![Bongspud](https://upload.wikimedia.org/wikipedia/commons/d/de/Bongspud.jpg)
A potato cannon is a pipe-based
cannon
A cannon is a large- caliber gun classified as a type of artillery, which usually launches a projectile using explosive chemical propellant. Gunpowder ("black powder") was the primary propellant before the invention of smokeless powder ...
that uses air pressure (
pneumatic
Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air.
Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...
), or combustion of a flammable gas (aerosol, propane, etc.),
to launch projectiles at high speeds.
They are built to fire chunks of potato, as a hobby, or to fire other sorts of projectiles, for practical use. Projectiles or failing guns can be dangerous and result in life-threatening injuries, including cranial fractures,
enucleation, and blindness if a person is hit.
The potato cannon can trace its origin to the
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
-era
Holman Projector
The Holman Projector was an anti-aircraft weapon used by the Royal Navy during World War II, primarily between early 1940 and late 1941. The weapon was proposed and designed by Holmans, a machine tool manufacturer based at Camborne, Cornwall. A ...
, which was a shipboard
anti-aircraft
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
weapon.
Launcher types
All spud guns propel projectiles down their barrels using pressurised gas in the same manner as a
firearm
A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions).
The first firearms originated in 10th-century China, when bamboo tubes ...
(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 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
A dry ice bomb is a simple explosive device. While their simplicity, ease of construction, high bursting pressure and loud noise make them appealing for recreational purposes, they can be unpredictable and dangerous. These bombs have led to many i ...
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 .
* 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
An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of anthrop ...
or
propane
Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...
), and triggers the ignition source (often using a
piezoelectric
Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied Stress (mechanics), mechanical s ...
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 meters, and there is a reported case of a cannon exceeding 500 meters of range.
Advanced combustion launchers may include metered propane or
calcium carbide
Calcium carbide, also known as calcium acetylide, is a chemical compound with the chemical formula of Ca C2. Its main use industrially is in the production of acetylene and calcium cyanamide.
The pure material is colorless, while pieces of tec ...
(
acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
) 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, especially when hairspray / alcohol is used as a propellant. Bottled oxygen can be added to the firing chamber, though this can cause an explosion of the pipe when firing, potentially injuring anyone nearby.
Pneumatic launchers
Pneumatic
Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air.
Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...
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 or
Presta valve
The Presta valve (also French valve (FV) or Sclaverand valve) is a tire valve commonly found in high pressure road style and some mountain bicycle inner tubes. It comprises an outer valve stem and an inner valve body. A lock nut to secure the s ...
but other assemblies to pressurise the cannon such as quick release connections with
ball
A ball is a round object (usually spherical, but can sometimes be ovoid) with several uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used f ...
or
check valve
A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction.
Check valves are two-port valves, meaning they have t ...
s 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
An irrigation sprinkler (also known as a water sprinkler or simply a sprinkler) is a device used to irrigate (water) agricultural crops, lawns, landscapes, golf courses, and other areas. They are also used for cooling and for the control of airbo ...
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
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 valves used in many brass instruments
* The va ...
. 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 .
Pneumatic spud guns are generally more powerful than combustion spud guns. A typical combustion gun generates average chamber pressures of about with peaks of around , while the average pneumatic gun can operate at pressures in the vicinity of . In recent times, it has become increasingly common for metal pneumatic launchers to use even higher pressures, sometimes up to or higher.
Dry ice launchers
![Dry ice montage](https://upload.wikimedia.org/wikipedia/commons/7/7e/Dry_ice_montage.jpg)
A
dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily a ...
cannon uses the
sublimation of solid carbon dioxide to generate the gas pressure to propel a projectile and is a variation of the burst disk cannon.
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
static friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
of the projectile jammed in the barrel. Tens of psi is most likely. The range is likely restricted to 100- yards.
A more modern example is the
dry ice bomb
A dry ice bomb is a simple explosive device. While their simplicity, ease of construction, high bursting pressure and loud noise make them appealing for recreational purposes, they can be unpredictable and dangerous. These bombs have led to many i ...
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 0.5 L plastic soda bottle is between 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.
* The piping and any reinforcement may be insufficiently strong for the high pressure spike when the dry ice bomb explodes and consequently rupture.
