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NEW ROCHELLE, NY
WHY SPIRALS?
REAL RAILROADS
- EASE CHANGE FROM
TANGENT TO
CURVATURE
- EASE CHANGE FROM
LEVEL TO
SUPERELEVATION
WHAT YOU’LL NEED
• POSTERBOARD
• SPLINE – BALSA OR PLASTIC
STRIP
• STRAIGHTEDGE
• CURVE TEMPLATE OR TRAMMEL
• RULER
• PINS
• MARKER
• KNIFE OR SCISSORS
• WORK BOARD
DEFINITIONS
Point of Tangency,
“PT”
Point of Curvature,
“PC”
Offset Length
Constant Radius
Spiral Transition
Center Line,
“CL”
SELECT CONSTRAINTS
- SELECT RADIUS
Example: 30”
- SELECT OFFSET
Example: ½”
- SELECT LENGTH (L)
Example: 12”