SpudFiles Wiki - User contributions [en]

Paintball

2007-01-29T02:04:43Z

Abcdefg:

A '''paintball''' is a small hollow sphere filled with a non-toxic, washable 'paint'. They are designed to splatter upon impact. 
They are commonly available for the game of paintball, and they are round and have a fairly uniform mass - generally good for accuracy in smoothbore barrels.

== Aerodynamics ==

Paintballs are assumed to have a Cd of about .5, as they are smooth spheres. 
They may be launched out of a curved barrel to increase range via the Magnus effect (the same at work in [[hop-up]] devices.

== Use and target performance ==

Paintballs are typically launched out of 3/4" CPVC, as that is the most commonly available that pipe that is a close match for their diameter. Some prefer 3/4" sch 80, and the ultimate is recognized as being 3/4" sch 120, although this pipe is extremely hard to find and not commonly used.
Sch 120 barrels are thicker and are a tighter fit, [http://forums.spudtech.com/topic.asp?ARCHIVE=true&TOPIC_ID=2772 decreasing sag and increasing velocity].

Paintballs are typically [[breech loading|breech loaded]], and their shape allows them to be stored in magazines/clips.

Upon impact with:

* A twig, a paintball typically ruptures.
* A water-filled milk jug, a paintball typically ruptures.
* A tree, a paintball ruptures.
* A rock, a paintball ruptures.
* A person, a paintball typically ruptures, resulting in laughter.

Due to their low sectional density, most launchers will fire a paintball too fast to be considered safe, which is generally considered to be 300 fps. Furthermore, actually making a reliable, accurate, and rapidly firing weapon is a complicated task that probably can't be done without a lathe. 
Even then, most fields won't let you play with your homebrew weapon; spud guns that fire paintballs should be considered target-practice devices only.

[[Category:Projectiles]]

Paintball

2007-01-29T02:04:32Z

Abcdefg:

A '''paintball''' is a small hollow sphere filled with a non-toxic, washable 'paint'. They are designed to splatter upon impact. 
They are commonly available for the game of paintball, and they are round and have a fairly uniform mass - generally good for accuracy in smoothbore barrels.

== Aerodynamics ==

Paintballs are assumed to have a Cd of about .5, as they are smooth spheres. 
They may be launched out of a curved barrel to increase range via the Magnus effect (the same at work in [[hop-up]] devices.

== Use and target performance ==

Paintballs are typically launched out of 3/4" CPVC, as that is the most commonly available that pipe that is a close match for their diameter. Some prefer 3/4" sch 80, and the ultimate is recognized as being 3/4" sch 120, although this pipe is extremely hard to find and not commonly used.
Sch 120 barrels are thicker and are a tighter fit, [http://forums.spudtech.com/topic.asp?ARCHIVE=true&TOPIC_ID=2772 decreasing sag and increasing velocity].

Paintballs are typically [[breech loading|breech loaded]], and their shape allows them to be stored in magazines/clips.

Upon impact with:

* A twig, a paintball typically ruptures.
* A water-filled milk jug, a paintball typically ruptures.
* A tree, a paintball ruptures.
* A rock, a paintball ruptures.
8 A person, a paintball typically ruptures, resulting in laughter.

Due to their low sectional density, most launchers will fire a paintball too fast to be considered safe, which is generally considered to be 300 fps. Furthermore, actually making a reliable, accurate, and rapidly firing weapon is a complicated task that probably can't be done without a lathe. 
Even then, most fields won't let you play with your homebrew weapon; spud guns that fire paintballs should be considered target-practice devices only.

[[Category:Projectiles]]

Bulk tank regulator

2007-01-29T02:01:08Z

Abcdefg:

[[Image:Pressure-regulator.jpg|thumb|right|300px|A high-pressure bulk tank regulator]]
A '''bulk tank regulator''' is used to regulate down the output pressure of bulk gas tanks, such as CO2 or scuba tanks. They are made in many different designs for use in welding, cutting, scuba diving, carbonization of beverages etc.

