Structures and materials of plain bearings. Leather, felt, velor homemade bearing. Do it yourself. On my own, on my own. What kind of wood were the bearings made from?

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Book title: Non-metallic Plain Bearings
Edition: Moscow, \"Engineering \"

Year of publication: 1949
Number of pages: 119
Format: Djvu

Non-metallic bearings have been known since ancient times. Wooden bearings lubricated with water and other lubricants have been used for many centuries. With the development of metallurgy and mechanical engineering, the requirements for strength, shape, and dimensions of machine parts have increased. In most cases, wooden bearings were replaced by metal ones. However, in some mechanisms, for example, in rolling mills, steamship engines and other machines in which it was desirable or inevitable to use water as a lubricant, hardwoods (backout, etc.) successfully competed with metals.From the beginning of the thirties of our century, bearings made of artificial resins began to be used in in combination with various organic and inorganic materials, i.e. from the so-called plastics, or plastics, which at a certain stage of production have plastic properties.Metals also have these properties.However, bearing plastics can only be in a plastic state once, and after curing ver it is impossible to bring them into this state. Metals are capable of a multiple plastic state. Thus, the term \"plastic \", or \"plastic \", does not fully reflect the distinctive features of this material. However, it is used in this book because there is no other accepted term.

Wood plastics were first used as a bearing material in the Soviet Union. Long before the war, the Soviet lower-1 ners Matveev and Galai irrefutably proved the technical and economic feasibility of their use on the experience of operating bearings made of this material in various machines. Plastic bearings have the resilient and extreme pressure properties of the finest hardwoods and, like metals, have high strength, density, and good machinability to produce smooth friction surfaces. The advantage of plastic bearings is that they perform well under high loads when lubricated with water. Water can also be used as a lubricant for bearings made of other materials, if the operating conditions of the bearing allow the formation of a liquid film. However, the viscosity of water is so low compared to the viscosity of lubricating oils that in most cases, when metal is rubbed against metal, a liquid film is not formed during lubrication with water and boundary friction occurs. In this case, the operation of the bearing depends mainly on the quality of the friction surfaces. The use of water lubrication for steel and bronze or for another pair of metals at increased loads leads to seizing and destruction of friction surfaces.

These properties have contributed to the widespread use of plastics for the manufacture of plain bearings in various areas of mechanical engineering (rolling mills, etc.). Under certain conditions, plastic bearings last up to 6 times longer than hardwood bearings (backout) and 10 times longer than bronze bearings, and at the same time consume significantly less power due to a sharp decrease in the friction coefficient. Successful experience in the use of non-metallic bearings in rolling mills, hydraulic turbines, hydraulic equipment suggests that after appropriate research work they will find application in other areas of mechanical engineering, for example, in crane building, road, construction, agricultural, transport, textile, chemical, food engineering, as well as machine tool building.

Along with significant technical advantages, the introduction of bearings made of plastics provides a number of economic benefits and, first of all, energy savings, increased productivity and reduced equipment downtime, reduced repair costs, saving non-ferrous metals and mineral lubricants. However, it must be emphasized that a number of issues related to the use of non-metallic bearings require further comprehensive study. Theoretical studies of friction issues in bearings made of plastics have not yet provided complete calculated data suitable for practical use. There is still no clear understanding of the phenomena that occur on the friction surface of bearings made of plastics due to the interaction of the lubricant flowing through the bearing and the lubricant absorbed by the plastic, and this creates special difficulties in analysis. To elucidate the phenomena associated with the operation of non-metallic bearings and effectively use the advantages in various fields of mechanical engineering and instrumentation, it is necessary to conduct a number of experimental studies.

Stacked wood-polymer plain bearing

wood in such an installation becomes twice as dense, three times as strong, four times as hard!

There is another interesting version of a machine for impregnating and pressing wood (see fig.). To reduce friction forces, rotating rollers are installed here along the perimeter of the inlet of the channel, the axis of which is perpendicular to the action of friction forces.

