22.09.2019
Railway gauge in Russia and other countries. Railway gauge in the Russian Federation and in Europe. Differences and characteristics
The basic norms for the arrangement and maintenance of the rail gauge of the jointless and link tracks are the same.
The main requirement in the design and installation of a rail track is to ensure the safety of trains at set speeds with a possible minimum of interaction forces between the wheel and the rail string, reducing the intensity of accumulation of residual deformations and the cost of maintenance and repair of a seamless track.
The track and the rolling stock are a single mechanical system, the components of which work interrelatedly and interdependently.
Railway carriages consist of unsprung and sprung parts. mass running gear rolling stock, directly interacting with the rails and separated from the rest of the mass of the crew by elastic links (for example, springs), is called unsprung mass. The rest of the crew is considered the sprung mass.
Both of these parts during the movement of crews (locomotives, wagons) perform complex oscillations both relative to the track and to each other. Oscillations occur mainly due to unevenness of the road and unevenness on the wheels, and also depend on the traction mode, resistance to movement of the wheels and a number of other reasons.
The vertical forces of action on the rail lashes of the wheels of a locomotive or wagon moving along the track are the sum of the own weight of the rolling stock per wheel (static load) and additional vertical forces arising from vibrations of the bolster structure and unsprung masses, caused, among other things, by track irregularities and wheels.
All listed vertical forces have a different nature and their own characteristics. Only the static load is constant in time, and all other forces are of a probabilistic nature.
In addition to vertical forces, the rolling stock also transmits horizontal transverse and longitudinal forces to the track.
When the carriages move in straight sections of the track, lateral forces arise associated with the wobbling of the rolling stock. The forces acting on the body and transmitted through the frame of the crew to the wheelsets are called frame forces. The lateral impact of the wheel on the rail string consists of the pressing force of the ridge on the rail head and the friction forces arising from the transverse sliding of the wheel along the rail.
Thus, the lateral effect of the wheel on the rail in straight sections of the track can be found as the algebraic sum of all these forces.
When the crew moves in the curve, additional horizontal forces arise - centrifugal force and guiding force.
Centrifugal force
J \u003d Q / gV 2 / 3.6 2 R
where Q - crew weight, N;
g - free fall acceleration, 9.81 m / s 2;
V - speed, km/h;
R is the radius of the curve, m;
3.6 is the conversion factor between speed in km/h and in m/s.
The centrifugal force J must be compensated by the force T arising from: the device for raising the outer rail in the curve
T = h/SQ
where h is the elevation of the outer rail, mm;
S - distance between wheel rolling circles, mm.
In connection with the action of the forces T, J and the forces of sliding friction of the wheels on the rails (Fig. 2.17), guiding forces arise Y 1, Y 2, which turn the carts.
The joint action of these forces can be replaced by their algebraic sum F np = J + T. If the centrifugal force J is fully compensated by the force T, then F np = J + T = 0.
If F np? 0, then there are additional lateral forces U pop, proportional to the values of the outstanding lateral acceleration
Y add \u003d ba np
where b is the coefficient taking into account the installation of the bogie in the rail track;
anp - outstanding lateral acceleration in m / s 2, has the form:
and np \u003d V 2 / 3.6 2 R - gh / S
Depending on the sign of the outstanding transverse acceleration, an overload of the outer or inner rail string may occur.
Thus, in a curved section of the path, the guiding force, lateral and frame actions depend on the centrifugal force, which, in turn, is proportional to the magnitude of the outstanding horizontal accelerations.
When passing along the path of the rolling stock, there are also forces acting along the path. The longitudinal movement of the rails caused by them relative to the sleepers or the entire track grid in the ballast is called track theft.
Among the many factors leading to track theft, the most significant are the resistance to movement of the train, the movement of the rails relative to the supports due to the bending of the rails under a moving load, the braking of the rolling stock, and a number of others.
Previously, the distribution of longitudinal thermal stresses along the length of the rail lash was considered (see Fig. 1.1). If there are sections with poorly fixed intermediate fastenings (loose or weakly fixed terminals) along the length of the lash, then when the train passes through these sections, local shifts of the lashes occur, leading to the formation of significant additional compressive or tensile forces of theft at their ends. Adding up with longitudinal temperature forces, the drag forces can cause buckling of a seamless track.
Having briefly considered the vertical and longitudinal forces acting on the seamless track when the rolling stock passes through it, let's move on to the issues of arranging the track gauge of the seamless track.
The outlines of the rail threads in the straight sections of the track are determined by the basic standards regarding the arrangement and maintenance of the rail track in relation to the direction in the plan, its width, the position of the rail threads in terms of level, and the slope of the rails.
