A potato cannon is a pipe-based cannon

Cannon

A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...

 which uses air pressure (pneumatic), Propellant, or Propane/Gas, or combustion of a gaseous fuel, to launch projectiles at high speeds. First invented during the 1980s by Conor Conor Gaul the popularity of the spud gun is widespread. They are built to fire chunks of potato

Potato

The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...

, as a hobby, or to fire other sorts of projectiles, for practical use. The projectile can be dangerous and result in life-threatening injuries, including cranial fractures, if a person is hit.

Launcher types

All spud guns propel projectiles down their barrels using pressurised gas in the same manner as a firearm

Firearm

A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...

 (although at a much lower pressure). There are four basic ways that spud guns may achieve this:

• By the combustion of a gaseous fuel-air mixture; this is generally called a combustion launcher, and its pressure is limited primarily by the energy density of the fuel-air mixture (less than 100 psi (0.6894757293 MPa) with all safe fuels).
• By the release of compressed gas (normally air) through a valve; such a launcher is typically referred to as a pneumatic launcher, and its power is limited primarily by the pressure of the air supply, be that from a compressor, manual pump or bottled gas.
• By the explosion of a dry ice bomb
  Dry ice bomb
  A dry ice bomb is a simple bomb-like device. While the simplicity and ease of construction, high bursting pressure, and sound make this dry ice activity appealing for recreational purposes, it can be unpredictable and dangerous, and has led to many injuries - and dry ice bombs are illegal in many...
  
   placed in the pipe before the projectile, generally referred to as a dry ice bomb cannon, these are limited in power by the materials and size of the dry ice bomb but firing pressures can be around 200–300 psi (1.4–2.1 MPa).
• By the combustion of a pre-pressurised fuel-air mixture; this is called a hybrid launcher, and yields higher pressures than that of a normal combustion spud gun, limited only by the construction of the launcher (generally a few hundred pounds-force per square inch).

Combustion launchers

Combustion powered spud guns typically have the least complex designs, the four basic elements of which are:

• A fuel system
• A combustion chamber
• An ignition source
• A barrel

In order to fire, the operator loads a projectile into the barrel, adds fuel to the combustion chamber (for example aerosols

Aerosol spray

Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. This is used with a can or bottle that contains a liquid under pressure. When the container's valve is opened, the liquid is forced out of a small hole and emerges as an aerosol or mist...

 or propane

Propane

Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...

), and triggers the ignition source (often using a piezoelectric barbecue igniter). The fuel then ignites, creating hot expanding gases, and forcing the projectile out of the barrel. Distances vary greatly depending on many factors, including the type of fuel used, the efficiency of the fuel/air ratio, the combustion chamber/barrel ratio, and the flight characteristics of the projectile. Common distances vary from 100 to 200 metres, and there is a reported case of a cannon exceeding 500 metres of range.

Advanced combustion launchers may include metered propane injection to ensure proper fueling, chamber fans to mix the fuel with the air and accelerate venting of the chamber after firing, multiple spark gaps (spark strips) to decrease combustion time, and high-voltage ignition sources (flyback circuits, stun guns, camera flashes, etc.).

Combustion launchers are usually less powerful than their pneumatic or hybrid counterparts.

Pneumatic launchers

Pneumatic launchers are considered a little more difficult to build due to the need of a completely airtight construction. These cannons have four basic components:

• A filling valve
• An air chamber
• A pressure release valve
• A barrel

In a pneumatic spud gun, air is pumped into the pressure chamber. After the desired chamber pressure is reached, the pressure release valve is opened, allowing the gas to expand down the barrel, propelling the projectile forwards.

The filling valve is usually a commonly available type such as a Schrader

Schrader valve

The Schrader valve is a brand of pneumatic tire valve used on virtually every motor vehicle in the world today. The Schrader company, for which it was named, was founded in 1844 by August Schrader...

 or Presta valve

Presta valve

The Presta valve is a valve commonly found in high pressure road style and many mountain bicycle inner tubes. It comprises an outer valve stem and an inner valve body...

 but other assemblies to pressurise the cannon such as quick release connections with ball or check valves have been used.

The pressure release valve is often one of a variety of commercially available types such as a plumbing ball valve, an irrigation sprinkler valve or a quick exhaust valve. Experienced builders often make their own valves for this purpose to gain greater flow and faster actuation. The most common custom design used is the piston valve

Piston valve

A piston valve is a device used to control the motion of a fluid along a tube or pipe by means of the linear motion of a piston within a chamber or cylinder.Examples of piston valves are:...

