Start a fire with air
8 Steps
To do this we need to make a firepiston, which is a device for starting cook, camp and signal fires with air.

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.

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## Step 1: So how does a firepiston work, anyway?

A firepiston can set an ember to burn as a result of energy being concentrated into a smaller and smaller space by compression of air resulting in a corresponding increase in the air's temperature.

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.

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Fred82664 says: Mar 6, 2009. 4:02 AM
Cool I will have to try this out,Is this the same principle that some Diesel Fuel engines start up ( the ones that do not have glow plugs ) ?
Speedmite says: Mar 9, 2009. 8:37 PM
Glow plugs heat up the engine when You start up a diesel. Thats all they do. Once the engine is hot, the pistons compresses the fuel and that plus the little bit of heat makes it work. I also do not know of any diesels without glow plugs, but it could be possible in hot areas. I'm a teenager thats a nerd and does nothing with trucks and I can tell you that. Sorry I did that. It just bothered me. and yes, its kind like that, but this isnt as powerful as a diesel and a lighter is easy to me compared to this. Just saying.
Fred82664 says: Mar 10, 2009. 8:52 AM
cool I like to see the younger generation thinking about other things then sex drugs and rock and role. there all good ,but I am in my 40s I know about the glow plug thing probably be for you was a twinkle in your dad's eyes. ( not meant to make ya feel bad ) older farm tractor did not use glow plugs some of the old Mac trucks and military vehicles did not use glow pugs. I think the use of glow plugs came in around the 60s ,I could be wrong on that thought as well as my thought that friction created the heat to light up the diesel fuel

by all means continue to feed your mind better things then drugs and Challenge current technology make it bettermake new ! (lol my life in some old folks home may be much better by you doing it lol)
difflock says: Apr 13, 2009. 7:14 AM
You are correct. Not all diesels do have glow plugs... Early diesels were just cranked over repeatedly, which created enough heat due to the compression to start the engine. However, cold weather made it hard to start the engine especially when high compression/high speed diesel engines appeared. Glow plugs were the most successful method of starting diesel engines in cold weather. Some of the methods used before are solid fuel blocks that were fitted into the cylinder head (rudementary glowplug), intake heaters (increase incoming air temp), and introducing ether into the intake. Some example of pre glow plug diesel engines are: - Field Marshall tractors (large single cylinder 2 stroke diesel) which used a solid fuel block, and then later a stogun cartridge style started which ignited fuel in the cylinder. -Stationary diesel engines, like Petter's and Lister's, which are low speed engines that didnt need glow plugs or heater - I believe that the Detroit Diesels featured the ether intake system. Hope that helps. By the way, I'm 19, but have been interested in old engines since I was born :P Old tractors that used TVO still produce the nicest smell :)
Fred82664 says: Apr 13, 2009. 7:41 PM
Yes this dose to you young lad you have my honers. you have done well in your studying and investing your knowledge to better living and only 19 at this point of time. I can see much more grate things coming from your efforts in the years ahead of you ! keep it growing
Speedmite says: Apr 14, 2009. 1:24 PM
Thank you.
average joe 1999 says: Jun 4, 2011. 3:32 PM
He obviusly wasnt talking to you.
difflock says: Apr 13, 2009. 7:22 AM
A youtube video of a Petter PAZ1

