FLYWHEEL BALANCE WEIGHTS TESTING AND ADJUSTING SUBJECT: Flywheel  Balance  Weights  On  D348,  0349  And  3412  Engines  With  Single-Bearing Generators BUSINESS: Building Services, Marine/Petroleum, Material Handling PRODUCT/APPLICATION: Engines With Single-Bearing Generators, Generator Sets On  D348  and  D349  Engines,  a  flywheel  balance  weight must  always  be  installed  when  making  a  single-bearing generator   installation.      On   3412   Engines   a   flywheel balance weight is required if the single-bearing generator rotor  weight  supported  by  the  flywheel  exceeds  800  lb (363   kg).      The   purpose   of   this   balance   weight   is   to minimize linear, first order vibration. Generator    manufacturer's    normally    balance    a    rotor within  very  small  deviation  limits.    Assuming  the  rotor  is balanced, there are two other   requirements  which  must be   met   before   the   exact   amount   and   location   of   the balance weight can be determined. 1. The  rotor  must  be  accurately  aligned  on  center with the crankshaft. 2. The flywheel supported weight must be known. Two   different   methods   are   used   with   single-bearing generators to center the rotor with the crankshaft. 1. Stamped,   close   tolerance,   drive   plates   center the rotor into one of the outer flywheel drive pilot bores. 2. An  extension  of  the  rotor  shaft  with  a  machined pilot  diameter  centers  the  rotor  directly  into  the flywheel pilot bearing bore. Rotor  alignment,  with  drive  plates  establishing  the  pilot into  the  flywheel,  is  subject  to  toleranced  variations  of several   parts.      The   accuracy   of   alignment   with   this method  is  not  adequate  to  allow  the  predetermination  of balance   weight   to   compensate   for   the   effect   of   rotor weight.    A  trial  and  error  method  is  required  to  reduce linear,  first  order  vibration  to  an  acceptable  level.    The procedure  is  discussed  in  EDS  73.1  under  Correction Action. An  extended  piloted  rotor  shaft  inherently  centers  and aligns  the  rotor  directly  into  the  flywheel    pilot-bearing bore.      The   drive   plates   then   retain   the   rotor   in   this centered  position  when  secured  to  the  flywheel.    This accurate initial alignment allows predetermining selection   and   location   for   adding   a   flywheel   balance weight. The   balance   weight   should   be   added   at   the   proper location  prior  to  installing  the  generator  with  extended rotor shaft pilot.  The amount of balance weight required depends  upon  rotor  weight  supported  by  the  flywheel. See  Figure  1  for  determining  flywheel  support  weight  or consult the generator manufacturer.  Charts A, B, and C list   the   appropriate   weight   for   ranges   of   rotor   weight supported   by   the   flywheel.      Figure   2   shows   flywheel locations for adding the required weight. No  operational  function  is  performed  by  the  extended shaft;    however,    it    is    recommended    for    applications where   balance   weight   is   required   to   counteract   the effects   of   crankshaft   supported   weight.      The   major advantage  being  selecting  and  installing  balance  weight before    assembly    virtually    eliminates    trial    and    error balancing after assembly. A  generator  manufactured  with  an  extended  rotor  shaft pilot  is  preferred  and  can  be  supplied  by  the  generator manufacturer.      Generators   without   an   extended   rotor shaft may be converted with a bolt-on extension.  Figure 3 has recommended dimensions. A bolt on shaft extension introduces additional machining  tolerances.    However,  if  carefully  made  and assembled to the rotor, the 109