. Multiple valves arranged to be triggered together are occasionally used as an alternative to a single larger valve.

The range of pneumatic cannons is more variable than the range of combustion spud guns due to the increased variation possible in the components. Typical ranges are slightly higher because of the greater power, but the maximum range of some high power pneumatic cannons has been said to be over 1000 metres (1,093.6 yd).

Pneumatic spud guns are generally more powerful than combustion spud guns. A typical combustion gun generates average chamber pressures of about 30 psi (206.8 kPa) with peaks of around 70–100 psi (482.6–689.5 kPa), while the average pneumatic gun can operate at pressures in the vicinity of 100 psi (689.5 kPa). In recent times, it has become increasingly common for metal pneumatic launchers to use even higher pressures, sometimes up to 500 psi (3.4 MPa) or higher.

Dry ice launchers

A dry ice

Dry ice

Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...

 cannon uses the sublimation of solid carbon dioxide to generate the gas pressure to propel a projectile.

The oldest examples simply involve dropping pieces of dry ice into a tube closed at one end and sealing the other end by jamming the projectile in. When the pressure of the carbon dioxide from the subliming dry ice builds high enough, the projectile will be blown out of the tube. The pressures of such devices are not very high as it only needs to build enough to overcome the friction of the projectile jammed in the barrel. Tens of psi is most likely.

A more modern example is the dry ice bomb

Dry ice bomb

A dry ice bomb is a simple bomb-like device. While the simplicity and ease of construction, high bursting pressure, and sound make this dry ice activity appealing for recreational purposes, it can be unpredictable and dangerous, and has led to many injuries - and dry ice bombs are illegal in many...

 launcher. A plastic bottle containing water has some dry ice added and is quickly sealed and dropped down a tube closed at one end. A projectile is inserted in after it. The water accelerates the sublimation of the dry ice and the pressure from the carbon dioxide gas produced eventually ruptures the plastic bottle and launches the projectile. The rupturing pressure of a standard plastic soda bottle is between 200 and 300 psi (1.4 and 2.1 MPa) in the open air but when confined in a pipe, it could be higher.

Due to the operation of a dry ice bomb cannon extra safety issues are present:

• The dry ice bomb used for propulsion can achieve bursting pressure in a matter of seconds to hours depending on the quantity of water and dry ice. If too little dry ice, it also may not achieve bursting pressure at all. These timing issues can cause belief that the cannon has failed to fire but attempting to unload the cannon may then provide the extra stress on the bottle needed for it to rupture.
• Piping and any reinforcement of such may be underestimating the high pressure spike when the dry ice bomb explodes and plastic tubing may rupture with such forces
• The recoil of such cannons can be very great due to the high pressure combined with the large internal diameter piping needed for the bottles (5–9 cm; 2–3½ in) resulting in them being ill-suited for hand held firing.

Compared to the operation of other spud guns, dry ice bomb cannons are similar in firing principle to a burst disk cannon of the pneumatic type; the plastic bottle performing the task of the burst disk albeit in a less controlled manner.

Another means of utilising dry ice in spud guns is to use the sublimation of dry ice to create substantial pressure behind a valve, and placing a barrel on the other side of that valve with a projectile loaded into it. Pressures behind the valve can reach upwards of 800 psi (5.5 MPa), and by quickly releasing the valve, the projectile can be launched. Whilst this method is more controllable and in many means safer than utilising a soda bottle as a burst disk (provided pressure rated valves and piping are used), it is limited in that quick release valves, such as ball valves, are generally not bigger in diameter than 1 or 2 inches. Additionally, they cannont be opened as rapidly as a soda bottle will rupture, and consequently there is less immediate airflow. However, this is offset by the fact that such a design can operate at more than double the pressure of a typical dry ice bomb launcher, as soda bottles will rupture at only 200–300 psi (1.4–2.1 MPa).

Hybrid launchers

A hybrid launcher consists of seven basic elements:

• A fuel system (usually metered propane)
• An air filling valve (see pneumatic launchers)
• One or more pressure gauges
• A high pressure combustion chamber
• A pressure-triggered main valve (burst disk)
• A barrel
• An ignition source (see combustion launchers)

A hybrid combines principles of the combustion and pneumatic spud gun. It uses a pre-pressurised mixture of fuel and air to get more power out of a given chamber volume.

