Engines  fitted  with  the  ordinary  rigid  bearings  require
to  be  erected  on  a  firm  foundation,  and  to  be  kept  in  perfect
line.  If,  by  the  settling  of  the  foundation,  or  from  any
other  cause,  they  get  out  of  line,  heating,  cutting,  and
thumping  result.  To  obviate  this,  modern  engines  are  often
fitted  with  self-adjusting  bearings  throughout ;  this  gives
the  engine  great  flexibility  and  freedom  from  friction.  The
accompanying  cuts  show  clearly  how  this  is  accomplished.
310  THE   STEAM-ENGINE   OF  TO-DAY.
The  pillow-block  has  a  spherical  shell  turned  and  fitted  into
the  spherically-bored  pillow-block,  thus  allowing  a  slight
angular  motion  in  any  direction.  The  connecting-rod  is
forged  in  a  single  piece,  without  straps,  gibs,  or  key,  and  is
mortised  through  at  each  end  for  the  reception  of  the  brass
boxes,  which  are  curved  on  their  backs,  and  fit  the  cheek-
pieces,  between  which  they  can  turn  to  adjust  themselves
to  the  pins,  in  the  plane  of  the  axis  of  the  rod.  The  ad-
justment for  wear  is  made  by  wedge-blocks  and  set  screws,
as  shown,  and  they  are  so  constructed  that  the  parts  cannot
get  loose  and  cause  a  break-down.  The  cross-head  has
adjustable  gibs  on  each  side,  turned  to  fit  the  slides,  which
are  cast  solidly  in  the  frame,  and  bored  out  exactly  in  the
line  with  the  cylinder.  This  permits  it  freely  to  turn  on  its
axis,  and,  in  connection  with  the  adjustable  boxes  in  the
connecting-rod,  allows  a  perfect  self -adjustment  to  the  line  of
the  crank-pin.  The  out-board  bearing  may  be  moved  an  inch
or  more  out  of  position  in  any  direction,  without  detriment  to
the  running  of  the  engine,  all  bearings  accommodating  them-
selves perfectly  to  whatever  position  the  shaft  may  assume.
