A shot tower is a

tower A tower is a tall Nonbuilding structure, structure, taller than it is wide, often by a significant factor. Towers are distinguished from guyed mast, masts by their lack of guy-wires and are therefore, along with tall buildings, self-supporting ...

designed for the production of small-diameter shot balls by

free fall In classical mechanics, free fall is any motion of a physical object, body where gravity is the only force acting upon it. A freely falling object may not necessarily be falling down in the vertical direction. If the common definition of the word ...

of molten

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

, which is then caught in a water basin. The shot is primarily used for

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...

s in

shotgun A shotgun (also known as a scattergun, peppergun, or historically as a fowling piece) is a long gun, long-barreled firearm designed to shoot a straight-walled cartridge (firearms), cartridge known as a shotshell, which discharges numerous small ...

s, and for

ballast Ballast is dense material used as a weight to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within ...

, radiation shielding, and other applications for which small lead balls are useful.

Shot making

Process

In a shot tower,

is heated until molten, then dropped through a

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

sieve A sieve (), fine mesh strainer, or sift is a tool used for separating wanted elements from unwanted material or for controlling the particle size distribution of a sample, using a screen such as a woven mesh or net or perforated sheet m ...

high in the tower. The liquid lead forms tiny spherical balls by

surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension (physics), tension is what allows objects with a higher density than water such as razor blades and insects (e.g. Ge ...

, and solidifies as it falls. The partially cooled balls are caught at the floor of the tower in a

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

-filled basin.. The now fully cooled balls are checked for roundness and sorted by size; those that are "out of round" are remelted. A slightly inclined table is used for checking roundness. To make larger shot sizes, a copper sieve with larger holes is used. The maximum size is limited by the height of the tower, because larger shot sizes must fall farther to solidify. A shot tower with a 40-meter drop can produce up to #6 shot (nominally 2.4mm in diameter) while an 80-meter drop can produce #2 shot (nominally 3.8mm in diameter).

Polishing Polishing is the process of creating a smooth and shiny surface by rubbing it or by applying a chemical treatment, leaving a clean surface with a significant specular reflection (still limited by the index of refraction of the material accordi ...

with a small amount of

graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

is necessary for

lubrication Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubrication mechanisms such as fluid-lubr ...

and to prevent

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

History

The process was invented by William Watts of

Bristol Bristol () is a City status in the United Kingdom, cathedral city, unitary authority area and ceremonial county in South West England, the most populous city in the region. Built around the River Avon, Bristol, River Avon, it is bordered by t ...

, England, and patented in 1782. The same year, Watts extended his house in Redcliffe to build the first shot tower.. Use of shot towers replaced earlier techniques of casting shot in moulds, which was expensive, or of dripping molten lead into water barrels, which produced insufficiently spherical balls. Large shot which could not be made by the shot tower was made by tumbling pieces of cut lead sheet in a barrel until round. The "wind tower" method, which used a blast of cold air to dramatically shorten the drop necessary and was patented in 1848 by the T.O LeRoy Company of New York City, meant that tall shot towers became unnecessary, but many were still constructed into the late 1880s, and two surviving examples date from 1916 and 1969. Since the 1960s the Bliemeister method has been used to make smaller shot sizes, and larger sizes are made by the cold

swaging Swaging () is a forging process in which the dimensions of an item are altered using Die (manufacturing), dies into which the item is forced. Swaging is usually a cold working process, but also may be hot working, hot worked. The term swage ma ...

process of feeding calibrated lengths of wire into hemispherical dies and stamping them into spheres.

Gallery

File:Sparks Shot Tower 129-131 Carpenter St Philadelphia PA (DSC 3819).jpg, Sparks Shot Tower, Philadelphia, USA (1808) File:Phoenix Shot Tower 02.jpg, Phoenix Shot Tower, Baltimore, USA (1828) File:Taroona Shot Tower.jpg, Shot Tower, Taroona, Tasmania, Australia File:Clifton hill shot tower melbourne australia.jpg, Clifton Hill Shot Tower, Melbourne, Australia (1882) File:Tour à plomb Bxl 01.JPG, Brussels Shot Tower, Belgium (1898) File:Colonial Ammunition Company Shot Tower.jpg, Colonial Ammunition Company, Auckland, New Zealand (1914) File:HU-TO-Kölesd11.JPG, Bojárd, Hungary (1936-1938) File:Lookout tower.JPG, Tata, Hungary (1939) File:Shot.tower.bristol.arp.jpg, Cheese Lane Shot Tower, Bristol, England (1969) File:Shottower wytheco.jpg, Jackson Ferry Shot Tower in Wythe County, Virginia, US

References

External links

{{Commons category, Shot towers
"Gravity Molds Shot In A Modern Tower", October 1944, Popular Science
detailed and large article on subject of Shot Towers Metalworking Ammunition