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Precision Tapered Roller Bearings

Minimum load
In order to provide satisfactory operation, tapered roller bearings, like all ball and roller bearings, must always be subjected to a given minimum load, particularly if they are to operate at high speeds or are subjected to high accelerations or rapid changes in the direction of load. Under such conditions, the inertia forces of the rollers and cage, and the friction in the lubricant, can have a detrimental influence on the rolling conditions in the bearing arrangement and may cause damaging sliding movements to occur between the rollers and raceways.
 
The requisite minimum radial load to be applied to standard tapered roller bearings can be estimated from

 

Frm = 0,02 C
Where
Frm
=
 minimum radial load, kN
C
=
 basic dynamic load rating, kN (see product table)

 

When starting up at low temperatures or when the lubricant is highly viscous, even greater minimum loads may be required. The weight of the components supported by the bearing, together with external forces, generally exceeds the requisite minimum load. If this is not the case, the single row tapered roller bearing must be subjected to an additional radial load, which can be achieved easily by applying preload. For additional information, refer to the section “Bearing preload”.
 
 
Equivalent dynamic bearing load
P
=
 Fr when Fa/Fr =re
P
=
 0,4 Fr + Yfa when Fa/Fr >re
The values of the calculation factors e and Y
can be found in the product tables.

 
 
 
Equivalent static bearing load
P0 = 0,5Fr + Y0Fa
When P0 < Fr, P0 = Fr should be used. The value of the calculation factor Y0 can be found in the product table.

 

Determination of axial load
When a radial load is applied to a single row tapered roller bearing, the load is transmitted from one raceway to the other at an angle to the bearing axis and an internal axial force will be produced in the bearing. It must be considered when calculating the equivalent bearing loads for bearing arrangements consisting of two single bearings and/or bearing pairs arranged in tandem.
 
The necessary equations are provided in table 3 for the various bearing arrangements and load cases. The equations are only valid if the bearings are adjusted against each other to practically zero clearance, but without any preload. In the arrangements shown, bearing A is subjected to a radial load FrA and bearing B to radial load FrB. Values of the loads FrA and FrB are always considered positive even when they act in the direction opposite to that shown in the figures. The radial loads act at the pressure centres of the bearings (dimension a in the product table).
 
In addition to an external force Ka acts on the shaft (or on the housing). Cases 1c and 2c are also valid when Ka = 0. Values of the factor Y can be found in the product table.
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