In order to fire, the operator first readies the pressure-triggered valve then injects several times the normal amount of fuel and appropriately more air. When the ignition source is triggered, the pressure from the combustion causes the main valve to open and propels the projectile out of the barrel with the released combustion gases. The hybrid is capable of higher velocities than a combustion or pneumatic spud gun because the pressure generated is higher than that in a combustion gun (for most fuels), and the shock wave moves faster than it can in a pneumatic (for most gases), due to the higher temperature. Projectiles fired by a hybrid have broken the sound barrier

Sound barrier

The sound barrier, in aerodynamics, is the point at which an aircraft moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several...

.

A hybrid using a fuel and air mix at twice atmospheric pressure is said to be using a 2X mix. Higher mixtures can be used and will produce even higher pressures. The fuel and air needs to be measured and matched carefully to ensure reliable operation; hence the use of accurate air pressure gauges and fuel meters.

Plastics

• PVC-U (Polyvinyl chloride, unplasticized)
  Polyvinyl chloride
  Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
  
  : Highly popular due to its availability and relatively low cost. PVC pipes are available in a wide variety of sizes and pressure ratings. In industry, however, they are illegal for compressed air applications—if they are damaged under pressure the plastic can fail explosively.
• ABS (Acrylonitrile butadiene styrene)
  Acrylonitrile butadiene styrene
  Acrylonitrile butadiene styrene is a common thermoplastic. Its melting point is approximately 105 °C ....
  
  : Another popular plastic piping material, more expensive and less common than PVC but available in the same sizes and pressure ratings. Unlike PVC it is used in compressed air systems as it splits rather than shatters on failure. It also has a greater temperature tolerance (−40 °C to +80 °C, or −40 to 175 °F) compared to 0 °C to +60 °C or 30 to 140 °F for PVC).

Both PVC and ABS piping are also available in forms which are not pressure rated. Use of unrated plastic piping and fittings is a common source of cannon failure and poses a much greater risk to a cannon operator.

Metals

• Steel
  Steel
  Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
  
  : The very high pressure rating of steel piping makes it a familiar sight on high-powered hybrid cannons. It is however much more expensive than any other common piping material. The extra weight and joining difficulties are also a consideration.
• Copper
  Copper
  Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
  
  : As a common plumbing material, copper pipes and associated fittings are readily available. They have higher pressure ratings and flow compared to similar plastic piping. The drawbacks are that copper is heavier, and up to four times the cost of PVC or ABS pipes of similar external diameters.
• Aluminium
  Aluminium
  Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
  
  : Aluminium is a lightweight metal with good corrosion resistance. Aluminium pipes are sometimes used as barrels on spud guns on their own and machined aluminium is a popular material for particularly unique designs.
• Brass
  Brass
  Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
  
  : Often brass fittings are used on spud guns for small parts of the construction like fuel systems, because it is one of the most common materials for small pipe fittings. Occasionally large parts of spud guns are machined entirely out of brass.

Manual

• Ball Valve
  Ball valve
  A ball valve is a valve with a spherical disc, the part of the valve which controls the flow through it. The sphere has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends...
  
  : Made out of either plastic or metal, ball valves are considered inferior by many enthusiasts due to their slow opening times. For those on a tight budget or in low-power setups, ball valves are ideal. Some choose to modify their valves by attaching a pneumatic actuator
  Pneumatic actuator
  A pneumatic actuator converts energy into motion. The motion can be rotary or linear, depending on the type of actuator.Some types of pneumatic actuators include:*Tie rod cylinders*Rotary actuators*Grippers...
  
   or spring
  Spring (device)
  A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
  
   to achieve a faster opening speed.
• Blowgun: A blowgun is a small hand held device used to blow away debris from a work area and is designed to be used attached to a compressed air line. It uses a sprung poppet valve operated by a lever to allow air through its body and out through a specially shaped nozzle. In spudgunning it is used to pilot larger valves—releasing a small volume of air to allow a piston or diaphragm to fly back and release a much larger volume of air into the barrel. It is also used as the primary valve for small cannons which fire airsoft
  Airsoft
  Airsoft is a sport in which participants shoot round non-metallic pellets launched via replica firearms.Gameplay varies in style and composition but often range from short-term skirmishes, organized scenarios, military simulations, historical reenactments, to competition target shooting events...
  
   pellets and so do not require high air flow. Blowguns can be modified to increase airflow.

