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Model "T" Fire Piston
Article and photographs by Rob Bicevskis
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Building the Plunger - The Piston - Syringe
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A hypodermic
syringe is "just what the doctor ordered" for
making a fire piston!
I was able to get some 6ml syringes from a
farmer's supply store. The inside diameter of
the syringe is just under 1/2" and the seal on the
plunger is almost exactly 1/2" |
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First, I
wouldn't suggest using just the syringe as a fire
piston. Doing so might be
dangerous as the syringe will likely shatter and you
could get hurt. I tired this. I inserted a screw
into the end of the cylinder to seal it off. I
then tried the contraption, and the plunger
shattered. Luckily I was wearing gloves - from
which I have to extract one of the fragments! . |
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I also tried using the syringe cylinder with a
wooden plunger and the cylinder blew apart.
Clearly syringes were not designed for the pressures
involved in the function of a fire piston |
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But... the
syringe does have one redeeming quality, the rubber
seal is perfect! Pull the plunger out of the syringe and remove
the rubber seal. The seal conveniently already has
a hole in it. Drive a small screw through the hole
in the plunger seal. Make a small pilot hole
in the end of the wooden dowel. Assemble the
two pieces and you're done. Note - with the
syringe gasket as a seal, the diameter of the dowel
is less critical. 7/16" dowel will work just
fine and will ensure that you don't need to reduce
the diameter. This saves an extra step. I don't know how much
variation there is in the sizes of the syringe
rubber seals, but with the syringes that I have, the
seal is perfect, and requires no fiddling to make it
work.
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Now you
should have a cylinder, and one or two plungers.
(Note that the plunger with the syringe seal also
has an O-ring groove. This grove is of course
unnecessary. I just happened to attach the
syringe seal to a piece of dowel that had previously
been used with an O-ring.) |
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| Done! |
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This is what
you should have ended up with. Review the two
videos above to get a feel for the amount of
friction you should have in your assembly. Also,
note the speed and force that is used to power the
plunger. The critical action is to generate as
much speed and pressure as quickly as possible.
It isn't all that critical how quickly the plunger
is removed. Most tinders will stay aglow for
many seconds. You will need some tinder to place
into the end of the plunger. My favorite is
tinder fungus. This isn't always so easy to
come by.
Char is a great alternative that is
readily made. Have a look at some of the pages
on tinder and char on this website.
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*** A word
of caution ***
Please be careful about the types of materials you
put into the fire piston. Any highly flammable
or volatile substance can easily cause the fire
piston to explode. Be safe. |
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Conclusions A simple
Fire Piston design has been presented. It
requires no special tools or materials. The
cost is absurdly low - even more so if you can get
some scraps from someone doing some plumbing work.
The simplicity and modularity of the design makes
for a great platform for experimentation. It
is a simple matter to substitute a new piece of
dowel and try different gaskets. You can try
the traditional string gasket, or maybe have a go at
the leather cup version. Try longer or shorter
cylinders. Try different diameters for the
design. Have fun and let me know how you make
out:
email
Rob |
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