Piper Arrow IV Turbo Maintenance Manual page 675

GENERAL.
DESCRIPTION AND OPERATION. (Refer to Figure 80-1.)
The gear reduction starting motor consists of six major components: The Commutator End Head
Assembly, The Armature, The Frame and Field Assembly, The Gear Housing, The Pinion Housing, and The
Bendix Drive Assembly. When the starting circuit is energized, battery current is applied to the starting motor
terminal. Current flows through the field coils, creating a strong magnetic field. At the same time, current
flows through the brushes to the commutator, through the armature windings to ground. The magnetic force
created in the armature combined with that created in the field windings begins to turn the armature.
The gear cut on the drive end of the armature shaft extends through the gear housing, where it is supported
by a roller bearing. The gear mates with the teeth of the reduction gear that drives the bendix shaft. The shaft is
keyed to the reduction gear. The Bendix drive is held in position on the shaft by a "spiral" pin. The shaft is
supported in the gear housing by a closed end roller bearing and in the pinion housing by a graphtized bronze
bearing.
When the armature turns the reduction gear, the Bendix drive pinion meshes with the flywheel ring gear by
inertia and action of the screw threads within the Bendix sleeve. A detent pin engages in a notch in the screw
threads which prevents demeshing if the engine fails to start when the starting circuit is de-energized.
When the engine reaches a predetermined speed, centrifugal action forces the detent pin out of the notch in
the screw shaft and allows the pinion to demesh from the flywheel.
TROUBLESHOOTING.
Refer to Chart 8001, Troubleshooting (Starter).
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
THIS SPACE INTENTIONALLY LEFT BLANK
3G12
80-00-02
Page 80-01
December 1, 1978