Shot tower

Shot tower, Tasmania (1870)
Clifton Hill Shot Tower, Melbourne
The Shot Tower, Bristol, England
Coops (Melbourne Central) Shot Tower, encased by the Melbourne Central cone
The Dubuque, Iowa shot tower

A shot tower is a tower designed for the production of small diameter shot balls by freefall of molten lead, which is then caught in a water basin. The shot is primarily used for projectiles in shotguns, and also for ballast, radiation shielding and other applications where small lead balls are useful.

Shot making

Process

In a shot tower, lead is heated until molten, then dropped through a copper sieve high in the tower. The liquid lead forms tiny spherical balls by surface tension, and solidifies as it falls. The partially cooled balls are caught at the floor of the tower in a water-filled basin.[1] 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.[2] 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).[3] Polishing with a small amount of graphite is necessary for lubrication and to prevent oxidation.

History

The process was invented by William Watts of Bristol, UK, and patented in 1782.[1][4] The same year, Watts extended his house in Redcliffe, Bristol to build the first shot tower.[5] 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.[6]

The "wind tower" method, patented in 1848 by the T.O LeRoy Company of New York City, which used a blast of cold air to dramatically shorten the drop necessary[7][8] 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 is used to make smaller shot sizes, and larger sizes are made by the cold swaging process of feeding calibrated lengths of wire into hemispherical dies and stamping them into spheres.[9]

Examples

Steel-framed 1916 Colonial Ammunition Company tower in Auckland, New Zealand
Name Location Country Year Notes
Berlin Shot Ball TowerBerlin RummelsburgGermany1908Nöldnerstraße 15 and 16. Used until 1939
Brussels Shot Tower BrusselsBelgium1885Kruitmolenstraat 60. Used until 1962. It is a circular brick tower 46 m high, with a diameter of 4.7 m at the base and 3.1 m at the top. Classified as cultural heritage since 1984. It stands at the site of a former black gunpowder factory known as 'La Poudrière'.
Cheese Lane Shot TowerBristol, EnglandUnited Kingdom1969A reinforced concrete tower built to replace the very first shot tower built in Redcliffe by William Watts[10]
Chester Shot TowerBoughton, EnglandUnited Kingdom1799A circular brick tower; the oldest surviving shot tower in the UK[11]
Clifton Hill Shot TowerMelbourne, VictoriaAustralia1882A brick structure that is 80.1 m (263 ft) high.[12] And the tallest remaining in Australia[13]
Colonial Ammunition CompanyMt Eden, AucklandNew Zealand1916A steel framed tower[14]
Coop's Shot TowerMelbourne, VictoriaAustralia188850 meters (160 ft) high[15]
Cox's Lead Works Shot TowerDerby, EnglandUnited Kingdom1809Demolished to make way for the development of Corporation Street in 1932
Daugavpils Shot Factory TowerDaugavpilsLatvia?Still in operation[16][17]
Drochtersen Shot TowerDrochtersen, Lower SaxonyGermany?
Dubuque Shot TowerDubuque, IowaUnited States1856
Fort Hayes Shot TowerColumbus, OhioUnited States1864Currently in use with the Fort Hayes Metropolitan Education Center
Helena Shot TowerSpring Green, WisconsinUnited States1831Preserved as part of a state park[18]
Jackson Ferry Shot TowerWythe County, VirginiaUnited States1790sNow part of a state park and open to the public during the tourist season.[19]
Lambeth Shot TowerLondon, EnglandUnited Kingdom1826In use until 1949, and was a feature in the 1951 Festival of Britain, before being demolished.
McCullough TowerLower Manhattan, New YorkUnited States1855-6The first shot tower constructed of an iron frame rather than masonry. Built by James Bogardus with a height of 175 ft (53 m). Demolished 1907.[20]
New Vienna Shot TowerNew Vienna, IowaUnited States?
Peters Shot TowerKings Mills, OhioUnited States1895
Pispala Shot TowerPispala, TampereFinland1908Height 55 m (180 ft). Used until 1972.
Phoenix Shot TowerBaltimore, MarylandUnited States1828
Redcliffe Shot TowerBristol, EnglandUnited Kingdom1782The first shot tower, built by William Watts, the inventor of the tower process for the manufacture of lead shot. Demolished in 1968.[10]
Remington Shot Tower Lonoke, ArkansasUnited States1969Moved from Bridgeport, Connecticut[21].
Rossie Shot TowerRossie, New YorkUnited States?
Sparks Shot TowerPhiladelphia, PennsylvaniaUnited States1808In use until 1913. Now part of a children's playground
Stelco Shot TowerMontreal, QuebecCanada?[22]
Tapham TowerLower Manhattan, New YorkUnited States1855-6Built by James Bogardus with a height of 217 ft (66 m). Demolished in the first decade of the 20th century.
Taroona Shot TowerHobart, TasmaniaAustralia1870
Torre de los PerdigonesSevilleSpain1885
Winchester Shot TowerNew Haven, ConnecticutUnited States?

