1939-01-01

Aircraft-Engine Valve Mechanisms 390136

NEMESIS of aircraft valve mechanism is false motion, Mr. Young believes. False motion in valve gear, he explains, is any motion of parts other than the theoretical, and it affects any part of the mechanism from the valve to the cam, since high loadings can be encountered which far exceed the calculated stresses. The result often is failure, either partial or complete, he contends, and illustrates this point by diagrams of actual valve motion under operating conditions. Emphasis is placed on other effects from the same cause, such as high seating velocities.
In a discussion of the hydraulic lash adjuster, the author stresses its effect on seating velocities and maintenance of fixed timing, referring particularly to air-cooled radial engines.
The importance of reduced operating temperatures of the valves is pointed out in regard to increased strength, and to improved fatigue and corrosion resistance.

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