The path in the plan must correspond to the design position. The position of the rail lashes in the plan is normalized and evaluated depending on the train speeds established on the section by the difference between adjacent bending arrows of rail lashes, measured from the middle of a chord 20 m long.
The difference between adjacent arrows in this case should not exceed:
- at speeds of 81-140 / 71-90 km / h - 10 mm;
- at speeds of 61-80 / 61-70 km / h - 15 mm;
- at speeds of 41-60 km / h - 20 mm;
- at speeds of 16-40 km / h - 25 mm;
- at speeds of 15 km / h - 30 mm.
The difference between adjacent bending arrows can also be checked from the middle of a chord with a length of 4, 10, 15, 25 and 30 m.
With a short unevenness directed inward on the track in straight sections of the track along any, and in curved sections of the track - along the outer rail, the difference between adjacent bending arrows, measured from the middle of a chord 4 m long, should not exceed:
- 8 mm at speeds up to 140 km/h;
- 9 mm at speeds up to 120 km/h; 14 mm at speeds up to 60 km/h;
- 15 mm at speeds up to 40 km/h; 18 mm at speeds up to 15 km/h.
- With a difference of arrows of more than 18 mm, the movement of trains is closed.
The distance between the inner running edges of the rail heads, measured 13 mm below the tread, is called rail gauge.
One rail thread (straightening) is aligned in the direction, and the other is set according to the template within the tolerances for the track width.
If a wheel pair is placed on a straight section of the track so that the crest of one wheel is pressed against the rail, will there be a gap between the crest of the second wheel and the working face of the head of the second rail? (Fig. 2.18). With a big gap? the wheels rest on the rails in a narrow strip, which can cause the wheels to fall inside the track. If there is no gap at all, jamming of the wheelset in the rail track may occur.
Example 2.1. Let us determine the width of the rail track, at which the failure of the wheels inside the track is possible. From fig. 2.18 shows that
S - (T + 2q + 2?)
where S is the width of the rail track in the straight section of the track, mm;
T - wheel attachment, mm;
q - ridge thickness, mm;
? - thickening of the ridge above the calculated plane, equal to 1 mm for wagon wheels, 0 mm for locomotive wheels.
On fig. 2.19 shows the wheel pair at the moment when the six-millimeter chamfer on the wheel coincides with the beginning of the rounding of the rail head. We can assume that this position of the wheel is the beginning of its failure in the rail track.
For a wagon wheelset, failure can occur with a gauge
S = 25 + 1 + 1437 + 130 - 6 = 1574 mm
where 25 is the minimum allowable thickness of a worn comb, mm;
1 - distance from the non-working face of the ridge at the calculated level to the vertical, from which the nozzle of the wheelset is measured, mm;
1437 - the minimum value of the nozzle of the wheelset, mm;
130 - full width of the wagon wheel, mm;
6 - chamfer width on the outer edge of the wheel, mm;
13 - horizontal distance from the beginning of the rounding of the rail head to its working edge, mm.
Such a gauge is considered unacceptable, at which the point of transition of the conicity of the wheel tread 1/20 to 1/7 coincides with the beginning of the rounding of the rail head, since in this case the rail gauge may expand. This can happen with a track width of 1574 - 24 = 1550 mm (see Fig. 2.19).
If we take into account the bending of the wagon axle and the elastic broadening of the track under the train load, then the validity of the existing ban on the gauge of more than 1548 mm becomes obvious.
Example 2.2. Let us determine the width of the rail track, at which jamming of the wheelset in the track is possible.
The dangerous limit of the track width by its narrowing is determined by the fact that with the greatest distance between the working faces of the crests of the wagon wheels 1443 + 2? 33 + 2? 1 = 1511 mm with a track width of 1511 mm
jamming of the wheelset. Therefore, the width of the rail track in straight lines less than 1512 mm is not allowed.
Earlier it was pointed out that the process of wobble of the wheels of the rolling stock is accompanied by the occurrence of sliding friction forces and the forces of the influence of the wheel flanges on the rails during the run. The former are relatively small, but the latter can reach values of 30–40 kN. These forces depend on the speed of the wheels running onto the rails during wobbling, which will be the higher, the greater the gap in the rail track? (See Figure 2.18).
The nominal width of the rail track in straight and curved sections of a seamless track with a radius of 350 m or more is 1520 mm; in curved sections of the track with a radius of less than 350 m up to 300 m inclusive - 1530 mm.
