Yale MPB040E Manual page 110

Brush Replacement
A brush for a hydraulic pump motor has an area of
approximately:
4.42 × 0.95 cm = 4.21 cm
(1.74 × 0.375 in. = 0.653 in
Brush springs for the hydraulic pump motor nor-
mally have a spring force of approximately:
5.2 to 7.4 Newtons
(20 to 28 ozf) when measured with a spring
scale as shown in Figure 5.
WARNING
Wear eye protection. Raise the drive wheels. Op-
erate the motor at low speed. Protect your fingers.
You are doing work close to moving parts of the
motor. Do not use a brush seater stone less than
60 mm (2.4 in.) in length.
NOTE: The brush springs used in motors made by
Yale have a constant force design. The force of the
brush spring against the brush stays almost constant
as the brush wears and becomes shorter in its brush
holder.
12
2
2
).
NOTE: New brushes made by the manufacturer are
normally made to fit the surface of the commutator
when they are installed. This contact surface must be
checked when new brushes are installed. The contact
surface MUST be approximately 85 percent of the
brush surface where it touches the commutator. A
small contact surface can cause burns and a rough
surface on the commutator. If the contact surface is
less than approximately 86 percent, the new brushes
must be made to fit the commutator better.
9. If new brushes must be made to fit the surface of
the commutator, see Stoning the Commutator.
Use a Brush Seater and Commutator Stone (No.
23-007M from the Ideal Company or an equiva-
lent brush seater stone). Stoning the commutator
is most easily done when the motor rotates
slowly. When the motor rotates at higher speeds,
the centrifugal force removes the abrasive parti-
cles from the commutator more quickly.
NOTE: To rotate the commutator of the traction mo-
tor without moving the truck, the drive wheels must be
raised. See How to Raise Drive Wheels in the Oper-
ating Manual or the YRM section Periodic Mainte-
nance for your lift truck.
0620 YRM 0294