Stone ball
Stone balls are made for different purposes. The oldest known stone balls that were made by hand, engraved, are neolithic stone balls in Scotland , the grave balls in Sweden from Nordic Iron and Viking Age and the stone spheres of Costa Rica , whose purpose is not explored. Stone balls were also made by hand for antique stone throwing machines and cannon balls until the 15th century. Stone balls also served as toys, such as marbles .
Recently, there has been a new and frequent use of stone balls for ornamental fountains or indoor fountains and as an architectural element. Large stone balls are set up for the design of public spaces or they are introduced into fountains as stone balls sliding on a film of water.
The largest known massive of stone existing stone balls have a diameter of three meters, such as the 15-piece Large globe from limestone in England and the spheres fountain in the Piazzale del Foro Italico in Rome , the massive from a piece of Carrara marble is. The largest stone ball sliding on a film of water (2010) is a football composed of 32 parts in front of the Donbass Arena in Donetsk , Ukraine . This stone ball weighs 28 tons and has a diameter of 2.75 meters.
Furthermore, there are some geological phenomena in which nature has formed spherical shapes that are not dealt with here. One of the most famous is in New Zealand .
Stone balls made of natural stone can basically be made from any solid rock . Stone balls made of artificial stone and concrete are also possible.
Historical stone balls
Scotland
About 420 about seven centimeters and some nine to twelve centimeters large engraved stone balls ( English: Carved Stone Balls ) made of diorite , serpentinite , diabase , basalt , sandstone , quartzite , gabbro and gneiss were found in Scotland , mainly in the northeast and a few in Orkney and Shetland as well as Ireland and England, the use and purpose of which is not precisely known. They date from 3000 to 2000 years BC. The Carved Stone Balls were found mainly in Aberdeenshire in Scotland. They are designed with different engravings and are assigned to the late Neolithic , the Bronze Age. They probably had spiritual and symbolic meanings.
Grave balls are used as grave symbols in Sweden during the Nordic Iron and Viking Age. These spherical shapes were found mainly on the Swedish mainland, but also on Åland , in the Österbotten region in Finland and on Gotland . The grave spheres lie on grave mounds, within round stone settings or on stone boxes . There are also specimens of grave spheres around Mälaren , in southern Norrland ( Härnösand near Sundsvall ) and near Småland . The largest grave ball in Scandinavia with a diameter of almost one meter is located on Gotland near the Roma monastery .
Costa Rica
300 stone balls were found in Costa Rica , mostly made of gabbro, a hard rock with granite-like properties, and about a dozen each made of shell limestone and sandstone. The size varies between a few centimeters and more than two meters in diameter. The heaviest weigh 15 to 16 tons. Other stone balls were found in Costa Rica in the province of Puntarenas in the southern and central part of the Pacific side of Costa Rica and further north on the Nicoya peninsula in the province of Guanacaste .
These stone balls were made by hand by carving and grinding, as can be seen from processing marks. In the vicinity of the stone balls, evidence from pre-Columbian times has been found, such as ceramics from the time 200 BC. BC – AD 600 and from AD 1000–1500 in the province of Puntarenas . These were probably made by the ancestors of the Boruca .
The age determination is difficult, especially because most of the balls have been removed from their location and are now e.g. B. adorn private gardens. To determine the age, only the examination of the respective excavation layers for man-made traces can be used.
Cannonballs
Cannon balls were originally large-caliber stone balls that were fired from the barrel of the stone rifle with the help of black powder . Stone balls were used as cannon balls until the 15th century because they were lighter than iron and could therefore be fired at longer distances. On impact they splintered into sharp splinters or they were used as wall breakers from a diameter of 50 to 80 cm. The use of the large-caliber cannons for wall breakers did not lead to the desired result because it was found that the stone balls splintered on impact with the wall and the desired breaking effect did not occur. The effect could be better achieved by repeatedly bombarding the same part of the wall with small-caliber cannons.
Since the stone balls were made by hand, they were imprecise, so so-called sabot were used, which better sealed the charge in the barrel of the cannon. The sabot provided the powder gases with a larger effective surface for under-caliber and imprecise stone projectiles.
The guns for the large-caliber projectiles were also too heavy for transport: The seldom used Faule Mette , for example, was such a giant gun from Braunschweig that weighed more than eight tons. It was able to shoot bullets with a diameter of 76 cm and a weight of 550 kg over a distance of more than two kilometers.
Artisanal stone balls
Primarily natural stones were used for stone balls in the last 200 years , which can be ground or polished in order to use them for decoration or in architecture. Soft rocks such as limestone and marbles or most hard rocks such as granite and gneiss are suitable for this purpose .
