Fire piston

A fire piston, which in the Philippines is known as a sumpak,^[1] 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.

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Description and use

A fire piston consists of a hollow cylinder range in size from around 3 inches to 6 inches or 7.5 cm to 15 cm long, sealed at one end and open at the other. A piston, about a quarter inch in diameter, can slide into the cylinder forming an airtight seal with the cylinder wall. The piston has a handle on the end to allow a firm grip to be applied to it and can be completely withdrawn from the cylinder. Primitive and modern versions were and are both made from wood, horn, anlter and bamboo. Lead was used to cast fire pistons both modern and primitively as well. Other metals have also been used in modern times. The piston has a notch or recess in its face into which a piece of tinder is placed. The piston must be rammed rapidly into the sealed cylinder with a single stroke. The compression of the air causes the temperature to rise rapidly to 260 degrees Celsius, or 500 degrees Fahrenheit. This is hot enough for the tinder on the piston face to ignite. It can then be withdrawn and transferred to a larger mass of kindling to create a fire.

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, Celebes, the Philippines, Madagascar ^[2] and South India. ^[3]

Fire pistons, or fire syringes as they were called then, were popular household tools throughout Europe until the match was invented. It is recorded that the first fire piston made its debut in front of scientists in 1802 and was patented in 1807 simultaneously in both England and France. What is quite interesting though is the discovery of an 1876 New York Times article that is sharing the discovery of a much earlier date. In a paper addressed by Professor Govi the week before, he was able to show that the fire piston was invented much earlier. In a book written by Father Boscovich, from Rome in 1755, “De Litteraria Expeditione per Pontifican Ditionem,” the “clever mechanism” was highly spoke of. It is here we find that the fire piston was invented in 1745 by Abbe Augustin Ruffo. This report also shows that the modern fire piston was invented through experiment with a blow gun in which required the end of the gun to be plugged, discounting theories that it was invented after primitive models.

The fire piston may have inspired Rudolf Diesel in his creation of the diesel engine.^[4]

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

Photos

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.

Firepistons have a compression ratio of about 25 to 1. This compares with about 20:1 for a modern diesel engine and 10:1 for a gasoline engine. The piston of the firepiston is made deliberately narrow so that the force on the piston is not too great which would make it impossible for unaided human strength to compress the air in the cylinder to its fullest extent. To maintain the compression ratio, the final compressed volume of the tinder and air must also be small relative to that 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 in the fire piston. The tinders that work in the fire piston combust at a very low temperature. Cotton fibers for example combust at 235 °C (545 °F) and have lit in fire pistons. This temperature, the right tinder and only about 3 pounds-force per square inch (20 kPa) of pressure work together to make this tool produce a coal.

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

Notes

References

• 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
• New York Times Article, 1876; http://query.nytimes.com/mem/archive-free/pdf?_r=3&res=9400E5D61F3FE73BBC4153DFB667838D669FDE&oref=slogin&oref=slogin&oref=slogin
• Arbor Scientific, Tools That Teach, Fire Syringe P1-2020; http://www.arborsci.com/Data_Sheets/P1-2020_DS.pdf