ROCKING-PISTON ENGINE.

An entirely new mechanism has been designed and proved by W. Salzmann Fahrzeugkonstruktionen, of Solothurn, Touringhaus, Switzerland. This year at Geneva they exhibited in public for the first time their rocking piston engine, in which gudgeon pins have been dispensed with and mushroom shaped pistons and connecting rods are made in one piece and run in appropriately waisted cylinder bores. In the absence of a gudgeon pin and skirt, each piston weighs only about half as much as its conventional counterpart. This, in turn, means that the primary vibration forces are small. In addition, since the ratio of connecting rod length to crank throw is in effect increased by the absence of a gudgeon pin, the angle swept by the rod as the crank rotates is small and so therefore are the secondary vibration forces. Indeed, on a four-cylinder in-line engine the primary forces are reduced to about 50% and the secondary forces to about 40% of their normal values. Because of the rocking motion of the piston at top dead center on the compression stroke, there is a natural transfer of the charge from one side to the other - an extension of the uniflow principle. Four-stroke and two-stroke prototypes of the Salzmann rocking piston engine are under development, both on test beds and in vehicles, and research is continuing with a diesel unit.