See also

  • Drop tube, a similar concept, but used for scientific experiments
  • Prill, a small granule of material formed by a similar process to shot-making. Often used in the chemical industry for solid chemicals.
  • Spray drying is a process of turning liquids into powder; many spray dryers also have the drops of liquid solidifying as they drop in a tower.

Further reading

  • "Up a shot tower". The Strand Magazine. 1891. p. 205.

References

  1. 1 2 "No. 422: Shot Tower", Engines, UH .
  2. ↑ Re: How the small lead shot (7–8 sizes) used for shotgun shells are made?, Mad sci, May 2001 .
  3. ↑ The Physics of Shot Towers (PDF)
  4. ↑ Minchinton, Walter (1993). "The Shot Tower" (PDF). The Shot Peener. 7 (3): 22.
  5. ↑ "Sheldon Bush and Patent Shot Company Limited, Cheese Lane, Bristol", Images of England .
  6. ↑ "150th", The Age, Melbourne, AU, archived from the original on 2006-02-12 .
  7. ↑ "Archived copy". Archived from the original on 2012-01-30. Retrieved 2013-09-12. , Lynne Belluscio, LeRoy Penny Saver News
  8. ↑ History of the American Shot Tower Archived August 11, 2005, at the Wayback Machine.
  9. ↑ "The romance of lead shot - Shotgunner – Guns Magazine – Find Articles at BNET.com". Archived from the original on 2006-05-05.
  10. 1 2 Efstathios, Tsolis (2007-03-10). "An Awkward thing" (PDF). University of Bristol. Retrieved 2015-03-19.
  11. ↑ "Chester Leadworks and Shot Tower", Images of England .
  12. ↑ Heritage, Victoria, AU .
  13. ↑ "Melbourne Central - Our Heritage". www.melbournecentral.com.au. Retrieved 2017-02-15.
  14. ↑ "Colonial Ammunition Company Shot Tower". Register of Historic Places. Heritage New Zealand. Retrieved 2010-03-02.
  15. ↑ "Victorian heritage directory". vhd.heritagecouncil.vic.gov.au. Retrieved 2017-02-15.
  16. ↑ DSR, LV .
  17. ↑ "Daugavpils Lead Shot Factory". Official Latvian Tourism Portal. Latvian Tourism Development Agency. 12 June 2013. Retrieved 12 September 2013.
  18. ↑ Tower Hill State Park Shot Tower, WI, US .
  19. ↑ Shot Tower Historical State Park, VA, US
  20. ↑ Gayle, Margot; Gayle, Carol (1998). Cast-iron Architecture in America: The Significance of James Bogardus. W. W. Norton & Company. pp. 169–174. ISBN 0393730158.
  21. ↑ "Remington Ammunition & Components Plant - Lonoke, AR". Waymarking.com. Retrieved 5 July 2017.
  22. ↑ http://www.waymarking.com/waymarks/WMDXNA_Montreal_Shot_Tower_Montreal_Qc_Canada
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