Electronic

• Sprinkler valve (otherwise known as a solenoid valve
  Solenoid valve
  A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports...
  
  ): The use of irrigation sprinkler valves as pneumatic valves has become increasingly popular for spudgunning. These valves are intended to be electronically triggered causing a solenoid to depressurise a diaphragm and allow airflow through. It is also possible to remove the solenoid and, instead, to actuate the valve manually with a blowgun to depressurise the diaphragm. Such modifications allow the valve to open as much as 3 to 5 times faster.

Pneumatic

• Diaphragm valve
  Diaphragm valve
  Diaphragm valves consists of a valve body with two or more ports, a diaphragm, and a "saddle" or seat upon which the diaphragm closes the valve. The valve is constructed from either plastic or steel....
  
  : A diaphragm valve is used in pneumatic cannons where the barrel is within the air chamber. It is a disk of flexible material mounted directly behind the barrel that seals it when pressure is increased behind the disk. The design is such that air leaks past the diaphragm from behind it to the chamber around the barrel, sealing the soft rubber against the butt of the barrel. Once the chamber is fully pressurised the compressed air behind the diaphragm is quickly vented, causing the centre of the diaphragm to flex backwards, exposing the butt of the barrel to the compressed air inside the chamber, which rapidly exhausts through the barrel, launching the projectile. Sprinkler valves have also been modified to act in the same manner a diaphragm valve operates; changing the triggering of the valve to a release of air controlled by a blo-gun valve, rather than electronically.
• Piston valve
  Piston valve
  A piston valve is a device used to control the motion of a fluid along a tube or pipe by means of the linear motion of a piston within a chamber or cylinder.Examples of piston valves are:...
  
  : The gold standard of pneumatic spudgunning is the piston valve, due to its extremely high rate of flow and opening speed. It works in an almost identical fashion to a diaphragm valve but replaces the flexible diaphragm with a hard rubber-faced piston. The valve opening is generally as wide as or wider than the barrel diameter, so there is very little constriction of airflow. Piston valves also open much faster than either ball or solenoid valves. However, construction of this type of valve is inherently complex, and some choose to order pre-built valves through the internet.
• Quick Exhaust Valve (QEV): a commercial piston or diaphragm valve in a metal body intended for the quick venting of pneumatic cylinders. In spudgunning they are ideal barrel sealing valves with faster opening times than custom piston valves and high flow rates. They can be commonly found in sizes from ⅛ inch to 1½ inches (3–40 mm) and sometimes even larger models. It provides an easy option for inexperienced spud-gun builders but the cost is usually greater than for any other valve type.
• Burst Disk Valve
  Rupture disc
  Burst disc redirects here. For the human back ailment see Spinal disc herniation.A rupture disc, also known as a bursting disc or burst diaphragm, is a non-reclosing pressure relief device that, in most uses, protects a pressure vessel, equipment or system from overpressurization or potentially...
  
  : Used in a few pneumatics but primarily in hybrid cannons, burst valves are considered the ideal pressure release mechanism as they allow an unobstructed flow of high pressure air. Burst disks have no moving parts, making them very reliable. They are very appealing for hybrid cannons because they can withstand the low pressure gas mix in the chamber before ignition, yet fail as planned upon successful ignition. The high pressure combustion gases are released into the barrel at a rate which generates greater velocities than a mechanical valve could allow. Pneumatic cannon burst discs work similarly. The disc and projectile are loaded, and the chamber is pressurised until the disc ruptures. Unfortunately, this usually does not give the operators much in the way of control over timing, although a puncturing mechanism can be used. Burst disks are of no specific material and may consist of plastic or thin sheet metal or foil.
• The Quick Dump Valve is a recent addition to the choices of valves for spudding. A QDV is a spool valve that is balanced under pressure with one end of the spool oriented toward the barrel. The spool is manually unbalanced allowing pressure between the end of the spool and the projectile in the barrel. The air pressure then forces the spool back and the projectile forward. Since the valve is triggered with no pilot pressure, the valve snaps open with no pilot pressure to hinder it. Currently it is not commercially for sale and must be hand built by the hobbyist like most piston valves.

Welding, soldering and gluing

• Solvent welding: used for similar plastic connections using solvent fittings, the solvent temporarily dissolves the polymer chains of the plastic and the parts to be joined are brought together. On rehardening, the polymer chains from each part are entangled and so form a solid weld.
• Metal welding
  Welding
  Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, with pressure sometimes...
  