Of course, it's hard to imagine that a "piece of wood" can replace a bearing with hardened steel balls rolling on a finely ground treadmill. But this is true. Take, for example, conveyors transporting ore, molding earth, foundry waste - in a word, very abrasive bulk materials. They mix with industrial dust, lubricating oil, vapors of technological liquids and form a “paste”, which is more dangerous for rolling bearings, these aristocrats of mechanical engineering, and nothing can be. Such an abrasive paste penetrates even through the seals of bearing assemblies and, as if with emery, abrades the running grooves of the bearings, or even completely, becoming solid and monolithic, jams the balls. At least two or three times a year it is necessary to stop the belt conveyors and replace the rollers. But wooden bearings, as tests have shown, can withstand here without replacement for a year and a half. And the roller itself, equipped with them, costs 3-4 rubles cheaper, since the metal in it is several kilograms less. And rollers, according to calculations of machine builders, need 5 million pieces a year - only for replacement!

Larger wooden bearings are even more beneficial - those that, for example, rotate augers with a diameter of a wagon wheel that transport cement in concrete plants. The loads on the bearings are so great and the cement so abrasive that the metal plain bearings have to be replaced every two

three months, stopping production. And wooden bearings have been standing here for more than a year!

Twice as long as metal bearings, wooden bearings serve in devices for the manufacture of artificial fibers, although they “bath” in hot alkalis and acids. Modified wood simply does not react with these enemies of metals.

The technology and equipment developed at the Institute of Mechanics of Metal-Polymer Systems make it possible to obtain compacted modified wood not only for bearings. electric loaders, forage harvesters, tamping machines and subway cars - this is not a complete list of machine-building parts made of wood.

In construction, the tree, too, seemed to be losing ground. Brick, reinforced concrete, aluminum - what to oppose them? But recently, inventions and developments have appeared that allow a different, much more optimistic assessment of the prospects of a tree in this area.

Let's think about it, we spend almost half of all harvested wood on the repair, restoration and replacement of cracked from the sun, swollen from water, corroded by insects and simply rotten wooden structures and structures. A quarter of all timber harvested during the year goes to the details of windows and doors, skirting boards, stadium stands, garden benches, country houses. We paint them, often varnish them, but time passes and we throw our wood, our labor into the landfill. Another thing is wood processed according to the method proposed by Moscow inventors. At the bottom of the bath with molten tin, a vertical pipe is mounted through which compressed air is supplied. The upper section of the pipe is just below the melt level, so a wave appears on the surface, which washes the processed wooden parts. The hot wave makes the surface of the wood absolutely smooth, revealing the texture. The temperature of the molten metal is almost 232 ° C, and the wood does not char, since the process takes place without air access, but it acquires decorative, antiseptic and other useful properties. The billet quickly passes through the wave - it turns out golden, at an average speed - brown, slowly - black, like bog oak. Ordinary building details - skirting boards, window frames, window sills - acquire in this font the sum of new valuable qualities.

The Belarusian Technological Institute has developed a technology that can be used to make bog out of freshly sawn oak in just a minute! A sheet is placed at the bottom of the steel mold

light oak veneer, coat it with resin, pour a layer of birch sawdust, cover it all with a second sheet of veneer and, finally, a polished sheet of stainless steel. The mold is put under a press and heated to 200 "C. At a pressure of 200-250 atm, birch sawdust "leaks juice." Part of the juice penetrates through the gaps between the walls and the lid of the mold, solidifies, seals it and turns it into a kind of chemical reactor, where hydrolysis takes place sawdust, sugars are formed, acetic, oxalic and other acids, furfural are released.In the presence of acids, a binder resin is formed that fastens the sawdust into a monolithic, durable and solid slab, lined with oak veneer.Simultaneously with this process, the diffusion of hydrolysis products occurs in oak veneers, and they darken.About a minute later, a bog oak is pulled out of the mold, no less beautiful and durable than it has lain in water, as it should be, for more than a century.

And here is a giant hyperboloid of a cooling tower - a wooden structure for cooling waste water at thermal power plants. This wooden skyscraper has not worked for three years, but has already lost a third of its mass. Hot water washed out the resinous and mineral substances from the wood. Another year or two, and we will have to stop the cooling tower for repairs, spend hundreds of cubic meters of first-class timber ... Or - forty-

The design of the installation for compaction and modification of wood in an ultrasonic field: 1 - casing, 2 - workpiece in the zone of contour sealing, 3 - magnetostrictive plates, 4 - rubber gaskets, 5 - waveguide, 6 - impregnation zone.

