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Bearings (mechanical)
A ball bearing A bearing is a machine element that constrains relative motion to only the desired motion and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Most bearings facilitate the desired motion by minimizing friction. Bearings are classified broadly according to the type of operation, the motions allowed, or the directions of the loads (forces) applied to the parts. The term "bearing" is derived from the verb " to bear"; a bearing being a machine element that allows one part to bear (i.e., to support) another. The simplest bearings are bearing surfaces, cut or formed into a part, with varying degrees of control over the form, size, roughness, and location of the surface. Other bearings are separate devices installed into a machine or mac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bearing Surface
A bearing surface in mechanical engineering is the area of contact between two objects. It usually is used in reference to bolted joints and bearing (mechanical), bearings, but can be applied to a wide variety of engineering applications. The choice of bearing surface depends on the application, load, speed, and operating conditions, and the design must be able to withstand high loads, resist wear and corrosion, and operate at high speeds. On a screw, the bearing area loosely refers to the underside of the head. Strictly speaking, the bearing area refers to the area of the screw head that directly bears on the part being fastened. For a cylindrical bearing, it is the projected area perpendicular to the applied force. On a spring (device), spring, the bearing area refers to the amount of area on the top or bottom surface of the spring in contact with the constraining part.. The ways of machine tools, such as dovetail slides, box ways, prismatic ways, and other types of machine s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ball Bearing2
A ball is a round object (usually spherical, but sometimes ovoid) with several uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used for simpler activities, such as catch or juggling. Balls made from hard-wearing materials are used in engineering applications to provide very low friction bearings, known as ball bearings. Black-powder weapons use stone and metal balls as projectiles. Although many types of balls are today made from rubber, this form was unknown outside the Americas until after the voyages of Columbus. The Spanish were the first Europeans to see the bouncing rubber balls (although solid and not inflated) which were employed most notably in the Mesoamerican ballgame. Balls used in various sports in other parts of the world prior to Columbus were made from other materials such as animal bladders or skins, stuffed with various materials. As balls are one of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agostino Ramelli
Agostino Ramelli (1531–ca. 1610) was an Italian engineer best known for writing and illustrating the book of engineering designs ''Le diverse et artificiose machine del Capitano Agostino Ramelli'', which contains, among others, his design for the bookwheel. Ramelli was born in Ponte Tresa or Mesanzena, today in Switzerland. During the Siege of La Rochelle (1572–1573), he successfully engineered a mine under a bastion and breached the fortification,"One Good Turn: A Natural History of the Screwdriver and Screw" Witold Rybczynski p.47 making him popular with his commander, Henri d'Anjou, who later became King Henri III of France. In 1588, Ramelli published ''Le diverse et artificiose machine del Capitano Agostino Ramelli'', or ''The various and ingenious machines of Captain Agostino Ramelli''. The book contains 195 designs, over 100 of which are water-raising machines, such as water pumps or wells.Brashear, RonaldRamelli's Machines Smithsonian Libraries. Other d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leonardo Da Vinci
Leonardo di ser Piero da Vinci (15 April 1452 - 2 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested on his achievements as a painter, he has also become known for #Journals and notes, his notebooks, in which he made drawings and notes on a variety of subjects, including anatomy, astronomy, botany, cartography, painting, and palaeontology. Leonardo is widely regarded to have been a genius who epitomised the Renaissance humanism, Renaissance humanist ideal, and his List of works by Leonardo da Vinci, collective works comprise a contribution to later generations of artists matched only by that of his younger contemporary Michelangelo. Born out of wedlock to a successful notary and a lower-class woman in, or near, Vinci, Tuscany, Vinci, he was educated in Florence by the Italian painter and sculptor Andrea del Verrocchio. He began his career ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Italy
Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land border, as well as List of islands of Italy, nearly 800 islands, notably Sicily and Sardinia. Italy shares land borders with France to the west; Switzerland and Austria to the north; Slovenia to the east; and the two enclaves of Vatican City and San Marino. It is the List of European countries by area, tenth-largest country in Europe by area, covering , and the third-most populous member state of the European Union, with nearly 59 million inhabitants. Italy's capital and List of cities in Italy, largest city is Rome; other major cities include Milan, Naples, Turin, Palermo, Bologna, Florence, Genoa, and Venice. The history of Italy goes back to numerous List of ancient peoples of Italy, Italic peoples—notably including the ancient Romans, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Nemi