Some regulators regulate flow instead of or in addition to pressure, a pure flow regulator is not useful in most spudgun applications, since it doesn't drop the output pressure from the tank to a safe level.

Safety

2006-11-26T00:02:40Z

Abcdefg:

Spudguns can be very dangerous if built or used improperly. However, if they are respected, they can be great fun.

==Launcher safety==
*As a very basic summary- DON'T BE AN IDIOT WITH THESE THINGS!!!!!
*Use good, safe [[cannon construction|construction methods]] and materials.
*Follow the rules of basic gun safety: never point the cannon at anything you don't want to destroy, and treat it as if it's loaded at all times. Never look down the barrel.
*Always make sure you are firing in a safe direction that is free of people, pets, livestock, cars, houses and other property. Use a solid backstop or make sure you have a clear landing area.
*Don't look into the chamber of a [[combustion cannon]] that has failed to fire. Fresh air can make a rich gas mixture lean enough to ignite.
*Don't use PVC cannons in cold weather. Sub-freezing temperatures makes PVC brittle and increases the chances of catastrophic failure.
*Don't use a cannon that is cracked or heavily scratched, or has been dropped on a hard surface. Joints may be weakened and the pressure ratings on damaged parts cannot be trusted.
*Don't use excessive pressure in a [[pneumatic cannon]]. [[PVC]] pipe is not rated for pressurized air because of the shrapnel risk, so use in a pneumatic gun is considered to be outside pipe specifications in the first place. Never exceed the pressure rating of the lowest rated part.
*Don't use overly powerful fuels in a [[combustion cannon]]. Solid fuels and very reactive gases such as [[hydrogen]] or [[acetylene]] are not suitable for use in spudguns. Don't use oxygen to enrich the mix in a PVC cannon.
*Use hearing protection when firing loud combustion and hybrid cannons, especially in an enclosed space. Use eye protection if there is a chance of splinters or other debris from the projectile hitting the target.

==Don't shoot living things==
A typical spudgun is capable of launching a potato weighing 50-150 grams a couple hundred yards with the muzzle energy of a powerful handgun. Longer distances are easily achieved with rocks, PVC darts, golf balls, and other aerodynamic projectiles.

This energy, even when carried by a projectile as fragile as the humble tuber, is easily capable of killing someone, or at least breaking bones or putting out eyes. As to property damage, most launchers can put a vegetable through a piece of 1/2" plywood, and many can put it through 3/4" - which is very significant considering the construction of most residential buildings.

The same applies to short/and or small-bore launchers too.

Despite their great potential to do harm, it is not looked upon well if you (attempt) to use your launcher as a hunting instrument. They are often hard to aim, leading to a low probability of a clean (humane) kill - plus; it is illegal to do so.

Some people don't take the extreme danger of a projectile fired from a potato cannon seriously enough. There are frequent news articles about people injured by potato guns firing projectiles other than vegetables, or people being accidentally shot while handling the gun.

Accidental discharges are the most likely cause of injury however some individuals lack the mental capacity to keep their guns pointed away from others at all times. When a potato gun is pointed at a human being the dangers are extreme. Do not under any circumstances let the barrel of a potato gun point towards another human, even if the gun is not loaded.

The bottom line is: don't aim a spudgun at anyone, at any time, even if you think it's not loaded.

==Ammo Safety==
Some advise against shooting bolts, coke cans full of concrete, and other hard objects out of your gun; saying things along the lines of:
"Anything that is much harder than a spud can cause grievous bodily harm if shot at another person, or any animal for that matter."
...in actuality, even a tater will cause "grievous bodily harm" if shot at another living being. The danger lies in an increased chance of ricochet when using sturdy ammo - use common sense, and don't fire non-shattering ammo at close targets.

Some caution should be taken with shooting loose sub-munitions, specifically gravel or stones, with a [[sabot]] behind them - there is a significant probability of them jamming up, and the barrel being overstressed when the sabot tries to keep moving through the blockage, leading to a failure. Always wrap your lose projectiles in something - paper towels, old socks, and plastic bags are all acceptable.

