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How does a drive assembly work?


A drive Assembly provides for positive engagement of the starter motors with the ring gear and protects the armatures from prolonged engagement. Once the starter motor stars rotating, the inertia of the drive assembly causes it to wind the spring forcing the length of the spring to change. This makes the spring move with the ring gear. Once the engine starts, the back drive from the ring gear causes the drive pinion to exceed the rotating speed of the starter. At this point, the drive pinion is forced back and out of mesh with the ring gear.

A limitation of the drive assembly lies in its dependance on a particular quantity of "clash" between the teeth of the pinion and also the ring gears, before they slip into place and mate completely. The teeth of the pinion are already spinning when they get in contact with the static ring gear and will keep rotating until they both align perfectly. This brings about a lot of wear and tear on both sets of teeth. Owing to this wear and tear, over the past years, the drive assembly has been superseded by the pre-engagement system using a solenoid.

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