Measurement of Piston-Ring Radial-Pressure Distribution

SOME of the difficulties involved in accurate determination of the radial-pressure distribution of a piston ring compressed to cylinder diameter are discussed. Specific experiments made with the NACA's specially designed piston-ring gage are described, and the results compared with those obtained by analysis.

Twelve equally spaced load-measuring elements were found to be sufficient to determine discrepancies in a ring of good quality.

A cylinder that is out of round by as little as 0.005 in. is capable of significantly affecting the radial-pressure pattern of a piston ring. The patterns for both cast-iron and steel rings varied with strain history.