About the Unit itself A ready-to-use fascinating apparatus to
demonstrate how temperature increases with
pressure. This scientific fact is
dramatically demonstrated by igniting cotton tinder in side the
clear cylinder as the plunger
compresses air in a cylinder.
A heavy aluminum rod fits inside a clear acrylic
tube. A piston tipped with O-rings and
fitted with a contoured handle is used to compress
rapidly the gas, raising the temperature
sufficiently to ignite a small piece of cotton in
The above link will take
you to an in-depth analysis of of Boyle's Law (PV=nRT).
To summarize that analysis compressing
the air in the cylinder into a smaller volume, we
are also increasing the temperature inside the
cylinder. Looking at the components of the
formula, a large increase in P (Pressure), results
from a significant reduction in V (Volume), with n
and R being constant, that leads to a large
increase in T (Temperature) which will ignite the
cotton tinder in the cylinder.
How to Use
1. The setup is quick and easy. First, pull out the
plunger and drop in a small piece of the cotton
2. Re-insert the
plunger gently so that it just enters the mouth of
the piston chamber.
3. Holding the
unit flat on a non-slip surface, push down the
plunger with some force and speed.
You will see a
flashof fire inside the clear
tube as the air is compressed, heated to a
that ignites the cotton tinder. The combustion
will last until all available oxygen in the
cylinder is used up.
Note: Allow sufficient
time for fresh oxygen to re-enter the cylinder
so that combustion will be supported for the
How it physically works:
Air gets very hot when compressed under high
pressure. If you have ever pumped up a bicycle
tire, you have noticed the heat generated. The
Unit has a "compression ratio" of approx. 18:1
(the volume of cylinder is 9ml and reduces to .5
ml when the plunger is compressed).
When the air in
the Fire Piston Demo Unit is compressed, it is
done so fast and efficiently that it results in a
temperature increase to well over 210oC
(378oF), the "flash ignition
temperature" of cotton. In fact it can reach
instantaneous temperature of over 260oC
(500o F) inside the cylinder!
behind Why It Works
When it is compressed rapidly, gas undergoes an
adiabatic thermodynamic process, one that occurs
without loss or gain of heat. As the volume is
reduced, pressure increases very quickly. The
temperature of the gas also rises, because there
is not time for the heat energy to transfer to
its surroundings as would normally happen. This
increase in temperature can cause flammable
substances to ignite with "hot air" alone, just
like a diesel engine!
How does a diesel engine work? A diesel engine
compresses air inside a cylinder (which leads to
an adiabatic temperature increase) and then
injects fuel at just the right moment so that it
combusts from the heat. The fuel combustion
forces the piston down, producing the engine's
power. This design, where fuel is directly
injected into the cylinder at the top of the
engine's compression stroke, prevents engine
knock, unlike a gasoline engine that uses a
spark plug for ignition. (The fuel in a diesel
engine combusts spontaneously from the heat,
rather than requiring a spark to ignite it.)
Since there's no danger of causing knock, the
diesel engine can use higher compression ratios
than gasoline engines.
Diesel engines with high compression ratios are
more efficient than gasoline engines, which is
why large trucks and ships use diesel engines.
When it was invented in the 1890s by Rudolf
Diesel, though, the engine was sneered at. A
diesel engine starts with an intake stroke,
where air is sucked into the cylinder as the
piston moves down. The next compression stroke
occurs when the piston moves back up,
compressing air rapidly in an adiabatic process.
In the power stroke, the fuel is injected and
ignites, pushing the piston down and powering
the engine with the energy produced. In the
exhaust stroke, the piston moves back up,
pushing the burned gases out.
The more flammable the
fuel, the lower the temperature required to
flammable than a heavier fuel (such as wood).
When the oxygen gas in the air surrounding
for your Fire Piston Demonstration Unit
Very little maintenance is needed.
Your plunger has been pre-lubricated and should
not need additional lubricant for sometime,
however additional lubricant is included with the
unit if you want to use it before each
demonstration o extend the life of the o-rings..
After each use,
clean out the cylinder with a wooden stick or
simply blow out the carbon dust from the small
fire you just made. The Demo Unit is ready to use
1. Suction stroke: Pure air gets sucked in by the piston sliding
2. Compression stroke: The piston compresses the air above and uses
thereby work, performed by the crankshaft.
3. Power stroke: In the upper dead-center, the air is max.
compressed: Pressure and Temperature are very high. Now the black
injection pump injects heavy fuel in the hot air. By the high
temperature the fuel gets ignited immediately (auto-ignition). The
piston gets pressed downward and performs work to the crankshaft.
4. Expulsion stroke: The burned exhaust gases are ejected out of the
cylinder through a second valve by the piston sliding upward again.
Use these buttons below the animation to slow down
or stop the engine's motion
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P.O. Box 31764
Cleveland, Ohio 44131 Tom@SurvivalSchool.com
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