* 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
light-gas gun
The light-gas gun is an apparatus for physics experiments. It is a highly specialized gun designed to generate extremely high velocities. It is usually used to study high-speed impact phenomena (hypervelocity research), such as the formation of ...
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 , 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 cannot 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 .
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 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
The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, th ...
.
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 need to be measured and matched carefully to ensure reliable operation; hence the use of accurate air pressure gauges and fuel meters.
Vacuum cannons
Vacuum cannons differ from typical pneumatic cannons in that they apply a negative pressure to the front of the projectile in order to "pull" it out of the barrel. They typically fire light projectiles and do not have any practical applications outside of demonstrating air pressure theory.
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.
PVC should not be used in this application without extensive experience and understanding of the forces at play.
*
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.
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 that are not pressure rated. The 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 is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
: 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 is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
: 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 (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
: 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 is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
: 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.
Valve types
Manual
*
Ball Valve
A ball valve is a flow control device which uses a hollow, perforated and pivoting ball to control fluid flowing through it. It is open when the ball's hole is in line with the flow inlet and closed when it is pivoted 90-degrees by the 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
A pneumatic control valve actuator converts energy (typically in the form of compressed air) into mechanical motion. The motion can be rotary or linear, depending on the type of actuator.
Principle of operation
A Pneumatic actuator mainly co ...
or
spring
Spring(s) may refer to:
Common uses
* Spring (season), a season of the year
* Spring (device), a mechanical device that stores energy
* Spring (hydrology), a natural source of water
* Spring (mathematics), a geometric surface in the shape of a ...
to achieve a faster opening speed.
*Blowgun: A blowgun is a small handheld 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’s 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 that fire
airsoft
Airsoft is a team game in which participants eliminate opposing players by tag (game), tagging them out of play with airsoft pellets, spherical plastic projectiles shot with mock air gun, air weapons(usually powered by an electronic motor) call ...
pellets and so do not require high airflow. Blowguns can be modified to increase airflow.
Electric
*Sprinkler valve (otherwise known as a
solenoid valve
A solenoid valve is an electromechanically operated valve.
Solenoid valves differ in the characteristics of the electric current they use, the strength of the magnetic field they generate, the mechanism they use to regulate the fluid, and the ty ...
): The use of irrigation sprinkler valves as pneumatic valves has become increasingly popular for spudgunning. These valves are intended to be electrically 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 valves (or membrane valves) consists of a valve body with two or more ports, an elastomeric diaphragm, and a "weir or saddle" or seat upon which the diaphragm closes the valve. The valve body may be constructed from plastic, metal, woo ...
: 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 blowgun valve, rather than electronically.
*
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 valves used in many brass instruments
* The va ...
: 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.
* 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.
*
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.
:Alternate designs have also been used which use a sharp projectile to puncture the burst disk, like a
mortar or using a manual puncturing device to trigger failure of the disk.
These allow total control over burst disk cannons without the need for hybrid technology and materials as simple as plastic tape can be used for the disk.
:Burst disk cannons have also been made which are fired electrically, using a
nichrome
Nichrome (also known as NiCr, nickel-chromium or chromium-nickel) is a family of alloys of nickel, chromium, and often iron (and possibly other elements) commonly used as resistance wire, heating elements in devices like toasters, electrical kettl ...
wire to trigger failure by heating.
Connections
Welding, soldering and gluing
*
Solvent welding
Plastic welding is welding for semi-finished plastic materials, and is described in ISO 472 as a process of uniting softened surfaces of materials, generally with the aid of heat (except solvent welding). Welding of thermoplastics is accomplishe ...
: 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: 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 (; ) is a process in which two or more items are joined by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involv ...
: commonly used in the construction of copper pipe based spudguns, a
solder
Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...
with a lower melting point than the copper is melted and drawn into the gaps between pipe and fitting with
capillary action
Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces li ...
, holding to pipe and fitting with a
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. This happens in presence of a gaseous phase or another liquid phase not miscible with th ...
action before hardening.
*
Gluing
Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation.
The use of adhesives offers certain advant ...
: the use of
epoxy
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
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 (also called duck tape, from the cotton duck cloth it was originally made of) is cloth- or scrim-backed pressure-sensitive tape, often coated with polyethylene. There are a variety of constructions using different backings and adhesi ...