For a gauge of 1520 mm, two types of gauge tolerances are provided depending on the speed of trains: +8, -4 mm - at speeds of more than 50 km / h and +10, -4 mm - at speeds of 50 km / h and less.
The top of the heads of both rail threads on straight sections should be at the same level. It is allowed to maintain a track with an elevation of 6 mm at the level of one rail thread above another. The length of such a straight section must be at least 200 m, with the exception of sections located between adjacent curves in the same direction.
When one rail strand is raised by 6 mm, the carriage will tilt slightly, which will lead to the appearance of a lateral force, which will slightly press the wheels against the lowered rail strand and make it difficult for them to wag. Since this rail thread is straightening, the wheel pressed against it will move more smoothly.
On double-track lines, an edge rail thread is placed higher so that a more stable inter-track rail thread becomes leveling.
On single-track lines, during the next medium repair, as a rule, they change the straightening thread.
The elevation of one rail thread above another in a straight section should end no closer than 25 m from the beginning of the elevation in the curve, if the elevated thread on the straight line coincides in level with the lowered thread in the curve.
If on straight sections of the track with an elevation of one rail strand above the other there is a bridge with a ride on ballast, then this elevation must also be preserved on it. On bridges with a ride on top and bridge beams, elevation is allowed with a bridge length of not more than 25 m. On bridges of greater length with bridge beams, in tunnels and on approaches to them with a length of 25 m, as well as on turnouts in straight sections of the track, allow an increase in one of the following: Noah rail thread above the other by 6 mm is prohibited.
The nominal slope of the outlet in terms of level from the norm of 6 mm to the zero position should not exceed 1.
Permissible deviations from the norms for the location of rail lashes in terms of level are ± 6 mm. If, for example, first the left rail lash is 6 mm higher than the right one, and then vice versa, then the minimum distance between such excesses should be at least 20 m, since a skew of the track is formed at a smaller distance. Distortions of the track include sharp changes in the position of the rail lashes in terms of level in different directions with a distance between the peaks of 20 m or less.
With such a misalignment, it is possible to unload one of the wheels of the car, which, in combination with large lateral forces, can lead to the derailment of the rolling stock.
On fig. 2.20 shows the position of the bogie when passing through the skew, measured on the base of the bogie, when the centers of both wheels of the rear and left wheels of the front wheelset are in the same horizontal plane, and the right wheel of the front wheelset is lowered.
In this case, the load on it from the spring decreases somewhat, i.e. is partially unloaded. If such unloading coincides with a strong lateral pressing of the wheel flange to the rail head, then it, rotating, can rise to the rail head, and then come off it.
Railway track is one of the main elements railway. The rail track is two parallel rails, which are located at a certain distance from each other. This distance is called the track width.
The track width is the main parameter of the rail track and is directly related to the dimensions of the wheel sets. Measured between the inner working faces of the rail heads. The railway track in Russia and Europe is different. This is due to various reasons - historical and strategic.
The most popular gauge in the world is the so-called Stephenson gauge. Its width is 1435 mm. It got its name from the English inventor of railways, George Stephenson (he invented the first passenger railway line in the direction of Liverpool - Manchester).
The European gauge is used on the railways of North America, China and most European countries. This is approximately 75% of the railways on the globe.
The railway track in the Russian Federation differs from the European one. Its width is 1520 mm (adopted from the 70s of the 20th century). It is used on all railways, subways and tram lines of the Russian Federation and most CIS countries, Finland, Mongolia. This is approximately 11% of the railways. According to studies, this gauge turned out to be the most optimal: it allows to increase the stability of the tracks during the operation of freight locomotives, trains, the wear of rails and wheelsets is reduced (up to 94%), the speed of movement increases, and the modernization of the rolling stock is not required.
Initially, the width of the Russian gauge was 1524 mm and was first used during the construction of the Nikolaev railway (mid-19th century). There are many opinions as to why such a value was adopted:
adopted American experience in the course of cooperation with consultants from the USA (at that time this gauge was popular in the southern states);
the proposal of Russian engineers who visited America before the start of construction of the Nikolaev railway.
military aspect: a different gauge would make it difficult to transport military supplies to enemy troops from Europe to Russia.
Different track widths do not interfere with passenger and freight traffic. When crossing the border, trains are rearranged to new wheelsets that correspond to the established track gauge (1435 mm or 1520 mm).
