Calculation rail gauge
ROLLING STOCK CARRIAGE PARTS
Features of the running parts of railway rolling stock that influence the design of the rail track are:
1) the presence of flanges (ridges) on wheel tires;
2) blind wheel attachment;
3) parallelism of axes within a rigid base;
4) transverse run-up of the axles of the rolling stock, as well as the presence of a rotary axle or bogie for some crews;
5) tapered bandages.
Wheel flanges, or ridges, are protruding parts of wheels designed to guide the movement of crews and prevent them from leaving the track. The wheelset of a railway carriage consists of an axle and two tightly mounted wheels with tires, the rolling surface of which in the middle part has a conicity of 1/20, and therefore the rails on straight sections are placed with an inclination inward to the track (also 1/20).
Locomotive (Fig. 1.1, a) and carriage (Fig. 1.1,6) wheels differ in size and cross-section shape.
Rice. 1.1. Cross profiles of wheels:
a - locomotive; b - carriage
At train speeds of more than 140 km/h, wear limit h , measured along the average rolling circle, should not exceed 5 mm. At lower speeds, rental of locomotive wheels and passenger cars up to 7 mm is allowed, and for freight cars - up to 9 mm.
The blind attachment of the wheels is a fixed attachment of them to the axle, i.e. the wheels rotate together with the axle. This design is due to the considerations that when the wheels are loosely mounted after wear of their hub and axle journal, it can take on an inclined position and fall inside the track.
Parallelism of axes assumes that during movement all axes that are part of the rigid base move parallel to each other. Otherwise, if the wheel pair is skewed, it may derail. The rigid base of the carriage is the distance between its extreme axles, which are part of one bogie. During movement, the axes of one cart remain parallel to each other. In addition to the rigid base, there is the concept of the full wheelbase L of the vehicle - the distance between its outer axles. The full L and rigid base L 0 of the crew are shown in Fig. 1.2.
Rice. 1.2. Full L and hard L 0 bases of various crews
The nature of the fit of the carriages into the curves, and therefore the necessary track width for this, is determined by the size of the rigid base.
Transverse runs in the axles of the rolling stock allow them to move along the geometric axis of the wheelset. The lack of lateral runways makes it difficult for crews to fit in. To fit them in, it is necessary to increase the track width.
In some multi-axle vehicles, to facilitate fitting, the outer supporting axles can be rotated by a certain limited angle.
Wheel set tires are tapered. The rolling surface of the wheels is assumed to have a slope relative to the horizon equal to 1/20. The conicity of the rolling surfaces of the tires softens the impacts of rolling stock wheels during their wobbling motion as a result of the occurrence of a horizontal component of the pressure of the wheel on the rail. The tapering of the tires requires a device for inclining the rails. It is arranged for central transmission of forces from the wheels to the rails. The amount of inclination is assumed to be equal to the conicity of the bandages, i.e. 1/20. The slope should not be more than 1/12 and less than 1/30 along the inner thread in a curve and 1/60 in all other cases.
CONSTRUCTION OF RAIL TRACK IN STRAIGHT SECTIONS OF THE TRACK
The track width in the Russian Federation is taken to be 1520 mm with a widening tolerance of 8 mm and a narrowing tolerance of 4 mm. At speeds up to 50 km/h, a widening of up to 10 mm is allowed. The track width is measured at a level located 13 mm below the rolling surface of the rail head. This is explained by the fact that the calculation plane is located 10 mm below the rolling surface of the rail head for new tires. With increasing wear, the rolling surface of the wheel tire, and therefore the design plane, decreases.
The top of the rail heads along both rail threads in straight sections of the track should be located at the same level with tolerances of ±5 mm. It is allowed to contain one rail thread 5 mm higher than the other. On double-track sections, the elevation is arranged on the edge of the track, and on single-track sections, as a rule, on the right rail along the kilometers. Elevations are not provided at turnouts.
There is a certain relationship between the rail track and the width of the wheelset. The width of the wheelset (wheel track) is narrower than the track width by the amount of the gap.
