High pressure compressor

[wyz2285]

Well, my hi-cap gas mags are selling quite well so part of my customers asked if I could charger their paintball tanks.
For both commercial interests and self convenience, I thought I'd need a compressor (pumping my PCP pump no longer an option ). Make it multi-stage it's kind hard also I need something reliable and simple so I don't mind buying an shop compressor for primary stage. I remember the "shoebox compressor" and I'm thinking about make something similar, use some bike gears and a electric motor, mounting everything in a steel/aluminium structure then cover with wood boards to reduce noise.
Any thoughts? I don't know what motor should use yet nor final stage pump diameter, just a rough idea.

[Ragnarok]

Well, I'd suggest serious caution, because HPA is a lot of energy if it goes screwy - no half-arsing here.

But, as far as the shoebox compressor design, I think that it'd be most improved by figuring out a way to have the two compression strokes not simultaneous. Thing is, that's splitting the motor's torque two ways for one half of the cycle... and then it just has to pull against a vacuum for the other half of the cycle.
If you don't split the torque two ways, you have more force on hand per compression stage and can increase the diameters of the pump cylinders, thus moving air faster.

Now, I don't know electric motors that well, but I'm assuming that design was for compactness - and possibly rigidity of the pump rods, tying them to each other - not because of some benefit gained from making the motor only have to work at half its power output.

[wyz2285]

Yeah I have thought about not having two compression once and I've this part quite figured out. I'm not looking for compactness, I'd rather have a big compressor that fills fast than a mini that take hours to fill a standard paintball tank.

[jackssmirkingrevenge]

have a look at the FX compressor:

http://www.airgunsofarizona.com/Review% ... ylord.html

It's basically a motorized hand pump.

The key is to keep it cool. Thermal fins or rings and a fan. Or a water jacket. Or both

[wyz2285]

Also thought about it, but I don't want to have the pump body move (don't want to have a 4500 filled tube bending over and over, even though not much). I'd machine some fins while making the pump body, then a big fan. Water sounds messy would be nice though.

[jackssmirkingrevenge]

You can have the body fixed and the piston driven by a crank.

Air cooling is definitely the easiest way to go (VW beetle anyone ) but water cooling doesn't have to be messy - if it's good enough for CPU cooling, why not?

http://www.tigerdirect.ca/applications/ ... &CatId=499

[wyz2285]

Yap, probably what I'm gonna do. Something like a car engine.
Need to look more into water cooling then. Need at least a water tank though.

[jackssmirkingrevenge]

You don't necessarily need a pump and radiator as such... it could be a large static jacket.

Robert explains: “My railgun design has a 1.75″ barrel under tension inside an aluminium tube filled with radiator coolant. There is nearly a gallon of coolant, and the barrel stays cool no matter how many shots I seem to fire, or how quickly they are shot. The brass nut on the front rides on a nylon bearing and can be tightened to get the best accuracy. I am a believer in the ‘tuner’ idea and this seems to work for me. The main tube is thick-walled aluminium 600mm (24″) long. There is a flange at both ends.

The fluid will help dampen vibrations, and if you need to move it you can always empty the jacket and refill it later.

[wyz2285]

The problem is how, as you can see if I want to use my hill mk3 pump the heat mainly come from the inner tube, witch slides inside the outer tube constantly. I can only use coolant/ lub jat if I want to liquid cooling

[jackssmirkingrevenge]

Who needs a multi stage pump?

Small bore and long stroke single stage with a disproportinally large coolant tank to keep things fresh.

Similar to what they do with submerged PCs: http://www.pugetsystems.com/submerged.php

A small heat exchanger is quite cheap: http://www.ebay.com/itm/Aluminum-Water- ... 3cd4205e40

A small pump can be had for a similiarly small amount of cash: http://www.ebay.com/itm/DC-12V-6W-Subme ... 35c72824f1

Simple, it works and will let you keep things cheap. Minimal dead volume is essential, a custom check valve might be required. Also, a reliable failsafe cut-off switch and maybe burst disk from a paintball tank is a must.

Don't forget a water trap, you don't want to promote corrosion.

[wyz2285]

But a long thin pump... The body and piston rod will be subjected to quite some stress specially if I want fast cycling.
Not going to use water, car engine coolant. Yeah I'd need a pressure sensitive failsafe switch and a port to bleed water. I've thought connecting a contact pin on a pressure gauge so when it reaches the max pressure it activate a relay to turn off the power... If I can't find a affordable pressure switch.

[jackssmirkingrevenge]

But a long thin pump... The body and piston rod will be subjected to quite some stress specially if I want fast cycling.

Not if adequately supported. Keep it from overheating and you'll be fine.

Not going to use water

By water trap I mean something to dry the air your are compressing, for example: http://www.airgunbuyer.com/details.asp? ... oduct=1797

[wyz2285]

I got you, was just saying I'm not gonna use water as coolant. I know what you're talking about the humidity in the air will condense into water in the pump. Don't know where to place the port without adding dead space though...

[CS]

For a pressure switch you could make the hand of a pressure gauge part of a switch. I've seen analog clocks being used as a time delay for explosives. http://www.instructables.com/id/How-To- ... -and-test/ Then there is the emotive that it work 99% of the time, but that 1%...

A pulley reduction could be used for torque.Then a scotch yoke mechanism for converting rotary to linear. All that stuff could be made out of plywood, and pivot on bolts.

Scotch yoke

[jackssmirkingrevenge]

For a pressure switch you could make the hand of a pressure gauge part of a switch.

I've thought connecting a contact pin on a pressure gauge so when it reaches the max pressure it activate a relay to turn off the power...

Is there an echo in here



Yup, simple to engineer