An
18th century invention by Benjamin Robins allowing a more-pracitcal use of
gunpowder in
ballistics.
Up to and through the early 18th
century, early-modern
European gunners and their
theories with gunpowder were
shaky at best. They had no
foundation for their preferences, and no rational
explanation for how their designs with the
explosive worked. With the advent of
the
ballistic pendulum, however, all this would change, leading to drastic
improvements in all forms of the
gun.
Gunpowder
Gunpowder, it must be understood,
was a relatively recent and under-developed
technology in the late 18th
century. European
armies of the time used
muskets, that, though cumbersome
(especially in
reloading) and
innacurate, served their purpose well enough –
if you
fired at a line of advancing
British, chances are you’d
hit
someone…
somewhere.
In the
1400s,
smiths innovated
the use of “
corned” gunpowder. They would mix gunpowder with
water, to form
uniformed cakes with the correct concentration of
grain – some of it very
coarse (the size of
corn grains and thus the name), and others with varying
sized
kernels from medium to very fine. The gunpowder
mills themselves could be
powered by water, mixing huge batches relatively easily. This allowed for much
safer
processing of gunpowder (It’s always better when there are no
explosions), as well as a
cheap manner of
manufacturing great amounts of it.
Late-
medieval and early-
modern
gunners generally preferred
fine gunpowder with
handguns, medium grains with
muskets and
rifles, and large-corned gunpowder for
cannons. They were correct in
their choices, but as time wore on,
little developments were made in the
industry.
In fact, if anything, a
counter-development took place, and by the mid-
18th century, during
the
French and Indian War, the
Europeans generally used gunpowder in a
willy-nilly fashion – fine with cannons, large with muskets, etc. This made
accidental explosions common, and also decreased the efficiency of use. Much
ammunition was wasted because of
scientific ignorance.
New Principles of Gunnery
In
1742, a
British mathemetician named Benjamin Robins published
New
Principles of Gunnery,
a work that told
gunners exactly how much
gunpowder, and of what kind, they
should be using. How did he do it? With a
ballistic pendulum.
Robins had the bright idea of
hanging a wooden
block from the
ceiling by two
cords. A
bullet, fired into the
wood, would
swing the block up at its
momentum, which could then be measured by
the swing’s
amplitude. This is a result of the
law of conservation of
momentum. Because an object’s momentum is the product of
mass and
velocity,
and momentum is
conserved, then
mv = (m + M)V
where “v” is the
velocity of the
projectile, “m” is the mass of the
projectile, “M” is the mass of the block, and “V” is the velocity of the
block.
This
equation is then morphed so that the projectile’s velocity is
expressed in terms of the block’s
amplitude/
momentum:
V=((m+M)/m)V
Repercussions
Being able to specifically measure velocity in relation to the
gunpowder charge
revolutionized ballistics. It was finally possible
to determine the
exact charge
necessary for a
specific effect; from then on,
gunpowder use could be more
efficient, ammunition
conserved, and
better guns
invented. Despite the fact that this device has long been made
obsolete, it is
still in use in
classrooms for
experiments of
momentum and
energy.