Other materials:
The arrangement of the rail gauge is closely related to the design and dimensions of the wheel sets of the rolling stock. The wheel pair consists of a steel axle, on which wheels are tightly mounted, having guide ridges to prevent derailment. The tread surface of rolling stock wheels in the middle part has a 1/20 conicity, which provides more uniform wear, greater resistance to horizontal forces directed across the track, less sensitivity to track failures and prevents the appearance of a groove on the tread surface, which makes it difficult for wheel sets to pass through turnouts. In accordance with this, the rails are also installed with a 1/20 underslope, which is achieved with wooden sleepers due to wedge-shaped linings, and with reinforced concrete sleepers - by a corresponding slope of the sleepers surface in the rail support zone. The distance between the inner edges of the rail heads is called track gauge. This width consists of the distance between the wheels (1440 + 3 mm), two thicknesses of the ridges (from 25 to 33 mm) and the gaps between the wheels and the rails necessary for the free passage of the wheelsets. The width of the normal (wide) gauge in straight and curved sections of the track with a radius of more than 349 m is adopted in the USSR 1520 mm with tolerances in the broadening direction of 6 mm and in the narrowing direction of 4 mm. Until 1972, a track gauge of 1524 mm was considered normal on our roads; narrowing it to 1520 mm is adopted to reduce the gap between the wheels and rails, which, at increased speeds, helps to reduce track disorders.In accordance with the PTE, the top of the rail heads of both track threads on straight sections must be at the same level. It is allowed to contain one rail thread 6 mm higher than the other on straight track sections along the entire length of each of them.
When constructing the track, the joints on both rail threads are located exactly one against the other along the square, which, compared with the location of the joints apart, reduces the number of impacts of wheel sets on the rails, and also allows you to harvest and change the rail and sleeper grid in whole links with the help of tracklayers.
In order to prevent each wheel pair from turning around a vertical axis, the wheel pairs of a wagon or locomotive are connected by two or more rigid frames. The distance between the extreme axles connected by the frame is called the rigid base, and between the extreme axles of the car or locomotive - the full wheelbase. The rigid connection of the wheelsets ensures their stable position on the rails, but at the same time makes it difficult to pass in curves of small radius, where they can jam. To make it easier to fit into curves, modern rolling stock is produced on separate bogies with small rigid bases.
:
A- electric locomotive VL8, b- one section of the locomotive TEZ, V- locomotive series FD,
G- four-axle gondola car
Features of the path device in curves
In curved sections, the track arrangement has a number of features, the main of which are: the elevation of the outer rail above the inner one, the presence of transition curves, the widening of the track at small radii, the laying of shortened rails on the inner rail thread, the reinforcement of the track, the increase in the distance between the axes of the tracks on two- and multi-line lines.Elevation of the outer rail It is provided for with a curve radius of 4000 m or less so that the load on each rail thread is approximately the same, taking into account the effect of centrifugal force, for uniform wear of the outer and inner rails, as well as the repayment of centrifugal acceleration, which negatively affects the comfort of passengers. The size of the elevation depends on the speed of the trains and the radius of the curve and usually does not exceed 180 mm (in Russia - 150 mm).
It is known that when the rolling stock follows a curve with a radius R centrifugal force occurs
where m is the mass of a rolling stock unit;
G is the weight of a rolling stock unit;
g - acceleration due to gravity
When the outer rail is raised by a value h there is a component of the weight force H, directed inside the curve.
Scheme of forces acting on the rolling stock in a curve when the outer rail is raised
It is clear from the figure that the ratio H/G is equal to the ratio h/s 1. Therefore H \u003d Gh / s 1.
For the same pressure on the rail threads, it is necessary that H balanced I, then the resultant N will be perpendicular to the inclined plane of the track.
Considering that the angle α is small and at the maximum allowable elevation of the outer rail of 150 mm cos α = 0.996, we can assume that H=I.
Then
Where
Substituting s 1 \u003d 1.6 m, g \u003d 9.81 m / s 2 and expressing the speed v in km / h, and the radius R in meters, we get the elevation in mm
Since in real conditions trains of different masses Q i pass along the curves, and with different speeds Vi, then for uniform wear of the rails, the root-mean-square speed is substituted into the above formula
At h=2.5v cf 2 /R in trains traveling at speeds above v cf, passengers and goods will be subject to an outstanding acceleration equal to the difference between centrifugal acceleration v2/R and directed to the center of the curve by acceleration gh/s 1
On the roads former USSR the permissible unabated acceleration is 0.7 m/s 2 and only in exceptional cases 0.9 m/s 2 . When trains move at a speed less than v cf The load on the inner rail will be greater than on the outer rail.
To ensure a smooth inscribing of the rolling stock, circular curves are matched with straight sections using transition curves. Between adjacent curves on the railway, direct inserts are provided with a minimum value of 30 to 150 m, depending on the category of the line and the direction of the curves (in one or in different directions).
