A Study of Piston-Ring Friction

A series of tests was made with a special engine equipped with a crosshead and an elastically mounted combustion cylinder. The apparatus permitted the isolation and measurement of the friction forces existing between the piston rings and the cylinder wall during operation of the engine. Various combinations of piston-ring and cyilnder-sleeve materials were investigated in addition to the effects of several engine operating conditions. It was found that under the conditions of the tests the use of a porous chromium-plated cylinder caused slightly greater ring friction than a smooth steel cylinder and that a porous chrome-plated top piston ring likewise increased the friction, although to a smaller degree. It was also found that piston-ring friction increased with increased engine speed and with increased manifold pressure, but decreased with increased cylinder jacket temperature.