Fire Piston dosn't fire??

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Sep 7, 2010
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So I thought I'd try my hand at making a fire piston. (Like how hard can that be?)

I had on hand some 3/8" aluminum bar stock and slightly larger aluminum tubing. The two fit together very nicely. I cut a piece of tubing 5" long and a piece of bar stock 6" long. I flared one end of the tubing and screwed a cap on the other end and sealed it with JB weld. I cut a small groove in the bar stock to fit a rubber "O" ring. I also drilled a small hole in the end of the bar stock that goes into the tubing for tinder. The two fit together very snugly with no leakage at all.

But I can't get it to fire...Anything, not even a match head. The only thing I can think of is that it's too large a diameter. In other words I'm trying to compress too much air, and I don't have the strength to do it. I've seen guys make them out of 1/4'' material on youtube, But I didn't think an extra 1/8" would make that much difference.

Can anyone help me out with this? What did..... or am I doing wrong?
 

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I even tried a larger "O" ring to make sure of a good seal.

Still won't fire anything.
 
can you push the plunger into the tube easily? and once down does it stay down? if so you dont have a tight enough seal.
 
can you push the plunger into the tube easily? and once down does it stay down? if so you dont have a tight enough seal.

No it's quite tight...When I force the piston down it pushes it self back out. so the seal is good. I just went and cut a second seat in it to add another seal. it now has 2 seals about 1/4" apart and still no fire. :(

I realy don't understand:confused:
 
maybe your combustion area is too big so it will get hot but not hot enough.

I didn't think that could be an issue? I drilled a whole less than 1/4" in diameter in the 3/8" piston. and only about 1/8" deep

Think that's too big?
 
Dry putting the whole thing under water and pressing the plugger in, to see if any air is leaking at all. Even just the smallest about leaking it won't fire.
 
How much space between the end of the piston and tube.There needs to be a little gap at the bottom.Been playing around with a couple,with a friend with the same results as you.Put a little space at the botton.Around 3/16ths and that solved the problem,fires up evertime so far
We also werent using the best char cloth.Made up some more with cotton waste.Tested the spark catching ability with a flint and steel.Used the new stuff as it took a spark everytime
Keep at it
Dan'l
 
How much space between the end of the piston and tube.There needs to be a little gap at the bottom.Been playing around with a couple,with a friend with the same results as you.Put a little space at the botton.Around 3/16ths and that solved the problem,fires up evertime so far
We also werent using the best char cloth.Made up some more with cotton waste.Tested the spark catching ability with a flint and steel.Used the new stuff as it took a spark everytime
Keep at it
Dan'l

Ahhh...That may be my problem. If I set it on the ground and hit the piston into the cylinder with a piece of 2X4 it does bottom out, but I have to realy hit it.

I'll make another cylinder and make sure I leave enough space at the bottom.
also I've noticed from watching some videos of other fire pistons that the hole I put in the bottom of the piston may not be deep enough. I'll try drilling that a bit deeper first.
 
Well I tried it again. Made a whole new piston and cylinder. I put 3 "O" rings on the piston to improve compression. That thing seals up tighter than Obama's birth certificate.
I left a good gap at the bottom and drilled a 3/8" hole in the piston.
NOTHING...
So I'm gona shelf this idea for a while and try it again in a few months.

Thanx for your help guys! I can't believe I can't get this to work. Freekin natives in Borneo have been making these things for 1000 years out of Bamboo string and spit.
I'm using modern materials and equipment and it won't even pretend that it might work.:mad:
So I'll put it on the back burner for a while and try again another day.
 
I gave up on fire pistons. Could never get them to work every single time. It's a neat idea... but I can make 10 billion fires with my .50" diameter fire steel. Good luck with it. They are hard to use little buggers.
 
Alright so I lied, I couldn't put it down (pissed me off too much)

I made another batch of char cloth and cooked it much longer this time.
I did get it to fire a couple times but not consistantly. I'll tweek it a bit more and once I get the hang of it I shouldn't have any more problems with it.
 
I've made and sold over a hundred fire pistons over the past few years. My compression chamber is about .71 cubic inches. Yours is about .47 (assuming that o-ring is .75" from the end). Seems your chamber is a bit small to me. I found that size through a lot of experimentation and it seems to be about the perfect ratio. I can fire mine the first time (with char cloth) almost every time I try.

A couple of things to keep in mind:
-How far up you put your o-ring dictates where the compression starts. The shafting below your o-ring takes up space (air) which changes your compression ratio. You want enough to be able to hold the piston in there, but not too much.
-It is incredibly important to have a flat bottom on the inside of your shaft. If you get ignition when you compress down to .01", then if you only reach .02" on the next try you've cut your compression pressure in half!
-Char cloth will always work best, so start there then after you get it to fire reliably you can move up to less flammable materials.
-Match heads lights off of a reaction with the striker material. I've never been able to get them to work in a fire piston (though I didn't try that many times).

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Thanx for the tips!!
K so now I have to make another one with a slightly larger compression chamber.
 
I made 2 fire pistons, I could not get either to fire... I gave up for real! I will come back to it some day.
 
Ha!!!

I got it firing every time now! WOOT!!!
Thanq Michaelmcgo!!
Now that I have the method figured out, I can start maknig a few more of these. sweet!!
 
is the O ring WELL greased? this is very important to help seal the chamber. Silicone grease (like plumbers use) works excellent. Be sure to get some UNDER the O ring, in the groove.
 
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