DETAILED DESCRIPTION OF STARTER

TM 9- 2920- 232- 34&P / TO 38X14- 2- 32

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EQUIPMENT DESCRIPTION AND DATA - CONTINUED

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DETAILED DESCRIPTION OF STARTER

NOTE

Reference numbers shown in parentheses refer to the sectional view of the

a. Major Components. The major components of the starter are the frame assembly (23), armature (22),

commutator end plate assembly (25), brush holder assembly (28), brushes (3), drive clutch assembly (19),

drive housing (16), solenoid relay assembly (8), lever housing (13), shift lever (15), and solenoid plunger (10).

b. Frame Assembly. The frame assembly consists of field windings (5), pole shoes (6), and field winding

terminal stud (4) mounted in and supported by the heavy steel cylindrical frame.

1) Field windings (5) are held in position on inside wall of the frame by the pole shoes (6). Each pole shoe is

secured in place by two screws (21). Field windings are electrically interconnected in an arrangement of

three pairs.

2) Each pair of field windings (5) are series connected, but reverse winding makes opposite polarity. All three

pairs have a common connection at the field winding terminal stud (4). The field winding terminal stud is

insulated from the frame in which it is mounted.

Armature. The armature (22) is made of copper and laminated steel assembled on a steel shaft. When

installed, the armature is supported by three sleeve bearings (17, 20, and 27) and is free to rotate in the frame

assembly.

1) A straight spline on drive end of armature shaft engages the internal spline of drive clutch--assembly (19)

so that it must rotate with the shaft but allows movement of the drive clutch assembly along the shaft.

2) Movement of drive clutch assembly (19) along the shaft provides the means of engaging and disengaging

starter drive pinion (18) from the teeth on an engine's starter drive gear.

3) A commutator, at end opposite drive end of the armature, provides selective electrical contact through

brushes (3) as the armature rotates. This selective contact allows electrical current to flow through each

armature winding in alternating directions as the armature rotates. As the current direction through a

winding changes, magnetic polarity of the associated armature pole is reversed. These changes in

polarity always force, in a pull and then push fashion, rotation of an armature pole past each pole shoe in

one constant direction.

d. Commutator End Plate Assembly. The end plate of commutator end plate assembly (25) provides closure for

that end of the starter frame and holds sleeve bearing (27) which supports the commutator end of armature

(22). Brush holder assembly (28) has six brush holders and is mounted on the inner surface of the end plate

but is electrically insulated from the end plate as necessary.

e. Brushes and Brush Holder Assemblies. Each brush is free to move in its brush holder only in a radial direction

with respect to the circumference of the commutator. A helical torsion spring (26) is used (two in 12--brush

starter) at each brush holder to keep a positive contact pressure between brush and commutator. These

springs and brush freedom in its holder accommodate change in brush length due to wear.

1) Alternate brush holders around commutator are electrically connected to provide one set of three brushes

(three pairs of brushes in p/n 1109972) in common circuit. This set is connected to brush holder terminal

stud (1).

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