Darrel Aune reproduction Cocobolo fire piston

A fire piston, sometimes called a fire syringe, is a device of ancient origin which is used to kindle fire. It uses the principle of the heating of a gas (in this case air) by its rapid (adiabatic) compression to ignite a piece of tinder, which is then used to set light to kindling.^[1]

[edit] Description and use

A fire piston consists of a hollow cylinder ranged in size from around 3 to 6 inches (7.5 cm to 15 cm) long, sealed at one end and open at the other, with a diameter of a quarter inch plus the width of the seal on the piston. A piston, about a quarter inch (ca 0.64 cm) in diameter, with some type of seal mounted in such a way that as the piston slides into the cylinder, an airtight seal is formed with the cylinder wall. The piston has a handle on the end to allow a firm grip to be applied to it, or a large enough surface area to 'whack' it on a hard surface without causing pain, and it can be completely withdrawn from the cylinder.

Native and modern versions are made from wood, animal horns, antlers and bamboo or wood. Lead was used to cast fire pistons in both modern and native versions. Other metals have also been used in modern versions. The piston has a notch or recess on or in its face, into which a piece of tinder is placed.

The compression of the air when the piston is quickly rammed into the cylinder causes the temperature to rise rapidly to 260 degrees Celsius, about 500 degrees Fahrenheit. This is hot enough for the tinder on or in the piston face to ignite with a visible 'flash' that can be seen if the cylnder is translucent or transparent.

The piston must be rammed quickly into the sealed cylinder (or vice-versa) with a single rapid stroke, or smacked down onto a hard surface (upside-down), and withdrawn almost as quickly, or the depletion of oxygen during the 'flash' will cause the tinder to go out just after it lights.

The smoldering ember can then be withdrawn from the face of the cylinder, transferred to a larger 'nest' of fine kindling material such as hemp rope fibers, or birch shavings, etc. The ember is then blown upon quite vigorously to create a flame, at which time various stages of larger kindling can be added until built into a proper fire.

[edit] History

Fire pistons have been used by native peoples of South East Asia and the Pacific Islands as a means of kindling fire since prehistory. They are found in cultures where the blow pipe is used as a weapon and this suggests they may have developed out of blow pipe construction. Their use has been reported from Burma, the Malay Peninsula, Indo-China, Borneo, Sumatra, Java, Kalimantan, Sulawesi, the Philippines, Madagascar ^[2] and South India.^[3]

An 1876 New York Times article^[4] reported the discovery of the earliest date of its use in the west. It reports an address by a Professor Govi that claimed a book written by Father Boscovich, of Rome in 1755, De Litteraria Expeditione per Pontifican Ditionem, (The Clever Mechanism) makes the claim that the fire piston was invented in 1745 by Abbe Augustin Ruffo. This report also claims that the modern fire piston was reinvented independently in the west through experiments with the air gun and not modelled after native designs.

It is recorded that the first fire piston made its wider debut in front of scientists in 1802 and was patented in 1807 simultaneously in both England and France. Fire pistons, or fire syringes as they were called then, were popular household tools throughout Europe during the early nineteenth century until the safety match was invented in 1844.

The fire piston may have inspired Rudolf Diesel in his creation of the diesel engine around 1892.^[5][6]

The device is still crafted and sold in the west by a few individuals who also supply larger survival and bushcraft companies.

[edit] As a scientific curiosity

A fire syringe is a piston-and-cylinder device used to demonstrate compression ignition. A typical fire syringe is a thick-walled transparent cylinder fitted with a metal piston which can travel to within a short distance of the bottom of the cylinder.

A 19th-century glass-cylinder fire syringe with a metal piston to which the tinder is attached.

Compression ignition is demonstrated by placing a matchhead or other piece of tinder at the bottom of the fire syringe and then plunging the piston forcefully into the cylinder. The tinder then bursts into flame due to the rapid rise in temperature which accompanies the sudden reduction in volume (and increase in pressure) of the air beneath the piston. The energy provided by the arm muscles working to compress the air is transferred into the much reduced volume of the air during compression and manifests itself as heat energy sufficient to ignite the tinder. Compression ignition is the principle underlying the operation of a Diesel engine.

[edit] Why it works

Rapid compression of a gas (known as adiabatic compression) increases its pressure and its temperature at the same time. If this compression is done too slowly the heat will leak away to the surroundings as the gas returns to equilibrium with them. If the compression is done quickly enough then there is no time for equilibrium to be achieved and the absolute temperature of the gas can suddenly become several times that of its surroundings, increasing the original room temperature of the gas to a temperature hot enough to set tinder alight. The air in the cylinder acts both as a source of heat and an oxidizer for the tinder fuel.

The same principle is used in the diesel engine to ignite the fuel in the cylinder rather than the spark plug used in the gasoline engine. It is closer, however, to the hot bulb engine, an early antecedent to the diesel, since the fuel (tinder) is compressed with the gas, while in a diesel it is injected when the gas is already compressed and at the high temperature.

Fire pistons have a compression ratio of about 25 to 1. This compares with about 20:1 for a modern diesel engine and 8:1 for a gasoline engine. The piston of the firepiston is made deliberately narrow so that the force on the piston is not too great to make it impossible for unaided human strength to compress the air in the cylinder to its fullest extent. To achieve the compression ratio, the final compressed volume of the tinder and air must be small relative to that of the length of the piston tube. These two factors together mean that only a tiny amount of tinder can be lit by a fire piston, but this is sufficient to light other tinder, and then to light a larger fire.

Easily combustible materials such as char cloth or amadou work well as tinder in the fire piston. The tinders that work best in the fire piston combust at a very low temperature. Cotton fibers for example combust at 235 °C (455 °F) and will light in fire pistons.

The physics and heat enthalpy equations of a fire piston are explained at General Problems 7.74

[edit] References

[edit] Bibliography

• Jamison, The Remarkable Firepiston Woodsmoke (1994) Menasha Ridge Press, Birmingham AL ISBN 0-89732-151-0
• Rowlands, John J. The Cache Lake Country (1947) ; W. W. Norton and Company, Inc., New York, NY
• Balfour, Henry , M.A. The Fire Piston Annual Smithsonian Report (1907)
• Fox, Robert The Fire Piston and Its Origins in Europe Technology and Culture, Vol. 10, No. 3 (Jul., 1969), pp. 355-370
• Arbor Scientific, Tools That Teach, Fire Syringe P1-2020; http://www.arborsci.com/Data_Sheets/P1-2020_DS.pdf

[edit] External links

• The Firepiston: Ancient Firemaking Machine
• University of Bristol, School of Chemistry: The Fire Piston
• A collection of antique fire syringes
• An equation describing the change in temperature during compression
• Photographs of a fire syringe
• The Naked Scientists - How a fire piston works