Niagara Air Parts: Starter Clutch; Failed Clutch/Drive Assembly;

Niagara Air Parts: Starter Clutch; Failed Clutch/Drive Assembly;

<p><strong><font color ="blue">Niagara Air Parts: Starter Clutch; Failed Clutch/Drive Assembly;
  ATA 8011 </font></strong></p>
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<p><em>(An A&P mechanic provides the following description, research, and photographs of a failed clutch assembly driven by a Prestolite starter. Effected “upstream assemblies” include a Continental O-200A engine and an entire Cessna 150M airplane—all bolted to the starter....) </em></p>
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<p>“While attempting to start the engine the starter was heard spinning, but the engine would not crank. </p>
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<p><em>(I) </em>disassembled and inspected the engine starter drive mechanism by removing the starter and clutch drive assembly from the rear accessory section of the engine. While inspecting the clutch drive assembly (Niagara Air Parts: P/N CAM641 500-20), <em>(I) </em>found the larger drive gear was separated from the shaft.” <em>(This gear is (normally) driven by the starter, but would now spin freely due to its separation from the shaft.) </em>“Upon closer inspection it appeared this drive gear was attached to the shaft by braising, as the mating surfaces were brass or copper in color. Due to the high rotational torque involved in the starting process, it would appear this method of attachment <em>(is) </em>insufficient. <em>(I) </em>spoke with a representative of Niagara Air Parts who advised <em>(a brazing type weldment) </em>is the normal process of attachment of the drive gear to the shaft. He said they have tested the operating strength of this process to a four ton load rating without failure. <em>(The representative further...) </em>explained the gear and shaft are heated to approximately 1700 degrees with copper used as brazing material between parts. </p>
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<p>He <em>(speculated) </em>engine kick-back on start or shutdown may have caused this <em>(gear/shaft separation). </em>Niagara requested the part be returned for inspection and analysis of the failure.” </p>

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