| Author | Message | ||
     Sub65chris |
hey all , i need to find a 5000 psi air valve that can be opened in about 1/100th of a second about 1/2 to 3/4 inch opening. I am trying to make a big nasty air rifle. it only needs to be opened not forced closed after each shot because the charge will be spent on the one shot. basically i want to make an air rifle that will throw a 200gr bullet about 1900-2000 fps. strange i know, but arent we all? So I need a valve , everthing else is set. the big thing is it really needs to open quickly, ay ideas? | ||
| Spiderman |
Contact M5 industries, AKA Mythbusters  | ||
| Sub65chris |
can you just email m5? | ||
| Interex2050 |
oooh... fun stuff Never worked with something with such a high psi though. I will let you know if I come up with something... You have certainly got my attention | ||
| Brumbear |
what about a 3/4" ball valve I have seen em used 1" on pumpkin guns | ||
| Hacksaw |
I hope you know not to have any and I mean any oil around 5000 psi of air. It will explode just like oil around oxygen. | ||
| Xb9 |
Only thing I know of that will open that quick is a rupture disk. One use and replace though. Rupture disk open almost instantaneously, and are the fastest acting pressure relief available. http://www.zookdisk.com/pdf_files/320101%20-%20PB. pdf http://www.zookdisk.com/pdf_files/321601%20-%20Uni on&ST.pdf I've worked at ZOOK for over twenty years, if you have any questions PM me. | ||
| Oldog |
what are you using for a breach and bbl what is the air source? 5K rated ball valve may be expensive! (Message edited by ol-dog on February 20, 2008) | ||
| Cowboy |
They can be had @ ant oilfield supply store. procede with caution 5000 psi can be nasty. | ||
| Sub65chris |
the general idea is to use a green mountain 45cal muzzle loader barrel that I already have. I have made a pressure vessle that holds 5000 psi adn is about 1.75 inches across. I am looking for a valve so I can carry multiple pressure vessles and change them out rather quickly for the next shot. so each vessle has a ball valve that will be opened to apply pressure to the fast action valve and allowing the entire volume of the vessle to be discharged when fired. So i have a pressure vessle with ball valve , charged before going to the range. A pressure expansion chamber that will accept the vessle at one end and have the fast acting valve at the other. so to load you make sure the fast action valve is closed, screw the pressure vessle in to the back, and open the pressure vessle ball valve charghing the pressure chamber. then you load the projectile like a muzzle loader and pull the trigger. wooosh bang and any other loud sound you can think of. the big issue is going to be manufacturing the vlave if need be and tuning the volume of the pressure vessle and pressure chamber to hold hte correct volume of compressed air so there isn't a long drawn out hissing sound and all the energy of the sompressed air is transfered to the progectile. the barrel is 38inches long so a 200 grain bullet should be in the barrel for about .019 of a second before exiting at 2000 fps. So my math was off before the valve needs to be completely open in .019 of a second. I am thinking of using arotary valve that is cross drilled so teh valve will rotate perpendicular to the barrel exposing the hole to the pressure chamber very quickly. that will make up for the friction caused by the high pressure. Also I am thinking of using a cast piece of bronze for the rotary portion, and copper rod for the pressure wipers aroung the bronze. I have some drawings here and i need a decent cad program to "build the parts" before i make the orders for really expensive materials. if any one knows of a good cad program let me know. ps what do you think? | ||
| Honu |
I have to ask, what do you use to pressure up the vessel to 5000 psig ??? | ||
| Sub65chris |
a tank pre charged to 5000psi from praxair, a welding supply company up here. | ||
| Sub65chris |
Honu -}by the way great collection! | ||
| Hexangler |
I like the rupture disk idea. Rated to 9000psi in 3/4". All you have to do is rig up a hammer and pin (carbide?) to pierce and rupture. Looks like danger though. Hex | ||
| Sub65chris |
scratch the rupture disk ideas i just called ZOOK and the prices are high for what im looking for. 29-90 dollars per disk one time use so way to much. good idea tho. | ||
| Hexangler |
Make your own disks. | ||
| Sub65chris |
Any ideas on how? I mean 5000 psi is scary! How would you do it? make a flat disk out of thin steel and have a big punch with a hole in the middle to rupture it? any ideas will help im just digging for anything right now. | ||
