Stubborn firepiston

[Kyle Kraft]

I built a fire piston from aluminum with a 1/2" bore and about 4" stroke...maybe a bit more, and I'm having trouble getting it to work consistently.  I made some charcloth from a 100% cotton shop towel and the piston worked on the first hit for a few times.  The o-ring seal is in excellent condition and the compression nearly shoots the piston out of the bore.

Could I be having a problem with the charcloth?  Is it made of the wrong density of cotton cloth?  I had a retired scoutmaster tell me to use cotton duck to make my charcloth.

Any help would be appreciated!!

[JAHNS79]

For making char cloth, almost any 100% cotton material will work well.  What have you been using as a lubricant?  some work better than others.

[Kyle Kraft]

I was using a light oil on the o-ring.  The thing that gets me is the piston worked when I was alone or with one other person but refused to perform in front of an audience

[JAHNS79]

In honesty what it sounds like to me, and I am not kidding or trying to be rude, you may be suffering from stage fright.  What I would suspect is that you are trying too hard to make the piston work for other people and striking differently than you would if you were trying to light it without onlookers.

[Kyle Kraft]

Thats entirely possible.  Are you saying that "pounding" the piston makes a real difference in whether the thing lights or not?  I figured that compression is compression and it didn't matter how forceful or rapid the stroke was.

This almost sounds a bit risque' doesn't it?

If the above does matter significantly, then what is the proper technique?  I was loading the charcloth and jamming the piston down on a bench or picnic table.  Also, should I quickly pull the piston out or do more slowly.  I was concerned that the cloth would die out if not ventilated promptly.

[Pat Norton]

Kyle, we found that the key is a deliberate fast depression of the piston with a light pause at the bottom.  This seems to work the best with our pistons. 

Due to the fact that your dimensions are different it is going to make a difference in how they work.  We found that the motion needs to be done quick and forcefully but you have to pause a bit in order for the heat to transfer to the cloth.

In finding the rhythm it took us quite a while.  You almost need to be in a zen state of mind with the piston and feel it working.  You have to spend time with it.  I know that sounds kind of goofy but it is a "feel" thing.

[Kyle Kraft]

Pat,

Thanks for the tip!  I'll try the pause at the end and let you know if it helps.