Devices transition curves due to the need for a smooth conjugation of the curve with the adjacent straight line both in plan and in profile. The transition curve in plan is a curve of variable radius decreasing from ∞ (infinitely large) to R- the radius of a circular curve with a decrease in curvature in proportion to the change in length. A curve with this property is a radioidal spiral whose equation is expressed as a series
Where WITH- transition curve parameter (C=lR)
Due to the fact that the length of the transition curve l small compared to WITH, it is practically enough to confine ourselves to the first two terms of the series of the above formula. In the profile, the transition curve in normal conditions is a sloping line with a uniform slope i = h/l.
. NPC- the beginning of the transition curve. CPC- end of transition curve
Broadening gauges are made to ensure that the rolling stock fits into curves. Since the wheel sets are fixed in the bogie frame in such a way that they are always parallel to each other within the rigid base, only one wheel set can be located along the radius in the curve, and the rest will be at an angle. This makes it necessary to increase the gap between the wheel flanges and the rails in order to avoid jamming of wheelsets. For a two-axle bogie to freely fit into a curve, the required track width is:S c \u003d q max + f n +4
Where f n- arrow bending the curve along the outer thread with a chord 2λ;
q max - the maximum distance between the outer edges of the wheel flanges;
4 - gauge narrowing tolerance, mm.
The following norms for the track width in curves are established:
at R≥ 350 m - 1520 mm;
at R = 349-300 m - 1530 mm,
at R≤ 299 m -1535 mm.
Laying short rails into the inner thread is necessary to exclude the spread of the joints. Since the inner rail thread in the curve is shorter than the outer one, laying rails of the same length in it as in the outer one will cause the joints to run forward on the inner thread. To eliminate the spread of joints at each radius of the curve, it is necessary to have its own value of rail shortening. For the purpose of unification, standard shortening of rail links 25 m long by 80 and 160 mm is used. Total number of shortened rails n required for laying in a curve,
n = e/k,
Where e- total shortening
k- standard shortening of one rail
The laying of shortened rails in the inner thread is alternated with the laying of rails of normal length so that the run of joints does not exceed half the shortening, i.e. 40; 80 mm.
Gain paths in curves are made at R<1200 м для обеспечения необходимой
равнопрочности с примыкающими прямыми. Для этого увеличивают число шпал на километр,
уширяют балластную призму с наружной стороны кривой, ставят несимметричные подкладки
с большим плечом в наружную сторону, отбирают наиболее твердые рельсы. В круговых
кривых на двух- и многопутных линиях увеличивается расстояние между осями путей
в соответствии с требованиями габарита, что достигается в пределах переходной кривой
внутреннего пути за счет изменения ее параметра С.
Extract from the Rules for the Technical Operation of Railways of the Russian Federation
Chapter III. Structures and devices of track facilities. Plan and track profile3.4. The railway track in relation to the radii of curves, the conjugation of straight lines and curves, the steepness of the slopes must comply with the approved plan and profile of the line.
3.5. Stations, sidings and passing points, as a rule, should be located on a horizontal platform; in some cases, their location on slopes not exceeding 0.0015 is allowed; in difficult conditions, an increase in slopes is allowed, but, as a rule, not more than up to 0.0025.
In especially difficult conditions at sidings and overtaking points of a longitudinal or semi-longitudinal type, and with the permission of the Ministry of Railways and at intermediate stations where maneuvers and uncoupling of a locomotive or wagons from the train are not provided, slopes of more than 0.0025 are allowed within the station platform. It is also allowed in especially difficult conditions with the permission of the Ministry of Railways, slopes of more than 0.0025 when lengthening the receiving and departing tracks at existing stations, provided that measures are taken against spontaneous departure of wagons or trains (without locomotives).
To prevent spontaneous departure of wagons or trains (without a locomotive) at stations, sidings and passing points, newly built and reconstructed receiving and departing tracks, which provide for the uncoupling of locomotives from wagons and the performance of shunting operations, should, as a rule, have a longitudinal profile with counterslopes in direction of the limiting arrows and comply with the regulations for its design.
In necessary cases, in order to prevent spontaneous exit of wagons to other tracks, provision should be made for the installation of safety dead ends, guard arrows, dropping shoes or arrows.
In all cases where stations, sidings and passing points are located on slopes, the conditions for starting trains of the established weight norm must be provided.
3.6. Stations, sidings and passing points, as well as individual parks and exhaust tracks should be located on straight sections. In difficult conditions, it is allowed to place them on curves with a radius of at least 1500 m.