Before the invention of the electrically powered stone saws , stone balls were handcrafted using various techniques. There are two traditional stonemason manufacturing techniques known as the chamfer technique or the quarter-cap technique. When using the bevel technique, the rough shape of a ball is first carved out of a stone block. Chamfers , beveled surfaces, are machined around the sphere according to the different radii. If the quarter cap technique is used, bevels are carved as eight quarter circles in a stone block with hand tools in the initially full-edged stone. During this process, two rings are created, so to speak, which delimit the sphere. The resulting so-called stone caps are then processed and the spherical rounding is adjusted. After these operations, the balls produced with the two methods have a rough surface and must be ground or polished, if required.
With these handicraft techniques it was possible to produce balls that were only limited in size by the stone transport equipment available .
Stone mills
The stone balls, which used to be made in stone mills, have to be roughly cut. The stones, which are roughly worked into a spherical shape, are placed between two discs. The upper and lower disks have running grooves, the radius of which corresponds to the later circumference of the finished stone ball. The stones are rounded by the grinding movement, whereby the upper grinding wheel is usually brought into rotation. After a few days, the stones are ground into shape, removed from the stone mill and then polished. The stone mills produce smaller stone balls with a small diameter of up to 15 centimeters.
Among the most important historical stone mills were the Untersberg marble ball mills near Marktschellenberg , those 40 grinding systems with which balls from Untersberg marble , a limestone that could be polished, were produced at the end of the 17th century . Historical stone mills are still or are in operation today.
Machine manufacturing
Sawing and polishing technology
Larger stone balls can nowadays be rounded by CNC-controlled stone circular saws in stonemasons up to a size of a little over a meter, usually in sawing processes. The prerequisite for this is either the presence of swiveling saw tables or swiveling so-called machine supports for the stone saws that drive the saw blade. After the stone ball shape has been produced, the stone surface is rough-sawn and shows traces of the saw blade or stone strips must first be cut off. In a further work process, the stone ball must therefore be ground and polished using hand-held grinding machines with appropriate grinding tools.
Stone balls sliding on a film of water
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The large stone balls, which slide in a stone fountain basin, are very popular with onlookers, because the stone balls, which weigh tons, can easily be moved with one hand, even by children.
So that stone balls slide, a water nozzle is usually built into the center of the well basin, which lifts the ball as soon as water emerges. The ball does not move and it is not continuously wetted with water.
This shortcoming is remedied by a special technical development based on a patent from the stone industry company Kusser in Aicha vorm Wald in Lower Bavaria . With a process developed by the Kusser company in Aicha vorm Wald, it is possible to manufacture large, calibrated stone balls with an accuracy of two hundredths of a millimeter. In the final work processes, a patented grinding machine is used, which grinds and polishes with the greatest possible precision. Only then is it possible for the large calibrated stone balls to float on a film of water.
The stone balls must be shaped exactly radially so that the stone ball slides on a film of water. For example, the stone ball with a diameter of two meters of the World Cup fountain moves when 200 liters of water per minute are fed into the fountain bowl at a pressure of 1.2 bar, a lower pressure than in any drinking water pipe. The pressure of a water column 12 m high is built up and the flow rate of 200 l / min causes the ball to float on the water film.
The amount of water required is determined by the accuracy of fit of the calibrated ball and the size and adaptation of the spherical cap. The fit of the dome, the negative shape of the soccer ball, places the same high demands on the elaboration as the ball.
One or two nozzles are built into the well basins so that the heavy balls rotate continuously and are wetted with water. When installing two nozzles, a circuit ensures that water emerges from only one nozzle alternately and hits the ball, thereby moving it. If only one nozzle is installed, the rotation is triggered by a discontinuous switching of an obliquely directed water jet. As soon as water flows, the ball moves and by rotating with the two patented methods mentioned above, it is permanently completely wetted with water.
Another method of making stone balls is based on making a polyhedron from a cuboid. The polyhedron is then rounded and polished.
In principle, all stone balls, regardless of their size, can slide on a film of water if they are made precisely enough. The Kugelbrunnen in Munich's Westpark , built in 1983, was the first property with this technology, which has been widely used since then. It is not known whether there is an upper limit on the size or mass of the balls.
The World Cup fountain in Munich consists of a fountain basin made of Tittlinger granite and a sliding stone football made of Impala , a norit , a granite-like rock. It is a stone ball with a diameter of two meters and a mass of 11.3 tons.
Since the Phenomena , a science exhibition in 1984, there has been a spherical fountain in Zurich that is fed with thermal water at 25 degrees.
For the soccer world championship 2002 , a first large stone soccer ball, which is composed of 32 stone pieces, was set up in front of the Toyota stadium in the Japanese city of Toyota ( position ).
The world's largest sliding granite football is located in front of the Donbass Arena of the Shakhtar Donetsk football club in Donetsk , Ukraine ( position ). The ball has a diameter of 2.70 m, a mass of 28 tons and is moved with 340 liters of water per minute and 2.4 bar pressure. It was set up in 2009.
