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Baseplate assembly protective element and liners for a friction wedge in the trolley of a cargo railway car

The objects of the operating tests were the experimental samples of elements made of polymer composite material (PCM) Oxafen intended for increasing wear resistance of the elements of the supporting assembly "center plate-baseplate" and of the friction wedge of the vibration dampener assembly of the trolley a cargo railway car of the type 18-100.

The following experimental elements were tested:

- wear-resistant gaskets in the shape of disks installed in the base plates of bolster beams;

- wear-resistant liners for friction wedges.
Executive summary
1. At the VNIIZhT Experimental Ring there were conducted operating tests of experimental elements made of PCM Oxafen:

  • wear-resistant gaskets in the shape of disks for the "canter plate-baseplate" assembly of the bolster beam of the cargo railway car trolley;
  • wear-resistant liners for friction wedges of the vibration dampener assembly of the cargo railway car trolley.

In the process of operation, the listed elements experience significant dynamic, static, impact and frictional effects.

2. The performed operating tests of gaskets in the shape of disks made of Oxafen material for the base plates of bolster beams showed that the usage of these gaskets can provide maintenance-free operation of the supporting assembly "center plate-baseplate" of the cargo railway car trolley under the conditions of the total network mileage of not less than 500 thousand km.

3. The measurement of the relative friction coefficient of the spring suspension unit of the trolley equipped with friction wedges with liners, carried out in accordance with the VNIIZhT standard procedure, showed that the average value of the indicator (coefficient) corresponds to the level for the loaded mode of operation for railway cars, standardized in accordance with GOST 9246-03.

4. A preliminary analysis of the results of tests of the experimental liners for friction wedges made of Oxafen material showed that they are operable in the friction unit of the vibration dampener of the cargo railway car trolley. With a railway car mileage at the VNIIZhT Experimental Ring corresponding to 300 thousand km of the total network mileage, the wear and tear of the beam-wedge friction couple is within the standard values. When using liners for friction wedges made of Oxafen material, the wear and tear of the surfaces of the bolster beam and the friction wedge can be minimized.
Methodology
The experimental samples of the disks were made according to the drawing TVG.010.00.003A, the liners for the friction wedges – according to the drawing TVG.010.00.001D.

The trolleys equipped with these elements were included in an experimental train weighing about 8,000 tons, which cruised along the second ring track of the VNIIZhT Experimental Ring at a constant average speed of 70 km/hr with the design load of 23.5 tons/axis.

The trolleys equipped with liners for the friction wedges were installed on the railway cars No.No. 60706371 and 60705613. The trolleys equipped with gaskets in the shape of disks for the base plates were installed on the railway cars No.No. 60706371, 67812776 and 65457558.

Periodic commission inspections of the railway cars with the lifting of the body and the rolling out of the trolleys were carried out in the railway car shop of the Experimental Ring. Before installation on the trolley, all the experimental elements made of PCM underwent the incoming inspection with regard to two indicators: appearance and conformity of their geometrical dimensions to the design documentation.
The results of the incoming inspection showed the following:

- in terms of their appearance, the tested elements entailed no negative comments; all the surfaces were smooth, without hazing, blow holes, cracks, cavities and swelling;

- the actual geometric dimensions of the elements corresponded to the drawing figures, with the exception of the following comments.

The initial thickness of the gaskets in the shape of disks was 7.2-7.4 mm, which is somewhat greater than the figure from the drawing (6.5 mm), which was originally calculated for steel gaskets. According to VNIIZhT experts, such a deviation is acceptable, since the polymeric material used for the manufacture of the elements has a sufficiently low hardness and high plasticity, in contrast to steel 30HGSA.

For most of the liners for the friction wedges, the actual diameter of the central guide pin was slightly greater (by 0.1-0.2 mm) than the diameter of the counter fitment hole in the wedge. This prevented a tight fit of the liners and, ultimately, led to breakdown of the pins. It should be noted that the guide pins of the liners in this design are not fitment ones. The fitment places are the grooves on the inner surface of the liners, which fit the fitment ribs on the inclined surface of the friction wedge. Initially, the guide pin was designed for polyurethane gaskets. For polyurethane liners, the pins could be pressed tightly into the holes due to the high elasticity of polyurethane.
During commission inspections, the condition of the surfaces and the wear and tear of the polymeric experimental elements were recorded, depending on the mileage.

