A potato cannon is a pipe-based cannon that uses air pressure (pneumatic) or combustion of a flammable gas (aerosol, propane, etc.) to fire projectiles, usually potatoes. A simple design consists of a pipe sealed on one end, with a reducer on the other end to lower the diameter of the pipe, which has the corresponding lower-diameter pipe attached to it, called the barrel. Generally, the operator loads the projectile into the barrel, then utilizes a fuel or air pressure (or sometimes both) to propel the projectile out of the cannon.
The range of the cannon depends on many variables, 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 100–200 meters (330–660 feet), and there is a reported case of a cannon exceeding 500 meters (1,600 feet) of range. The potato cannon can trace its origin to the World War II-era Holman Projector, which was a shipboard anti-aircraft weapon.
Potato cannons are sometimes referred to as ‘spud guns,’ however that is also the name of a small toy gun used to fire a fragment of potato. To operate, one punctures the surface of a potato with the gun’s hollow tip and pries out a small pellet which fits in the muzzle. Squeezing the grip causes a small build-up of air pressure inside the toy which propels the projectile. Unlike potaoro cannons, the devices are usually short-range and low-powered.
Potato cannons by nature are hazardous and can present safety issues if poorly constructed or used. Projectiles or failing guns can be dangerous and result in life-threatening injuries, including cranial fractures, enucleation, and blindness if a person is hit. Therefore, users should follow the same rules as if handling a conventional firearm, but given the frequently improvised materials and construction used in potato cannons, it is particularly important for the user to use basic ear and eye protection when operating a potato cannon. In some jurisdictions potato cannons are outlawed or have restrictions on their use and may require licenses and certification of the gun.
Potato cannons utilize fluid pressure to propel projectiles down their barrels in the similar manner as a firearm (although at a much lower pressure). There are three basic methods that to achieve this. The first is a combustion cannon powered by the combustion of a gaseous fuel-air mixture. The second is a pneumatic cannon powered by the release of compressed gas through a valve. And third, a hybrid cannon, is powered by combustion of a pre-pressurized fuel-air mixture. The maximum pressure output of a combustion cannon is limited by the combustion pressure of the fuel-air mixture. Pneumatic cannons are generally more powerful but limited by the pressure of the air supply, be that from a compressor, manual pump or bottled gas. Hybrid cannons yield the highest pressure output and are limited only by the construction of the cannon (generally a few hundred pounds-force per square inch).
Advanced combustion cannons may include metered propane or calcium carbide (acetylene) 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.). The pressure release valve of a pneumatic cannon 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.
Although potato cannons 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. For example, 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. 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 potato cannon, but they use the same methods of operation. Additionally, in film and theatre productions, pneumatic cannons (such as an air mortar) 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.
The Daily Omnivore 
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