Lake Nemi (, , also called Diana's Mirror, ) is a small circular volcanic lake in the Alban Hills south of Rome in the Lazio region of Italy. It takes its name from Nemi, the largest town in the area, which overlooks it from a height. It was formed in an ancient volcanic crater created at least 36,000 years ago. The lake is famous for its great Nemi ships, sunken Roman ships built under Caligula. Archaeology and history From the 6th century BC, the lake and its forest were sacred to the goddess Diana Nemorensis and the site of the festival Nemoralia. The sacred grove of Aricia, Italy, Aricia was where a priest called the Rex Nemorensis reigned until he was killed by a challenger. The monumental Temple of Diana (Nemi), sanctuary of Diana was built around 300 BC as the centre of the religion. In Roman times up to 6 large villas lay on the rim of the crater taking advantage of the cool summer air and fine views over the lake and the sea. Only one villa is known to be on the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nemi Ships
The Nemi ships were two ships, of different sizes, built under the reign of the Roman emperor Caligula in the 1st century AD on Lake Nemi. Although the purpose of the ships is speculated upon, the larger ship was an elaborate floating palace, which contained quantities of marble, mosaic floors, heating and plumbing, and amenities such as baths. Both ships featured technology thought to have been developed historically later. It has been stated that the emperor was influenced by the lavish lifestyles of the Hellenistic period, Hellenistic rulers of Syracuse, Italy, Syracuse and Ptolemaic Egypt. Recovered from the lake bed in 1929, the ships were destroyed by fire in 1944 during World War II. The larger ship was 73 m (240 ft) in length, with a beam of 24 m (79 ft). The other ship was 70 m (230 ft) long, with a beam (width) of 20 m (66 ft). Location Lake Nemi (, ) is a small circular volcanic lake in the Lazio region of Italy, south of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roman Empire
The Roman Empire ruled the Mediterranean and much of Europe, Western Asia and North Africa. The Roman people, Romans conquered most of this during the Roman Republic, Republic, and it was ruled by emperors following Octavian's assumption of effective sole rule in 27 BC. The Western Roman Empire, western empire collapsed in 476 AD, but the Byzantine Empire, eastern empire lasted until the fall of Constantinople in 1453. By 100 BC, the city of Rome had expanded its rule from the Italian peninsula to most of the Mediterranean Sea, Mediterranean and beyond. However, it was severely destabilised by List of Roman civil wars and revolts, civil wars and political conflicts, which culminated in the Wars of Augustus, victory of Octavian over Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and the subsequent conquest of the Ptolemaic Kingdom in Egypt. In 27 BC, the Roman Senate granted Octavian overarching military power () and the new title of ''Augustus (title), Augustus'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wheel
A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machines. Wheels, in conjunction with axles, allow heavy objects to be moved easily facilitating movement or transportation while supporting a load, or performing labor in machines. Wheels are also used for other purposes, such as a ship's wheel, steering wheel, potter's wheel, and flywheel. Common examples can be found in transport applications. A wheel reduces friction by facilitating motion by rolling together with the use of axles. In order for a wheel to rotate, a Moment (physics), moment must be applied to the wheel about its axis, either by gravity or by the application of another external force or torque. Terminology The English word '':wikt:wheel, wheel'' comes from the Old English word , from Proto-Germanic language, Proto-Germanic , ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hand Drill
A hand drill is the simplest primitive method to produce rapid rotary motion of a rod. It consists in holding the rod vertically between both hands and moving these back and forth, in opposite directions, as in rubbing them. The rod typically is one or two feet long and half an inch in diameter. Hand drills have been used by many primitive societies as a fire drill to start a fire. It is still often learned as a useful survival skill. A hand drill could also be used as a tool for drilling holes in hard materials such as wood, stone, or bone. For either use, the hands must also exert downward pressure while spinning the rod. As a result, the hands drift down the rod, and must be periodically raised to the top again. These interruptions can be avoided by cutting a notch at the top of the shaft, tying a cord through it, and then inserting the thumbs through loops in the cord. However, skilled operators can either maintain pressure with their hands almost stationary verti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Djehutihotep
Djehutihotep ("''Thoth is satisfied''") was an ancient Egyptian nomarch of the fifteenth '' nomos'' of Upper Egypt (''" the Hare"'') during the twelfth dynasty, c. 1900 BC. Biography Djehutihotep lived under the reigns of Amenemhat II, Senusret II, and Senusret III and was one of the most powerful nomarchs of the Middle Kingdom. His tomb—the only one among the necropolis of Deir el-Bersha that wasn't damaged by the explosives used in recent quarrying methods—is well known for the great quality of its decorations, a work carried out by an artist named Amenaankhu. For this reason, it is believed that Djehutihotep died prior to the strict measures reducing the power of the nomarchs that were established by Senusret III. Indeed, as their charge became hereditary at the end of the Old Kingdom, the nomarchs became local rulers effectively, although not nominally, independent of the pharaohs. This situation led to excesses in the exercise of power that worsened stead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
