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Need help with a fire piston

Discussion in 'Bushcraft' started by gunbunny, Jul 9, 2010.

  1. gunbunny

    gunbunny Never Trust A Bunny

    I recently got a fire piston from my sister as a gift. She also got one for my father and her husband. They tried to use it, but couldn't get the charred cloth to ignite. Then I gave it a try. I cleaned all of the oil off the piston, put some char cloth in it, and rammed away... To no avail.

    You guys make it look too easy. With one stroke out pops a burning cherry. Not so in my case- I couldn't even get the piston to bottom out because of the pressure. I would pull the piston back out and it was room temperature.

    I then tried to pump the fire piston furiously, and the outer casing would start to get hot, but when I pulled the piston back out, there was no fire.

    My brother-in-law used a mallot to try to get his piston to bottom out, but it made no difference.

    What are we doing wrong?
  2. melbo

    melbo Hunter Gatherer Administrator Founding Member

    Is it buffalo horn or synthetic? Are you at a higher than normal altitude? Friction making the sides heat up is not the heat that makes it work. I also don't know (It's been a few years since I've had mine out), if it needs to bottom out.

    My buffalo horn FP is a little temperamental because the gasket is wound thread and it can't be too loose or too tight. However, the clear synthetic one has an O-ring and has never failed.

    Which ones did you get?
  3. gunbunny

    gunbunny Never Trust A Bunny

    It has a brass cylinder and an aluminum cylinder. The gasket is a rubber o-ring with some kind of white grease. I tried to clean as much of the oily grease from near the end of the piston as possible. When I packed the hollow, I didn't let the charcloth stick out past the end.
  4. SLugomist

    SLugomist Monkey++

    isn't a fire piston based on the same principle as a diesel engine? the compression makes igniting the high flash point material happen.

    I would think the oil/grease is to seal the setup, so you get the pressure needed to ignite.
  5. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    The aluminum might not be too good, it may transfer the heat out too quickly. Brass is better in that respect, but maybe not by much. Wood is probably the best choice, if a good fit can be achieved. Yes, it is diesel ignition, and no, bottoming is not going to make it any hotter, in fact if it does, something isn't working right. If you run the numbers, you should be able to get about an 18:1 compression to get good ignition, and maybe a lot less will work.
    Brokor likes this.
  6. gunbunny

    gunbunny Never Trust A Bunny

    It definetly has compression, as I cannot get the piston to go any further than about 2/3 or 3/4 of the way down the cylinder. If the aluminum is the culprit, I'll try packing the hollow a little differently, starting with some dryer lint, and then putting the charcloth on top, sticking out past the end of the piston. Maybe that will insulate the charcloth from the aluminum.

    I'm sure this thing has to work- I mean, why build a quality product and not have it do what it is made for? [slow]
  7. sticks65

    sticks65 Monkey++

    Are you giving it a short sharp hit?

    I found that if you give it a really sharp hit with the palm of you hand that mine worked better,but now mine has a crack in it because the wood dried out so im going to make a brass one next.
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