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The term "cant deficiency" is defined in the context of travel of a rail vehicle at constant speed on a constant radius curve. Cant itself is a British synonym for the superelevation of the curve, that is, the elevation of the outside rail minus the elevation of the inside rail. Cant deficiency is present when a vehicle's speed on a curve is greater than the speed at which the components of wheel to rail force normal to the plane of the track. In that case, the resultant force (aggregated force of gravitational force and centrifugal force) exerts the outside rail more than the inside rails, in which it creates lateral acceleration toward outside of the curve. In order to reduce cant deficiency, the speed can be reduced or the superelevation can be increased. The amount of cant deficiency is expressed in term of required superelevation to be added in order to bring the resultant force into balance between the two rails. In the contrary, it is said to be "cant excess" if the resultant force exerts more against the inside rail than the outside rail, for instance, a high superelevation curve with a train traveling at a low speed. ==Forces== The forces that bear on the vehicle in this context are illustrated in the following figure. A vehicle's motion at speed ''v'' along a circular path embodies centripetal acceleration of magnitude ''v''2/''R'' toward the center of the circle, the curvature of that path being 1/''R'' where ''R'' is the radius of the circle. This centripetal acceleration is produced by horizontal forces applied by the rails to the wheels of the vehicle, directed toward the center, and having sum equal to ''Mv''2/''R'' where ''M'' is the mass of the vehicle. The net horizontal force producing the centripetal acceleration is generally separated into components that are respectively in the plane of the superelevated (i.e., banked) track and normal thereto. The component normal to the track acts together with the much larger component of gravitational force normal to the track and is generally neglected. It can slightly increase the vertical load seen by the vehicle suspension but it does not create lateral acceleration as perceived by passengers or and does not cause lateral deflection of the vehicle suspension. The track is superelevated so that the component of the acceleration of gravity in the plane of the track will provide some fraction of the horizontal acceleration in the plane of the track due to the circular motion. Referring to the figure above, it can be seen that the components of gravitational and centripetal acceleration in the plane of the track will be equal when the following balance equation is satisfied, where α is the bank angle. : For a given curve radius and bank angle (i.e., superelevation) the speed V that satisfies the balance equation is called the balancing speed and is given by : For reasons that will be mentioned below, passenger vehicles usually traverse a curve at a speed higher than the balance speed. The amount by which the actual speed exceeds the balance speed is conveniently expressed via the so-called cant deficiency, i.e., by the amount by which the superelevation would need to be increased to raise the balance speed to the speed at which the vehicles actually travel. Letting ''gaugese'' denote the rail gauge from low rail gauge side corner to high rail field side corner, letting ''super_el'' denote the actual superelevation, and letting ''Vact'' denote the actual speed, it follows from the definition that the cant deficiency, ''CD'', is given by the formula : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cant deficiency」の詳細全文を読む スポンサード リンク
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