In particularly difficult conditions, it is allowed to reduce the radius of the curve to 600 m, and in mountainous conditions - up to 500 m.
3.7. The plan and profile of the main and station tracks, as well as sidings belonging to the railway, must be subjected to periodic instrumental checks.
The organization of work on instrumental verification of the plan and profile of the tracks, the preparation of relevant technical documentation, as well as the preparation of large-scale and schematic plans of stations is entrusted to the railway track services with the involvement of design institutes, design and survey and design and estimate groups to carry out these works.
Track distances must have:
- drawings and descriptions of all structures and devices of the track facilities available at the distance, as well as the relevant standards and norms;
- scale and schematic plans of stations, longitudinal profiles of all main and station tracks, marshalling yards, as well as sidings where the locomotives of the road turn.
When erecting new facilities on the territory of the station, expanding or transferring existing ones, any organization performing such work must immediately transfer to the head of the distance of the track and the head of the station the executive documentation that determines the connection of the facility to the existing development of the station.
rail gauge- these are two rail threads installed at a certain distance from one another and attached to sleepers, beams or slabs. The device and maintenance of the rail track depend on the design features of the running gear of the rolling stock.
These include the presence of flanges (ridges) on the wheels that hold the wheels on the rails and direct the movement of locomotives and wagons. The wheels are tightly pressed onto the axle and together with it form a wheel pair. The axes of the wheelsets, united by a common rigid frame, always remain mutually parallel.
The rolling surface of the wheels is not cylindrical, but conical in shape with a slope in its middle part of 1:20.
The distance between the inner edges of the wheels is called the nozzle T = 1440 mm with a maximum tolerance of ± 3 mm.
The distance between the extreme axles fixed in the frame of one bogie is called a rigid base.
The distance between the extreme axles of a wagon or locomotive is called the full wheelbase of a given unit.
So, the full wheelbase of the VL-8 electric locomotive is 24.2 m, the rigid base is 3.2 m.
The distance between the working faces of the wheel flanges is called the width of the wheelset.
The thickness of the flanges of the wheelsets must be no more than 33 mm and no less than 25 mm. In order for a wheelset with the widest nozzle and unworn wheel flanges to fit inside the track, its width must be 1440 + 3 + 2 × 33 = 1509 mm, but the wheelset will be clamped (wedged) between the rails.
Track width is the distance between the inner edges of the rail heads, measured 13 mm below the tread. The gauge on straight sections of the track and in curves with a radius of 350 m or more should be 1520 mm. On existing lines, up to their transition to a 1520 mm gauge, on straight sections and in curves with a radius of more than 650 m, a gauge of 1524 mm is allowed. In curves with a smaller radius, the track width is increased in accordance with the Rules for Technical Operation (PTE).
Gauge tolerances are set for broadening plus 8 mm, for narrowing the gauge minus 4 mm, and in sections where speeds of 50 km / h or less are set, tolerances of +10 for broadening, -4 for narrowing are allowed (PTE TsRB-756.2000). Within tolerances, the track width should change smoothly.
Rail underlay. In straight sections of the track, the rails are not installed vertically, but with an inclination into the track, i.e. with a slope to transfer pressure from the bevel wheels along the rail axis. The conicity of the wheels is due to the fact that the rolling stock with such wheelsets has a much greater resistance to horizontal forces directed across the track than cylindrical wheels, the "wobble" of the rolling stock and the sensitivity to track failures are reduced.
Variable conicity of the rolling surface of the wheels from 1:20 to 1:7 (Fig. 4.35) is given in order to avoid the appearance of grooved wear of the wheels and for a smooth transition from one track to another through the turnout. Rail threads must be in the same level. Permissible deviations from the norm depend on the speed of trains.
Fig. 4.35. The most of the time ïAxies are ïCHANISHYSHYSHYSHYSHYSHYALY - the: 1 - îANYSHYLYENLYYLEL; 2 - layer, extruded
expanded polystyrene 40 mm thick
On long straights it is allowed to keep one rail thread permanently 6 mm higher than the other. With this position of the rail threads, the wheels will be slightly pressed against the lowered straightening thread and move more smoothly. On double-track sections, the straightening thread is the inter-track thread, and on single-track sections, as a rule, it is the right one along the course of kilometers.
