Fire Piston

2014-11-27

This was just a fun project I (Karl) wanted to do before my junior year at school started. A fire piston uses the principle that compressed air gets hotter, just like a diesel engine uses compression to ignite the fuel. This piston uses char cloth as a fuel and is a way to light a campfire without matches. Every year I was in Boy Scouts I completed in the Klondike fire building competition. One way you can get more points is to use friction to start the fire. I guess this is how I got interested in the fire piston. Although I never used it in competition, I still like the concept.

I started with a cylinder of aluminum and milled it down to an nice size that fits comfortably in one hand.

Using a drill in the fixed chuck I created a hole for the piston.

You can see that the tool stock in this picture is new. I had a lot of problems with the tool stock that came with the lathe. You can see the shim in the photo above. The tool stock below has fine height adjustments and holds a cut off tool nicely.

Sharp tools held steady make a big difference in how this lathe works, I found. A couple of times the tool jammed and it broke the plastic gears inside the lathe. My dad took the entire lathe apart and put in the new gears. Here I am cutting off the handle for the piston.

This photo shows how I faced the piston handle. Building the fire piston was also a good way to learn how to use the new tool mount and dial gauge we got before my brother and I started our next big project: a double acting, non-oscillated, uni-flow valve steam engine.

Here is the finished handle.

This is a dial gauge that we got. It adds considerably to the precision of my work. It especially helps when you put a piece back in the jaws to get it perfectly re-aligned.

One other thing I learned from the breakdown was how to grind and sharpen the steel bits. This is one with compound angles that is useful for turning flat, smooth surfaces.

Here I am turning the inner rod. Adding oil helps carry away the chips which makes the cutting go better.

This shows the end of the rod with a cavity for the char cloth.

Getting the black o-ring to fit just right is key to making the piston function. This is where the tight seal keeps the air in the piston. My brother Erik and I went to McLendon's hardware to get the right size and he helped me with some of the project.

The completed fire piston.

With one quick plunge of the rod into the piston, the char-cloth is a glowing ember that can be set to a nest of tinder to start a fire.