High Quality OEM service bearings 30211 Tapered roller beairngs

Specifications

  High Quality OEM service bearings 30211 Tapered roller beairngs

Description of tapered roller bearings:

Tapered roller bearingsare bearings that can take large axial forces (i.e., they are good thrust bearings) as well as being able to sustain large radial forces.

The inner and outer ring raceways are segments of cones and the rollers are also made with a taper so that the conical surfaces of the raceways and the roller axes if projected, would all meet at a common point on the main axis of the bearing.

Tapered roller bearings have the rolling elements under the form of frustra of cones. They roll on tapered surfaces which, if extended, converge towards a single point on the bearing axis.The rollers are guided tangentially by the cage and axially by the big rib of the outer ring, on which they have point contact. As between rollers and raceways there is linear contact, tapered roller bearings can take heavy radial loads. They can also take heavy axial or combined loads, depending on the contact angle caused by the tapered rolling elements. The contact angle is the angle of the outer raceway generatrix. Tapered roller bearings can be manufactured in the versions : single, double and four row rollers.Basic types and constructive versions:

-single row

Single row tapered roller bearings

Single row tapered roller bearings are of separable design, i.e. the outer ring and the inner ring with rollers and cage assembly can be separately mounted. These two assemblies are interchangeable.

Tapered roller bearings can be manufactured both in standardized constructive versions with dimensions series 320, 302, 322, 303, 323, 313 and with non-stand-ardized dimensions, mm or inch.

Tapered roller bearings can carry only single direction axial loads. Under pure radial loads, an axial force occurs which is supposed to distance the bearing rings in axial direction. Therefore, tapered roller bearings are generally pair mounted on both ends of the shaft, in X or O arrangements, so that the shaft will be axially located in both directions (table 4). Thus, the optimum clearance in these two bearings can be adjusted.

Single row tapered roller bearings can also be manufac-tured with rib on the outer ring. This design is to be used when the housing cannot be manufactured with shoulder, but only with a passed through bore. In this case, axial location can be provided by the bearing ring.

Paired single row tapered roller bearings

If tapered roller bearings are pair mounted in X or O arrangements, the load carrying capacity increases and loads can be taken in both directions in the same bearing.

These bearing sets have guaranteed clearance after mounting since the distance rings are mounted between the bearing rings.

For certain applications, paired bearings can be delivered with small clearance or lightly preloaded.

 Double row tapered roller bearings

Double row tapered roller bearings are used where load carrying capacity should be greater, loads should be taken in both directions and axial space is smaller than in case of a set of two single row tapered roller bearings.

Double row tapered roller bearings can have the rollers in face- to-face arrangement, double inner ring and two outer rings respectively or the rollers in back-to-back arrangement, i.e. double outer ring and two inner rings.

The first design provides greater stiffness, can take tilting moments and shaft expansions can be compen-sated.

The bearings of the second design can be manufac-tured with tapered bore so that they can be frequently mounted dismounted.

Double row tapered roller bearings can have or not distance rings with lubrication holes, mounted between the simple rings.

In case of bearings with distance rings, the bearing clearance or preload are pre-adjusted; in case of those without distance rings, bearing clearance and preload can and should be adjusted while mounting.

Double row tapered roller bearings with rollers in back-to-back arrangement can also be manufactured in the following two versions:

-with rib on the outer ring; the housing has no shoulder and the bearing is axially located by the rib;

-with two seals; this design is used in motor vehicles construction. The bearings are delivered filled with grease and relubrication is not needed.

Dimensions

Tapered roller bearings are manufactured with the fol-lowing dimensions:

-metric dimensions (mm), according to ISO 355;

-inchdimensions;

Misalignment

As between rollers and raceway there is a linear contact, tapered roller bearings have low capacity to compensate for errors of alignment between shaft and housing.

Permissible values of misalignment between shaft and housing are given in table 1, depending on bearing size and load magnitude.

 Tolerances

Tapered roller bearings are generally manufactured to the normal tolerance class ISO and AFBMA, respectively (for bearings with inch dimensions).For certain applications (e.g. bearings for machine-tools), they can be also manufactured to tolerance classes P5 and P6X or 3 AFBMA.

Single row tapered roller bearings have the outer rings interchangeable with the inner ring - rollers - cage assembly (if they have the same mark) and also with bearings produced by other companies, according to ISO and AFBMA respectively.

The parts of the two and four row tapered roller bearings are non-interchangeable.

Radial and axial clearance

In case of tapered roller bearings, clearance should be in radial direction, but it is measured and adjusted in axial direction. As tapered roller bearings are dismountable, their clearance is not guaranteed by design and it is adjusted while mounting. Thus, optimum clearance can be obtained for that application.

 In case of double and four row tapered roller bearings with distance rings between bearing rings, the clearance is guaranteed and its values are given in table 2. The bearing parts are numbered for each bearing so that the prescribed clearance on each row should be observed while mounting.

 Cages

Small and medium sized tapered roller bearings are generally fitted with pressed sheet cages. Large sized bearings are generally fitted with machined steel or brass cages, with welded pins. In some cases, median or large sized bearings can also be fitted with machined steel or brass cages. In all cases, the cage is guided on rollers. For small and medium sized bearings, glass fibre rein-forced polyamide 6.6 cages can be successfully used if the operating temperature doesn't exceed +120°C. They have low weight, are noiseless in operation and have low coefficient of friction.

Designs and some technical data are given in table 3.

 Equivalent dynamic radial load

Equivalent dynamic radial load can be calculated using the following equations:

-for single row tapered roller bearings: P_r = F_r, kN, ??? when F_a/F_r <=e

P_r = 0,4 F_r + Y F_a, kN, when F_a/F_r > e

-for paired bearings and double or four-row tapered roller bearings: 

                                                          P_r = F_r + Y₁ F_a, kN, when F_a/F_r <= e

       P_r = 0,067 F_r + Y₂ F_a, kN, when F_a/F_r > e

For single row tapered roller bearings, the Fa values can be calculated using the equations in table 4. These equa-tions are available when bearings are mounted so that axial clearance is in fact zero without preloading. FrA and FrB should always be considered as being positive, even if they act in the opposite direction to that in the figure.

In case of paired bearings and of double or four row tapered roller bearings, F_a and F_r are the loads acting upon the paired bearings or single bearings.

The values of e, Y, Y₁ and Y₂ are given in bearing tables.

Equivalent static radial load

 Equivalent static radial load can be calculated using the equations:

-for single row tapered roller bearings:

                                                    P_0r = F_r, kN,     when F_a/F_r <=1/2 Y₀

P_0r = 0,5 F_r + Y₀ F_a, kN, when F_a/F_r > 1/2 Y₀

-for paired bearings and double or four-row tapered roller bearings:

P_0r = F_r + Y₀ F_a, kN

  F_a is calculated as in case of equivalent dynamic radial load. The values of Yo are given in bearing tables.

 Abutment dimensions

  The mounting dimensions of tapered roller bearings are given in the bearings tables, for single row tapered roller bearings. These dimensions are also available for bear-ings with ribs and for standardized paired bearings. For the other types of tapered roller bearings, the mounting dimensions should be adapted depending on the cross section size and mounting chamfer.