Cast railroad brake shoe and method of making same

Claim 1

A RAILROAD BRAKE SHOE CAST TO SHAPE AND COMPRISING A REINFORCING METAL BACK, AN ATTACHING LUG AT THE BACK AND A SHOE BODY HAVING A WEAR FACE LOCATED BELOW THE BACK AND CAST INTEGRAL WITH THE BACK AND THE LUG, SAID SHOE BODY HAVING A METAL MATRIX SELECTED FROM THE GROUP CONSISTING OF ALUMINUM-SILICON ALLOY, STEEL AND CAST IRON CAST AS A CONTINUOUS PHASE THROUGH AND CAST ABOUT A SUBSTANTIALLY UNIFORM DISPERSION OF SOLID PARTICLES INCLUDING AT LEAST TWO KINDS OF PARTICLES SELECTED FROM THE GROUP CONSISTING OF CHROMITE, SILICON CARBIDE, IRON GRIT, ALUMINA, EMERY, GARNET, STEEL SHOT, MULLITE, GRAPHITE AND SILICA WHICH REMAIN SUBSTATIALLY UNDISSOLVED IN SAID MATRIX AS A DISCONTINUOUS PHASE, SAID PARTICLES IN THE PORTION OF THE SHOE BODY LYING BETWEEN THE WEAR FACE AND SAID BACK BEING OF SUBSTANTIALLY UNIFORM DISTRIBUTION, SAID PARTICLES BEING NOT LARGER THAN ABOUT ONE-QUARTER INCH AVERAGE DIAMETER AND COOPERATING WITH THE METAL MATRIX TO AFFORD A DYNAMOMETER MEAN FRICTION COEFFICIENT OF NOT LESS THAN ABOUT 0.15 AND A WEAR RATE NOT MORE THAN ABOUT 3.85 CUBIC INCHES PER 100 MILLION FOOT POUNDS OF ENERGY EXERTED THEREON DURING DYNAMOMETER BRAKING UNDER THE FOLLOWING DYNAMOMETER CONDITIONS: WHEEL LOAD LBS 7190 BRAKE SHOE LOAD LBS 7190 SPEED M.P.H. 60 SINGLE BRAKE SHOE WHEEL DIAMETER INCHES 36 AND SUBSTANTIALLY ALL OF THE PARTICLES EACH BEING INDIVIDUALLY ENVELOPED BY THE METAL AFFORDING SAID MATRIX.