3 -- DB

Technical  characteristics

Paired taper roller bearings are used where ei- ther the load capacity of single bearings does not meet the requirements,or to overcome the time consuming adjustment under the conditions of a  mass mounting.

Paired taper roller bearings consist of two mat- ched single row taper roller bearings using spa- cers for a specific axial clearance or a preload.

Depending on the particular requirements,such pairs may be supplied arranged either in tandem arrangement (suffix DT),in face to face arrange- ment (suffix DF),or in back to back arrangement

(suffix DB)as shown in the sketch below.

Other arrangements are produced upon order re- quest.

Bearing pairs

Tandem arrangement,suffix DT

Bearings in tandem arrangements are used where the  actual  thrust  force  exceeds  the  load  capacity of a  single  bearing.

In tandem arrangements the thrust forces  are  ac- commodated  in  one  direction  only  and  distribu- ted  to  both  bearings  equally.

Taper roller bearings in tandem arrangement can  only  accommodate  axial  loads  acting  in  one direction,therefore  they  should be mounted against  other  bearing  that supports  axial  loads in the  opposite  direction

In  tandem  arrangement,taper  roller  bearings  re- quire  two   spacers  for   matching  as  a  unit,hence the  desired  total  width  of  the  bearing  arrange- ment  mustbe  defined  when

ordering.

Face to face arrangement,suffix DF

Thrust  forces  are  accommodated  in  both  direc- tions  and  in  each  direction  forces  are  supported by  one  of  matched  the  tapered  roller  bearings.

In  taper  roller  bearings  arranged  face  to  face,  the  load  lines  converge  towards  the  axis  of  the bearings,which   makes   these   arrangements    less suitable  to  support  tilting

moments  due  to  their lower   stiffness

Attention:   for  bearingpairs  arranged  face  to  face the  heating of the shaft will cause either a  reduc- tion  of  axial  internal  clearance  or  an  increase  in preloading   forces.

Back to back arrangement,suffix DB

Thrust  forces  are  accommodated  in  both  direc- tions  and  in  each  direction  forces  are  supported by  one  of  matched  the  tapered  roller  bearings.

Bearings  arranged  back  to  back  provide  very  ri- gid   bearing    arrangements.They   also    effectively support tilting moments because the load lines diverge towards the bearing axis of the

bearings.

Taper roller bearing pairs arranged back to back require two spacers for matching as a unit,the desired total width of bearing arrangement must be defined at ordering.

Misalignment

Generally,taper roller bearings arranged in pairs should not be exposed to misalignments as they may generate considerable additional forces cau- sing high running noise levels.If those

misalign- ments can not be avoided,VEO recommends using the face to face arrangement,due to the lower rigidity of this disposition.

Such additional forces due to misalignment will shorten the service life of taper roller bearings significantly.

Tolerances

Paired VEO taper roller bearings are produced in normal tolerance class (PN)as standard.

These VEO bearings can be produced with closer tolerances according to customer requirements.

The total width tolerance of VEO-taper roller  bearing units arranged face to face consist of the internal axial play of the bearing pair and twice the width deviation of the each single bearing, 

Cages

VEOtaper roller bearings are fitted with pressed steel cages as standard.

Because the cages of taper roller bearings usually protrude   beyond   the   bearing   faces,special care  must  be  taken  to  follow  the   recommended abutment   dimensions.

Internal clearance

VEO  taper   roller  bearing  pairs  arranged  face  to face  (suffix  DF)are  standard   produced  with  axial internal   clearances   values,as   listed   in   thetable below.

When  we  indicate the  suffix  C..(special  clearan- ce),the  two or  three-figure  number  immediately following the  Cgives  themean  axial  internal  clea- rance  in  μm.This  indicates  that the

clearance   is -30/+30   μm   of   this   number,eg.,C200   indicates an axial clearance between  170  μm and 230  μm.

VEO also  produces  other  bearing  units  with  alter- native  internal  clearances  according  to  customer's specifications  on   request.

Veo in the face layout becomes a shaft internal gap of the axial direction of the cone roller bearings

Minimum   load

For effective operation of taper roller bearings a minimum bearing load of approximately 2%of the dynamic load rating Cr is required.

Equivalent  dynamic  bearing  load

In the case of single row taper roller bearing pairs arranged face to face the following formula should be used:

    then:P=F,+Y₁·Fa

or when  then:P=0,67·F,+Y₂·F

F₂and F,indicate the forces acting on the bearing pairs.

Equivalent  static  bearing  load

When single row taper roller bearings are arran- ged in pairs face to face the equivalent static load on the bearing unit is:

Po 。=F,+Y₀·F

Abutment   and   fillet   dimensions

Paired single row taper roller bearings must be supported axially by surrounding machine com- ponents in a satisfactory manner.

The bearing rings,however,must contact adja- cent parts with their side faces only.

The bearing chamfers must not contact the shoul- der fillet radii of shaft or housing shoulders.

Therefore,the  largest  fillet   radius(rg)must  be kept smaller than the minimum fillet dimension of the bearing rings(rs)as listed in the bearing tables

Recommendations  for  the  dimensions  of  adjacent parts  are  given  in  DIN  5418(Mounting  dimensions of rolling  bearings),as  well  as  in  the  bearing  ta- bles.

Supplementary designations

The  product  tables  show  the  standardized  bea- ring  configurations  updated  on  the  edition  of  this catalogue.These   standardized   configurations   co- rrespond to  suffix  or  suffixes  of

each  bearing.

In   any   case,VEO   can   offer,under   requirement, alternative   designs,comprising   the   ones   showed in   the   following   table   or   many   others,whose mention  exceeds  the  purpose  of

the  present  ca- talogue,and   can   be   found   in   specific   technical publications  of  concrete  applications  or  series  of specific   bearings.

Should  you  need  a  special  design  not  existent  in these  pages,please  contactour  Sales   Department  in VEO Bearings Europe.