Rice. 2.1. Scheme for determining the gap δ between the rail track S and the wagon track q
In Fig. Figure 2.1 shows a diagram for determining the size of the gap between the wheel flange and the rail head. The diagram shows:
S - rail gauge width, S = mm;
q - wheel pair width (wheel track);
T - wheel attachment, T = 1440±3mm at a speed of more than 140 km/h with tolerances +3 -1;
d - wheel flange thickness, d max = 33 mm, d min = 25 mm; at a speed of more than 140 km/h d min = 28 mm;
μ - thickening of the wheel flange in the section above the design plane; for carriage wheels μ =1mm; for locomotive μ=0;
δ is the gap between the wheel flange and the working edge of the rail.
From the one shown in Fig. 2.1 of the diagram shows that the rail track differs from the wheel track by the amount of gap δ:
where q = T +2d + 2μ.
Since the dimensions included in these expressions have tolerances, there are minimum, normal and maximum values δ:
δ min = S min - q max ;
δ 0 = S 0 - q 0 ;
δ max = S max - q min .
If we substitute numerical values into these expressions, we obtain the results shown in table. 1.
Table 1
| Wheel name | Travel speed, km/h | S, mm | q, mm | δ, mm | ||||||
| max | normal | min | max | normal | min | max | normal | min | ||
| Locomotive | Up to 140 | |||||||||
| Over 140 | ||||||||||
| Carriage | Up to 140 | |||||||||
| Over 140 |
Thus, on straight sections of the track, the gap between the wheel flange and the working edge of the rail ranges from 5 to 39 mm. When loaded cars move, the wheel pair axle bends upward with its convexity, since the load from the car to the wheel pair is transmitted through the axle box unit located outside the rail track. As a result, the wheel track can be reduced by 2 - 4 mm or more. Under the influence of rolling stock wheels, elastic compression of the rail threads occurs, i.e., elastic widening of the track by 2 mm in straight sections, and by 4 mm or more in curves.
The positive role of the gap is to eliminate jamming of rolling stock wheels between the rail threads, and therefore to reduce movement resistance and reduce lateral wear of rails and wheel flanges.
However, an excessive amount of clearance increases the angles of approach of the wheel flanges to the rail in straight lines and when entering curves, which increases horizontal forces and leads to disruption of the track in plan. In this case, the service life of the rails and wheels of the rolling stock is reduced, and the smooth movement of trains deteriorates, especially when high speeds, operating costs increase.
The dangerous limit in the direction of narrowing the track is determined from the condition of jamming of the wheelset with the maximum attachment, i.e.
Spre (min) = q max = T max + 2d max + 2μ = 1443 + 2·33 + 2·1 = 1511 mm.
Rice. 2.2. Scheme for determining the maximum permissible (maximum) rail gauge S prev (max)
The dangerous limit in the direction of widening the track is determined by preventing the wheel from falling into the track. The design diagram is shown in Fig. 2.2. From the figure we see that
Spre (max) = T min + d min + μ + 130 - 30 - r 1,
where d min is the minimum value of the ridge thickness, d min = 25 mm;
μ - thickening of the ridge in the section located above the design plane, μ = 1 mm;
T min - minimum value of wheel attachment, T min = 1437 mm;
S pred (max) = 1437 + 25 + 1 + 130 - 30 - 15 = 1548 mm.
Taking into account the elastic deflection of the rails under load, as well as the bending of the axles of loaded cars, limit value The track width in the widening direction is set to 1546mm. The presence of a track that exceeds dangerous limits, both in the direction of narrowing and widening, is not allowed and is considered a malfunction of the highest degree.
The design of the rail track is closely related to the design and dimensions of the wheel pairs of the rolling stock. The wheelset consists of a steel axle on which wheels are tightly mounted, having guide ridges to prevent derailment. The rolling 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 its faults and prevents the appearance of a groove on the rolling surface, which makes it difficult for wheelsets to pass along turnouts. In accordance with this, the rails are also installed with a 1/20 inclination, which for wooden sleepers is achieved through wedge linings, and for reinforced concrete ones - by a corresponding inclination of the surface of the sleepers in the area where the rails support. The distance between the inner edges of the rail heads is called track width. This width is the sum of the distance between the wheels (1440 + 3 mm), two thicknesses of the flanges (from 25 to 33 mm) and the gaps between the wheels and rails necessary for the free passage of the wheel pairs. 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 as 1520 mm with tolerances for the widening side of 6 mm and for the narrowing side of 4 mm. Until 1972, the normal track width on our roads was 1524 mm; its narrowing to 1520 mm was adopted to reduce the gap between the wheels and rails, which, at increased speeds, helps to reduce track disturbances.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 sections of the track over the entire length of each of them.
