The springs are manufactured in accordance with regulations or standards like DIN EN 14200 or according to the specifications of the applicable UIC sheets. Forged spring brackeds are generally used for standard springs in the freight waggon sector. For special springs like for passenger coaches, pioneer trains, locomotives or narrow-gauge railways, it is no longer possible to forge bundles in small quantities. In such cases we use burned spring brackeds. But here too, the quality is checked and ensured before using by the expansion test according to UIC 821.
Standard leaf springs / trapezoidal springs for freight wagons are still made from ribbed spring steel in the dimensions 120×16 according to EN10092-2 (formerly ribbed steel according to DIN 1570). However the dimensions 90×13 or 90×16 are still used for older types of springs. There are many springs, especially in the narrow gauge area, that require smaller dimensions. Here is often no possibility to obtain this dimension as ribbed spring steel. In such cases we manufacture the springs in consultation with the customer from flat spring steel with a pressed-in end rib. Similar to the ribbed spring steel, the end rib fulfills the function of guiding the spring leaves laterally.
Thanks to our large material store for ribbed and flat spring steel we have access to almost all the necessary dimensions. If the required dimension is not in stock we can usually create the desired cross-section by reworking (milling to width / grinding to thickness) out of an bigger dimension.
Parabolic springs for freight wagons are usually made of material 1.8159 / spring steel according to EN10089: 51CrV4 (formerly 50CrV4) in a width of 120 mm.
Leaf springs / trapezoid springs
The traditional leaf spring / trapezoidal spring consists of several stacked spring leaves of decreasing length. The contact surfaces of trapezoidal springs are greased (graphite-containing grease) before assembly. Standard springs for freight wagons generally consist of 8 or 9 spring leaves with a spring length of 1200 or 1400 mm (elongated dimension of the main spring leaf).
The main spring leaf or the so-called main layer, together with the spring bracked, ensures that the spring is guided in the vehicle. The main spring leaf can have different ends (see e.g. DIN 5542):
The classic leaf spring for freight cars is a single-stage spring. This means that there is only one load level and the spring has a linear force / displacement curve.
In most cases, the spring bracked of a leaf spring is pressed warm (glowing red).
A solvent-based paint or primer is recommended for corrosion protection in new production, as a water-based paint will not stick to the sides of the spring leaves if the grease residue of the graphite-containing fat is possible. In the area of repair / refurbishment, the leaf springs are usually preserved with Elaskon 20/35. In principle, however, the type of corrosion protection should always be agreed together.
Parabolic springs for rail vehicles consist of a few spring leaves of the same length (usually 4 to 5 leaves) with a constant width (standard width in the freight car area = 120mm). In the spring-effective area, the individual spring leaves are rolled out parabolically. This means that the leaf thickness between the spring bracked and the leaf end / contact surface follows the function of a square parabola as follows:
h(x) = thicknes of leaf; hP = hight of theoretical parabola; l = length of leaf (one side)
Since the leaf thickness would run towards zero due to the function towards the end of the spring arm, the non-resilient end area of the lower spring leaves is usually allowed to run out in a uniform leaf thickness in practice. In the main spring leaf, however, the area of the spring eye is kept somewhat thicker in practice than in the lower spring leaves due to the greater load in order to achieve a sufficient eye wall thickness.
Due to the special manufacturing process of these springs and the increase in residual stress due to shot peening under pre-tension, the spring leaves must not touch in this area and are structurally separated from each other by air gaps.
Probably the most commonly used form of parabolic spring in freight cars is the two-stage spring. This means that there are two load levels. The second load level does not apply from the beginning, but only takes effect from a defined load state.
The spring bracked of a parabolic spring is always pressed cold, since a warm pressed bracked can have a negative effect on the previously created residual stress.
In contrast to trapezoidal springs, the individual spring leaves of parabolic springs are already provided with corrosion protection before assembly. After assembly, the entire spring is then covered again with a covering layer. In principle, however, the type of corrosion protection should always be agreed together.
General recommendations for leaf springs / trapezoidal springs and parabolic springs for rail vehicles
we recommend repairs / refurbishments at: