Two-hundred-ton halftone: how bells are born
Meanwhile, this expression has nothing to do with raspberry. Its roots should be sought in the Belgian city of Mechelen, the recognized center of bell art and bell music in Europe. In French transcription, this city is called Malin, with an emphasis on the last syllable
How did it happen that it is customary to characterize the harmonious bell ringing, one of the original symbols of Russia, with an expression of French-Belgian origin? The fact is that casting a bell with a given pitch of musical tone is an extremely difficult engineering and craft task, which for a long time was only possible for selected European masters. Imagine that a bronze giant weighing tens of tons should fall into the note as accurately as a weightless violin string pressed by the musician's sensitive fingers. The Orthodox bell ringing is based on a rhythmic pattern, not a melody, therefore the exact pitch of the main tone of the bell is not as important as the richness of the timbre. Russian bells have always been distinguished by a powerful, "magnificent" sound, but not musicality. But when it came to music - for example, the construction of chimes or carillon (carillon is a musical instrument consisting of 23-70 bells, selected according to the musical scale, and keyboard) - I had to turn to Belgian or Dutch masters. The bells for all the carillons that have ever played in Russia, from the first one brought by Peter I from Flanders to the last one built three years ago in Peterhof, were produced abroad.
Valery Nikolayevich Anisimov, the founder of the largest Russian specialized bell company “Vera”, is convinced that musical, correctly selected according to the timbre and tone of the bell, are necessary for a truly magnificent ringing. At his factory, built from scratch in the suburbs of Voronezh, Valery Nikolaevich for 20 years improved the manufacturing technology of bells, which is significantly different from the traditional one. Over the entire history, the Voronezh plant has produced about 17, 000 bells, which are appreciated both in Russia and in the USA, Europe, Japan and Korea. Valery Nikolaevich proudly showed us the construction of the plant, most of which was developed by him personally, and offered to enjoy the ringing of bells, during the casting of which the singing voice was paramount.
In the Middle Ages, casting large bells was a real show. Melting furnaces, a foundry pit and scaffolds were built on the square, bronze was cooked with a large crowd of people. Kindle the stove, the master walked along the crowd with a hat, offering grateful spectators "throw silver for ringing." In front of an enthusiastic audience, he threw the collected coins directly into the oven. Where was it possible for onlookers to discern that the silver was sent not to the smelter, but to the furnace, to the coals. When the people dispersed, the cunning master raked out a well-deserved increase for the performance from the furnace with ash.
Today, as many centuries ago, bells are cast from bell bronze - an alloy of copper and tin in a ratio of 4: 1. If you increase the proportion of tin, the bell will sound more loudly and for a long time, however, the timbre color will become poorer, only the main tone will sound bright. In addition, an overly long sound is also undesirable: when playing in an ensemble, rhythmic accents are lost, a long sound is mixed with the sound of other bells, and this mixture is far from always harmonious. “For the purpose of the experiment, bells were even cast from pure zirconium, ” says Valery Nikolaevich, “their sound, which can only be called pleasant with a stretch, lasted up to five minutes.”
It’s not so easy to make bronze that sounds good. An alloy of copper and tin may consist of various structures called phases. The alpha phase of bronze has a dendritic structure: in it, the more refractory alloy components form long, interconnected branches. When tin is added to molten copper, bronze forms with a predominance of alpha phase. In such a metal, the dendritic structure promotes the propagation of sound vibrations. When the bronze is already melted (this usually happens at a lower temperature), a large number of beta-phase grains are formed in its structure. The metal with a granular structure sounds dull. Needless to say, when melting old bells into new ones, the result is far from ideal. In 1735, when the famous Tsar Bell was cast from the fragments of the crashed Great Assumption Bell, they still did not know about it. However, the 200-ton giant was still not destined to call.
Bakery for a giant
The quality of bronze directly depends on the technical capabilities of the enterprise. There are several varieties of smelting furnaces. To melt copper, introduce tin into it and make bronze, a smelter is needed, the temperature of which reaches 1300 ° C. The melting point of the finished bronze is lower than that of copper. To melt it, a smaller furnace is suitable.
