Steelyard balance
Encyclopedia
A steelyard balance or steelyard is a straight-beam balance
with arms of unequal length. It incorporates a counterweight
which slides along the calibrated
longer arm to counterbalance the load and indicate its weight. A steelyard is also known as a Roman steelyard, or Roman balance.
(or fulcrum) which is very close to one end of the beam. The two parts of the beam which flank the pivot are the arms. The arm from which the object to be weighed (the load) is hung is short and is located close to the pivot point. The other arm is longer, is graduated and incorporates a counterweight which can be moved along the arm until the two arms are balanced about the pivot, at which time the weight of the load is indicated by the position of the counterweight.
, wherein, when balanced, the weight of the object being weighed, multiplied by the length of the short balance arm to which it is attached, is equal to the weight of the counterweight multiplied by the distance of the counterweight from the pivot.
, the steelyard was in use among Greek craftsmen of the 5th and 4th centuries BCE, even before Archimedes
demonstrated the law of the lever theoretically.http://www.fas.harvard.edu/home/news_and_events/releases/math_10012007.html Roman and Chinese steelyards were independently invented around 200 BCE. Steelyards dating from 100 to 400 CE have been unearthed in Great Britain
. Steelyards and their components have also been excavated from shipwrecks of the Byzantine period in the Mediterranean and the Red Sea, such as the 7th-century wreck at Yassi Ada, Turkey, and the mid-first millennium shipwreck at Black Assarca Island
, Eritrea. The Oxford English Dictionary
suggests that the name "steelyard" is derived from the Steelyard
, the main trading base of the Hanseatic League
in London
in the 14th century.
n steel-yard is a variant which consists of a bar with a fixed weight attached to one end, a movable pivot point and an attachment point for the object to be weighed at the other end. Once the object to be weighed is attached to its end of the bar, the pivot point, which is frequently a loop at the end of a cord or chain, is moved until the bar is balanced. The bar can be calibrated so that the object's weight can be read off directly from the position of the pivot. This type is known in Sweden
, Denmark
and Norway
.
Weighing scale
A weighing scale is a measuring instrument for determining the weight or mass of an object. A spring scale measures weight by the distance a spring deflects under its load...
with arms of unequal length. It incorporates a counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...
which slides along the calibrated
Calibration
Calibration is a comparison between measurements – one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device....
longer arm to counterbalance the load and indicate its weight. A steelyard is also known as a Roman steelyard, or Roman balance.
Structure
The steelyard comprises a balance beam which is suspended from a pivotLever
In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...
(or fulcrum) which is very close to one end of the beam. The two parts of the beam which flank the pivot are the arms. The arm from which the object to be weighed (the load) is hung is short and is located close to the pivot point. The other arm is longer, is graduated and incorporates a counterweight which can be moved along the arm until the two arms are balanced about the pivot, at which time the weight of the load is indicated by the position of the counterweight.
Mechanism
The steelyard exemplifies the law of the leverLever
In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...
, wherein, when balanced, the weight of the object being weighed, multiplied by the length of the short balance arm to which it is attached, is equal to the weight of the counterweight multiplied by the distance of the counterweight from the pivot.
History
According to Mark Schiefsky of Harvard UniversityHarvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
, the steelyard was in use among Greek craftsmen of the 5th and 4th centuries BCE, even before Archimedes
Archimedes
Archimedes of Syracuse was a Greek mathematician, physicist, engineer, inventor, and astronomer. Although few details of his life are known, he is regarded as one of the leading scientists in classical antiquity. Among his advances in physics are the foundations of hydrostatics, statics and an...
demonstrated the law of the lever theoretically.http://www.fas.harvard.edu/home/news_and_events/releases/math_10012007.html Roman and Chinese steelyards were independently invented around 200 BCE. Steelyards dating from 100 to 400 CE have been unearthed in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
. Steelyards and their components have also been excavated from shipwrecks of the Byzantine period in the Mediterranean and the Red Sea, such as the 7th-century wreck at Yassi Ada, Turkey, and the mid-first millennium shipwreck at Black Assarca Island
The Shipwreck at Black Assarca Island, Eritrea
- Overview :Discovered in 1995 by tourists, the shipwreck at Black Assarca Island, Eritrea was surveyed in 1995 and excavated in 1997 by the Institute of Nautical Archaeology under the auspices of the Ministry of Marine Resources of Eritrea. Directed by Ralph K. Pedersen , the expedition...
, Eritrea. The Oxford English Dictionary
Oxford English Dictionary
The Oxford English Dictionary , published by the Oxford University Press, is the self-styled premier dictionary of the English language. Two fully bound print editions of the OED have been published under its current name, in 1928 and 1989. The first edition was published in twelve volumes , and...
suggests that the name "steelyard" is derived from the Steelyard
Steelyard
The Steelyard, from the German Stalhof, was in the Middle Ages the main trading base of the Hanseatic League in London.-Location:It lay on the north bank of the Thames by the outflow of the Walbrook, in the Dowgate ward of the City of London. The site is now covered by Cannon Street station and...
, the main trading base of the Hanseatic League
Hanseatic League
The Hanseatic League was an economic alliance of trading cities and their merchant guilds that dominated trade along the coast of Northern Europe...
in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
in the 14th century.
Function
Steelyards of different sizes have been used to weigh loads ranging from ounces to tons. A small steelyard could be a foot or less in length and thus conveniently used as a portable device that merchants and traders could use to weigh small ounce-sized items of merchandise. In other cases a steelyard could be several feet long and used to weigh sacks of flour and other commodities. Even larger steelyards were three stories tall and used to weigh fully laden horse-drawn carts.With sliding pivot
A ScandinaviaScandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
n steel-yard is a variant which consists of a bar with a fixed weight attached to one end, a movable pivot point and an attachment point for the object to be weighed at the other end. Once the object to be weighed is attached to its end of the bar, the pivot point, which is frequently a loop at the end of a cord or chain, is moved until the bar is balanced. The bar can be calibrated so that the object's weight can be read off directly from the position of the pivot. This type is known in Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
and Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
.