Piston valve

2006-11-25T23:59:23Z

Abcdefg: extra info

A '''piston valve''' is a [[pilot valve|pilot]] operated valve. It is very similar to a [[diaphragm valve]] in theory, but replaces it's flexible diaphragm with a rigid cylinder. There are 2 varieties; barrel sealing and chamber sealing.

== Barrel sealing valve ==

In a barrel sealing valve, the piston seals against the breech of the barrel. this is the most common piston valve design.

=== construction ===

The piston is often a well fitting cup-shaped object, such as a end cap. To provide a sealing face, a piece of rubber is attached, typically with a bolt. Equalization is accomplished by simply allowing the air to leak past the piston and into the chamber. Some people will machine their own pistons, in which case they often build [[O-ring]]s into them. With the O-rings, you need to make a small equalization hole; sometimes this is fancied up to be a homemade [[check valve]].

Because a piston is heavier and harder than a diaphragm, and PVC is somewhat brittle, it is recommended that a bumper of sorts is built into your pilot volume. Common bumpers include heavy-duty rubber hose, and such. This is labeled "'''F'''" in the "use, barrel sealing" diagram.

These valves are often used on [[coaxial]]s and [[over/under]]s. In an over/under, the valve is built in a "T" fitting. The barrel is put co-axially through one end, the pilot and piston are put in the opposite one, and a chamber is connected to the perpendicular opening with a 90° elbow.

=== Use ===
[[Image:Wpiston.PNG|frame|top=pressurized, bottom=firing]]
Operation:
#Air is added by filling behind the piston (C).
#The piston (E) slides forwards, and seals against the barrel (A). (Alternatively, one can use a spring to move the piston forwards, which allows one to fill [slowly at first, to allow the pressure to equalize] from the chamber.)
#More air is added, and leaks around the piston (or through a small equalization hole) and into the chamber (B), filling it to the desired pressure.
#The pilot valve (D) behind the piston is opened, the pressure in the [[pilot|pilot volume]] (C) drops, and the higher pressure in the chamber area pushes the piston away from the barrel.
#The air flows around from the chamber, and into the barrel, propelling the projectile.

-A bolt style valve= named after the bolt in a paintball marker, uses an object to hold the piston, rather than gas. the object is removed by the trigger.

The performance of these valves can be calculated with the [[GGDT]].
If your valve [[honking|honks]], it is probably a good idea to invest in a better [[pilot valve]].
[[category:valves]]

Pneumatic cannon

2006-11-25T23:56:47Z

Abcdefg:

[[image:pneumatic ballvalve cannon.jpg|right|thumb|300px|Pneumatic ball valve cannon]]
A '''pneumatic cannon''' is a cannon powered by pressurized gas, usually air or CO2. They are more complex than [[combustion cannon]]s but also more powerful, and their performance is more consistent.

Pneumatic launchers consist of five basic elements:

*Compressed gas storage reservoir ([[chamber]] for short)
*Filling valve (bicycle [[Schrader valve]]s, [[quick disconnect]]s, etc.)
*Firing valve ([[ball valve]]s, [[sprinkler valve]]s, [[piston valve]]s, bolt-style valves(see piston valves) [[quick-exhaust valve]]s, and [[burst disk]]s are the most common)
*[[Barrel]]
*[[Pressure gauge]] (for safety & repeatable launches)

In order to fire, the operator loads a projectile into the barrel, fills the chamber with a compressed gas (air [[compressor]]s, hand pumps, [[Pressure regulator|regulated]] bottled gas, and 12 gram [[CO2 cartridge]]s are common filling methods), and activates the main valve thus dumping the air in the chamber to the barrel.

The expansion of the compressed gas propels the projectile down the barrel. The barrel length determines the amount of energy transferred to the projectile and ultimately the velocity of the projectile.

High performance launchers use techniques such as [[sprinkler valve modification|modifying valves]] for faster opening times, using homemade valves, and maximizing the amount of airflow through the valve.

The [[GGDT]] (gas gun design tool) is highly recommended to those interested in pneumatic launchers.