TRUCK SPRINGS. A general term used to describe any of the several types of springs used in
the suspension systems of trucks to provide a degree of vertical cushioning of the car and its load.
TURNOUT. An arrangement of a switch and a frog with closure rails by means of which rolling
stock may be diverted from one track to another. Another name for "TRACK SWITCH."
WHEEL FLANGE. The tapered projection extending completely around the inner rim of a
wheel, the function of which, in conjunction with the flange of a mate wheel, is to keep the wheel
set on the track by limiting lateral movement of the assembly against the inside surface of either
WHEEL PLATE. The part of the wheel between the hub and the rim.
WHEEL RIM. The portion around the outer circumference of the wheel that forms the edge of
the tread. The thickness of the rim is a measure of the amount of wear remaining in the wheel.
WHEEL TREAD. The slightly tapered exterior running surface of the wheel that comes in
contact with the top surface of the rail, and serves as a brake drum on cars with conventional
WYE TRACK. A triangular arrangement of tracks on which locomotives, cars, and trains may
YARD. A system of tracks within defined limits used for the makeup of trains, car storage and
YARD LIMITS. Trackage where yard operating procedures apply.
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