A typical die-cast spud gun.

A pneumatic potato cannon

A spud gun refers to either a classic child's toy which is used to fire small pieces of potato using a small volume of air at low pressure, or a larger pipe-based cannon which uses higher air pressure or combustion of a gaseous fuel to launch larger projectiles (usually potatoes). These launchers are built and fired as a hobby. Image File history File linksMetadata Download high-resolution version (1024x768, 140 KB)By Richard Wheeler (Zephyris) 2007. ... Image File history File linksMetadata Download high-resolution version (1024x768, 140 KB)By Richard Wheeler (Zephyris) 2007. ... Download high resolution version (1632x1232, 744 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (1632x1232, 744 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Air pressure can refer to: Atmospheric pressure, the pressure of air environmentally Pressure of air in a system Category: ...

Launcher Types

All spud guns propel projectiles down their barrels using pressurised gas in the same manner as a firearm (although at a much lower pressure). There are three basic ways that spud guns may achieve this: A Glock 22 hand-held firearm with internal laser sight and mounted flashlight, surrounded by hollowpoint ammunition. ...

• By the combustion of a gaseous fuel-air mixture; this is generally referred to as a combustion launcher, and its pressure is limited primarily by the energy density of the fuel-air mixture (less than 100 psi (7 bar) 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 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 psi).

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 or propane), and triggers the ignition source (often using a piezoelectric BBQ 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 some cannons exceed 500 metres of range.^{[citation needed]} Aerosol spray can Aerosol spray is a type of canister that sprays an aerosol when its button is pressed or held down. ... Propane is a three-carbon alkane, normally a gas, but compressible to a liquid that is transportable. ... Piezoelectricity is the ability of certain crystals to produce a voltage when subjected to mechanical stress. ...

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

A large pneumatic design: The projectile is loaded in the muzzle (not pictured), which is then attached to the cannon (at 2). The air reservoir (3) is filled to 120 PSI using the Schrader valve (4). Upon opening the solenoid valve (1), the air from the reservoir is transferred to the projectile, which is fired out of the muzzle.

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: Image File history File linksMetadata Pneumaticspudgun989. ... Image File history File linksMetadata Pneumaticspudgun989. ... A schrader valve on a bicycle tire. ... Pneumatics, from the Greek πνευματικός (pneumatikos, coming from the wind) is the use of pressurized air in science and technology. ...

• 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 or Presta valve but other assemblies to pressurise the cannon such as quick release connections with ball or check valves have been used. A schrader valve on a bicycle tire. ... The Presta valve is a valve (commonly) found in high pressure road style bicycle tyres. ...

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

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 (1km).^{[citation needed]}

Pneumatic spud guns are generally more powerful than combustion spud guns; a typical combustion gun generates chamber pressures of 10-70 PSI / 69 - 483 kP , while the average pneumatic gun can operate at pressures in the vicinity of 100 psi / 690 kP, or higher.^{[citation needed]}

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. U.S. Navy F/A-18 at transonic speed. ...

A hybrid using twice as much fuel and air as a comparable combustion gun 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.

Primary Materials

Plastics

• PVC-U (Polyvinyl chloride, unplasticized) - 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.^[1]

• ABS (Acrylonitrile butadiene styrene) - 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.^[2] It also has a greater temperature tolerance (-40°C to +80°C compared to 0°C to +60°C 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 much more of a risk to a cannon operator. Polyvinyl chloride Polyvinyl chloride, (IUPAC Polychloroethene) commonly abbreviated PVC, is a widely used thermoplastic polymer. ... Monomers in ABS polymer Acrylonitrile butadiene styrene, or ABS, (chemical formula (C8H8· C4H6·C3H3N)n is a common thermoplastic used to make light, rigid, molded products such as piping, golf club heads (used for its good shock absorbance), automotive body parts, wheel covers, enclosures, protective head gear, and toys including...

Metals

• Steel - 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 - 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 drawback is that copper is up to four times the cost of PVC or ABS pipes of similar external diameters and of greater weight.

