[SML] SML Fireworks Basics

[Dan Sheehan]

similar to combustion in a gasoline-fueled engine

rapid burning, initiated at the time and place of the spark plug firing,
before top-dead-center is reached during the compression stroke,
creates an expanding volume of gas with a pressure vs time profile
to push the piston down during the power stroke.

get it wrong, so the pressure rises enough to cause [some of] the
 remaining fuel/air mix to explode (all go off at once, instead of a moving
flame front),
is called "ping" if very mild,  is called a destroyed engine if more severe.

On Sat, Jul 7, 2018 at 11:26 PM, Michael Powers via Stagecraft <
stagecraft at theatrical.net> wrote:

> Dave Vick is correct. Gunpowder, whether black powder, modern smokeless or
> Pyrodex, does not explode. They just “burn” exceedingly fast.
> While the difference may seem so small as to be meaningless, I assure you
> it is not!  Exploded or detonated propellant would result in gun barrels
> and launch tubes bursting at the breech while the intended projectile might
> travel only a “relatively” short distance and that at “relatively” slow
> speed.  Gunpowder works because it specifically does not explode but burns
> or deflagrates very very rapidly, producing a gas with many, many times the
> volume of the gunpowder.  Just as steam is a vapor a volume of a magnitude
> greater than the water creating it.  The pressure from the expanding gas
> pushes the shell/bullet out of the barrel with the pressure continuously
> building as the still burning propellant increases the pressure behind the
> projectile until it exits the barrel/launch tube.  You’ll remember from the
> cartoon what Elmer Fudd’s shotgun looked like after Bugs Bunny stuffed a
> carrot down the barrel before Elmer pulls the trigger.  The “blossom”
> effect you see is real (although it would probably take more than a carrot)
> as the pressure “slowly” builds to a critical point at which time the
> barrel bursts at the thinnest point, the muzzle.  If gun powder exploded or
> detonated we would not have fire arms or fireworks as we know them today.
>
> Michael Powers
> USMC '65-'69
> ETCP Rigger #820 (Ret'd)
>
>
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>


-- 
...Dan Sheehan
Fixer of things that break
TD Walpole (MA) Footlighters
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