"Arfa Daily" wrote in message
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"Captain Midnight" wrote in message
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"**THE-RFI-EMI-GUY**" wrote in message
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I assume the can is open on one end like a soup can, not a coke can. I
think the water is there to provide an airtight, frictionless seal for
more effect. Keeping the firercracker dry is tricky. This looks like a
good use for the hundreds of firecrackers I have left over!

What he is simulating is the explosion that happens in one of your cars
engine cylinders. A car engine operates on a series of small controlled
explosions. In your car, the explosive force drives a piston down,
pushing a connecting rod which in turn rotates a crankshaft. A car
engine has 4 to 8 cylinders which fire sequentially and smoothly. The
links below illustrate this with a single cylinder like a lawnmower
engine. These are "internal combustion engines".

My sister did a similar science project years ago with a coffee can
fitted with a spark plug and filled with a very small amount of gasoline
or ether. A plastic lid was placed on top and an ignition coil made a
spark which blew the plastic lid off. Not as dramatic as a fire cracker.

http://www.keveney.com/otto.html
http://en.wikipedia.org/wiki/Four-stroke_cycle

Dumb_Blonde wrote:

Thank you in advance for your time. I found a neat project to do with
my 14 year old son, but would like to know the science behind it so it
will be educational.

Here is the video link.


http://www.metacafe.com/watch/470767...ct_experiment/

It is a fire cracker experiment, and I know he will love it, but I am
clueless as to how this makes my car run.




--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©


Their is no explosion in a properly operating internal combustion engine.
The fuel merely heats the air. The expansion of the air pushes the
piston.
An explosion called detonation or knock can put a hole in the piston.
Some
engines require higher octane fuel to keep knock from occurring.


That seems to me to be a misleading description of the principles of an
internal combustion engine. The fuel is mixed with the air in a very
carefully controlled ratio, highly compressed, and is then set light to,
either by a spark in the case of a gasoline engine, or by self ignition
from the rapid heating of the mixture during compression, in the case of a
diesel. It burns or combusts, and what comes out of the exhaust, after the
burning, is not air, but a fully reduced residue of the burning process.
The burning of the mixture under such intense pressure, in what is
essentially a fully contained space, takes place at such speed, it would
usually be considered to be representative of a controlled explosion.
Detonation knock is normally as a result of the timing of the ignition
source not being ideal for the engine in question. The detonation process
should be started just before the piston reaches top dead centre, so that
by the time the burning has spread fully from the initiating point - ie
the spark plug - through the entire mixture, and is thus at its fiercest,
the piston has rolled over past its point of being momentarily stationary,
and is just beginning on its way back down the cylinder. The rapidly
burning ( exploding ? ) mixture will then deliver maximum thrust to the
piston, driving it down the cylinder bore. If the mixture starts to burn
too early, it will reach maximum energy output before the piston has
reached the top, so will oppose the upward movement of the piston, which
is still occuring, leading to the pre-detonation knock.

Maybe it is just semantics, and some may disagree, but that has always
been my take on how an engine works, ever since I was first rebuilding
them as a kid, because I couldn't afford repair shop prices !!

Arfa

Just as a matter of interest, I just looked up the word " explosion " at

http://dictionary.reference.com/browse/explosion

and interestingly, the first result, 5th definition, specifically mentions
the internal combustion engine. The third result, definition 1a also seems
to cover it neatly, as does the twelfth

Arfa