NEW YORK TERMINAL DISTRICT

MAKE A SPIRAL

TRANSITION

TEMPLATE

ETHAN EILERTSEN

NEW ROCHELLE, NY

WHY SPIRALS?

REAL RAILROADS

- EASE CHANGE FROM

TANGENT TO

CURVATURE

- EASE CHANGE FROM

LEVEL TO

SUPERELEVATION

WHY SPIRALS?

MODEL

RAILROADS

- LOOKS GOOD

- IT’S FUN

- NO RIGOROUS

MATHEMATICS

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”

HOW TO MAKE A TEMPLATE

LAY OUT TANGENT AND

OFFSET USING OFFSET OF ½”

Offset

Tangent

HOW TO MAKE A TEMPLATE

LAY OUT RADIUS TO MEET

OFFSET LINE AND MARK

CENTER OF TRANSITION

HOW TO MAKE A TEMPLATE

MARK L/2 (6”) EITHER SIDE OF

CENTER – THIS IS LENGTH OF

TRANSITION

HOW TO MAKE A TEMPLATE

CENTER THE SPLINE ON THE

MARK

HOW TO MAKE A TEMPLATE

PIN SPLINE ON TANGENT AND

ON CURVE. NO PINS WITHIN

SPIRAL!

HOW TO MAKE A TEMPLATE

TRACE AROUND SPLINE AND

MARK PT, CL, AND PC

HOW TO MAKE A TEMPLATE

CUT TO THE LINE (TRANSFER

MARKS TO THE OTHER SIDE

FOR A LEFT-HAND CURVE)

HOW TO USE THE TEMPLATE

LAY OUT TANGENT AND 1/2”

OFFSET

Tangent

Offset

HOW TO USE THE TEMPLATE

LAY OUT RADIUS AND MARK

SPIRAL CENTER

Radius

Center of Spiral

HOW TO USE THE TEMPLATE

LAY TEMPLATE ON CENTERLINE, ALIGN

WITH TANGENT AND CURVE, AND

TRACE

HOW TO USE THE TEMPLATE

COMPLETED SPIRAL – TRACK FLOWS

FROM TANGENT THROUGH SPIRAL TO

RADIUS

BIBLIOGRAPHY

TRACK PLANNING FOR REALISTIC OPERATION

– ARMSTRONG - 1963

A MANUAL OF CIVIL ENGINEERING – RANKINE

– 1883

THE TRANSITION CURVE OR CURVE OF

ADJUSTMENT – KELLOGG - 1907