When constructing a track, the joints on both rail threads are placed exactly opposite each other along a square, which, compared to the arrangement of joints staggered, reduces the number of impacts of wheel pairs on the rails, and also makes it possible to prepare and change the rail and sleeper grid in whole links using track layers.
To prevent each wheel pair from rotating around a vertical axis, the wheel pairs of a carriage or locomotive are connected by two or more rigid frames. The distance between the outer axles connected by the frame is called the rigid base, and between the outer axles of a car or locomotive - the full wheelbase. The rigid connection of the wheel pairs ensures their stable position on the rails, but at the same time makes it difficult to pass in small radius curves, 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 TEZ diesel locomotive, V- FD series locomotive,
G- four-axle gondola car
Features of path design in curves
In curved sections, the track structure has a number of features, the main of which are: the elevation of the outer rail above the inner, the presence of transition curves, widening of the track at small radii, laying of shortened rails on the inner rail thread, strengthening of the track, increasing the distance between the axes of the tracks on double- and multi-track lines.Elevation of outer rail is provided for a curve radius of 4000 m or less so that the load on each rail thread is approximately the same, taking into account the action of centrifugal force, for uniform wear of the outer and inner rails, as well as the suppression of centrifugal acceleration, which negatively affects the ride comfort of passengers. The size of the elevation depends on the speed of trains and the radius of the curve and usually does not exceed 180 mm (in Russia - 150 mm).
It is known that when rolling stock follows a curve with a radius R centrifugal force occurs
where m is the mass of a unit of rolling stock;
G is the weight of a unit of rolling stock;
g - gravity acceleration
When the outer rail is raised by an amount h the weight force component appears N, directed inside the curve.
Diagram of forces acting on rolling stock in a curve when the outer rail is elevated
From the figure it is clear that the ratio H/G is equal to the ratio h/s 1. Therefore H = Gh/s 1.
For equal pressure on the rail threads it is necessary that N balanced I, then the resultant N will be perpendicular to the inclined plane of the path.
Considering that the angle α is small and with a maximum permissible elevation of the outer rail of 150 mm cos α = 0.996, we can assume that H=I.
Then
Where
Substituting s 1 = 1.6 m, g = 9.81 m/s 2 and expressing the speed v in km/h, and the radius R in meters, we obtain the elevation in mm
Since in real conditions trains of different masses Q i and at different speeds pass along curves V i, then for uniform wear of the rails, the root mean square speed is substituted into the given formula
At h=2.5v avg 2 /R in trains traveling at speeds above v cf, passengers and cargo will be subject to an outstanding acceleration equal to the difference between the centrifugal acceleration v 2 /R and acceleration gh/s 1 directed towards the center of the curve
On the roads former USSR the permissible outstanding acceleration is 0.7 m/s 2 and only in exceptional cases 0.9 m/s 2 . When trains move at speeds less than v avg the load on the inner rail will be greater than on the outer one.
To ensure smooth fit of rolling stock, circular curves are connected to straight sections using transition curves. Straight inserts are provided between adjacent curves on the railway minimum value from 30 to 150 m depending on the category of the line and the direction of the curves (in one direction or in different directions).
Devices transition curves is associated with the need for a smooth coupling 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 proportional to the change in length. A curve with this property is a radioidal spiral, the equation of which is expressed as a series
Where WITH- transition curve parameter (С=lR)
Due to the fact that the length of the transition curve l small compared to WITH, in practice it is enough to limit ourselves to the first two terms of the series of the given formula. In the profile, the transition curve in normal conditions is an inclined line with a uniform slope i = h/l.
