. The Street railway journal . e small ridges produced by the saw. Then again, it is highlj improb-able that a rail will be under no strain at one of the extremes of temperature,but that the point of no strain will be at an average temperature. So that un-der these considerations, it is not probable that the strain in a rail will ever ex-ceed one-third the figure given above, or about 4000 lbs. per square inch—astrain which is absolutely -without danger of any kind. The most essential feature of a joint is that the platesshall have as much bearing as possible. There is littlegained in making a
. The Street railway journal . e small ridges produced by the saw. Then again, it is highlj improb-able that a rail will be under no strain at one of the extremes of temperature,but that the point of no strain will be at an average temperature. So that un-der these considerations, it is not probable that the strain in a rail will ever ex-ceed one-third the figure given above, or about 4000 lbs. per square inch—astrain which is absolutely -without danger of any kind. The most essential feature of a joint is that the platesshall have as much bearing as possible. There is littlegained in making any of the flanges wider than others, fora joint is like a bridge in this respect, that the weakestpart determines the strength of the whole. That portionof the rail which generally determines the width of thejoint plate flanges is under the head, and whatever widthof bearing may be obtained here should be used at theother points. It is extremely important that the jointplates should fit the rail and that when drawn up by the. bolts, the bearing surfaces shall bein contact with the rail with auniform pressure over their en-tire surface. In order that theplates may not bend under thestrain of the bolts, and destroythis bearing, they are alwaysmade convex. This is a properfeature, but even an arch, whennot of sufficient thickness to carryits load will fail, as have manyjoint plates by being pulled inagainst the web of the rail. clearly shows the result ofsuch action. The bearing insteadof being distributed over a sur-face is concentrated along a line. FIG. 80.—BUCKLED JOINT The effect of this is to rapidlyPLATES. wear away the parts of the rail (Original pcsition is shown and joint in contact, and thus by dotted lines.) loosen the joint. One cause forthis lies in the size ofthe bolt used, without increasing the thickness of theplates proportionately. Larger bolts are used, because oftheir tendency to remain tight, due to the frictional resist-ance of a largel
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
