Fire Piston

A fire piston is a device that uses the heat created from rapidly pressuring a gas to ignite a piece of char cloth.  The main components are a cylinder, a plunger and an O ring.  You can buy a commercial fire piston for $20 to $50.  This article will show you how to build one for less than $10.  The most expensive material needed is a piece of copper pipe.  I paid $5.92 for a 24" piece at Lowe's.  If you can get your hands on a scrap piece, that would be ideal, or split the cost with 3 friends who want to make one also.  You could make it out of 1/2" PVC pipe, but I doubt it would be very durable.  The remaining items are in the $1-$2 range.



Materials 
1/2" copper pipe (5" long)
1/2" copper pipe end cap
wooden cabinet knob
3/8" oak dowel (about 6")
rubber O ring (#6)
wood glue
petroleum jelly

Tools
hacksaw or pipe cutter
file
sandpaper
propane torch
flux / solder
saw
pocket knife
small round file or sandpaper wrapped around a small drill bit
drill
1/4" & 3/8" drill bits

Procedure
Cut the 1/2" copper pipe to 5".  Solder the end cap on.  You can find soldering videos on YouTube.  Chamfer the inside of the open end of the pipe with the corner of a file, then smooth with sandpaper.  This allows the piston to slide in easily.


Mark the one end of your 3/8" oak dowel 1/4" from the end.  Score the line with your knife.  Carefully whittle along the line to make a groove.  Use a tiny round file, or very small drill bit with sandpaper wrapped around it to deepen and smooth the groove.  Test fit your O ring.  It should slide into the cylinder with a tight fit, but without being pushed out of the groove.




Mark the center of the end of your dowel.  Use a 1/4" diameter drill bit (brad point works best) to drill a 1/4" deep hole in the end.  This will receive the char cloth.



Drill out the the cabinet knob to 3/8" to fit the end of the dowel.


Cut the dowel so that it it comes about 1/8" from bottoming out when you push it in all the way.  You don't want to bottom out and extinguish your char cloth. Use wood glue to glue the dowel in the knob.

Using the Fire Piston
Put a tiny piece of char cloth into the recess in the end of the dowel.  (Post on how to make char cloth coming soon!) Lubricate the O ring with petroleum jelly, oil, or spit.  Fit it into the end of the cylinder.  Place the closed end on the cylinder on a firm surface.  Push the knob hard and fast.  Pull out the dowel and see if you have an ember in your char cloth.  It may take several practice tries to get the hang of it.  Blow on the ember and transfer to a ball of tinder.  Blow on this until you get flames.



Here is a link to a video that shows you how to make one:
https://www.youtube.com/watch?v=YKJksRIBzNc




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