. NPK- the beginning of the transition curve. PDA- end of the transition curve
Widening gauges are made to ensure that the rolling stock fits into curves. Since the wheel pairs are fixed in the bogie frame in such a way that within the rigid base they are always parallel to each other, in a curve only one wheel pair can be located along the radius, 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 wheel pairs jamming. To freely fit a two-axle bogie into a curve, the required track width is:S c =q max +f n +4
Where f n- arrow bending curve along the outer thread at chord 2λ;
q max - maximum distance between the outer edges of the wheel flanges;
4 - tolerance for narrowing of the track, mm.
Installed the following standards track width in curves:
at R≥ 350 m - 1520 mm;
at R = 349-300 m - 1530 mm,
at R≤ 299 m -1535 mm.
Laying shortened rails into the internal thread is necessary to prevent the joints from running apart. 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 curve radius, it is necessary to have its own amount of rail shortening. For unification purposes, standard shortenings of 25 m long rail links by 80 and 160 mm are used. Total number shortened rails n required for laying in a curve,
n = e/k,
Where e- general 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 the joints does not exceed half the shortening, i.e. 40; 80 mm.
Gain paths in curves are produced 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 Technical Operation of Railways of the Russian Federation
Chapter III. Structures and devices of track facilities. Path plan and profile3.4. The railway track in relation to the radii of curves, the conjugation of straight lines and curves, and 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, no more than 0.0025.
In especially difficult conditions, at sidings and passing 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 the locomotive or cars from the train are not provided, slopes of more than 0.0025 are allowed within the station area. In particularly difficult conditions, with the permission of the Ministry of Railways, slopes of more than 0.0025 are also allowed when extending the receiving and departure tracks at existing stations, provided that measures are taken against the spontaneous departure of cars or trains (without locomotives).
To prevent spontaneous departure of cars or trains (without a locomotive) at stations, sidings and passing points, newly built and reconstructed receiving and departure tracks, which provide for the uncoupling of locomotives from cars and the performance of shunting operations, should, as a rule, have a longitudinal profile with counterslopes in side of the limiting arrows and comply with the standards for its design.
In necessary cases, to prevent the spontaneous exit of cars onto other tracks, provision should be made for the installation of safety dead ends, safety switches, release shoes or switches.
In all cases where stations, sidings and passing points are located on slopes, conditions for starting trains of the established weight norm must be ensured.
3.6. Stations, sidings and passing points, as well as separate parks and exhaust routes 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 - to 500 m.
3.7. The layout and profile of main and station tracks, as well as access roads belonging to the railway, must be subject to periodic instrumental inspection.
The organization of work on instrumental verification of the plan and profile of the tracks, the production of relevant technical documentation, as well as the drawing up 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 this work.
The path distances must have:
- drawings and descriptions of all structures and track facilities available at the distance, as well as relevant standards and norms;
- large-scale and schematic plans of stations, longitudinal profiles of all main and station tracks, marshalling humps, as well as access roads where the locomotives of the road turn.
When constructing new facilities on the territory of the station, expanding or moving existing ones, any organization performing such work must immediately transfer the executive documentation to the head of the track and the head of the station, defining the linking of the facility to the existing development of the station.
1.5.
Rail trackrailway tracks
Interaction between track and rolling stock. Rail track is calleddistance between the inner working edges of the rail heads, measuredlocated 15 mm below the tread surface (at the level of wheel contact with rail head). The main condition for constructing a rail track isensures the safety of trains with installed speedgrowths. The design of the rail track, its dimensions and the magnitude of permissible deviations from the norms depend on the design of the running gear of the moving system.stav and, in turn, affect their design, dimensions and tolerances. Features of the rolling stock chassis are as follows:
- the presence of ridges on the wheels (Fig. 1.78);
- blind attachment of wheels to the axle;
-
constancy of distances between int
early wheel edges;
- parallelism of axes;
- conicity of the rolling surface.
Combs are necessary in order tocontrol the movement of wheels along the rail and prevent derailment.
Blind attachment of the wheel to the axle, in which the wheel rotates along with the axle,eliminates wear on the wheel hub and axle hub and thanks to thisThe wheel must not be tilted, which is dangerous for movement.
Constancy of the distances between the inner edges of the wheels of all axles is necessary to ensure the safety of rolling stock movementalong the track. The distance between the track threads is constant and the compositionis 1520 mm. With this track width, the distance between the inner edges of the wheels is 1440 mm with tolerances of ±3 mm and is called the nozzle
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(see Fig. 1.78). For rolling stock traveling in trains at speeds of more than 140 km/h, tolerances are +3, -1 mm.
