Home Page T-51 overloaded  which  may  cause  an  edge cord  failure  that  propagates  across  the entire belt width.  Angular misalignment often results in high belt-tracking forces as  well  which  cause  accelerated  belt edge wear, sometimes leading to flange failure or belts tracking off of the pulleys. Parallel:    Parallel  misalignment results from pulleys being mounted out of line from each other (see Figure 26). Parallel misalignment is generally more of a concern with V-type belts than with synchronous belts because V-type belts run in grooves and are unable to free float on the pulleys.  Synchronous belts will generally free float on the pulleys and essentially self-align themselves as they run.  This self- aligning can occur as long as the pulleys have sufficient groove face width beyond the width of the belts.    If  not,  the  belts  can  become  trapped  between  opposite  pulley  flanges  causing  serious performance problems.  Parallel misalignment is not generally a significant concern with synchronous drives  as  long  as  the  belts  do  not  become  trapped  or  pinched  between  opposite  flanges.    For recommendations on groove face width, see Table 34, on page T-65. Allowable  Misalignment:    In  order  to  maximize  performance  and  reliability,  synchronous drives  should  be  aligned  closely.    This  is  not,  however,  always  a  simple  task  in  a  production environment.  The maximum allowable misalignment, angular and parallel combined, is 1/4°. 11.2   Practical Tips Angular  misalignment  is  not  always  easy  to  measure  or  quantify.    It  is  sometimes  helpful  to use the observed tracking characteristics of a belt, to make a judgment as to the system's relative alignment.  Neutral tracking "S" and "Z" synchronous belts generally tend to track "down hill" or to a state of lower tension or shorter center distance when angularly misaligned.  This may not always hold  true  since  neutral  tracking  belts  naturally  tend  to  ride  lightly  against  either  one  flange  or  the other  due  to  numerous  factors  discussed  in  the  section  on  belt  tracking.    This  tendency  will generally hold true with belts that track hard against a flange.  In those cases, the shafts will require adjustment to correct the problem. Parallel  misalignment  is  not  often  found  to  be  a  problem  in  synchronous  belt  drives.    If clearance  is  always  observable  between  the  belt  and  all  flanges  on  one  side,  then  parallel misalignment should not be a concern. SECTION 12    INSTALLATION AND TAKE-UP 12.1   Installation Allowance When  designing  a  drive  system  for  a  manufactured  product,  allowance  for  belt  installation must be built into the system.  While specific installation allowances could be published, as they are for  larger  industrial  belt  drives,  small  synchronous  drive  applications  are  generally  quite  diverse, making it nearly impossible to arrive at values that apply in all cases.  When space is at a premium, the necessary installation allowance should be determined experimentally using actual production parts for the best possible results. 12.2   Belt Installation During  the  belt  installation  process,  it  is  very  important  that  the  belt  be  fully  seated  in  the Fig. 26    Parallel Misalignment