The measurements were carried out using a caliper, designed for external and internal measurements (for example, SHTS-11-200 or an equivalent). The measurement error was ± 0.05 mm.

For the base plate gaskets in the shape of disks, measurements were made of their thickness along the outer and inner perimeter.
The wear and tear were determined according to the formula:

I = l1 – l2,

where l1 – the characteristic size of the element before the operating tests;

l2 – the characteristic size of the element measured after a certain run of the railway car.
The degree of wear and tear of the liners for the friction wedges was estimated from the change in their thickness, measured from the working (supporting) surface of the wedge to the surface of the fitment groove.

The evaluation of the test results was carried out taking into account the correspondence coefficient of the testing conditions with the Experimental Ring operating conditions in the railway network. According to the VNIIZhT method, the coefficient of this correspondence is approximately 3. It is assumed that the mileage at the VNIIZhT Experimental Ring equal to 160 thousand km corresponds to 500 thousand km of the general network mileage.

Tests of gaskets in the shape of disks in the center plate-baseplate assembly

The results of the operating tests of the gaskets in the shape of disks are presented in Table 1.
Table 1. Results of operating tests of gaskets in the shape of disks
The indicated test results testify that:
  • At the first stage (before 60 thousand km of mileage) there was no wear and tear of the disks. At the same time, in a number of cases, a certain thickening of the outer edge of the discs was observed, due to which, obviously, the process of their layer-by-layer wear and tear occurred later on.
  • The degree of wear and tear in the tested gaskets is not the same. It amounted to 0 to 3.3 mm at the mileage of 150-154 thousand km and to 1 to 3 mm at the mileage of 170-180 thousand km. This may be due, inter alia, to the different quality of the surface of the baseplate and the center plate on different bolster beams.
  • During commission inspections, a mirror mating of the bearing surfaces of the baseplate and center plate between which a polymeric disk was inserted was observed. With the increase in the mileage, the appearance of a thin layer of the material transferred from the disk to the metal was observed on the bearing surfaces of the baseplate and center plate. There was no wear and tear of the surfaces of the baseplate and center plate.
  • The main purpose of the disk gasket is to protect the bearing surfaces of the baseplate and center plate from damage and wear and tear. As a result of the tests it was shown that this goal was achieved.
The requirements for wear resistance of contacting surfaces are determined based on the condition that the wear and tear of the latter does not exceed the normative values before the first major overhaul of the railway cars. For the railway cars already in operation, the requirement of a maintenance-free run of 500 thousand km is established.

The total mileage of the railway cars with the experimental gaskets at the VNIIZhT Experimental Ring was from 200 to 230 thousand km, which corresponds, according to the VNIIZhT method, to the total network mileage of 600-720 thousand km.

At the same time, the maximum wear and tear of Oxafen gaskets in terms of 500 thousand km of the total network mileage was less than 3 mm, which corresponds to the normative requirements for the bearing surface of the "center plate-baseplate" assembly.
Taking into account the results of the tests carried out, the gaskets in the shape of disks made of Oxafen material can provide a maintenance-free run of the "center plate-baseplate" assembly of the trolley of the 18-100 cargo railway car up to 500 thousand km.
The results of operating tests of the Oxafen liners installed on the friction wedges of the vibration dampener assembly are shown in Table 2.
Table 2. Results of operating tests of experimental liners for friction wedges
The indicated test results testify that:
  • No damage was found on the working surfaces of all the tested liners. Some liners under the influence of operational factors had minor splits (with an area of not more than 1 cm 2) outside the working surface. The inclined surfaces of the bolster beams adjoining the wedges were in good condition, they were smoothly ground without wear and damage to the surfaces.
  • The VNIIZhT staff, in accordance with the standard methodology, measured the coefficient of relative friction of the spring suspension unit of the trolley, which includes friction wedges with liners. The measurements showed that the average value of the coefficient of relative friction practically corresponds to the level of this indicator standardized by GOST 9246-03 for the loaded mode of operation of a railway car.
The mileage of the railway car with the experimental liners totaled 99 thousand km, which, according to the VNIIZhT method, corresponds to 300 thousand km of the total network mileage.

In accordance with the repair rules, the total wear of the beam-wedge friction pair must not exceed 3 mm per 100 thousand km of mileage.

From the preliminary analysis of the test results it follows that the Oxafen liners are operable in the friction unit of the vibration dampener of the cargo railway car trolley. With their usage, the wear and tear of the surface of the bolster beam and the friction wedge can be minimized.
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