You just crank the engine over and then flick the decompression lever...causing the engine to rapidly compress air causing heat...
dkop1 says: Oct 11, 2010. 11:07 AM
I love my fire piston. I got mine from Wilderness Solutions, (the "Scout" model)
and it's never failed me. It did, however, take me a long time to learn how to turn that ember into a roaring blaze. I've never had problems lighting a fire, but I was accustomed to using flint and steel, or ferrocerium rods.
Any suggestions on natural tinder for fire pistons though? all I've ever used is char-cloth.
Feb 1, 2008. 9:09 PM
This is something I'll have to do in the future. It combines technical things with fire which is an irresistible combination. It'd make a great grill ignitor (I like to grill with real wood)
spylock says: Oct 21, 2009. 8:33 AM
I dont know if you have heard of this,not very technical,but take paper egg cartons fill with sawdust or dryer lint then pour melted wax into each section,when cooled seperate them,they will each burn about ten minutes,a little longer if useing sawdust.
Oct 21, 2009. 2:03 PM
Yeah, actually knapweed and grass clippings work well for that also.  There's actually an instructable on it.
tictaclad says: Sep 12, 2010. 2:44 PM
I take a paper towel, fold it 4 times so its like 1 inch wide ( you have to tear the paper towel) and then soak most of it in wax. leave a little bit without wax so you can light it. they burn for like a candle.
franklinonline says: Oct 31, 2009. 8:54 AM
Have you tried nitrate soaked paper? if it doesnt blow it up, you might get a open flame? Nice lighter with nature fuel possible if you fuel ran out.
spylock says: Oct 21, 2009. 8:17 AM
This is where Ive been making my mistakes,I didnt fill the cap,none of the other people told me of this step,thanks.
jphphotography says: Aug 16, 2009. 5:59 PM
I've been looking through all the info on the net on fire pistons and how to make them. I have to say for how simple they look they are fiendishly difficult to make. I finally ordered one so I had a starting point LOL. I'm getting closer now, the current prototype works but not consistently enough for me. Hopefully after a few tweaks it'll be solid and I'll post my own instructable. Another thing I noticed is that some of the materials listed in various fire piston how to's aren't easy to find. For example the longest brass nipple I can find is 4", other people used copper pipe but I can't find anything smaller than 1/2" so its been a challenge just to get the materials let alone getting it to work. Its all fun stuff though!
forlack says: Jul 15, 2009. 10:52 PM
Digging into that website Melon gave down there in the comments, NASA gives you two formulas based on the laws of entropy that you can use to calculate the temperature due to volume changes.

The first is to calculate the pressure change due to the compression ratio (or volume change)
p2 / p1 = (v1 / v2) (gamma)

Knowing that you can then use the second formula which relates pressure change to temperature change.

T2 / T1 = (p2 / p1) ( (gamma - 1) /gamma)

"Gamma" is just a number that depends on the gas. For air, at standard conditions, it is 1.4. (this is a simplification)

For the full workout go to http://wright.nasa.gov/airplane/compexp.html.
Now obviously this has some simplifications, but it should get you a good approximation. Plus their breakdown is for pistons in general which is good.

BTW Temperature is in Kelvin. Using the above equations and with the following:

Compression ratio of 25:1; initial temperature of 25c. The final temperature will be equal to 807c...pretty hot.
jphphotography says: Jul 5, 2009. 8:59 PM
How did the potassium nitrate saturated coffee filters work? Back in high school we used to make smokebombs with that stuff and we'd soak newspaper in a saturated solution of potassium nitrate to act as a slow burning fuse.
sharlston says: Mar 9, 2009. 10:41 AM
any more ideas please email them to mattyts@live.co.uk this is so cool
K.hall86 says: Feb 1, 2008. 3:20 PM
have you experimented with a stainless rod?? the stainless would have more resilience, although you would need more advanced cutting tools. although you might also need to experiment with the width of the o-ring grove...i can see the grove depth and width playing a key role in this. i would assume that the optimum grove width and depth would be the diameter of the ring. that way the ring would have no "slop" in the thrust direction, and it would also guard the ring from trying to roll out of the grove....i am of course assuming a lot here...lol you might try making a piston in very large scale at first....large diameters have tons of structural integrity..it might help work out the kinks in the small scale experiments...
n0ukf says: Nov 14, 2008. 1:53 PM
Have you ever tried to work with stainless? it's tougher to cut than regular mild steel (which is tougher cutting than aluminum)
watermelon (author) says: Feb 3, 2008. 2:50 PM
I use to carry stainless steel mini mess kits. It is not until you add things up that weight becomes a factor. Aluminum rod has enough strength and corrosion resistance plus workability to make it an excellent material for the job, especially for field use were weight is a factor. Commercial units use a variety of materials. The purpose of testing various configurations is to optimize your own personal firepiston to match the characteristics you need - like building a bow to match your height and strength.
chi chi chippy says: Sep 28, 2008. 7:55 PM
i have tried to make own out of pvc i saw on a website but i cant get it to start the tinder any one got any suggestions
watermelon (author) says: Sep 29, 2008. 6:50 PM
You can always make the length longer to gain a greater compression ratio, but PVC is not a material I would use due to the temperature at which it begins to soften and the low pressure at that temperature required to deform it. Clear polycarbonate, however is often used to make demonstration models. You might also consider making one out of a chunk of wood or a piece of bamboo. The lignin which binds the cellulose fibers in wood together is very resistant to degradation.
SPININSPUR says: Aug 25, 2008. 9:32 AM
has anyone come up with one small enough to be put on a key chain. How small can one be made so that the compression aspect is not compromised.i would like to make one as small as possible to carry.
chi chi chippy says: Sep 24, 2008. 5:55 PM
you can make one as small as you want but the smaller, the less tinder (char cloth/twine)you can use. i mean ive seen one as thin as a pencil.
Kinnishian says: Feb 2, 2008. 12:33 PM
Very nice guide. But I think explanations are overcomplicated.