: 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 joint it creates.
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
A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of an iron beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer of ...
joints: on large steel spudguns, pipe and fittings are sometimes bolted together by means of flanges with a
gasket
Some seals and gaskets
A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. It is a deformable material that is used to c ...
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
Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...
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 (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in 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. The projectile cannot travel faster than the gas particles, which are limited to travel at the speed of sound. The problem is solved by increasing the speed of the particles, either by:
*Using lighter molecules, as occurs when
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in 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 or more, but achieving these pressures is difficult. CO
2 gas, although it can reach these pressures, is not suitable due to its high density.
Supersonic
Supersonic speed is the speed of an object that exceeds the speed of sound ( Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately . Speeds greater than five times ...
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
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
are documented phenomena in gases.
The highest projectile speed recorded from a spud gun is (approximately 2.7 times the speed of sound) with a 20 mm plastic slug from a hybrid using a pre-ignition mixture of air and propane.
Supersonic velocities have been obtained using the related
vacuum bazooka with a
de Laval nozzle
A de Laval nozzle (or convergent-divergent nozzle, CD nozzle or con-di nozzle) is a tube which is pinched in the middle, making a carefully balanced, asymmetric hourglass shape. It is used to accelerate a compressible fluid to supersonic speeds ...
. This also relies on significantly lowering the density of the gas.
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 CO
2 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. Such cannons can be dangerous: the
Phillie Phanatic injured a fan with a hot dog cannon in June 2018.
Such "air cannons", as they are often called, 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 (such as an
air mortar
An air mortar (or debris mortar) is a device used to create movie special effects, consisting of pressurized air or gas forced through a tube to propel material (dirt, glass, fake blood) to create a bursting or splattering effect.
A cinema journ ...
) 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.
*Golf ball launchers: at some charity outings players can make a donation and launch a golf ball over 300 yards and use that as their tee shot. Usually the vendor hired by the event organizer launches the ball for safety and liability reasons.
Industry
![Gas gun bird scarer](https://upload.wikimedia.org/wikipedia/commons/2/2d/Gas_gun_bird_scarer.jpg)
*
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 seco ...
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: This can mean:
** A pneumatic spudgun
**
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
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a po ...
s close to the device) to scare birds from crop fields or near airport runways.
*
Chicken cannons: Many aircraft parts must be able to survive the impact of a bird in flight, known as a
birdstrike
A bird strike—sometimes called birdstrike, bird ingestion (for an engine), bird hit, or bird aircraft strike hazard (BASH)—is a collision between an airborne animal (usually a bird or bat) and a moving vehicle, usually an aircraft. The term ...
. Pneumatic guns are used to project a bird, typically a dead
chicken
The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult m ...
, into a product designed to imitate a birdstrike. Aircraft canopies, engines, and critical
flight control surfaces
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
Development of an effective set of flight control surfaces was a critical advance in the development of aircraft. Ea ...
will normally undergo this type of stress testing to determine whether they are strong enough to withstand a birdstrike in flight.
*
Shock tube
: ''For the pyrotechnic initiator, see Shock tube detonator''
The 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.
*
Pneumatic line thrower Pneumatic line throwers can be used for a variety of applications including underway replenishment (UNREPS), replenishment at sea (RASing), ship to ship line deployment, ship to shore line deployment, water rescue, high angle rescue, cable running i ...
s for launching lines for rescue missions or between ships for
replenishment at sea
Replenishment at sea (RAS) (North Atlantic Treaty Organization/Commonwealth of Nations) or underway replenishment (UNREP) (U.S. Navy) is a method of transferring fuel, munitions, and stores from one ship to another while under way. First develope ...
as well as a number of other applications.
Military
*
Combustion light-gas gun
A combustion light-gas gun (CLGG) is a projectile weapon that utilizes the explosive force of low molecular-weight combustible gases, such as hydrogen mixed with oxygen, as propellant. When the gases are ignited, they burn, expand and propel t ...
s are weaponised combustion cannons which burn a low-molecular-weight gas such as hydrogen to provide a higher
specific impulse
Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine (a rocket using propellant or a jet engine using fuel) creates thrust. For engines whose reaction mass is only the fuel they carry, specific impulse i ...
