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I'm new here, and I come up with my first post as I'm interested in pneumatic cannons. I looked around here, also on google, but couln't find an answer to this rather simple question:
you know the special air handpumps that are used for high pressure air rifles, their performance ranges from 200 to 300 bar. they are used to either fill the air tanks or the rifles directly.
why is it noone builds a pneumatic launcher with these pumps making use of their high performance? I mean, ok it's lots of work to pressure t
them up and so on, but in terms of max pressure they would be extremly strong, yet simple to build/maintain and cheap (as air is free) to operate.
For example, I see many CO2 launchers, but due to the nature of this gas they are restricted to "only" around 60 bars. why not go highter with normal air? is there no material that could take the high pressure?
to clarify: MY idea is NOT to incorporate a pressure regulator to restrict the pressure in the chamber to lower values, but to actually make use of the higher pressure the handpump can provide.
thanks for all replies, I'm really curious about this one.
PS: here is such a handpump
http://www.para.de/Handpumpe-300-bar-fu ... -Dominator
the problem to connect the pump to the launcher/chamber should be the smallest problem.
A typical pneumatic spudgun uses a more efficient valve, a larger calibre and dump a lot more air than commercial air rifles, so such high pressure is not needed for high performance - still some examples that use such pressure though.
There are plenty of high mix hybrid spudguns however that generate upwards of 200 bar on firing.
Okay, so high performance spudguns don't need that high pressure, but... wouldn't higher pressure make them even more efficient?
Looking at a "typical" pneumatic launcher, powered by "normal" air with a handpump and, let's say, a golf ball caliber.
why is it spudguns like this would fire with pressures between 6 and 30 bar most of the time? why aren't they build using 200 bar or more? somehow I still don't get it.
sorry for being noob :-/
ps: I want to look at pneumatic only. hybrid is nothing for newcomers
Yes, but higher pressure implies stronger materials and construction, which is not something most have access to.
A 30 bar golf ball launcher with a long barrel and fast valve will give you tremendous performance, more than most people "need".
A 200 bar pneumatic needs the same sort of construction as a high mix hybrid, so it's not for n00bs either
I dont think many people realize just how much pressure 200-300 bar is, especially in something as large as a golf ball caliber, the forces on your chamber and valve are going to be tremendous. That isnt to say it can be done, but as jack said definitely not for n00bs. It would also take quite a while to pump up a decent sized chamber with one of those pumps.
Patience is a virtue, get it if you can, seldom in a women, never in a man.
A 200 bar golf ball launcher would have to be made out of materials few have access to or money for, not to mention the absolutely insane time it would take to fill the chamber with so much air.
By "efficient" do you mean higher muzzle energy/velocity or do you mean a greater % efficiency, comparing stored energy in the compressed air to muzzle energy?
It is also worth noting that with a very efficient valve, it is possible to get close to the maximum expansion rate of a gas at lower pressures than 300 bar.
I see, thanks a lot for your answers. That really makes sense, I also wouldn't even know what kind of materials to use for 200 bar, not speak of valves...
Saefroch: By "efficient" I meant velocity. Also, can your please elaborate your last point a bit more? If I got it right, then with an efficient valce 30 bar doesn't necessarily lead to less velocity than 300 bar??? That sounds interesting.
Because the volume of each stroke is minuscule. To pump up a golf ball size cannon to 200 bar with one of those would take a lot of hard work for a long time.
It's not going to be free either, because you'd notice your food bills rising quite fast. Mind you, you could scrap that gym membership if you were trying to fire more than twice a week.
And, as saefroch says, in terms of velocity, you'll find that 200 bar can't give you significantly more than mundane pressures would. You could do it in a shorter barrel, but air cannot expand faster than its own speed of sound, so except in cases where adiabatic heating, shock effects or dieseling might be playing a part, you'd still be reined in by that limit.
Last edited by Ragnarok on Sun Jul 24, 2011 3:17 pm, edited 1 time in total.
Does that thing kinda look like a big cat to you?
A 100mL chamber at 300 bar will give you more performance than a 1000mL chamber at 30 bar, but it really depends what you want to get out of your launcher.
Say you want to put golf balls through a fridge at 50 metres, a reasonably sized pneumatic launcher with an efficient piston valve and 5 bar in a large chamber will be more than up to the task.
I understand. So, what does - in average - have the bigger effect on velocity? chamber size or pressure?
let's say: what is more powerful? a 1000ml chamber at 5 bar, or a 500ml at 10 bar?
is there any default limit for the chamber size? e.g. saying it should have a minimum size of x ml to be efficient?
Ragnarok: you did the elaboration job for saefroch. thanks. may I ask, what is the pressure threshold as of which aditional bar will not increase the velocity anymore (air)? there has to be a constant value, determined by natural laws.
If I got it right the 200 bar handpump would not provide for a more powerful source then 12 gramm CO2 cartridges then, despite these "only" have around 60 bar, like all CO2 tanks have? what a surprise! thanks for sharing your experience here guys!
I haven't read up on the thread but here is my simple answer. People who want that kind of power will go hybrid because it doesn't take as much effort to charge the gun to such high pressure. Know what I mean?
Does OP mean PSI and and not bar?
200-300 bar is essentially a bomb, do any type of compressor pumps even go that high? sounds impossible.... also wouldn't a golf ball explode under that pressure before it even leaves a barrel?
No. Ever seen a punkin chunkin cannon?
Infinite pressure. The question you're asking sadly displays a lack of scientific understanding. The valve opening speed, flow parameters, barrel length, chamber volume, and many other things affect muzzle velocity. Increasing chamber pressure will always increase velocity, but with a good build you'd be hard pressed to tell the difference between 200 and 300 bar.
No, it might. It depends on the build and how good your measuring equipment is.
I beg to differ, a bomb probably generates pressures far above 300 bar, which is entirely achievable, it just requires a very small pump diameter if you're to use a reasonable amount of force. A golf ball would probably survive just fine.
First and foremost, I'm talking about bar, not psi. The handpump I was referring to is really capable of building up that pressure. And I really won't to stick to pneumatic here and not go hybrid.
Other than that...
I came up with my third question because of Ragnarok's statement
"air cannot expand faster than its own speed of sound, so except in cases where adiabatic heating, shock effects or dieseling might be playing a part, you'd still be reined in by that limit."
So I concluded that the velocity gain due to higher pressure decreases, the higher the pressure becomes. I know about all the other factors, and also that the velocity will never actually remain unchanged as pressure increases, I was just wondering where the rational limit lies. You say under certain conditions you can't tell a big difference between 200 and 300 bar (same gun of course). But between 5 and 20 - I assume - you will be able to tell a notable difference. So my question was, as of which pressure heigth is additional pressure becoming less relevant? Do you know what I mean?
It is also worth noting that with a very efficient valve, it is possible to get close to the maximum expansion rate of a gas at lower pressures than 300 bar."
- so, assuming such an efficient valve and general build, what exactly would those "lower pressures" be? (bar)
Sorry it's late and English is not my mother tongue, hope I still make sense here
Pressure is not the only determinate of muzzle velocity, BY FAR. In theory, with a chamber of truly epic proportions and a barrel of incredible length, it is possible to get very close to the SOS in the propellant gas with only a pressure of 1 bar.
The "rational limit" is so incredibly dependent on so so many things. Are you shooting a steel slug with a ball valve cannon or are you shooting a saboted AA battery with 3" QDV?
The "lower pressures" could be anywhere. It depends on the build and projectile. Run GGDT simulations with something you'd actually build and see what you get.
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