THE principal problem in changing over to cast-iron pistons at this time is in designing them for low weight and adequate strength, Mr. James concludes. In the final analysis, he points out, the design of the cast-iron piston is controlled by the ability of the foundry to cast thin sections to close tolerances. As soon as this part of foundry technique improves, cast-iron pistons can be made lighter and, possibly, as light as the present designs of aluminum pistons, Mr. James states.
The greater weight of cast-iron pistons, imposing increased loads on the bearings, connecting rods, and piston pins, is much more difficult for the designer to overcome than are such problems as oil consumption, engine friction, piston scuffing, piston slip and rattle, and similar factors, the author avers.
Mr. James' paper is made up of a series of experiences of various engineering departments who have undertaken the switch from aluminum to cast-iron or cast-steel pistons. Compiled at the suggestion of the Passenger-Car Activity Committee, the paper gives comparative data covering all important phases of piston engineering.
