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HomeSurvivalFireFire Pistons

Fire Pistons - An Introduction

Article and Photos by Rob Bicevskis


Various Experimental Fire Pistons

A while back, I posted an article on some experiments that I had done in the building of fire pistons: Some Thoughts on Fire Pistons

Of course, since most people have never heard of a fire piston - the article was only valuable to a narrow group of people.
Everyone else went: "huh?"  If you're a "huh" person, read on.

If you want to build a fire piston, please check out Model T Fire Piston.

 
What is a Fire Piston?
 
A fire piston is a really neat method of generating a "coal" which can be used to light a fire.  It is a very simple device that consists of two parts, a plunger and cylinder. The cylinder is nothing more than a piece of material that has had a hole bored part way into it.  The plunger is made to fit into the hole in the cylinder.  The plunger has a small hole in the end.  This contains a piece of tinder - the stuff that we want to light.  The plunger also has some sort of gasket near its tip.  This gasket makes an air-tight seal with the cylinder.

A bit of physics: PV=nRT

This formula basically says that Pressure, Volume and Temperature are closely related.  As we decrease volume, pressure goes up, and so does temperature.  As we rapidly press the plunger into the cylinder, we can generate a sufficiently high pressure, and more importantly, temperature, to light our tinder.

 
Sound impossible?  Check out this video of a fire-piston in action.

By the way - this is almost exactly the same process that occurs in a diesel engine.  Another example of a principle that we think of as being "modern" but whose application was recognized long ago!

You can also check out this page to see another fire piston design and can view a video which shows a coal being produced.

 
Types of Fire Pistons
 
The photos above show fire pistons made from various types of plastics.  This was done to enable better experimentation and visibility into the process that occurs.

Originally, fire pistons were made of bamboo. This provided a ready-made cylinder with one end sealed.

This picture shows a wooden fire piston made by Jeff Wagner.  Note that in this case the plunger gasket is made from string.

Here is a fire piston made of PVC plumbing pipe.
 
Construction Details
 
 
There are two critical items in the construction of a fire piston:  the cylinder bore, and the gasket on the plunger.

The cylinder bore needs to be straight, smooth and as consistent in diameter as possible.  The plunger needs an air-tight gasket that seals well, but presents a minimum amount of friction.

This picture shows one building technique.  The cylinder is made from plastic tubing.  One end is sealed with a piece of plastic rod.  The rod can be sealed to the tubing with glue, or in this case with an O-ring.  The hole that is shown accepts a screw which keeps the plug in place.

This is the fire piston that was used in the above video clip.
 

Here is a close-up of the plunger end.  This design used a leather "cup" as a seal.

The leather cup is screwed into the end of the plunger.  The screw also fastens a few coils from a spring to the end of the plunger.  This is a convenient way to hold the tinder.

Another view of the plunger end loaded with tinder fungus.
Here is another fire piston design.

The cylinder is a piece of polycarbonate rod with a hole bored into one end.

The plunger is another piece of polycarbonate that is also bored out.  The hole in the plunger is used as a holding area for tinder pieces.  The end of the plunger is sealed with a screw and O-ring. Adjusting the tension on the screw allows one to squeeze the O-ring to get the perfect trade-off between gasket friction vs. air-tightness.

Another view with the plunger assembled and ready to go.
 
Variations
 

Have another look at this picture (below) and some other variations.

The very top fire piston uses a very long narrow bore - this gives lots of pressure and heat.

The next model down is a dual-ended fire piston.  Instead of permanently sealing one end of the cylinder, two plungers are used.

The other pictures show minor variations in bore sizes and plunger sizes and materials.

 

Hopefully this page has provided a brief overview into fire pistons.  For some more in-depth information, check out Some Thoughts on Fire Pistons.

There are many different materials, construction techniques and operating tips that can provide for a wide range of variations.  Let me know the results of your experiments:  email Rob