In enterprises of heavy engineering, as a rule, there are small smelting furnaces with a capacity of up to 1.5 tons. Bronze of the desired composition is cooked in them, which is stored as solid billets. To cast a large product, whether it be a propeller for an atomic icebreaker or a bass bell, the workpieces are sent to a mixer - a large furnace with a temperature of 1000-1100 ° C (too small to melt copper, but enough for bronze). Indeed, for the propeller, the predominance of the alpha phase is not so critical. By the way, it is engineering plants to this day that receive the largest bell orders. For example, the largest operating bell in Russia, a 72-ton giant for the Holy Trinity St. Sergius Lavra, was cast in 2003 at the Baltic Shipyard in St. Petersburg. And the “Firstborn” (27 tons) and “Evangelist” (35.5 tons) that sound with him in a minor triad were made at the ZIL automobile plant.
Anisimov’s factory installed two giant smelting furnaces with a total capacity of 100 tons, developed by Valery Nikolayevich himself. Each furnace consists of a metal casing lined with refractory bricks from the inside and a pair of diesel burners. The furnaces are installed at the height of the second floor on the hydraulic cylinders - with their help, you can swing the tanks, mixing the hot metal, and then send the freshly prepared bronze through the gutters into a melting form. Using both furnaces at the same time, a giant 100-ton bell can be cast from freshly prepared bronze in one step, while achieving an ideally homogeneous metal structure with a predominance of the alpha phase.
“It’s only at first glance chaos here, ” Valery Nikolaevich shows us the casting section of large bells, “in fact, everything is strictly in place. Here on this soft earthen hill we turn over the bells to gain access to the internal profile. And the base of the crane at the gate is not at all a broken technique, but a rotating base on which you can install a bell of any size for turning. Ordering unique machines for such a specific purpose as making bells would cost an astronomical amount. Engineering savvy allows us to make production cost-effective. ”
Going down into a deep foundry hole, we find a wax model - an exact copy of the future 14-ton bell, which will be cast in a few days. Decorators with soldering irons scurry around the model - they attach wax bas-reliefs, icons, jewelry and inscriptions made in advance in the art workshop. When the model is ready, it will be covered with a metal mold, inside which a paste-like mixture will be poured. The mixture solidifies in half an hour, and after 12 hours it becomes as hard as concrete. They burn the form with gas burners or even make a fire under it, as was done many centuries ago. Wax is removed. The resulting casting mold made of refractory ceramics with jewelry accuracy repeats the smallest details of the surface of the future bell, including all jewelry. With us, Valery Nikolaevich heats up the stigma on the model and leaves a thumbprint in the molten wax. “This print will be accurately displayed on the surface of the bell, ” he explains, “this is a sign of exceptional casting quality that does not require further processing.”
According to the wax false model, they make a shape for the outer surface of the bell. Its inner surface is defined by a rod. A core is a brickwork, coated with the same paste-like mixture, which gives the shape of the inner surface of the bell. Like the mold, the core is fired and transformed into ceramic. Subsequently, it is covered with a form, and bronze is poured into the gaps - the future bell.
For the bell to sound clear, it is necessary that it in all sections, from top to bottom, have the same thickness over the entire circumference. The slightest displacement of the form and the rod relative to each other leads to the fact that the resonant frequencies from different sides of the bell turn out to be different, the tone floats, the ringing turns out to be "wailing" and non-musical. Of course, perfect symmetry is also required from the forms themselves. With traditional technology, this is almost impossible to achieve. “We still have old wooden molds and rods in our courtyard, ” Valery Nikolaevich shows. Their outlines are close to the shapes of the finished bell. “Earth” was applied on the surface of the mold and the core — as the foundry workers call a mixture of sand and a binder — for example, liquid glass (stationery glue). The shape and the rod were combined and bronze was poured between them. One could not count on perfect symmetry with such a technology, one could only hope.
