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A swingnose crossing or moveable point frog is a device used at a railway turnout to eliminate the gap at the common crossing (a.k.a. frog) which can cause damage and noise. == Fixed crossing == On a fixed railway crossing, the wheels need only drift by a small angle, say 1 in 20, before the vehicle may start to go in the wrong direction at the V of a V-crossing. This problem can limit the maximum speed of vehicles using the crossing. In addition, the open gap at a fixed V-crossing forms a weak point on the railway line where the heavily loaded wheel must bump across the resulting gap of about 10 cm, supported only by the portion of the wheel tread which is on the wing rail. This pounds the rail so much that the steel can deform and/or wear away. This damage may easily spread to other components including the wheels, and the noise can be a nuisance. Scheduling repair of damage can also be a problem in high traffic locations. Swingnose crossings virtually eliminate the gap at V-crossings allowing for higher vehicle speeds. The swingnose crossing overcomes the problem of the gap by moving the point of the V-crossing from side to side, synchronised with the selected direction of the turnout. The wheels are supported the entire way on their treads, and do not produce noise and vibration that would otherwise occur. Swingnose crossings are also useful where heavy rail and light rail vehicles, which have different wheel profiles, share the same track. 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「Swingnose crossing」の詳細全文を読む スポンサード リンク
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