. The elements of railroad engineering . s have been made showingthat with high-degree curves the resistance is about poundper ton per degree for American bogie trucks of about 5 feet wheelbase at slow speed; that it is considerably more than this forcurves of small degree and long rigid wheel base, even pounds per ton per degree. The usual allowance made bylocating engineers in America is from of a pound to i poundper ton per degree. This is perhaps not much too large for low-degree curves, is certainly not too large for a long-wheel base ona curve of low degree, but is to
. The elements of railroad engineering . s have been made showingthat with high-degree curves the resistance is about poundper ton per degree for American bogie trucks of about 5 feet wheelbase at slow speed; that it is considerably more than this forcurves of small degree and long rigid wheel base, even pounds per ton per degree. The usual allowance made bylocating engineers in America is from of a pound to i poundper ton per degree. This is perhaps not much too large for low-degree curves, is certainly not too large for a long-wheel base ona curve of low degree, but is too large for 5 or 6 foot trucks onsharp curves. Observation has seemed to show that the resistanceper degree is greater on flat curves than on sharp curves. Anattempt to discuss the action of a truck on a curve and to developa rational theory for curve resistance that shall agree with obser-vation will be made. Relation of Wheel and Rail. — Car wheels are slightly coned,tV inch in 2f inches, the tread joins the flange by a fillet curve. Fig. 76 of f-inch radius, the flange is not straight at any point, but iscurved. The fit of a new wheel and rail is shown in Fig. 76. ACTION OF A TRUCK ON A CURVE 171 The comer of an American Society of Civil Engineers rail sectionis rounded with a /^^-inch radius, and between the gauge sideof the rail and an arbitrary point in the fillet curve of the wheelflange there is a space of f\ inch, giving a so-called f-inchplay between the gauge of the wheels as set on the axles and thegauge of the track. With engine drivers a larger allowance ismade, up to | inch. Owing to the coning of the wheel and the12-inch curve of the rail top, the wheel bears on the rail as indi-cated in the figure; and if moved over toward the rail about i^inch, a point on the fillet curve would come into bearing well upon the top of the corner curve of the rail. If the wheel be movedstill farther against the rail until the fV-inch play is used up,then the wheel would be lift
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectrailroadengineering
