The thick-walled outer rings of the track rollers can support high radial loads. If these track rollers are used against a shaft as a raceway, the outer rings undergo elastic deformation, Figure 1.

Compared to rolling bearings supported in a housing bore, track rollers have the following characteristics:

• modified load distribution in the bearing. This is taken into consideration by the basic load ratings C_r w and C_0r w that are decisive for life calculation.
• bending stress in the outer ring. This is taken into consideration by the permissible radial loads F_r per and F_0r per. The bending stresses must not exceed the permissible strength values of the material (due to the risk of fracture).

For bearings under dynamic circumferential load, the effective dynamic load rating C_r w is used.
C_r w is used to calculate the basic rating life.

The permissible dynamic radial load F_r per must not be exceeded.

If the basic static load rating C_0r w is lower than the basic dynamic load rating C_r w, C_0r w is used.

For bearings under static load, when stationary or with only infrequent motion, the effective static load rating C_0r w is used. C_0r w is used to calculate the static load safety factor S₀.

The permissible static radial load F_0r per must not be exceeded.

In addition to the permissible radial load of the bearing, the permissible radial load of the mating track must also be taken into consideration.

The basic load ratings stated are valid only in conjunction with a shaft as a mating track that is hardened (at least 670 HV) and ground (R_a 0,3).

The fatigue limit load C_ur w is defined as the load below which – under laboratory conditions – no fatigue occurs in the material.

The general methods for calculating the rating life are:

• the basic rating life to DIN ISO 281
• the adjusted rating life to DIN ISO 281
• the expanded calculation of the adjusted reference life to DIN ISO 281-4.

These methods are described in Catalogue HR1, Rolling Bearings, in the section Technical Principles, Load carrying capacity and life.

In comparison with Catalogue HR1, Rolling Bearings, the following values must be exchanged:

• C_r = C_r w
• C_0r = C_0r w
• C_ur = C_ur w.

The carriages LFCL, LFL..-SF, LFLL, LFKL and the bogie carriage LFDL contain four track rollers LFR.

The equivalent principle applies here. The corresponding parameters are taken into consideration in the basic load ratings C_y, C_0y, C_z, C_0z and the permissible moment ratings M_0x, M_0y and M_0z.

In the case of track rollers with a profiled outer ring, calculation is carried out exclusively by means of the basic rating life to DIN ISO 281.

The operating life is the life actually achieved by a rolling bearing. It may differ significantly from the calculated rating life.

This may be due to wear or fatigue as a result of:

• deviations in the operating data
• insufficient or excessive operating clearance (roller, guideway)
• contamination
• inadequate lubrication
• operating temperature too high or too low
• reciprocating motion with very small stroke length, which can lead to false brinelling
• vibration – false brinelling
• very high shock loads (static overloading)
• prior damage during installation.

Due to the variety of installation and operating conditions, it is not possible to precisely determine the operating life in advance. The most reliable way of arriving at a close estimate is by comparison with similar applications.

The parameter for static loading is the static load safety factor S₀. This indicates the security against impermissible permanent deformations in the bearing and is determined by means of the following formula:

Track rollers are regarded as heavily loaded at a static load safety factor of S₀ ＜ 4.

For applications with normal operating conditions, a value S₀ ＞ 4 is required.

When using individual track rollers, for example in conjunction with guideways, the permissible load of the guideway should be taken as decisive where necessary.

Static load safety factors S₀ ＜ 1 lead to plastic deformations of the rolling elements and raceway, which can impair smooth running. This is only permissible for bearings with small rotary motions or in secondary applications.

In order to ensure that the outer ring is driven and to prevent slippage or lifting of the track roller from the mating track, the track rollers must be subjected to a minimum load in dynamic operation.

In general, the minimum load is determined by the ratio C_0r w/F_r ＜ 60.

If shafts with a lower surface hardness are used (such as X46, X90), a hardness factor must be applied, see formula and Figure 3.