Explain the working of a standard Bendix drive used in starter motor

Subject: Automobile Engineering

Topic: Electrical System, Starting Systems & Alternator

Difficulty: High

1 Answer

Bendix drive is used to engage starter pinion with flywheel gear. For fastening this unit with the armature starting motor shaft the drive heads is keyed to the end of armature shaft while the other parts are free from armature shaft & drive head. They are only connected through the spring which is attached to the head & steeve carrying pinion. When the current passes into the starting motor the armature begin to turn at full speed causing the transmission of turning effect to the threaded steeve.

Although the pinion is turned very little, yet it is moved forward by the spiral thread till it engaged with the teeth of the flywheel of pinion is prevented by a collar attached on sleeve, because of this pinion start rotating as it is mesh with engine flywheel. The flywheel rotates & engine starts.

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The starter pinion & flywheel gear do not reunion mesh but are automatically disengaged by the Bendix drive as soon as engine start because in comparison to the rotation of the starting motor,the engine rotate the pinion much faster after it starting causing damage to the starter motor. This disengagement is affected due to pinion rotation much faster by the engine in comparison to the rotation of starting motor at the time of the engine actually start. Therefore, the starting motor will be also protected due to pinion meshing out of the flywheel gear because of its screwing back on the spiral threaded sleeve when the starter switch is released by the operator.

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