Service Manual

7. Check adjustment of the BBC cable as described
under BBC Adjusting the Blade Brake, page
26.
8. Slide the black plastic transmission cover into
place making sure that the belt slides into the
grooves provided. Some contact between the
belt and the cover may be evident.
NOTE:
It may be necessary to push the
transmission back slightly to get the
transmission cover to slide
in completely.
9. Place the upper BBC cover into position on the
housing and secure with the
two self-tapping
flanged head capscrews.
IO. Check for proper operation of all controls,
especially the BBC, and adjust as necessary.
BBC UNDER DECK COMPONENTS
BBC Under Deck Components Operation
Brake Plate Assembly: The brake plate assembly (see
Figure
91) consists of the brake plate, the brake pad,
brake plate hub, brake plate lever, a bushing, seal and
the idler pulley. See Figure
91. The brake plate has two
important functions.
U
Figure 91
First, it controls tensioning and loosening of the BBC
belt by pivoting on the brake plate bushing. This
controls engagement and disengagement of the
blade.
It is spring loaded by the brake plate spring
assembly
in the disengaged position.
Secondly,
it provides the breaking action necessary to
stop the blade within three seconds of release of the
control bar. (The three second time frame is mandated
by federal law.) When
in the disengaged position, the
brake pad that is
affixed to the brake plate touches the
brake drum.
Because of the orientation of
the pivot point, the brake
pad, and
the brake drum, this type brake is termed
’self-energizing’.
It is named as such because when
the brake drum is rotating
in its normal direction, the
brake pad and brake drum are actually wedged
together which produces more friction and
a lower
stopping time. This is desirable because
it greatly
reduces the
input force required.
Brake Plate Spring Assembly: The brake plate spring
assembly spring loads the brake plate assembly
so
that the belt is in the disengaged position and the
brake pad is spring loaded into the brake drum. The
assembly consists
of a rod which slides through a slot
in the brake plate in a spring. The rod is attached to
the deck housing and
the spring provides the force
necessary for braking action. Note that there is no
retainer securing the rod to the brake plate.
Split Sheave Pulley and Blade Assembly: The split
sheave pulley design used on the
VP mower provides
the clutching action that allows the engine to keep
running while the blade is stopped.
In this split sheave pulley type clutch, there are 4
primary parts involved, the crankshaft or rotating
spindle, the upper pulley sheave, the lower pulley
sheave and a bearing block. See Figure
92.
FLYWHEEL
DRUM
BLOCK
SCREEN
Figure 92
Vacu-Power Mower 53 BBC System