  : used to form strong joints between similar metals by melting the points of connection together. It is an uncommon process in spudgun construction due to the equipment necessary to make the welds.
• Soldering
  Soldering
  Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a lower melting point than the workpiece...
  
  : commonly used in the construction of copper pipe based spudguns, a solder
  Solder
  Solder is a fusible metal alloy used to join together metal workpieces and having a melting point below that of the workpiece.Soft solder is what is most often thought of when solder or soldering are mentioned and it typically has a melting range of . It is commonly used in electronics and...
  
   with a lower melting point than the copper is melted and drawn into the gaps between pipe and fitting with capillary action
  Capillary action
  Capillary action, or capilarity, is the ability of a liquid to flow against gravity where liquid spontanously rise in a narrow space such as between the hair of a paint-brush, in a thin tube, or in porous material such as paper or in some non-porous material such as liquified carbon fiber, or in a...
  
  , holding to pipe and fitting with a wetting
  Wetting
  Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting is determined by a force balance between adhesive and cohesive forces.Wetting is important in the bonding or adherence of...
  
   action before hardening.
• Gluing
  Glue
  This is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....
  
  : the use of epoxy
  Epoxy
  Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
  
   resin in small designs is common for the making of custom parts but it is rare to see glues used for structural connections. Epoxy resin is mostly used in applications where normal fittings would limit the possibilities.
• Duct tape
  Duct tape
  Duct tape, or duck tape, is cloth- or scrim-backed pressure sensitive tape often sealed with polyethylene. It is very similar to gaffer tape but differs in that gaffer tape was designed to be cleanly removed, while duct tape was not. It has a standard width of and is generally silver or black...
  
  : sometimes used in simple cannons, it is unsuitable for sealing any significant pneumatic pressure and if used on a combustion cannon the heat produced can soften the adhesive and melt the tape, greatly weakening any seal or join it creates.

Mechanical joints

• Compression Fittings
  Compression fitting
  Compression fittings are used in plumbing and electrical conduit systems to join two tubes or thin-walled pipes together. In instances where two pipes made of dissimilar materials are to be joined , the fittings will also be made of one or more compatible materials appropriate for the connection...
  
  : primarily seen on copper pipe spudguns, the compression fitting squeezes a metal ring against the pipe between a nut and the fitting body to form the connection. Easier than solder fittings and requiring only a spanner they are much more expensive and are of greater weight.
• Threaded Fittings
  Threaded pipe
  A threaded pipe is a pipe with screw-threaded ends for assembly.- Tapered threads :The threaded pipes used in some plumbing installations for the delivery of gases or fluids under pressure have a threaded section that is slightly conical . This is called a "tapered thread"...
  
  : commonly available in BSP
  British standard pipe thread
  The British Standard Pipe thread is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external with an internal thread.-Types:...
  
   or NPT
  National pipe thread
  National Pipe Thread Tapered Thread is a U.S. standard for tapered threads used on threaded pipes and fittings. The taper rate for all NPT threads is measured by the change of diameter over distance. The angle between the taper and the center axis of the pipe is 1° 47′ 24″...
  
   (not interchangeable) they generally require a fitting attached to a pipe by other means to allow screwing into another threaded fitting. The exception to this is steel pipe, the ends of which can have the appropriate thread cut into them.
• Flange
  Flange
  A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
  
   joints: on large steel spudguns, pipe and fittings are sometimes bolted together by means of flanges with a gasket
  Gasket
  thumb|sright|250px|Some seals and gaskets1. [[o-ring]]2. fiber [[Washer |washer]]3. paper gaskets4. [[cylinder head]] [[head gasket|gasket]]...
  
   sandwiched between them to provide an airtight joint.
• Cam Locks: on spudguns with interchangeable barrels a cam lock is sometimes used to connect barrels to the cannon as it provides a quick and simple solution to switching barrels. Two levers either side of the socket side of the fitting rotate internal cam
  Cam
  A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
  
  s to lock in or release the plug side of the fitting to which a barrel is attached.

The sound barrier

It is rare for a spud gun to be powerful enough to break the sound barrier, although there are some cases of this happening using specialized designs. The spud guns used are typically hybrids; but some pneumatic cannons have achieved the feat, either by using a special low density gas, such as helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

, or high pressures combined with a fast valve. There is also one reported case of a combustion design achieving super-sonic velocities.