Two other floating stone balls made of one piece, the larger one with a diameter of 2.65 meters, are located in Richmond , Virginia, in front of the Science Museum of Virginia (positions: Earth , Moon ). The large sphere is called the Grand Kugel based on the German word Kugel and was the largest sliding stone sphere in the world made of one piece at the time of its installation. The two stone spheres thematize earth and moon, taking into account the size ratio of earth and moon as well as the distance to each other. These spheres are made of hard rock, the type of the bright impala.
Probably the world's largest solid stone ball made of one piece is located in Italy on the Piazzale del Impero in Rome not far from the Mussolini obelisk in the fountain of the spheres ( position ). The globe, three meters in diameter, weighs 37 tons and is made of Carrara marble . It was opened to the public in a ceremony on May 9, 1937 , along with other Foro Mussolini buildings by Benito Mussolini .
Composite stone balls
One is composed of 15 parts of stone ball in English Swanage from English limestone , the big globe in the year 1887. This globe is one with a diameter of three meters of the largest stone balls in the world of limestone, the Portland-limestone ( position ).
Hollow stone ball
A stone football, which is composed of several ten centimeter thick stone slabs and has a diameter of 2.008 meters, is located in front of the EM stadium in Wals-Siezenheim near Salzburg in Austria . This soccer ball was set up on the occasion of the 2008 European soccer championship . It is composed of 32 stone parts and consists of 20 hexagonal parts of the light French camouflage granite and 12 parts of the South African impala. This stone soccer ball is not polished and is hollow inside. The 2.4 ton ball rests firmly on a base made of Untersberg marble . This stone soccer ball was made by an artisan stonemason.
Trivia
The back of the 5,000 colones -Geldscheins from Costa Rica shows a stone ball.
In the first Indiana Jones film Raiders of the Lost Ark from 1981, Indiana Jones , an archeology professor and adventurer, is almost overrun by stone balls in a film scene.
In the computer-animated movie The Incredibles, there is a chase scene of the spherical omnidroid, which is similar to the stone ball scene from the movie Raiders of the Lost Ark .
See also
Web links
- Carved stone balls from Scotland. University of Glasgow, accessed January 9, 2014 (Prehistoric Stone Balls from Scotland).
- Pictorial representation of the grinding processes in a traditional stone mill
Individual evidence
- ↑ Images of spherical shapes that were formed in nature on geo-aktuell.de , accessed on May 11, 2010
- ↑ Information on the website britishmuseum.org ( Memento of the original from October 3, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed on May 13, 2010
- ↑ Information on the National Museum Scotland , accessed on May 13, 2010 (English)
- ↑ Martin Javier: Costa Rica's Pre-Columbian Spheres . Information with an interview by Ifigenia Quintanilla on costaricainfotravel.com, researcher from 1990 to 1995 and editor of a book about the stone balls of Costa Rica. Archived from the original on May 9, 2011. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Accessed May 2010.
- ^ Patent specification for the production of stone balls with stone saws , accessed on May 12, 2010
- ↑ Patent for the device for supporting and driving a floating ball , accessed on May 10, 2010
- ↑ One meter of water column (mWS) = 9.807 kPa ≈ 0.10 bar
- ↑ Press information about the World Cup fountain on niederbayern.de ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , accessed on May 11, 2010
- ↑ Compare to this paragraph: Josef Kusser: Device for supporting and driving a floating ball . German Patent Office, patent specification 3802561C2, granted 1992. Accessed May 17, 2010
- ↑ Kugelbrunnen 2-meter ball (illustrations of the production), accessed on October 24, 2012
- ^ Saar dictionary of art: Wadgassen, Tobin Brunnen
- ↑ No. 1130 in the fountain guide of the city of Zurich ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 906 kB), accessed on October 14, 2012
- ^ Image of the stone soccer ball in front of the Toyota Stadium in the Japanese city of Toyota on japan-photo.de , accessed on April 30, 2010
- ↑ Information provided by the manufacturer at an event organized by the Wirtschaftsjunioren Passau ( Memento of the original from August 4, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed on May 23, 2010
- ↑ World's largest swimming soccer ball: Illustration and information on kusser.com ( Memento of the original from February 5, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed April 30
- ^ Website of the Science Museum of Virginia ( Memento from September 22, 2012 in the Internet Archive ), accessed on May 1, 2010
- ↑ Grand Kugel at Science Museum of Virginia , accessed May 1, 2010
- ↑ Production of the stone football for Salzburg on moser-stein.at ( memento of the original from December 2, 2010 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed May 9, 2010
- ↑ Information about the production of the stone football on handwerkspreis.at , accessed on May 9, 2010
