SpudFiles

Apparently, one can get up to 3600 psi with one of these: http://www.pyramydair.com/cgi-bin/acces ... sory_id=81
Now this could be extremely useful with a potato cannon. You might even be able to make a pneumatic supersonic cannon with pressures like that. The problem is that apparently none of these pumps have npt threads. Some of them have specialized air gun threads, and some of them have bspp threads. I was thinking that there was probably some adapter out there that could adapt between bsp and npt, but I couldn't find any. Also, maybe there was a bsp-hose and then hose-npt, but that also seemed scarce. Keep in mind that all the fittings have to be able to stand up to 3600 psi. Anyone know how to adapt between bsp and npt in these circumstances?

at $190, its a pretty penny for a hand pump, besides, what chamber can hold 3600 PSI??? if you could harness that much energy into a pnuematic you could put a marble through a house! Good luck finding a npt adapter that will stand up to 3600 PSI.

What do you think the CFM of that thing is? If its decent you could get a HPA tank and fill it for free instead of paying, which is always good.

I find it hard to believe that it actually pumps up to 3600psi, i had a look at the link and it does not appear to be a typo.
Anyone else think that 3600psi is a bit unrealistic for a stirrup pump?
I would be cool if it did go that high, instant Mach 2-3!

Maybe it's for air rifles that have crazy small chambers, I believe they have pistons in them that can reach a similar pressure.

Novacastrian wrote:I find it hard to believe that it actually pumps up to 3600psi

They're sold as an alternative to SCUBA tanks at over 4,000 psi so yes, they do go up to that sort of pressure - though not all of them are as simple as a bike pump internally, such as the FX pump.

Maybe it's for air rifles that have crazy small chambers, I believe they have pistons in them that can reach a similar pressure.

All commercial air rifles I've seen - anything from the Girandoni of old to the ultra modern AirForce Talon - operate with hammer valves, I've never seen one that uses any sort of exhaust valve arrangement - when you're using that sort of pressure, valve efficiency comes second to practicality.

And a hammer valve is the paintball type where there is a "hammer" that hits a spring valve, and opens the tank for a short time right?

and, to whoever said "what chamber will hold 3600 psi??", well mcmaster sells nipples that are rates for up to 10000 and though they are small, and not terribly cheap, if you string them together, you could get a nice chamber...

jackssmirkingrevenge wrote:

Maybe it's for air rifles that have crazy small chambers, I believe they have pistons in them that can reach a similar pressure.

All commercial air rifles I've seen - anything from the Girandoni of old to the ultra modern AirForce Talon - operate with hammer valves, I've never seen one that uses any sort of exhaust valve arrangement - when you're using that sort of pressure, valve efficiency comes second to practicality.

I meant the break-barrel ones which you pump, don't they have some sort of piston and spring in them? But I just realised I contradicted myself, you wouldn't be able to use a pump on a break-barrel design, not sure what I was thinking there

NPT and BSP are adaptable to each other by the way,the threads are nearly same as I have used large and small BSP/NPT threaded parts together many times without trouble.

So is anyone upto the task of using one of these pumps on a gun at these pressures?

rna_duelers wrote:So is anyone upto the task of using one of these pumps on a gun at these pressures?

DYI is well on the way, though he seems to have a penchant for helium, and given the benefits of lighter gas, rightly so. For the price of one of these pumps it's more worthwhile getting prefilled cylinders.

qbnbountyhunter wrote:at $190, its a pretty penny for a hand pump, besides, what chamber can hold 3600 PSI??? if you could harness that much energy into a pnuematic you could put a marble through a house! Good luck finding a npt adapter that will stand up to 3600 PSI.

Hmmmm.... I've got a Soda stream bottle that is just asking for 3500 PSI
and it's rated for it...



I have come across this style of pump, a few times before.. Generally via homemade Air rifle site's... But I will have to check... I believe they suit solid stainless steel piston valve guns.. Although they can reach high PSI level's, I believe the pressure is incremental for effort needed to pump... as in once you hit 2000PSI you better weight 75kg's+ if you want to get to 3500PSI without killing yourself...

You also need to vent the unit each time you want to disconnect it from the gun... Obviously at 3500PSI you cant just pop off the valve...

I would think it more suitable for small chamber cannon's...

WHAA Are you sayibg a soda bottle can take 3500 psi your pretty dumb.

Maniac wrote:WHAA Are you sayibg a soda bottle can take 3500 psi your pretty dumb.

you realy should know what your talking about before you open mouth and insert foot

a soda stream bottle is an aluminum co2 tank that is used in soda fountains, and yes it will hold that much pressure. some people have tried thes to pump up their paintball tanks, most gave up after the first time as they decided it was to much work.

ohh sorry I had never heard of that before i just thought he meant soda bottle. My bad.

rna_duelers wrote:
So is anyone upto the task of using one of these pumps on a gun at these pressures?


DYI is well on the way, though he seems to have a penchant for helium, and given the benefits of lighter gas, rightly so. For the price of one of these pumps it's more worthwhile getting prefilled cylinders

Yep, I am on the way. The parts from McMaster should be shipping now, and I started the valve casing today on the lathe at school. Apparently, the steel that I'm using for the casing (which was essentially free at $4), is harder than the high speed steel toolbit Luckily we have lots of carbide bits, and lots of free time.

Lots of pressure vessels can take 3600 psi. 10kpsi rated nipples are overkill. SCH 80 seamless steel of any diameter up to 4" can definitely take it, and SCH 160 seamless steel of any diameter available can take it.

You will not get muzzle velocities of over ~500 m/s (~1625 fps) with room temperature air, even with a frictionless barrel, no matter what the pressure. That's the whole reason I went for helium; higher velocity and far less recoil (and safer than air, due to helium's inertness)

To adapt the bike pump, just go to a machine shop, and get them to make you an adapter from it's output threads to whatever threads you want.

If you intend on making a larger high pressure cannon, you'll have to take the mass of the gases themselves into account, as their mass builds up alarmingly quickly. Someone came on here a while ago talking about a huge 17 kpsi cannon he wanted to build. Even at 10 k, the gases would have weighed over 20 pounds.