Home Page T-45 angular shaft alignment, resulting in belt movement. Belt Installation Tension:  Belt tracking is sometimes influenced by the level of belt installation tension.    The  reasons  for  this  are  similar  to  the  effect  that  varying  torque  loads  have  on  belt tracking. When problems with belt tracking are experienced, each of these potential contributing factors should  be  investigated  in  the  order  that  they  are  listed.    In  most  cases,  the  primary  problem  will probably be identified before moving completely through the list. 9.8   Pulley Flanging Pulley guide flanges are necessary to keep synchronous belts operating on their pulleys.  As discussed previously in Section 9.7 on belt tracking, it is normal for synchronous belts to favor one side of the pulleys when running. Proper flange design is important in preventing belt edge wear, minimizing noise and preventing the belt from climbing out of the pulley.  Dimensional recommendations for custom-made or molded flanges are included in tables dealing with these issues. Proper flange placement is important so that the belt is adequately restrained within its operating system.  Because design and layout of small synchronous drives is so diverse, the wide variety of flanging situations potentially encountered cannot easily be covered in a simple set of rules without finding exceptions.  Despite this, the following broad flanging guidelines should help the designer in most cases: Two Pulley Drives:  On simple two pulley drives, either one pulley should be flanged on both sides, or each pulley should be flanged on opposite sides. Multi  Pulley  Drives:    On  multiple  pulley  (or  serpentine)  drives,  either  every  other  pulley should be flanged on both sides, or every pulley should be flanged on alternating sides around the system. Vertical Shaft Drives:  On vertical shaft drives, at least one pulley should be flanged on both sides, and the remaining pulleys should be flanged on at least the bottom side. Long Span Lengths:  Flanging recommendations for small synchronous drives with long belt span  lengths  cannot  easily  be  defined  due  to  the  many  factors  that  can  affect  belt  tracking characteristics.    Belts  on  drives  with  long  spans  (generally  12  times  the  diameter  of  the  smaller pulley  or  more)  often  require  more  lateral  restraint  than  with  short  spans.    Because  of  this,  it  is generally a good idea to flange the pulleys on both sides. Large  Pulleys:    Flanging  large  pulleys  can  be  costly.    Designers  often  wish  to  leave  large pulleys unflanged to reduce cost and space.  Belts generally tend to require less lateral restraint on large pulleys than small and can often perform reliably without flanges.  When deciding whether or not  to  flange,  the  previous  guidelines  should  be  considered.    The  groove  face  width  of  unflanged pulleys  should  also  be  greater  than  with  flanged  pulleys.    See  Table  34,  on  page  T-65  for recommendations. Idlers:    Flanging  of  idlers  is  generally  not  necessary.    Idlers  designed  to  carry  lateral  side loads from belt tracking forces can be flanged if needed to provide lateral belt restraint.  Idlers used for this purpose can be used on the inside or backside of the belts.  The previous guidelines should also be considered.