The difficulty in breaking the barrier arises from the speed of the particles within the gas. If the projectile is travelling at, or near to that speed, then the gases simply cannot keep up with it to provide the accelerating force. The problem is solved by increasing the speed of the particles, either by:

• Using lighter molecules, as occurs when helium
  Helium
  Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
  
   is used in a pneumatic.
• Heating the gases to far higher temperatures, and thus giving them more energy. This allows hybrids and combustions to achieve supersonic velocities.
• Using steel and much higher pressures of 800 psi (5.5 MPa) or more, but achieving these pressures is difficult. CO₂ gas, although it can reach these pressures, is not suitable due to its high density.

Supersonic

Supersonic

Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...

 velocities may theoretically be attained by pneumatics with a sufficiently large "dead space" between the main valve and projectile. The incoming air can raise the pressure rapidly in this dead space, creating high temperatures sometimes sufficient to achieve supersonic velocities. This particular effect has not yet been successfully used, but has been discussed, as both adiabatic and shock heating

Shock wave

A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

 are documented phenomena in gases.

The highest projectile speed recorded from a spud gun is 933.3 m/s (3,062 ft/s) (approximately 2.7 times the speed of sound) with a 16.6 gram (1.4940149401494E-06 gr) 20 mm plastic slug from a hybrid using a 1 MPa (145 psi) pre-ignition mixture of air and propane.

Practical uses

Although spudguns are created and used for the purpose of recreation there are other devices which work on identical principles in many other fields with more serious uses.

Entertainment

• Promotional sports cannons: Portable pneumatic cannons which run on bottled CO₂ are common at large sports games in the U.S. where they are used to project items such as T-shirts or wrapped food into the audience. They tend to be made of higher quality materials than an average pneumatic spudgun but they use the same methods of operation.
• Special effects cannons: In film and theatre productions pneumatic cannons are often used as a pyrotechnic-free method of material projection. These can vary from simple ball valve, manually operated models to electronically triggered designs operated from a remote control panel depending on the exact requirements.

Industry

• Hail cannon
  Hail cannon
  A hail cannon is a shock wave generator claimed to disrupt the formation of hailstones in the atmosphere.These devices frequently engender conflict between farmers and neighbors when used, because they are repeatedly fired every 1 to 10 seconds over the period when a storm is approaching and until...
  
  s: these are very large devices which consist of a combustion chamber and a large funnel shape mounted on top of it. A gas mix is ignited in the combustion chamber and the funnel directs the blast wave upwards. They are intended to protect crops from hail damage by disrupting hail formation with the shock waves. There has however been no scientific proof of their effectiveness.
• Air cannons
  Air blaster
  An air blaster or air cannon is a de-clogging device composed of two main elements: a pressure vessel and a Triggering mechanism...
  
  : This can mean:
  • A pneumatic spudgun
  • Air blaster
    Air blaster
    An air blaster or air cannon is a de-clogging device composed of two main elements: a pressure vessel and a Triggering mechanism...
    
    , a compressed air device to unblock clogging in large storage containers (e.g. silo
    Silo
    A silo is a structure for storing bulk materials.Silo may also refer to:* Silo , a 3D modeling software* Silo , a defunct chain of retail electronics stores* SILO , used in Linux...
    
    s) for powdery material.
  • Air cannon (mechanics), a compressed air device for creating high pressure shock waves under water
• Bird scarers: these devices are essentially automatic combustion cannons. They require bottled propane gas and a lead-acid battery. At intervals they ignite a propane/air mix to produce a loud explosion (up to 150 decibel
  Decibel
  The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
  
  s close to the device) to scare birds from crop fields or near airport runways.
• Chicken cannon
  Chicken Cannon
  Chicken Cannon may refer to:*The NASA Chicken Gun, a device used in aircraft testing*The Chicken Cannon featured on the satirical Canadian television show Royal Canadian Air Farce...
  
  s: Many aircraft parts must be able to survive the impact of a bird in flight, known as a birdstrike. Pneumatic guns are used to project a bird, typically a dead chicken
  Chicken
  The chicken is a domesticated fowl, a subspecies of the Red Junglefowl. As one of the most common and widespread domestic animals, and with a population of more than 24 billion in 2003, there are more chickens in the world than any other species of bird...
  