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 is the study and practice of using, transporting, storing and disposing of firearms and ammunition, including the training of gun users, the design of weapons, and formal and informal regulation of gun production, distribution, and ...
), 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 "
Workaholics
''Workaholics'' is an American sitcom created and predominantly written by Blake Anderson, Adam DeVine, Anders Holm, and Kyle Newacheck, all of whom star in the series. ''Workaholics'' originally ran on Comedy Central from April 6, 2011, to Marc ...
" episode "To Friend a Predator", a Potato Gun is used in an attempt to stop the protagonist, but instead hits Blake in the back.
* In ''
The Trailer Park Boys'',
Julian,
Ricky Ricky may refer to:
Places
*Říčky (Brno-Country District), a village and municipality in the Czech Republic
*Říčky v Orlických horách, a village in the north of the Czech Republic
* Rickmansworth, a town in England sometimes called "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'',
Jack Sawyer
Jack Sawyer (born May 6, 2002) is an American college football defensive end for the Ohio State Buckeyes.
Early life and high school career
Sawyer grew up in Pickerington, Ohio Where he Attended St. Pius K-8 Catholic school. Attended Pickerington ...
suggested to
Burt Gummer
''Tremors'' is a 1990 American monster horror comedy film directed by Ron Underwood, produced by Brent Maddock and S. S. Wilson, written by Maddock, Wilson, and Underwood and starring Kevin Bacon, Fred Ward, Finn Carter, Michael Gross, and ...
that they build a potato gun to fight the
Ass-Blasters. Using parts from a junkyard, they formed a variant of a potato gun that shot makeshift flaming arrows that were deadly to the Ass Blasters and killed two.
* In an episode of Nickelodeon's ''
Drake & Josh
''Drake & Josh'' is an American teen sitcom created by Dan Schneider for Nickelodeon. The series follows two teenage stepbrothers Drake Parker (Drake Bell) and Josh Nichols (Josh Peck) as they live together despite opposite personalities. The ser ...
'', 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 Kurt Schrute III () is a fictional character on ''The Office (U.S.)'' and is portrayed by American actor Rainn Wilson. Dwight's character was a salesman and the assistant to the regional manager, at the fictional paper distribution compan ...
on the
U.S.
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
version of ''
The Office
''The Office'' is a mockumentary sitcom created by Ricky Gervais and Stephen Merchant, first made in the United Kingdom, then Germany, and subsequently the United States. It has since been remade in ten other countries.
The original series of ...
'' has mentioned owning a spud gun in more than one episode.
* In 14th episode of Season 4 of ''
Prison Break
''Prison Break'' is an American serial (radio and television), serial drama television show, television series created by Paul Scheuring for Fox Broadcasting Company, Fox. The series revolves around two brothers, Lincoln Burrows (Dominic Purce ...
'', a combustion potato gun is used by
Michael Scofield
Michael Scofield, portrayed by Wentworth Miller, is a fictional character and one of the two main protagonists of the American television series ''Prison Break''. The character first appeared in the series pilot, in which he deliberately goes t ...
to launch
40 mm
40 mm grenade (also styled 40mm grenade) is a generic class-name for grenade launcher ammunition ( subsonic shells) in caliber. The generic name stems from the fact that several countries have developed or adopted grenade launchers in ...
smoke grenade
Smoke grenades used at demonstrations in Paris, 2008
upBritish L83A1 Smoke Grenade manufactured in May 2008. This grenade has already been used.
A smoke grenade is a canister-type grenade used as a signaling device, target or landing zone mark ...
s.
* ''
The Simpsons
''The Simpsons'' is an American animated sitcom created by Matt Groening for the Fox Broadcasting Company. The series is a satirical depiction of American life, epitomized by the Simpson family, which consists of Homer, Marge, Bart, Lisa, ...
'' character Maude Flanders was killed by air-cannon launched T-shirts in the eleventh season episode, "
Alone Again, Natura-Diddily
"Alone Again, Natura-Diddily" is the fourteenth episode of the eleventh season of the American television series ''The Simpsons'', and marks the final regular appearance of the character Maude Flanders. In the episode, she is killed in an acciden ...
".
* In ''
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
When property developer Robert Stiles' limousine gets stuck in a sink hole on Possum Lodge's propert ...