Parallelism of the axes is necessary to avoid misalignment of the axes and failurewheels inside the track. To ensure parallelism of the axis, a gesture is combined what frame? Distance between extreme axes remaining parallelOur movement in both straight and curved sections of the path is called
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rigid crew base. Distance between the outer axles of the carriage - the full wheelbase (Fig. 1.79).
The longer the rigid base, the more complexher crew movement in curves. For abouteasier fit into crooked cars,diesel locomotives and electric locomotives with more than three axles are placed on a bogiekakh, combining two or three axes. Gesturewhich crew base will be the distance betweenalong the outer axles of the trolley (see Fig. 1.79). Conicity of the rolling surfaceprovides more even wearwheels and rail heads due tolateral movements of the wheel at vicrew laning with bevel wheelsmi in straight sections of the route. Wheelrolls along the rail mainlysloping rolling surface 1:20, which therefore wears out much more than part, I have The final slope is 1:7 (writing 1.80). Poi one-
A similar surface inclination of 1:20 would result in uneven wear to the rapid formation of local saddle-shaped wear (gutter). Passage along the crosspiece, transition from the frame rail to the point and back if availableGrooved wheel wear is accompanied by sharp shocks and impacts. An inclination of 1:7 promotes uniform wear on the tread surface. In Fig. 1.80 is shown as a dotted line and prevents groove wear. The 1:7 slope and 6:6 chamfer also create favorable conditions for rolling wheels from the pressed tip to the frame rail and back. Comb thickness wheels are allowed according to the PTE (Table 1.6).
Table 1.6
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Track width in straight sections.
Normal track width in straightIn areas and curves with a radius of 350 m or more, there should be 1520 mm between the inner edges of the rail heads (PTE, clause 3.9). The deviations should not exceed -4 mm for narrowing, +8 mm for widening, and -4 mm, +10 mm in areas with speeds of 50 km/h or less. Consequently, the track width ranges from 1530 mm to 1516 mm. In order to to prevent the wheels of the rolling stock from jamming in the rut, in which
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The table shows that the maximum gap for locomotives is 39 mm, and the minimum is 7 mm. For cars, 29 and 5 mm, respectively. The more for sight, the more the rolling stock wobbles in straight lines and the stronger the sidewayshigh impacts of the ridges when running onto the rails.With smaller gaps the movementthe process occurs more smoothly. This is what determined the normal width gauge 1520 mm (reduction by 4 mm compared to the previously existing one).
The top of the rail heads of both rail lines of the track on straight sections must be at the same level. Allowed on straight sections of the routepress one rail thread 6 mm higher than the other throughout the straight section. When one rail thread is raised by 6 mm, the crew slightly it tilts and from this tilt a lateral force will appear, which will lightly press the wheels against the lower thread and make it difficult for them to wobble and move The movement of the rolling stock will be smoother.
Construction of rail tracks in curved sections. For that to fitlearn how to fit rolling stock into curves and move along them, railThe owl track in curves has the following features:
- track widening for radii less than 350 m:
- elevation of the outer rail above the inner rail;
- transition curves in places where straight sections meet curves;
- shortened rails on internal rail threads;
Increased distances between paths when there are two or more paths.
Track width in curves.
Widening the rail gauge in curves is done
For that so that rolling stock with a long rigid base can passalong curves without jamming of wheel sets. Rules of technical operationtations (PTE, clause 3.9) set the track width in curved sections of the track at a radius
From 349 to 300 m.................................................... ................................1530 mm
From 299 m and less................................................... ................................1535 mm
On sections of railway lines where a comprehensive replacement of the rail and sleeper grid has not been carried out, it is allowed on straight and curved sectionsOn tracks with a radius of more than 650 m, the nominal gauge size is 1524 mm. At In this case, on steeper curves, the track width is assumed to be:
At radius
From 650 to 450 m.................................................... ................................1530 mm
From 499 to 350 m.................................................... ................................1535 mm
From 349 m and less................................................... ................................1540 mm
Tolerances on curved sections, as well as on straight sections, should not exceednarrowing -4 mm, widening +8 mm. Track widths less than 1512 mm and more than 1548 mm are not allowed. The transition from the widened gauge to the normal one is made within the transition curve with a deviation of 1 mm/m.
