Brake Tests

279 so modified. This is shown by a comparison of the wear factors given for shoes “C” and “D” as compared with shoe “A,” and shoe “G” as compared with shoe “ E.” 542. A comparison of the shoe wear per 100 000 000 foot pounds of work done under single shoe and clasp brake conditions is shown in the following table :— Comparison of Single and Clasp BRAKE Shoe Wear Per 100 Million Foot Pounds Work Done. — Kind of Shoes Plain Ratio of Wear Solid to Slotted. Per Cent. Ratio of Wear Single Solid to Clasp Solid. PER Cent. Ratio of Wear Single Slotted TO Clasp Slotted. PER Cent. Type “A” Solid TYPE “B” Slotted Single 4.382 3.105 3.921 2.937 111.7 105.9 .... 133.5 Clasp 543. A comparison of plain solid and plain slotted brake shoes under single and clasp brake conditions shows:— A.—That the superior durability of the plain slotted shoe as com- pared with the plain solid amounts to 11.7 per cent, under single shoe brake conditions and 5.9 per cent under clasp brake conditions. B.—That with plain solid shoes the durability will be increased 41.1 per cent, under clasp brake conditions as compared with that under single shoe conditions. C.—That with plain slotted shoes the durability will be increased 33.5 per cent, under clasp brake conditions as compared with that under single shoe conditions. 544. The table on page 280 gives the data of comparative wear and cost of plain and flanged shoes. 545. A comparison of flanged and plain shoes on the basis of dura- bility with the costs assumed, shows: A.—That the net cost per pound of metal available for wear is 4 per cent, more for flanged shoes than it is for plain shoes. B. —That the wear of the flanged solid shoes per unit of work done is 19 per cent, less than for plain solid shoes, and for flanged slotted 26 per cent, less than for plain slotted shoes, or 30 per cent, less than plain solid shoes. C.—That the wear of plain slotted shoes per unit of work done is 5 per cent, less than the wear of plain solid shoes, and the wear of the flanged slotted is 13 per cent, less than the wear of flange solid shoes.