  , into a product designed to mitigate a birdstrike. Aircraft canopies, engines, and critical flight control surfaces will normally undergo this type of stress testing to determine whether they are strong enough to withstand a birdstrike in flight.
• Shock tube
  Shock tube
  For the pyrotechnic initiator, see Shock tube detonatorThe shock tube is an instrument used to replicate and direct blast waves at a sensor or a model in order to simulate actual explosions and their effects, usually on a smaller scale...
  
  s: used to test hypersonic and supersonic combustion ramjets.

Military

• Combustion light gas gun
  Combustion light gas gun
  Combustion light gas gun technology is one of the areas being explored in an attempt to achieve higher velocities from artillery to gain greater range. Conventional guns use solid propellants, usually nitrocellulose-based compounds to develop the chamber pressures needed to accelerate the...
  
  s are weaponised combustion cannons which burn a low molecular weight gas such as hydrogen to provide a higher specific impulse
  Specific impulse
  Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
  
   than relatively high molecular weight conventional solid propellants.

Safety

Spud guns by nature are hazardous and can present safety issues if poorly constructed or used.

Users should follow the same rules as if handling a conventional firearm (see gun safety

Gun safety

Gun safety is a collection of rules and recommendations that can be applied when handling firearms. The purpose of gun safety is to eliminate or minimize the risks of unintentional death, injury or damage caused by improper handling of firearms....

), but given the frequently improvised materials and construction used in spudguns, it is particularly important for the user to use basic ear and eye protection when operating a spudgun.

Legal issues

In some jurisdictions spud guns are outlawed or have restrictions on their use and may require licenses and certification of the gun.

In popular culture

• In the Bugsy Malone
  Bugsy Malone
  Bugsy Malone is a 1976 musical film, very loosely based on events in New York City in the Prohibition era, specifically the exploits of gangsters like Al Capone and Bugs Moran, as dramatized in cinema...
  
  movie, a similar device called a "splurge gun" fires cream
  Cream
  Cream is a dairy product that is composed of the higher-butterfat layer skimmed from the top of milk before homogenization. In un-homogenized milk, over time, the lighter fat rises to the top. In the industrial production of cream this process is accelerated by using centrifuges called "separators"...
  
   pellets.
• In The Trailer Park Boys, Julian, Ricky, Bubbles, Corey and Trevor use spud guns to investigate the enormous damage to their crops of cannabis. This was because real guns would attract too much attention.
• In the film Tremors 3: Back to Perfection
  Tremors 3: Back to Perfection
  Tremors 3: Back to Perfection is a direct-to-video 2001 comedic monster movie, the third in the Tremors series featuring the subterranean worm-creatures dubbed "Graboids". It was directed by Brent Maddock and stars Michael Gross...
  
  , Jack Sawyer suggested to Burt Gummer
  Burt Gummer
  Burt Gummer is a fictional character, played by actor Michael Gross, from the Tremors film series and the short lived SciFi Channel TV program of the same name...
  
   that they build a potato gun to fight the Ass-Blasters
  Graboid
  The graboid is a fictional species that acts as the primary antagonist of the Tremors film series. As Suzanne Ferriss and Mallory Young explain, the "destruction of 'graboids', as they are quickly dubbed, becomes the central tension of the film." The creature made its debut in the 1990 film...
  
  .
• In an episode of Nickelodeon's Drake and Josh, Drake buys a potato gun, accidentally hitting Josh, making him drop the weights he was lifting, causing him to break his foot.
• Dwight Schrute
  Dwight Schrute
  Dwight Kurt Schrute III is a character on NBC's The Office portrayed by Rainn Wilson. He originally exactly resembled Gareth Keenan from the original UK version of The Office. Dwight is the top salesman and former acting manager for the Dunder Mifflin Paper Company and has won numerous awards for...
  
   on the U.S.
  United States
  The United States of America is a federal constitutional republic comprising fifty states and a federal district...
  
   version of The Office has mentioned owning a spud gun in more than one episode.
• In 14th episode of Season 4 of Prison Break
  Prison Break
  Prison Break is an American television serial drama created by Paul Scheuring, that was broadcast on the Fox Broadcasting Company for four seasons, from 2005 until 2009. The series revolves around two brothers; one has been sentenced to death for a crime he did not commit, and the other devises an...
  