• Aluminium - Aluminum is a lightweight metal with good corrosion resistance. Aluminium pipes are sometimes used as barrels on spudguns on their own and machined aluminium is a popular material for particularly unique designs.

For other uses, see Steel (disambiguation). ... For other uses, see Copper (disambiguation). ... “Aluminum” redirects here. ...

Valve Types

Manual

• Ball Valve - 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 or spring 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 pellets and so do not require high air flow. Blowguns can be modified to increase airflow.

A ball valve (like the butterfly valve, one of a family of valves called quarter turn valves) is a valve that opens by turning a handle attached to a ball inside the valve. ... A pneumatic actuator converts energy (in the form of compressed air, typically) into motion. ... Helical or coil springs designed for tension A spring is a flexible elastic object used to store mechanical energy. ... This article is about the sport. ...

Electronic

• Sprinkler valve (otherwise known as a Solenoid valve) - 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.

A solenoid valve is an electromechanical valve for use with liquid or gas controlled by running or stopping an electrical current through a solenoid, which is a coil of wire, thus changing the state of the valve. ...

Pneumatic

• Diaphragm valve - 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.

• Piston valve - 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 1/8" to 1.5" 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. (An exception to this is within the UK, where QEVs are relatively inexpensive.)

• Burst Disk Valve - 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.

Diaphragm valves (or membrane 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. ... Piston valve in a brass instrument 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. ... A rupture disk is a pressure relief device that protects a vessel or system from overpressurization. ...

Connections

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.^[3]
• Metal welding - used to form low weight joins between similar metals by melting the points of connection together. It is an uncommon process in spudgun construction due to the costs of using metal for construction and for the equipment necessary to make the welds.
• Soldering - commonly used in the construction of copper pipe based spudguns, a solder with a lower melting point than the copper is melted and drawn into the gaps between pipe and fitting with capillary action, holding to pipe and fitting with a wetting action before hardening.
• Gluing - the use of epoxy resin in small designs is common for the making of custom parts but it is rare to see glues used for structural connections. Copper glue such as JustForCopper has been used occasionally as a cold replacement for soldering in a copper based spudgun.

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ... (De)soldering a contact from a wire. ... Look up glue in Wiktionary, the free dictionary. ... Plastic Welding is the process of welding plastic parts together. ... Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. ... (De)soldering a contact from a wire. ... A solder is a fusible metal alloy, with a melting point or melting range of 180-190°C (360-370 °F), which is melted to join metallic surfaces, especially in the fields of electronics and plumbing, in a process called soldering. ... Capillary action, capillarity, or capillary motion is the ability of a substance (the standard reference is to a tube in plants but can be seen readily with porous paper) to draw a substance up against gravity. ... Wetting of different fluids. ... Look up glue in Wiktionary, the free dictionary. ... In chemistry, epoxy or polyepoxide is a thermosetting epoxide polymer that cures (polymerizes and crosslinks) when mixed with a catalyzing agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A. The first commercial attempts to prepare resins from epichlorohydrin occurred in 1927 in...

Mechanical Joints

• Compression Fittings - 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 - commonly available in BSP or NPT (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 Joints - on large steel spudguns, pipe and fittings are sometimes bolted together by means of flanges with a 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 cams to lock in or release the plug side of the fitting to which a barrel is attached.

A compression fitting 15 mm isolating valve // Compression fittings are used in plumbing to join two tubes or thin-walled pipes together. ... A threaded pipe plug; note that the threaded portion is slightly conical and so touches the calipers at only two points. ... The British standard pipe thread (BSP thread) is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. ... Threaded pipe and elbow National Pipe Thread is a U.S. standard for tapered (NPT) or straight (NPS) threads used to join pipes and fittings. ... For the vacuum component, see Vacuum flange. ... Some seals and gaskets 1. ... monkey ...

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, typically by using a special gas, such as helium. There is also one reported case of a combustion design achieving super-sonic velocities. For other uses, see Helium (disambiguation). ...