The work of the track in curved sections is more difficult than in straight sections., because when rolling stock moves along curves, additional lateral forces appear, for example, centrifugal force. The features of the track gauge in curves include: increasing the gauge in curves of small radii, raising the outer rail thread above the inner one, connecting straight sections with circular curves by means of transition curves, laying shortened rails on the inner thread of the curve. On double-track lines in curves, the distance between the axes of the tracks increases. Gauge widening on curved sections of our roads is done at radii of less than 350 m.
The need for broadening It is caused by the fact that the wheel pairs included in a common rigid frame, while maintaining the parallelism of their axes, make it difficult for the bogies of the rolling stock to pass along curves. In the absence of broadening, the necessary gap between the wheel flanges and the rail disappears, and an unacceptable jammed passage of the rolling stock occurs. In this case, there is a great resistance to the movement of the train, as well as additional wear of the rails and wheels, and traffic safety is not ensured.
The smaller the curve radius and the larger the rigid base, the wider the track should be.
Elevation of the outer rail. When the crew moves along the curve, a centrifugal force is generated that is directed outward of the curve. This force creates an additional impact of the wheel on the outer rail thread, greatly wearing out the rails of this thread. If both rail threads are set at the same level in the curve, then the resultant of the centrifugal force and the weight force will deviate towards the outer rail, overloading it and, accordingly, unloading the inner rail. In order to reduce the lateral pressure on the rails of the outer thread, reduce their overload, achieve uniform wear of the rails of both threads and relieve passengers of discomfort, they arrange an elevation of the outer rail h (Fig. 4.36).
Fig. 4.36. Scheme of acting forces in the device of the elevation of the external rail in the curves
In this case, the vehicle leans towards the center of the curve, part of the weight force H will be directed inside the curve, i.e. in the direction opposite to the centrifugal force. Therefore, tilting the carriage by means of the outer rail elevation device balances the centrifugal force. This equalizes the impact on both rails.
With curve radii of 4000 m or less, an elevation of the outer rail thread is made, which can be from 10 to 150 mm. This elevation depends on the speeds of the trains, their gross mass and the daily number of trains on the curve under consideration and the radius of the curve. Retraction of the elevation of the outer rail, i.e. a gradual decrease in the increased outer thread to zero is done smoothly. Deviation of the calculated elevation in terms of level is allowed depending on the speed of trains.
Transition curves. To smoothly fit the rolling stock into the curves, a transition curve is arranged between the straight section and the circular curve, the radius of which gradually decreases from an infinitely large value at the point where it adjoins the straight section to a radius R at the point where the circular curve begins. The need to insert spiral curves is caused by the following. If a train from a straight section of the track enters a circular curve, where the radius of curvature immediately changes from ¥ to R, then the centrifugal force instantly acts on it. At high speeds, the rolling stock and the track will experience strong lateral pressure and wear out quickly. When arranging transition curves, the radius slowly decreases, respectively, and the centrifugal force slowly increases - a sharp lateral pressure on the train and the track will not occur. On the railways of the Russian Federation, transition curves are built along a radioidal spiral, i.e. apply a curve with a variable radius of curvature. They are accepted in standard lengths from 20 to 200 m.
Within the transition curves, the elevation of the outer rail and the widening of the gauge, arranged in circular curves, are smoothly diverted, and the widening of the intertrack is also made.
There are special tables for breaking down the transitional and following circular curves, that is, for marking their position on the ground.
Laying shortened rails in curves. The inner rail thread in the curve is shorter than the outer one. If all the rails of the same length are laid along the inner thread of the curve as along the outer thread, then the joints along the inner thread will run forward relative to the joints on the outer thread and they will not be located along the square, as is customary on our network. To eliminate a large run of joints in a curve, rails of a shortened length are laid along the inner thread. Three types of rail shortening are used: 40, 80 and 120 mm for 12.5 m rails and 80 and 160 mm for 25 m rails. Large shortenings are used on steep curves. The laying of shortened rails is alternated with rails of normal length so that the run or underrun of the joints does not exceed half of the standard shortening, i.e. respectively 20; 40; 60 and 80 mm. During the operation of the track, the run or underrun of the joints is allowed in curves - 8cm plus half of the standard shortening of the rail in this curve.
rail gauge- this is the distance between the inner side faces of the rail heads, measured at a level of 13 mm below the tread surface, in our country, at the beginning of the construction of railways, it was taken equal to 5 feet, that is, 1524 mm. In most other countries, the normal gauge is 1435 mm. In India, Pakistan, Ceylon, Spain, Portugal, Argentina and Chile, the gauge is 1676 mm, in Brazil, Northern Ireland - 1600 mm, in Japan and a number of African countries - 1067 mm.
In many countries there are narrow-gauge roads with a gauge of 750, 600, 500 mm and other sizes.