Depending on the type of friction in the bearing, there are plain bearings, in which the bearing surface of the axle or shaft slides over the running surface of the bearing, and rolling bearings in which rolling friction develops due to the installation of balls or rollers between the bearing surfaces of the axle or shaft and the bearing.

Rolling bearings have a number of advantages over plain bearings.

• In modern mechanical engineering, plain bearings are limited to only some areas, for example, for high-speed shafts, in the mode of operation of which the durability of rolling bearings is very small;
• for axles and shafts requiring precise alignment;
• for very large diameter shafts for which standard rolling bearings are not manufactured;
• when bearings, according to assembly conditions, must be split (for example, for a crankshaft);
• when, in connection with the perception of shock and vibration loads by the bearing, the damping effect of the oil layer of the plain bearing is used;
• when operating bearings in water, aggressive environment, etc.,
• when rolling bearings are inoperable;
• for low-speed axles and shafts of non-critical mechanisms, when plain bearings are simpler in design and cheaper than rolling bearings
.

Depending on the direction of the perceived load, plain bearings are distinguished:

• radial for the perception of radial, i.e., perpendicular to the axes and shafts, loads;
• stubborn, or thrust bearings, for the perception of loads located along the axial lines of the axles and shafts;
• angular contact for the perception of both radial and axial loads.

With the simultaneous action of radial and axial loads on the axle or shaft, a combination of radial and thrust bearings is usually used, and radial thrust plain bearings are used much less frequently. Basic requirements for plain bearings:

• structures and materials of bearings must ensure minimum friction losses and wear of the shafts, have sufficient strength and rigidity to withstand the forces acting on them and the deformations and shocks caused by them;
• the dimensions of the rubbing surfaces must be sufficient to absorb the pressure acting on them without squeezing out the lubricant and to remove the heat developed from friction;
• assembly of bearings, installation of axles and shafts and maintenance (especially lubrication on the go) should be as simple as possible.

To reduce friction in bearings, increase efficiency, reduce wear and heat to a minimum, rubbing surfaces are lubricated with oil or other lubricant. Depending on the thickness of the oil layer, the bearing operates in the mode liquid, semi-liquid or semi-dry friction.

With liquid friction, the working surfaces of the shaft and bearing are completely separated by a lubricant layer, the thickness of which is greater than the sum of the roughness of the processing of the surfaces of the shaft and bearing. With semi-dry friction between the shaft and the bearing, dry friction predominates, and with semi-fluid friction, liquid friction predominates. There are also boundary friction, at which a continuous layer of oil is so thin that it loses the properties of a viscous liquid.

The most favorable mode of operation of a plain bearing is with liquid friction, which provides wear resistance, resistance to shaft seizing and high efficiency of the bearing. To create this friction, there must be hydrodynamic (produced by the rotation of the shaft) or hydrostatic (from the pump) overpressure in the oil layer. To obtain fluid friction, bearings with hydrodynamic lubrication are usually used, the essence of which is as follows. The shaft, when rotating under the action of external forces, occupies an eccentric position in the bearing (Fig. 1, a) and entrains oil into the gap between it and the bearing. In the resulting oil wedge, hydrodynamic pressure is created, which provides fluid friction in the bearing. The distribution diagram of the hydrodynamic pressure in the bearing along the circumference is shown in (Fig. 1, a), along the length - in Fig. (1b). Since the design of bearings with hydrostatic pressure is more complicated than the design of bearings with hydrodynamic pressure, they are mainly used for heavy low-speed shafts and other machine parts and assemblies (for example, heavy ball mills, large telescopes, etc.).

The plain bearing consists of a housing and liners placed in it (Fig. 2, a; 3), on which the axle or shaft directly rests. the body is usually made of cast iron, bearings to reduce friction are made from materials that, when paired with the shaft trunnion, have an insignificant coefficient of friction. Replacing bushings when worn is much cheaper than replacing the entire bearing. In manual drives, where bearing wear is insignificant, bushless plain bearings are also used (Fig. 2, b). The plain bearing is made either in a separate housing (Fig. 2; 3), bolted to the part on which it is installed, or in a housing made as one piece with the part, for example, a machine frame, a gearbox housing, etc. The outer shape of the housing bearing is determined depending on where the bearing is installed (Fig. 2; 3).

