An Improved Method of Measuring Piston Ring Wall Thrust

Abstract

An important factor in the selection of piston rings is the thrust the ring is capable of exerting on the cylinder wall. A common inspection method of selecting rings consists of wrapping a band around the ring and determining the tangential force required to close the ring gap to the required working value. This method giving as it does a result which is of the nature of an average is unsuitable for the comparison of rings having wall thrust patterns of different form. The piece of apparatus described was designed originally for comparing the wall thrust patterns of new and used rings and has also been used to study the effect of variation of ring “toe-out” and ovality. This work has indicated that there is a definite limit to increasing the toe-out and ovality with a view to stiffening the ring at the horns and beyond this limit increase of toe-out and ovality is accompanied by rapid and progressive break-up of the wall thrust pattern.