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Boom Pendants
Figure  12-21.Lattice  boom  crane  control  levers.

Equipment Operator Basic - Beginning construction equipment operators manual
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boom hoist lines are reeved. The height of the gantry provides an angle between the boom pendant lines and boom that reduces the compression forces placed on the boom during raising and lifting operations. On some models of cranes, the gantry is adjustable, allowing it to be lowered so the crane can travel bridges. WARNING Refer   to   the   operator’s under  wires  and manual   for instructions  on  how  to  raise  and  lower  the gantry.  A  trial-and-error  method  of  lowering  or raising the gantry can cause serious injury or death. NOTE: Raising the boom while the gantry is in the  lowered  position  lowers  the  angle  between  the pendants   lines   and   boom.   This   places   unseen compression stresses on the boom; therefore, always raise the gantry before raising the boom or lifting a load. Boom Mast Some  models  of  cranes  are  equipped  with  a  boom mast  instead  of  a  gantry.  The  boom  mast,  sometimes called live  mast, consists of a structural frame hinged at or near the bottom of the boom butt (fig. 12-19). Figure 12-19.—Boom mast. 12-10 The  tip  of  the  boom  mast  supports  the  boom  hoist sheaves and boom pendant lines. The boom mast works like  the  gantry,  as  it  increases  the  angle  between  the boom pendants and boom, decreasing the compression forces placed on the boom. Bridle Assembly The  bridle  assembly  is  part  of  the  boom suspension  system  and  is  sometimes  called  a  floating harness.  The  bridle  assembly  may  be  connected  to the boom mast or as a floating harness on a crane equipped with a gantry. The bridle assembly is the connection point for the boom pendant lines and is an assembly  of  sheaves  in  which  the  boom  hoist  wire rope  reeves  through. Boom Stops Boom  stops  are  designed  to  prevent  the  boom from going over backwards in case a load line breaks. They  will  not  stop  the  boom  if  the  operator  forgets  to disengage  the  boom  hoist  control  lever.  However, some  models  of  cranes  are  equipped  with  a  boom upper limit switch that prevents the operator from raising  the  boom  past  a  preset  boom  angle.  This switch  also  prevents  operators  from  raising  the  boom into the boom stops.    Most  cranes  that  are  equipped with the upper limit switch also have a bypass switch that allows the operator to raise the boom past the preset boom angle. Two  types  of  boom  stops  are shown in figures 12-18 and 12-19. House Assembly The house assembly is a revolving superstructure that sets on top of the carrier frame (fig. 12-20). It provides a mount for the hoist mechanisms and engine and is sometimes called the machinery deck.  The operator’s  cab  and  counterweight  are  attached  to  the home  assembly. OPERATOR’S CAB.—  The control levers for a lattice boom crane are located in the operator’s cab. The control levers that are shown in figure 12-21 are typical of  most  cranes. Typical  crane  controls  areas  follows: 1.  The  swing  lever,  when  pulled  towards  you, rotates the house assembly in one direction, and when pushed, the house assembly rotates in the opposite direction.







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