There are one-piece (Fig. 2) and split (Fig. 3) plain bearings. The body and shells of a one-piece bearing are one-piece. The liner is made in the form of a sleeve (Fig. 4, a), which is pressed into the bearing housing. The split bearing housing consists of two parts (Fig. 3): grounds 1, which perceives the load from the axis or shaft, and covers 2 attached to the base of the housing with bolts or studs. There are usually two inserts in a split bearing - top 3 and bottom 4. Sometimes multiple bearings are used.

The design of one-piece bearings is simpler and cheaper than split bearings, but they are inconvenient when mounting axles and shafts. Therefore, these bearings are usually used for the end journals of axles and shafts of small diameters. Split bearings are convenient for mounting axles and shafts and allow clearance adjustment by bringing the cover and base closer together, so they are most widely used. For proper operation of a plain bearing, it is recommended to split its housing perpendicular to the direction of the load perceived by the bearing. To prevent lateral displacements of the cover relative to the base of the body, the body parting plane is usually made stepped (see Fig. 3) or centering pins are provided.

In the event of a large deformation of the shaft or the impossibility of precise mounting, apply self-aligning plain bearings, the liners of which are usually made with spherical bearing surfaces (Fig. 4, a), and sometimes with bearing surfaces in the form of a narrow belt with low angular rigidity (Fig. 4, b). In sliding bearings of high-speed lightly loaded shafts, as well as in bearings of high bearing capacity, self-aligning segmented inserts are used to prevent vibration of the shafts when operating in liquid friction mode (Fig. 4, c), which, due to the formation of several oil wedges, ensure stable operation of the bearings and high bearing capacity . In the sliding thrust bearing (Fig. 6, a), the annular heel rests on the support ring, which, for self-alignment in the event of a shaft misalignment, is mated with the thrust bearing housing along a spherical surface and is protected from rotation by pins. To create oil wedges in the bearings that provide fluid friction, radial grooves are made on the working surface of the ring (Fig. 5, a) and bevels in the circumferential direction are made on the segments separated between them (Fig. 5, b). The grooves serve to spread the oil, and the bevels of the segments - to get oil on the working surfaces of the heel and thrust bearing. With constant rotation of the shaft, the bevels are made one-sided (see Fig. 5, b), with reversible two-sided. To increase the bearing capacity and reliability of the bearings, sliding bearings with self-aligning segments are used (Fig. 5, c), in which the formation of oil wedges occurs automatically during operation.

Bearing housings are usually made of cast iron SCH15, SCH18 and SCH20. Plain bearing shells are made of bronze, cast iron, plastics and other materials. Cast iron or bronze liners with babbitt filling are widely used.

Inserts made of light anti-friction materials - babbits and lead bronzes - are made bimetallic; in these liners, a thin anti-friction layer is welded onto a steel, cast iron (see Fig. 4, a, b) or bronze (in critical cases) base. Bimetallic inserts made of lead bronzes are stamped from a steel strip onto which bronze is applied. Bronze liners made of tin, aluminum, silicon, etc. bronzes are usually made solid homogeneous (see Fig. 2; 3). Bronze liners have high strength and rigidity, work well on impacts, but run in relatively slowly.

Inserts with babbitt fill run in well, anti-jamming struts, young trunnions with them are minimal. These bushings have proven themselves particularly well at high speeds and constant rotation of the axes and shafts in one direction. When working with shocks and reverse rotation of the axis or shaft, bronze liners are recommended. With long breaks in work and low peripheral speed of the axis or shaft, liners made of antifriction cast irons are used, which are much cheaper than bronze ones, or liners with babbitt filling.