Just for one simplification that anyone with some algebra could understand involving why it gets so hot.

Use the formula PV=nRT

Where P = atmospheric pressure. V = volume of gas (air). n = atoms of gas in mols. R = gas costant .0821 and T = Temperature in kelvin.

Keeping in mind P, n, and R remain the same anyone can determine T with simple algebra.

You can use suggestion or not it's still a good guide.
wizodd says: May 2, 2008. 6:26 AM
Easier than that. You need a compression ratio of about 25:1 Calculate the volume of the cylinder. V Calculate the volume that remains with the piston fully in. Vc V:Vc should be 25:1 or more. Note that the wider the cylinder and the smaller the tinder hole, the shorter the stroke length. Nearly any materials can and have been used to make these. The ones for sale on the net are art pieces-like custom knives. When the British first found these, they couldn't believe that they hadn't been invented somewhere 'civilized' as they found them pretty much everywhere the blowgun has been invented. They were just becoming very popular in Europe when the match "lucifer" was invented. Despite the then major disadvantages of the match (early ones tended to light TOO easily, like in your pocket!) Once you've got one they have a number of advantages over the standard lighters ('flint' & steel) in that they are wind and waterproof--if you're not actually under water, it will ignite, and more reliably than most lighters. No fuel to buy as nearly anything that is fluffy and burns will ignite.
watermelon (author) says: Feb 3, 2008. 1:15 AM
The math is quite a bit more complicated than juxtaposing the Equation of State for an Ideal Gas, as the Adiabatic process involves the Laws of Thermodynamics and must include the Enthalpy Equation. (See Entropy of a Gas)
Kinnishian says: Feb 3, 2008. 2:05 PM
Hmm....Alright :-) My mistake then. We covered the basics of gases earlier, and now we're into enthalpy and entropy. But, I don't think we've put them together yet. My favorite class it tis... Is the difference in the mathematics considerable? Oh, and I suppose we just started trying to determine the K constant for entropy. But I don't understand that yet. Maybe I should go do my homework now :p.
watermelon (author) says: Feb 4, 2008. 12:35 PM
Detroit would most likely hire an engineer at a high wage who could model a firepiston mathematically.
Kinnishian says: Feb 5, 2008. 2:49 PM
...=/

I was just trying to ask how accurate 'my method' would be?

And you know. So, right, thanks.
watermelon (author) says: Feb 5, 2008. 7:19 PM
Sometimes in school teachers will make it seem like if you learn only what they are teaching at the moment that you will know everything there is to know and that there is nothing beyond unless you come up with it. Then all of the sudden its like walking off a cliff when you find out they only scratched the surface. The pressure, temperature and volume relation of a gas is important to know but that is far from all there is. Check out air conditioning and refrigeration systems. A repair technician could probably help you to understand what happens with temperature when a gas is compressed at various ratios. Those are the guys I would ask.

shadeofsound says: Sep 10, 2008. 12:37 AM
so incredibly true there
Senseless says: Feb 2, 2008. 7:46 AM
Dang nice Instructable. It reminds me of an old pump design that let's you lift a small volume of water ten feet using a larger volume of flowing water like from a stream but without the need for it to drop like a typical dam system uses to generate force. I can't remember the name of the thing it's been around since the 1800's or so. This will bug me all weekend now trying to remember what it was called LOL.
Saint_Awesome says: Feb 22, 2008. 5:44 PM
We call this a 'waterfall bong', check out youtube for more.
wgrover says: Feb 2, 2008. 3:41 PM
Hi Senseless, it's a hydraulic ram if I'm not mistaken:

Hydraulic ram
Senseless says: Feb 2, 2008. 4:36 PM
Thanks! That's it exactly! I'll be able to sleep tonight LOL. It's like getting a song stuck in your head...
Feb 10, 2008. 3:32 AM
Wow,
incorrigible packrat says: Feb 6, 2008. 7:20 PM
Neato. I wonder if one could be made from a hatchback lift assist cylinder, or maybe one of those little pneumatic cylinders from the surplus store.
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