To improve the interaction of the track with the rolling stock, the Rules for the technical operation of railways, approved by the Ministry of Railways in 1970, reduced the gauge from 1524 to 1520 mm.
Normal track width applies to straight sections and curves with a radius of 350 m or more. For curves with a radius of 349 to 300 m, it is 1530 mm, and for curve radii less than 300 m, it is 1535 mm. The widening of the track in curves of small radii is arranged to facilitate the passage of rolling stock along them. In curves with a radius of 650 to 300 m, the gauge may have an additional broadening by the amount of actual lateral wear of the rail head, but not more than 1530 mm in curves with a radius of 650-450 m, 1535 mm - in curves with a radius of 449-350 m and 1540 mm - in curves with a radius of 349 m or less.
Due to the impossibility to provide an absolutely accurate gauge when assembling the rail-sleeper grid and its invariability in operation, tolerances in the gauge content are set equal to +8 and -4 mm. This means that at the rate of 1520 mm, the track width can vary from 1528 to 1516 mm. For curved sections, the same tolerances are used, but with one limitation - the track width of more than 1548 mm is not allowed in any cases, since such an increase creates the danger of a possible spread by its part of the wheel with an increased conicity of the surface.
If the permitted train speeds of 50 km/h or less are set on the section, the gauge may be widened up to 10 mm and narrowed by 4 mm.
On existing lines, until they are transferred to the 1520 mm gauge, the following gauges are allowed: on straight sections and in curves with a radius of 350 m or more - 1524 mm; in curves with a radius of 349 to 300 m - 1530 mm, and with a radius of 299 m or less - 1540 mm.
There are separate sections with a gauge of 1524 mm, where curves with the following gauges are still preserved: with radii from 650 to 450 m - 1530 mm; with radii 449 to 350 m - 1535 mm; with radii of 349 m and less - 1540 mm.
Until the transition to the 1520 mm gauge, it is allowed to maintain the track according to these standards.
In severe conditions (mountain lines, intra-factory tracks, etc.), when very steep curves are used and the track width of 1548 mm is insufficient, additional widening can be allowed, but on condition that counter rails and other devices are laid, excluding the possibility of wheels falling inside the track .
The most favorable is free inscribing into the curve of the rigid base of the locomotive or wagon (Fig. 1), when the front axle is pressed by the crest of one wheel to the outer rail thread, and the rear axle touches the crest of the inner rail thread; in this case, the rear axle is located in the direction of the radius of the curve. In this case, the rigid base of the rolling stock unit is installed completely freely inside the track.
The most unfavorable type of entry is jammed fit(Fig. 2), in which both extreme wheels in a rigid base are pressed by ridges to the rail. Such fitting causes a very large resistance to the movement of the train and unsafe pressure of the wheels on the rails. An inscription, by its nature, occupying an intermediate position between free and wedged, is called forced.
At present, bogie locomotives (electric locomotives and diesel locomotives) and bogie freight and passenger cars are in circulation almost everywhere on our railways, having a rigid base from 1.8 m for a four-axle gondola car to 4.4 m for an electric locomotive.
The transition to short-base rolling stock made it possible to unify the width, gauges on straight and curved sections (with a radius of 350 m or more), with the exception of a relatively small stretch of tracks in mountainous areas, access, connecting, intra-factory and station, having curve radii of less than 350 m.
When trains pass through curves the track experiences significant additional impacts from the wheels of the rolling stock. To avoid sharp impacts of the wheel flanges on the rails when the train enters the curves, significant overloads of the outer rail threads due to the appearance of centrifugal forces, facilitate the fitting of the rolling stock into the curves and passing along them:
- increase the track width;
- prevent distortion of the design curvature of the path;
- outer rail threads are located above the inner ones;
- in the places of conjugation of straight sections of the track with curves, transition curves are arranged;
- reduce the distance between sleepers;
- lubricate the side surfaces of contact between the wheel flanges and the rails.
Of great importance for the interaction of rolling stock and track in curves is the size of the rigid base of locomotives and wagons. On the roads of the Russian Federation, bogie locomotives (electric locomotives and diesel locomotives) and freight and passenger cars with a rigid base from 1.8 m for a four-axle gondola car to 4.4 m for an electric locomotive are in circulation. Short-base rolling stock has much better conditions for passing along curves, and this made it possible to unify the gauge on straight and curved sections (with a radius of 350 m or more). Only on a relatively small stretch of tracks in mountainous areas, on access, connecting, intra-factory and station tracks, where the curve radii remained less than 350 m, is the gauge widened.
