was from the female end. Probably a misunderstanding because I forgot that the male end may not be attached to a tool/launcher, but could be on a hose.
If that's the danger, I think it's perfectly safe with launchers. Several pounds of launcher can't whip like a hose...

The Series 21 socket seems to have 5 microscopic ball bearings around the inside which pinches the plug, and which can move outwards when the sleeve is moved back. It's the same basic principle as you mentioned, but I guess the ball bearings are fairly friction free by nature.
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Unread postAuthor: dongfang » Sat Aug 25, 2007 5:18 pm

Hi

I also had those bike pump hoses falling apart on me several times...

I would suggest a nice, long, relatively thin copper between the valve and the hose. Maybe running up the outside of the pump stem and down again, or simply a spiral around it, and attached with heat insulating plastic strips or clamps. Purpose: Radiator, simply. An intercooler.

Regards
Soren
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Unread postAuthor: FeLeX » Sun Aug 26, 2007 8:51 pm

Hey guys I know this is probably gonna make me sound dumb but how exactly do high pressure pumps work? Whats different from regular ones?
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Unread postAuthor: mopherman » Sun Aug 26, 2007 8:53 pm

FeLeX wrote:Hey guys I know this is probably gonna make me sound dumb but how exactly do high pressure pumps work? Whats different from regular ones?

the small diameter pump heads dont provide enough surface area for too much pumping dificulty. they are basicaly just real skinny pumps.
(sorry for the post bombing guys lol)
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Unread postAuthor: SpudBlaster15 » Sun Aug 26, 2007 9:36 pm

High pressure pumps can reach higher pressures more easily due to less cross sectional area. A standard bike pump has an inside diameter of ~1.25", and my pump has an inside diameter of ~0.79". This means that to reach the same pressure, I will be required to exert (1.25<sup>2</sup>)/(0.79<sup>2</sup>) = ~2.5 times less force when using the homemade pump.
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