A couple of years ago I purchased a fire piston, but I was never really satisfied with its performance.  So, I vowed to make myself one.  However, my initial attempts (using 1/4 inch copper tubing and 1/4 inch dowel, and 1/4 inch O-ring) were not entirely successful.  Although I get compression, it is not sufficient to ignite the charcloth.  It could be that when I sweet the cap on the tubing, there is a small leak or perhaps I need a better O-ring seal ... but I have one piston that uses 2 O-rings!

So, in my effort to make one of these, last night I ran across these videos for a home made fire piston.

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I whipped one together this afternoon, and it works like a charm!  It also has an advantage of making a nice large ember (as opposed to my 1/4" version).  BTW:  My compression tube is ~ 5 inches.

dd

Nice [smiley=thumbup.gif]

OK.  The 5 inch version is working fine.

The new 4 inch version is working fine.

Now the 4.5 inch version made from 1/4 inch copper tubing & 1/4 inch dowel rod is working fine (with a single O-ring).  I guess the sweat joint seal was better than I thought.  Just needed a bit more lube and patience.

dd

Been playing in my shop (a bit crude since I was looking more at function than cosmetics):

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12:00 made from 1/4" copper tubing with cap and 1/2" pine dowel piston
10:00 and 2:00 made from 1/2" copper stubout w/ 1/2" oak dowel piston
4:00 and 8:00 made from 1" pine dowel with 1/2" oak dowel piston
6:00 made of 1/2" copper tubing with cap and 1/2" oak dowel piston

All are functional, 1/2" copper based units produce superior compression.  Unit at 6:00 is shortest (4" overall); unit at 10:00 is longest (6" overall).  All wood unit at 8:00 is the lightest (1.5 oz.). Each unit also uses a rubber O-ring about 1/4" from the end of the piston.

dd

Very interesting DD. I've never seen or heard of this before. I wonder how changes in humidity would affect the wooden ones.

db wrote on Apr 2^nd, 2011 at 6:00am:

I wonder how changes in humidity would affect the wooden ones.

My guess is that the all wood model would suffer a bit from humidity, especially since the 1" dowel I used is pine (which is relatively porous).  I bought a 1" dowel in oak that I'll use for a "re-make" of an all wood unit.  Since it is more dense, I'm hoping that it would be a better combo for purposes of compression.  

In any event, if I take one of these to the field, it would most likely be the 6:00 unit.  It is a fraction shorter than the all wood (8:00) unit and only weighs 1.75 oz.  One thing that cannot be seen on the metal units is that the compression is so good that a string has been added around the base of the handle so that it can reach the top of the piston.  The string creates a slight air gap in the O-ring allowing you to fully compress the unit for travel.  Otherwise, it is a real battle to get the piston all the way to the bottom and have it stay there.  There was enough natural "air bleed" in the all wood units that the string was unnecessary.

(Note:  All of the commercial wood units I've seen have a metal sleeve insert to avoid the "air bleed" issue in the cylinder walls.)

dd