The secret of perfect symmetry of the large bells of the Vera plant lies in a single rotating base, on which all preparatory and foundry work is carried out. At the bottom of the foundry pit there is a heavy metal disk machined on the machine with an accuracy of 0.02 mm. The location of the bolts welded into it is also precisely calculated. First, brickwork is built in the center of the disk, which is coated with a mixture - this is the future core. A pen is screwed to the disk - something like a giant cutter, exactly repeating the internal profile of the bell. The pen rotates around the workpiece, cutting a rod that is perfectly symmetrical about the center of the disk. The core remains in place, and a wax model is built directly on top of it. She is also rolled with a pen. Thus, a perfectly accurate mutual arrangement of the mold and the rod is achieved. A metal mold is mounted on a disk with bolts. Before installing, the edges of the mold and the disc are cleaned to a shine so that not a single grain of sand falls between them. Thanks to this, it is possible to remove the external form for firing and return it back without allowing the slightest distortion.
The director of the Belgian Royal Carillon School, the world-famous composer and musician Joe Haazen, says about Russia: “We have different bell traditions. In Russia, a bell is born, and it is used as it was born. And we have the bell set up to be musically flawless. ” Valery Nikolaevich Anisimov believes that it is worthwhile to step back from the Russian tradition in order to work on the voice of the bell both before and after casting.
The tone and timbre of the sound of the bell depend on its mass and shape, in particular the wall thickness. Depending on the given tone and mass, the master calculates the profile of the bell (meaning the profile of the vertical section) according to previously known proportions that have developed historically. Profiles differ in bending and wall thickness, the shape of the so-called "shoulder" - the transition from the crown to the walls. For example, in the French profile this transition occurs abruptly, in German - in two bends, in Russian - with a smooth step (see. Figure). A smooth transition of the Russian profile allows the crown part of the bell to partially participate in sound vibrations along with the walls. The main tone of the bell is determined by the diameter and thickness of the battle - the thickest lower part of the bell into which the tongue strikes. With the help of special tables, the master determines what kind of battle the bell should have at given mass and tone. All other sizes are determined in proportion to the battle in accordance with the selected profile.
The bell with thinner walls sounds lower and longer. Grinding the finished bell from the inside, you can change the thickness of the walls, tuning it exactly to the desired tone. If the lower part of the bell (battle) is responsible for the main tone, then, rising higher and higher, we will be able to regulate ever higher overtones (oscillations of a higher frequency than the main one). Unlike a string, a bell can produce not only harmonious harmonic overtones that are multiples of the fundamental frequency, so this adjustment is especially important.
In practice, the adjustment is carried out as follows: a microphone is placed in front of the bell (or an oscillation sensor is connected), which is connected to the spectrum analyzer. Currently, it is customary to track the spectrum with a resolution of 64 bands, that is, study 64 overtones. Observing the graph, the master selects the frequency that he wants to correct, raises the cutter to the desired height and grinds the part of the bell that is responsible for this particular overtone. The result is monitored in real time. Alternatively, the generator signal can be sent to the bell at the desired frequency. When the desired belt is sharpened to the required value, the sensor will record the resonance. С помощью тонкой настройки можно добиться самых разных результатов — к примеру, вывести на первый план только гармоничные обертона, сделав звук прозрачным и светлым. А тембр карильонного колокола лучше обеднить, сконцентрировав внимание лишь на основном тоне.
Между прочим, обточка внутреннего профиля колокола — весьма хитрая инженерная задача. Имеющиеся на машиностроительных заводах карусельные станки, на которые можно было бы поставить колокол, как правило, имеют весьма скромное ограничение по высоте заготовки — до 1, 6 м. Для настройки 35-тонного благовеста, изготовленного для Саввино-Сторожевского монастыря в Звенигороде, использовали специально разработанный станок, который размещали внутри лежащего на боку колокола.
На прощанье Валерий Николаевич поделился с нами своей мечтой: построить настоящий русский карильон, каждый колокол которого будет произведен и отстроен на родине. мы уверены, что точные производственные технологии и трепетное отношение к музыкальному звуку позволят ему воплотить проект в жизнь. и гармоничный звон этих колоколов уже язык не повернется назвать малиновым — ведь произведены они будут не в бельгийском Мехелене, а у нас, в Воронеже, в России.The article was published in the journal Popular Mechanics (No. 11, November 2008).