Fitting the rolling stock into the curve can be free,linear and forced. Most favorable for interactionrolling stock and tracks free fit into the rigid base curvelocomotive or carriage (Fig. 1.82). When fitting freely, the comb is front axle wheel is pressed against the outer rail thread and guidesmovement of the crew, and the ridge of the rear axle touches the inner rail thread,in this case, the rear axle is located along the radius of the curve. In this case the gestureThis base is located completely freely in the rail track.
The most unfavorable is jammed fit(Fig. 1.83), in which the outer wheels rest against the outer rail with their ridges thread, and the inner wheels rest against the inner rail thread. Jammed inscription is not allowed, since it is accompanied by significant increased resistance to train movement, excessive wear of the rowing
Rail track- this is the distance between the inner side edges of the rail heads, measured at a level of 13 mm below the rolling surface; in our country, at the beginning of the construction of railways, it was taken to be 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 adopted 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 track width 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 from 349 to 300 m it is equal to 1530 mm, and for curve radii less than 300 m - 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 track width may have an additional widening 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 of ensuring an absolutely accurate gauge width when assembling the rail and sleeper grid and its invariability in operation, tolerances in the gauge content are set at +8 and -4 mm. This means that with a standard of 1520 mm, the track width can range from 1528 to 1516 mm. For curved sections, the same tolerances are applied, but with one limitation - a track width of more than 1548 mm is not allowed in any cases, since such an increase creates the danger of possible expansion by part of the wheel with an increased conicity of the surface.
If permissible train speeds of 50 km/h or less are established on a section, the gauge may be widened by up to 10 mm, and narrowed by 4 mm.
On existing lines, until they are transferred to a 1520 mm gauge, the following gauge width is allowed: on straight sections and in curves with a radius of 350 m or more - 1524 mm; in curves with a radius from 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 gauge widths are still preserved: for radii from 650 to 450 m - 1530 mm; with radii 449 to 350 m - 1535 mm; for radii of 349 m and less - 1540 mm.
Before switching to 1520 mm gauge, it is allowed to maintain the track according to these standards.
In difficult conditions (mountain lines, internal factory tracks, etc.), when very steep curves are used and the track width of 1548 mm is insufficient, additional widening can be allowed, but subject to the installation of counter rails and other devices that exclude the possibility of wheels falling inside the track .
The most favorable is free fit into the curve of the rigid base of a locomotive or car (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 outer wheels in a rigid base are pressed by ridges to the rail. This fit causes very high resistance to the movement of the train and unsafe pressure of the wheels on the rails. An inscription that, by its nature, occupies an intermediate position between free and jammed, is called forced.
On our railways, bogie locomotives (electric and diesel locomotives) and bogie freight and passenger cars are currently in use almost everywhere, 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-wheelbase rolling stock made it possible to unify the width and gauges on straight and curved sections (with a radius of 350 m or more), with the exception of a relatively short length of tracks in mountainous areas, access, connecting, in-plant and station tracks with curve radii of less than 350 m.
When trains pass through curved areas 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 curves, significant overloads of the outer rail threads due to the appearance of centrifugal forces, to facilitate the fitting of rolling stock into curves and passage along them:
- increase the track width;
- prevent distortion of the design curvature of the track;
- outer rail threads are placed higher than the inner ones;
- in places where straight sections of the track meet curves, transition curves are arranged;
- reduce the distance between sleepers;
- lubricate the side surfaces of contact between the wheel flanges and the rails.
The size of the rigid base of locomotives and cars is of great importance for the interaction of rolling stock and track in curves. On the roads of the Russian Federation, mainly bogie locomotives (electric 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-wheelbase rolling stock has much better conditions for passing along curves, and this made it possible to unify the track width on straight and curved sections (with a radius of 350 m or more). Only on a relatively short distance of tracks in mountainous areas, on access, connecting, in-plant and station tracks, where the radii of curves remain less than 350 m, is the gauge widened.
