micro pump

[jon_89]

After reading the topics on how to build a air pump I was thinking if building a micro shock pump would be plausible. The only thing I can think that would be wrong is the amount of force required to get high pressures.

[jackssmirkingrevenge]

I've given this matter some thought before after seeing the pump made for this tiny thing. As I showed elsewhere on this forum, for a given mass of air, the smaller the chamber and higher the pressure you'll get more power, so for small calibre launchers it make sense (if you have materials that can withstand it) to have a tiny chamber at very high pressure.

[jon_89]

yeah i have seen that before. any idea what kind of materials would be needed?

[jackssmirkingrevenge]

Any idea what kind of materials would be needed?

You could easily make it with the sort of materials and techniques I used to make my pen gun project - basically different gauges of brass tubing and a good helping of epoxy resin

[SPG]

If you're really thinking micro, then the force needed won't even be that great. If you think about it, you need to divide the air pressure you want over the the area of your "piston" face. So you want 100psi and you've got a 1 inch piston you'll have to put in 100lbs of force - not impossible, especially if you use a lever. Halve the piston area and you'll only need 50lbs of force, halve it again and 25lbs and so on. That's how the tiny pump in JSR's link gets you such high pressures, because it has a tiny piston area.

Now if you're then using this for a micro pneumatic you've also got the advantages that none of the vales, pistons, etc in the gun have that much pressure on them, so you can use weaker springs, and so on. Small bore tubing, tends to have a higher pressure rating than large bore tubing of the same material.

This is the other great advantage to high pressure micros, the materials needed to make them aren't as far out there as high pressure big guns.

[jackssmirkingrevenge]

This leads me to contemplate another version of the pen gun, the same construction could easily take 800 or so psi, it's only the schrader that's the real limiting factor.

[SPG]

What about the valve used in CO2 Tyre inflators? They're usually only ABS and yet they're quite happy holding back the 800 odd psi in the CO2 Cartridge, mainly of course because they've got such a small valve face.

[jon_89]

Yeah JSR I want to make something similar to your pen gun with a little pump attached to the bottom. Is there any way to get around from using a schrader valve?

[jackssmirkingrevenge]

Schraders should be ok for 800-900 psi.

I think this will make an interesting distraction from all the auto talk For my next trick, I was thinking of the pneumatic marker gun project - the main failing of the pen gun project was that the barrel was far too tiny. In something like this you can fit a larger barrel (4.5-6mm), larger chamber and maybe even an integral suppressor to complete the covert weapon theme...

[Sticky_Tape]

Ok JSR are you some kind of sorceror or somthing? Remember when I was sending you PM s about your shock pump? Well I was going to make a small gun that would use 1/2 inch copper for the chamber and 6mm pipe for the barrel and I was going to call it a marker gun. Well anyway if you are going to make a marker gun use 3/4 inch copper instead of 1/2. The 1/2 doesn't have enough volume in around the barrel. I made a scale drawing of a gun that used 1/2inch and there wasn't much room.

[jackssmirkingrevenge]

Eye of newt, and toe of frog,
Wool of bat, and tongue of dog,
Adder's fork, and blind-worm's sting,
Lizard's leg, and howlet's wing,
For a charm of powerful trouble,
Like a hell-broth boil and bubble.

*evil cackle*

*disappears in a puff of acrid green smoke*

[SpudUke5]

*As we look for the notorious wizard, nicknamed JSR, our only clues waere a metal pen, and a puddle of hardening epoxy*

I just had to go along,

[jackssmirkingrevenge]

That is actually how I mix my epoxy, in a big black pot over a fire while wearing a point hat

[MrCrowley]

That is actually how I mix my epoxy, in a big black pot over a fire while wearing a point hat

<A HREF="">Witch!</a>

[jackssmirkingrevenge]

<A HREF="">Witch!</a>

I figured it would be either you or Ragnarok that would link to that

I got better...Burn her anyway!

Anyway, back to the jist of the thread:

Well anyway if you are going to make a marker gun use 3/4 inch copper instead of 1/2. The 1/2 doesn't have enough volume in around the barrel. I made a scale drawing of a gun that used 1/2inch and there wasn't much room.

The thing is the markers I have are 3/4" external diameter - I know this because they make great ammunition - now the question is, do I make it marker sized, as I did with the pen gun, or do I make it small enough to fit in a marker body? I'll do some measuring when I get home.