THREE newly developed instruments-for piston-ring measurement, for ascertaining the radial pressures exerted and for determining “How rough is smooth?”-are described and their uses discussed. The last is a device to determine the smoothness of cylinder finish and predetermine piston-ring life. By all these means, the minute dimensions and characteristics of piston-rings can be studied and evaluated.
The authors call attention to the progress made in the last few years in piston-ring design, together with the important factors contributing to successful performance and long life of piston-rings. They state that considerable work has yet to be done before complete specifications for all diameters and types of ring can be given to the industry; however, the progress they describe has been made in ring equipment for high-speed engines under 4 in. in cylinder diameter. They believe that the fundamentals apply to piston-rings for all uses. Future developments will, in their opinion, make it necessary to deviate somewhat from present practice and make obsolete even the things that seem satisfactory today.
