A steelyard balance, steelyard, or stilyard is a straight-beam balance with arms of unequal length. It incorporates a counterweight which slides along the longer arm to counterbalance the load and indicate its weight. A steelyard is also known as a Roman steelyard or Roman balance.
The steelyard comprises a balance beam which is suspended from a lever/pivot 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. [1]
The steelyard exemplifies the law of the lever, 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. [2]
According to Thomas G. Chondros of Patras University, a simple steelyard balance with a lever mechanism first appeared in the ancient Near East over 5,000 years ago. [3] According to Mark Sky of Harvard University, the steelyard was in use among Greek craftsmen of the 5th and 4th centuries BC, even before Archimedes demonstrated the law of the lever theoretically. [4] The Latin name statera comes from the Ancient Greek στατήρ (statḗr). Roman and Chinese steelyards were independently invented around 200 BC. Steelyards dating from AD 100 to 400 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 steel combined with yard , influenced by an allusion to the Steelyard, the main trading base of the Hanseatic League in London in the 14th century. [5]
Large steelyard balances (known as cart balances), both public and private, were a common feature in agricultural areas in England from the eighteenth century forward. An example of a public cart steelyard remains at Soham, Cambridgeshire and another is to be seen at Woodbridge, Suffolk. [6] [7] [8]
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.
A Scandinavian steelyard 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 is 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, Norway and Finland .
A pulley is a wheel on an axle or shaft enabling a taut cable or belt passing over the wheel to move and change direction, or transfer power between itself and a shaft. A sheave or pulley wheel is a pulley using an axle supported by a frame or shell (block) to guide a cable or exert force.
In science and engineering, the weight of an object is the force acting on the object due to acceleration or gravity.
A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is divided into three types. It is one of the six simple machines identified by Renaissance scientists. A lever amplifies an input force to provide a greater output force, which is said to provide leverage, which is mechanical advantage gained in the system, equal to the ratio of the output force to the input force. As such, the lever is a mechanical advantage device, trading off force against movement.
A trebuchet is a type of catapult that uses a rotating arm with a sling attached to the tip to launch a projectile. It was a common powerful siege engine until the advent of gunpowder. The design of a trebuchet allows it to launch projectiles of greater weights and further distances than that of a traditional catapult.
A counterweight is a weight that, by applying an opposite force, provides balance and stability of a mechanical system. The purpose of a counterweight is to make lifting the load faster and more efficient, which saves energy and causes less wear and tear on the lifting machine.
A safety valve is a valve that acts as a fail-safe. An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve. A leak tight, lower cost, single emergency use option would be a rupture disk.
A crane is a type of machine, generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It is mainly used for lifting heavy objects and transporting them to other places. The device uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in transportation for the loading and unloading of freight, in construction for the movement of materials, and in manufacturing for the assembling of heavy equipment.
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A drawbridge or draw-bridge is a type of moveable bridge typically at the entrance to a castle or tower surrounded by a moat. In some forms of English, including American English, the word drawbridge commonly refers to all types of moveable bridges, such as bascule bridges, vertical-lift bridges and swing bridges, but this article concerns the narrower historical definition of the term where the bridge is used in a defensive structure.
A scale or balance is a device used to measure weight or mass. These are also known as mass scales, weight scales, mass balances, and weight balances.
A vertical-lift bridge or just lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck.
An analytical balance is a class of balance designed to measure small mass in the sub-milligram range. The measuring pan of an analytical balance is inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. This enclosure is often called a draft shield. The use of a mechanically vented balance safety enclosure, which has uniquely designed acrylic airfoils, allows a smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent natural convection from forming air currents inside the enclosure from causing an error in reading. Single pan mechanical substitution balance is a method of maintaining consistent response throughout the useful capacity of the balance. This is achieved by maintaining a constant load on the balance beam and thus the fulcrum, by subtracting mass on the same side of the beam as which the sample is added.
A fly system, or theatrical rigging system, is a system of ropes, pulleys, counterweights and related devices within a theater that enables a stage crew to fly (hoist) quickly, quietly and safely components such as curtains, lights, scenery, stage effects and, sometimes, people. Systems are typically designed to fly components between clear view of the audience and out of view, into the large space, the fly loft, above the stage.
The Roberval balance is a weighing scale presented to the French Academy of Sciences by the French mathematician Gilles Personne de Roberval in 1669.
The history of measurement systems in India begins in early Indus Valley civilisation with the earliest surviving samples dated to the 5th millennium BCE. Since early times the adoption of standard weights and measures has reflected in the country's architectural, folk, and metallurgical artifacts. A complex system of weights and measures was adopted by the Maurya empire, which also formulated regulations for the usage of this system. Later, the Mughal empire (1526–1857) used standard measures to determine land holdings and collect land tax as a part of Mughal land reforms. The formal metrication in India is dated to 1 October 1958 when the Indian Government adopted the International System of Units (SI).
A balanced-arm lamp, sometimes called a floating arm lamp, is a lamp with an adjustable folding arm which is constructed such that the force due to gravity is always counteracted by springs, regardless of the position of the arms of the lamp. Many lamp brands, as well as other devices, use this principle.
In common usage, the mass of an object is often referred to as its weight, though these are in fact different concepts and quantities. Nevertheless, one object will always weigh more than another with less mass if both are subject to the same gravity.
The compound lever is a simple machine operating on the premise that the resistance from one lever in a system of levers acts as effort for the next, and thus the applied force is transferred from one lever to the next. Almost all scales use some sort of compound lever to work. Other examples include nail clippers and piano keys.
A double-beam drawbridge, seesaw or folding bridge is a movable bridge. It opens by rotation about a horizontal axis parallel to the water. Historically, the double-beam drawbridge has emerged from the drawbridge. Unlike a drawbridge, a double-beam drawbridge has counterweights, so that opening requires much less energy.
Since ancient times, traditional mathematics in Ethiopia have related to various aspects of astrology, the calendar, and measurements of physical properties such as length, weight, and distance. Ethiopians used alternate units of measurement which differ from fundamental law; traditionally, scaling and counting values have been described using draft animals such as goats, mules, sheep, or camels, and in modern times, steelyards.
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