Firepistons seem so high tech that it's hard to believe they were not developed at MIT or Carnegie Melon under a top secret DARPA contract with unlimited funding. Since the firepiston is also given credit for Rudolf Diesel's invention of his Diesel engine it is quite surprising that the firepiston was not invented by Diesel himself or by one of his contemporaries or the likes of Ben Franklin and other European and American pyro based device inventors of the 16th, 17th and 18th centuries.
What historians note is that the firepiston was most likely invented in conjunction with the invention of the blow gun by prehistoric South East Asians since firepistons are normally found in the possession of those who use blowguns. The need to dislodge the internal partitions at each connecting joint inside a length of bamboo by ramming a rod or piston through the membrane, and in the course of doing so, rapidly compressing the air thereby setting dust particles or the membrane alight, is the reasoning behind co-invention.
I was so amazed at the technology and the science behind it that after building my own firepiston to prove to myself that the science and technology was real I could not resist sharing the science, technology and construction of my first firepiston with you by creating this instructable.
Here then is a description of how to make your own working firepiston to see first hand for yourself that the science and technology do in fact work. I left lots of room for improvement in materials, workmanship and degree of completeness for possible use in the field, if going beyond a demonstration is what you want to do.
Step 1: So how does a firepiston work, anyway?
The principle of increasing temperature by method of compressing air is explained by the Adiabatic process in which the internal energy of a gas must increase when a mass of air is rapidly compressed (or the volume of space containing a mass of air is rapidly decreased). The resulting increase in internal energy results in a rise in the temperature of air sufficient to light an ember, just like the pressure produced by an ice skater's blade is sufficient to increase the internal energy of the ice, which turns ice under the blade into water.
You can envision the effect in a 2D graph (below) with pressure as the ordinate (vertical) and volume as the abscissa (horizontal) and the adiabat or curve of constant entropy as the inverse relation curve. (Black lines are the curves of constant entropy.)
Rapid compression by a factor of 25 to 1 produces sufficient internal energy to send the air temperature to 800 degrees Fahrenheit. This temperature is sufficient to ignite a piece of char cloth for use in kindling a fire.
After several tries and some fine tuning (better sealing with more lubricant) I was able to produce embers with char twine using the apparatus I constructed.