A blasting machine or shot exploder (commonly called a plunger) is a portable source of
electric current
An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge c ...
to reliably fire a
blasting cap to trigger a main
explosive
An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...
charge. It is mostly used in
mining
Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...
and
demolition
Demolition (also known as razing and wrecking) is the science and engineering in safely and efficiently tearing down buildings and other artificial structures. Demolition contrasts with deconstruction (building), deconstruction, which inv ...
.
The use of the term "machine" dates from early designs that used an
electrical generator operated by winding a rotary handle or pushing down a T-handle. Modern blasting machines are battery-powered and operated by key switches and push-buttons, and do not resemble the older designs.
History
The first satisfactory magnetic induction blasting machine was constructed in 1878 by Henry Julius Smith of Mountain View, New Jersey. Its mechanism consisted of a T-handle that was pushed down; the lower end of the handle was a
rack that drove a pinion, which in turn drove a
high-voltage magneto, which generated the high voltage that is required to detonate the blasting cap.
Design
A typical "capacitive discharge" blasting machine works by charging a
capacitor from a
battery, then discharging the capacitor through an external circuit, called the firing line, to fire the blasting cap.
"Buzz Box: BB-30 Blasting Machine"
, Blasters Tool & Supply Company, accessed 2012-07-09 While the machine is idle, an "internal shunt" is connected across the output terminals so that any stray voltages induced in the external circuit, for example by nearby radio transmitters, are harmlessly short-circuited without triggering the blasting cap. The machines also typically include an "abort" feature to discharge the internal capacitor without firing the cap.
In popular culture
Despite the older "T-Handle" design no longer being used, this design of blasting machine is most closely associated with ''Looney Tunes
''Looney Tunes'' is an American media franchise produced and distributed by Warner Bros. The franchise began as a series of animated short films that originally ran from 1930 to 1969, alongside its spin-off series ''Merrie Melodies'', during t ...
'', and the character Wile E. Coyote, due to his penchant for attempting to use explosive materials to capture or incapacitate the Road Runner, often ending in disaster for the Coyote as the explosive either backfires, the machine does not work properly, or the T-handle gets stuck.
References
External links
*
Shot Blasting Machine
{{Mining equipment
Mining equipment
Demolition