| Natexlh1000 |
How many PSI do poppet valves from engines have to take? | ||
| Rotorhead |
I recommend that you revisit the 5000PSI idea. The Myth Busters episode that lunches the chicken at the airplane windscreen. It was not the high PSI that luanches the projectile, It is the volume of air release not the PSI. You will find that most of the Pumkin chunkin' guns run at a much lower PSI than 5000 and huge volume. | ||
| Oldog |
I would be concerned about the rifle bbl at thoes pressures. | ||
| Reepicheep |
I wonder if you could rig a small plate, that rotates up against a lip, with a tab driven by a muzzleloader percussion cap, or pistol primer. The primer goes "bang", pushes the plate open for a bit to let enough air out to fire the projectile, and the plate swings back closed again and is resealed by the pressure. It would then be a "repeater" of sorts. You can probably "tune" the on time by the amount of the primer blast that hits the plate, by the mass of the plate, and by the size of the plate. Sounds like a really fun way to incur some sort of crippling injury. I'd work my way up in pressure ;) | ||
| Natexlh1000 |
I admire you for trying cool things but .22 bullets are so cheap + effective + safe. I would be really worried about carrying around that kind of pressure. That having been said, All of the air rifles that I've had used about the same mechanism. A poppet valve being held shut by a weak spring and the pressurized air chamber. When the trigger is pulled, a weight much like a firing pin+hammer is dropped upon the poppet valve opening it quickly. Whatever valve you use, will have to open fast or else you waste your charge. I would suggest using a lower pressure and a heavier projectile. | ||
| Sub65chris |
but .22 bullets are so cheap + effective + safe. --- perfect, i know the winter projects are getting to me i need to ride. The primer is a cool idea, i will have to think. I just got off the phone with a buddy of mine who runs a machine shop. We are going to talk on monday about building a valve like the valve off of a french horn. rotate the valve to expose a pre drilled hole the size you want. It would be snapped open by a large spring adn held closed by the trigger. I will post after the meeting. as far as the lower pressure higher weight idea, most of the bogbore airguns now are doing exactally that. I figure that the barrel has a volume of 16.53ci and the volume of my pressure vessle is about 84ci. the vessle will completely evacuate through a .45 in hole in about .021 of a second.that is assuming the valve has a zero lock time. so the barrel will have to be around 39 in long( i think ) to account for lock time and gas expansion. So my first conclusions are -need a fast valve( very fast) -need to figure the rate of expansion of the gas -need to figure the rate of energy transfer to the bullet from the gas -calculate the barrel length with above information - mabye just stop drinking so much coffee -work on buell more -loose weight etc. i will post more further down the line, | ||
| Slaughter |
You will have to build a pneumatic operated fast acting valve. There's no way to do it manually. I'll see if I can find a schematic around here somewhere. By the way - you do know that the physics of compressed air, nitrogen or even hydrogen are going to limit you to high subsonic muzzle velocites unless you really bend the rules (check LLNL's "SHARP" gun) Had a project for NAVSPECWAR a decade back but never could get muzzle velocities anywhere near practical needs... and we could get 15,000 psi in a lab gun (using a barrel from a 20mm cannon with a sabot for a 50 cal round) (Message edited by slaughter on February 20, 2008) | ||
| Hexangler |
You will have to build a pneumatic operated fast acting valve. ...or electronic solenoid? Hex | ||
| Hexangler |
...or one of these   | ||
| Sub65chris |
Slaughter - damn physics, i will continue to look but you really took the wind out of my sails. Hexangler - the rail gun would be cool but my wife doesnt want the basement full of expensive electromagnets. | ||
| Brumbear |
with 5000psi you could hurl a chevy that kind of pressure can really screw you up I have been cut bye 800psi hyd oil and burnt as well. Do be careful | ||
| Slaughter |
I can't find my sketches... I'll go and just make a simple schematic of how the fast acting valve works - back in a few... | ||
| Hexangler |
Rail guns don't use electro-magnets. Those are inferior "coil guns". Rail guns use just two conductive rails (could even be carbon fiber) and a very high dc current! Look 'em up. There are small experimental versions all over youtube and google. Big'ens from the navy too! Hex |