The difficulty in breaking the barrier arises from the speed of the particles within the gas. If the projectile is traveling 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 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 or more, but achieving these pressures is difficult. CO₂ gas, although it can reach these pressures, is not suitable due to its high density.

It should be noted that supersonic velocities may be attained in some rare case due to an excessive "dead space" between the air release valve and projectile. The blast of incoming air can raise the pressure so rapidly in this dead space that high temperatures, sometimes sufficient to achieve supersonic velocities, can occur. For other uses, see Helium (disambiguation). ... A United States Navy F/A-18E/F Super Hornet in transonic flight. ...

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 US 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 cannons: 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: although this is another term for a pneumatic spudgun, it is also the commercial name for a device used to dislodge jammed material in silos. They vary in size depending on the requirements but operate in the same way as a large piston valve pneumatic cannon. An air chamber is charged with compressed air from the supply airline and when required, a solenoid actuated valve is used to trigger (otherwise known as piloting) a quick exhaust valve which in turn pilots a much larger piston valve, allowing the chamber of compressed air to blast into the silo. Multiple air cannons may be installed on a silo, arranged in specific patterns for the most effective results.

There are very few or no other articles that link to this one. ... Air cannon is a de-clogging equipment composed of two main elements : a pressure vessel (storing air pressure), and a triggering mechanism (high speed release of compressed air). ...

Military

• The FN 303 is a handheld, short range, less lethal weapon which uses compressed air from an attached high pressure bottle to fire blunt, staining, pepper spray or combined projectiles from a 15 round drum.

The FN 303 is a semi-automatic less-lethal launcher manufactured by Fabrique Nationale de Herstal. ... Less-lethal weapons, non-lethal weapons, non-deadly weapons, or, more recently, compliance weapons are weapons intended to be unlikely to kill or to cause great bodily injury to a living target. ... Pepper spray (also known as OC spray (from Oleoresin Capsicum), OC gas, capsicum spray, or oleoresin capsicum) is a lachrymatory agent (a chemical compound that irritates the eyes to cause tears, pain, and even temporary blindness) that is used in riot control, crowd control and personal self-defense, including defense...

Safety

Spud guns by nature are hazardous and can present safety issues if poorly constructed or used. See Spud Gun Safety. // While all spud guns have the capability to seriously injure or possibly kill their operator or bystanders, when built correctly and used in a responsible manner they can be operated in relative safety. ...

Legal Issues

See Article: Spud Gun Legality
In many countries spud guns are outlawed or have restrictions on their use and may require licenses and certification of the gun. Below is a list showing the legality of spud gun in different places around the world. ...

Trivia

• A character in the British TV series Bottom was named after this toy.
• In the Bugsy Malone movie, a similar device called a "splurge gun" fires custard pies
• 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, desert Jack suggested to Burt that they could build a potato gun (Spud gun) to fight the Ass-Blasters after Burt's bunker & entire armoury was destroyed.

Bottom was a British sitcom (aka britcom) of the early 1990s (and later a series of stage shows) written by Rik Mayall and Adrian Edmondson. ... Bugsy Malone is a 1976 musical film, very loosely based on events in Chicago, Illinois in the Prohibition era, specifically, the exploits of gangsters like Al Capone as dramatized in cinema. ... A custard pie is a pie crust filled with a cooked custard. ... The Trailer Park Boys is a 1999 sixty-seven minute low-budget independent film that served as the basis and pilot for the later hit Canadian mockumentary comedy series Trailer Park Boys. ...

See also

• Plastic Pressure Pipe Systems
• Pumpkin chunking

Plastic Pressure Pipe Systems have been in use since the 1950s. ... Pumpkin chunking (or punkin chunkin or pumpkin chucking) is hurling vegetables (usually pumpkins) by mechanical means over great heights and distances so as to smash and dash them for entertainment. ...

References

External links

• UK Spud gun Community, European spud gunners welcome
• GardenBallistics.co.nr - Home made cannons and ballistic inventions
• "spudding handbook" (wiki)
• NeoSpud.com
• Gas Gun Design Tool, simulation program for pneumatic guns
• Guide to constructing a combustion powered cannon