  , a combustion potato gun is used by Michael Scofield
  Michael Scofield
  Michael J. Scofield is the main protagonist in the American television series Prison Break. He is portrayed by Wentworth Miller. The character first appeared in the series pilot as a man who stages a bank robbery in order to get sent into the prison where his older brother, Lincoln Burrows , is...
  
   to launch 40 mm smoke grenade
  Smoke grenade
  Smoke grenades are canister-type grenades used as ground-to-ground or ground-to-air signaling devices, target or landing zone marking devices, or as screening devices for unit movements. Smoke grenades are normally considered non-lethal, although incorrect use may cause death...
  
  s.
• The Simpsons
  The Simpsons
  The Simpsons is an American animated sitcom created by Matt Groening for the Fox Broadcasting Company. The series is a satirical parody of a middle class American lifestyle epitomized by its family of the same name, which consists of Homer, Marge, Bart, Lisa and Maggie...
  
  character Maude Flanders was killed by air-cannon launched T-shirts in the eleventh season episode, "Alone Again, Natura-Diddily
  Alone Again, Natura-Diddily
  "Alone Again, Natura-Diddily" is the fourteenth episode of the eleventh season of The Simpsons, and marks the final regular appearance of the character Maude Flanders. In the episode, she is killed in an accident while watching a speedway race, devastating Ned Flanders and prompting Homer to find a...
  
  ".
• In Duct Tape Forever
  Duct Tape Forever
  Duct Tape Forever is a 2002 comedy film based on The Red Green Show. It was written by Steve Smith, the actor who plays Red Green.-Plot:...
  
  (the movie based on The Red Green Show
  The Red Green Show
  The Red Green Show is a Canadian television comedy that aired on various channels in Canada, with its ultimate home at CBC Television, and on Public Broadcasting Service stations in the United States, from 1991 until the series finale April 7, 2006 on CBC...
  
  ) Edgar K. B. Montrose says to sell them as toys to the kids to raise money.
• In the movie Aliens in the Attic the kids build a spud gun that they use to fight aliens invading Earth.
• A Mythbusters
  MythBusters
  MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...
  
  episode tested a potato cannon held together by duct tape compared to one held together using PVC bonding agent.
• In the TV series House, M.D.
  House (TV series)
  House is an American television medical drama that debuted on the Fox network on November 16, 2004. The show's central character is Dr. Gregory House , an unconventional and misanthropic medical genius who heads a team of diagnosticians at the fictional Princeton-Plainsboro Teaching Hospital in...
  
  episode "The Dig
  The Dig (House)
  "The Dig" is the eighteenth episode of the seventh season of the American medical drama House. It first aired on April 11, 2011. This is the 150th episode of the series. Wilson and Cuddy, interestingly, do not appear in this episode.-Plot:...
  
  ", House is attending a spud gun show with Thirteen, where he uses the spud gun to threaten a teenage competitor.
• A spud gun was one of the many different weapons used in Bully
  Bully (video game)
  Bully, also known as Canis Canem Edit for the PAL PlayStation 2 version, is an open world video game released by Rockstar Vancouver for the PlayStation 2 on 17 October 2006 in North America, and 25 October 2006 in the United Kingdom...
  
  , a game made by Rockstar Games
  Rockstar Games
  Rockstar Games is a major video game developer and publisher based in New York City, owned by Take-Two Interactive following its purchase of UK video game publisher BMG Interactive. The brand is mostly known for Grand Theft Auto, Max Payne, L.A...
  
  . There were two types. One can be carried around the map, but could only carry eight potatoes before having to get new ammunition. The other one was a mounted gun that the Nerds used at the observatory during a story mission.

Other types of pneumatic gun

• Pneumatic gun
• Airgun
• The FN 303
  FN 303
  The FN 303 is a semi-automatic non-lethal riot gun designed and manufactured by Fabrique Nationale de Herstal. The FN 303's projectiles have been specifically designed to break up on impact, reducing risks of penetrating injuries...
  
   is a handheld, short range, less lethal weapon which uses compressed air from an attached high pressure bottle to fire blunt, staining, pepper spray
  Pepper spray
  Pepper spray, also known as OC spray , OC gas, and capsicum spray, is a lachrymatory agent that is used in riot control, crowd control and personal self-defense, including defense against dogs and bears...
  
   or combined projectiles from a 15 round drum.
• Some paintball guns are pneumatic.

External links

• How Pneumatic Potato Cannons Work—Audio slideshow from the National High Magnetic Field Laboratory
• Spud gun building instructions— Spud Gun plans, animations, construction how-to's