'' (the movie based on ''
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 (PBS) in the United States (airing on more than 100 PBS affiliates a ...
'') 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'' is a science entertainment television program, developed by Peter Rees and produced by Australia's Beyond Television Productions. The series premiered on the Discovery Channel on January 23, 2003. It was broadcast internatio ...
'' episode tested a potato cannon held together by duct tape compared to one held together using PVC bonding agent. Another episode, testing MacGyver myths, supplied Adam and Jamie with the materials to build a potato cannon as part of a challenge to "MacGyver" up a way to signal a rescue helicopter; however, they used the piping and other supplies present to build a large kite instead.
* In the TV series ''
House, M.D.
''House'' (also called ''House, M.D.'') is an American medical drama television series that originally ran on the Fox network for eight seasons, from November 16, 2004, to May 21, 2012. The series' main character is Dr. Gregory House (Hugh L ...
'' episode "
The Dig", House is attending a spud gun show with Thirteen, where he uses the spud gun to threaten a teenage competitor who taunts House.
*A spud gun was one of the many different weapons used in ''
Bully
Bullying is the use of force, coercion, hurtful teasing or threat, to abuse, aggressively wikt:domination, dominate or intimidate. The behavior is often repeated and habitual. One essential prerequisite is the perception (by the bully or by ot ...
'', a game made by
Rockstar Games
Rockstar Games, Inc. is an American video game publisher based in New York City. The company was established in December 1998 as a subsidiary of Take-Two Interactive, using the assets Take-Two had previously acquired from BMG Interactive. Foun ...
. There were two types. One can be carried around the map, but could only fire eight potatoes before having to get more ammunition. The other one was a mounted gun that the Nerds used at the observatory during a story mission facing a second boss.
*In ''
Iron Man 3
''Iron Man 3'' (titled onscreen as ''Iron Man Three'') is a 2013 American superhero film based on the Marvel Comics character Iron Man, produced by Marvel Studios and distributed by Walt Disney Studios Motion Pictures. It is the sequel to ''Ir ...
'', Tony meets a boy named Harley, who owns a potato gun which he uses to threaten Tony. At the end of the movie, as thanks for his help, Tony builds Harley a newer and better potato gun.
*The game
Scrap Mechanic has 4 variants of spud guns: a single shot spud gun, a double barrel spud shot gun which fires French fries, a 'spudling' gun which is a triple barrel Gatling gun, and a mountable spud gun which can be mounted on your creations
*The Australian Comedy Show
SuperWog
superwog1 or just simply ''Superwog'', is a YouTube duo consisting of two Australian brothers, Theodore and Nathan Saidden. The channel consists of various videos including comedies and skits. They have gained over 3 million subscribers and 456 ...
features a Spud gun in episode 3 of season 2, ‘the magpie‘ in which Superwog(Theo) and Johnny build a spud gun to combat a swooping magpie however they miss the intended target and hit a bystander
See also
*
Airgun
An air gun or airgun is a gun that fires projectiles pneumatically with compressed air or other gases that are mechanically pressurized ''without'' involving any chemical reactions, in contrast to a firearm, which pressurizes gases ''chemica ...
*
FN 303
The FN 303 is a semi-automatic less-lethal riot gun designed and manufactured by Fabrique Nationale de Herstal.
The FN 303 uses compressed air to fire projectiles from a 15-round drum magazine. It is designed to incapacitate the target through b ...
*
Paintball gun
*
Plastic pressure pipe systems
Plastic pipe is a tubular section, or hollow cylinder, made of plastic. It is usually, but not necessarily, of circular cross-section, used mainly to convey substances which can flow—liquids and gases (fluids), slurries, powders and masses of sm ...
*
Pneumatic gun
*
Pumpkin chucking
Punkin chunkin, or as it is sometimes called pumpkin chucking, is the sport of hurling a pumpkin solely by mechanical means for distance. The devices used include slingshots, catapults, centrifugals, trebuchets, and pneumatic (air) cannons.
P ...
*
Vacuum bazooka
References
External links
{{Commons category, Potato cannons
How Pneumatic Potato Cannons Work—Audio slideshow from the National High Magnetic Field Laboratory
Spud gun building instructions— Spud Gun plans, animations, construction how-tos
Air guns
Pneumatic weapons