In some plain bearings, ceramic-metal bearings made of iron or bronze powders with the addition of graphite and other impurities are used by pressing under high pressure and subsequent sintering at high temperature. The advantage of ceramic-metal inserts is the high porosity of their materials (the pore volume is 15...40% of the insert volume), due to which they are impregnated with oil and can work for a long time without lubrication. Plastic bushings for plain bearings are made from wood-laminated plastics (chipboard), textolite, fiberglass, polyamides (capron, nylon, 68 and AK-7 resins are used in domestic practice) and fluoroplastics (Teflon). The main advantages of plastic liners are the absence of shaft sticking, good running-in, the possibility of lubrication with water or other liquid. The most common liners are made of textolite and chipboard, which are widely used in rolling mills, ball mills, hydraulic and other heavy-duty machines. Inserts made of textolite and chipboard are made in sets of individual elements that are installed in metal cassettes (Fig. 7, a). Textile fiber, and sometimes textolite liners are made integrally pressed. Nylon, nylon and teflon liners are made on a metal base, on which a thin layer of nylon, nylon or teflon is applied. These bearings (especially Teflon bearings) paired with a steel trunnion have a very low coefficient of friction and can run without lubrication.

In some bearings, liners made of wood (backout, boxwood and other hardwoods), rubber and some other materials are used.

The construction of wooden inserts is the same as for chipboard inserts and they have the same applications.

Rubber bushings are mainly used in bearings operating in water, for example, in bearings of hydraulic turbine rotors. Advantages of rubber liners - high compliance, compensating for manufacturing inaccuracies; reduced sensitivity to the ingress of solid particles on the working surface of the liner; possibility of lubrication with water. In rubber liners, a rubber layer is placed inside a steel sleeve (Fig. 6, b) and provided with longitudinal grooves to enhance the cooling of the bearing and remove abrasive particles from it.

For some simple plain bearings, housings, bushings and liners are standardized by GOST 11521-82, 11525-82 and 11607-82...11610-82. Non-normalized plain bearings are manufactured according to departmental standards.

Publication date: 21/08/2009

According to the State Television Company "Tomsk", during the reconstruction of the local GRES-2 (located in the Siberian city of Tomsk, owned OJSC "TGC-11") when disassembling an old Japanese-made steam turbine, it was found that all turbine bearings were made of ... mahogany. Turbine with a capacity of 30,000 hp (29 MW) was installed back in 1948 and worked until 2001.

Initially, the turbine was on one of the ships of the Japanese Imperial Navy. However, after World War II, when part of the Japanese ships were transferred to the USSR and then scrapped, the steam plant from one of these ships was removed and brought to Tomsk to the GRES-2, which was then being completed. After the war, the recovering Soviet economy required more and more energy, but many machine-building plants at the beginning of the peace period were still unable to produce much, as the post-war devastation and the need to switch to the production of civilian products affected. Therefore, in the then USSR, they were forced to install machines from the former fascist countries (Germany, Japan and their allies) received as trophies and under reparation agreements at power plants. Often the equipment was already worn out, there was no technical documentation at all, and significant adaptation to local conditions was required. But, in spite of everything, in 1952 Tomsk power engineers managed to put into operation the second stage of GRES-2, on which a turbine was installed, which once worked on a warship from a distant land of the rising sun. For almost half a century, the Japanese turbine served Tomsk residents faithfully, and only at the beginning of the 21st century it was finally stopped.

In the photo: the beginning of the construction of the Tomsk State District Power Plant-2 (1943-1945)

Photo: TGK-11

Immediately after the war, they were forced to use captured equipment at the Tomsk State District Power Plant No. 2, which was under construction. So a turbine with mahogany bearings from a Japanese warship also got there.

At present, the old turbine has been completely dismantled, and a modern Russian one, the T-50 with a capacity of 50 MW, manufactured by the concern, is being installed in its place. "Power Machines". Its launch is scheduled for September 30 this year. The service life of the new turbine should be 30-40 years.

Brief information

Because of the harsh operating conditions, plain bearings are often used in power turbines. Plain bearings made of wood materials can be found in older installations. As the main structural material for such bearings, hardwoods (for example, boxwood and backout) and wood plastics were used. Modern turbines use plain bearings made of metal and synthetic alloys. Both rolling bearings and progressive magnetic bearings are used. More information about these types of bearings can be found in the article. .