The mathematical relationship connecting curve lead (CL), switch lead (SL), and crossing lead (L) is expressed as__________________?
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Answer: B. L =CL-SL
Explanation
The crossing lead (L) is geometrically defined as the difference between the curve lead (CL) and the switch lead (SL), expressed as L = CL - SL. Track geometry principles dictate that subtracting the switch lead from the total curve lead yields the exact crossing lead distance. This mathematical relationship ensures accurate layout and positioning of turnout components during field installation. Turnout geometry involves complex surveying calculations to connect split switches smoothly with the V-crossing nose. Switch lead represents the distance from the theoretical nose of switch to the heel of the switch assembly. Curve lead measures the distance from the switch toe to the theoretical intersection point of the turnout curves.
Adding switch leads to crossing leads would yield incorrect track lengths violating fundamental turnout geometry rules. Averaging curve and switch leads produces meaningless values that do not correspond to any actual physical turnout dimension. Formulas suggesting crossing leads equal total curve leads ignore the essential spatial contribution of the switch assembly.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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