reduction. Normally the float capability of a crane is such that a curve of
300 feet radius can be traversed with a safety factor greater than two and
without a gage reduction.
Minimum Radius. It is desirable that the radius of the central
portion of the curve be not less than 80 feet, except where extreme space
limitations force this condition.
Float for New Cranes. Prior to purchase of new cranes, the
existing track system is to be investigated to determine the gage to which the
crane must be built and the amount of lateral float required in the crane.
Transferring from One Track System to Another. When cranes are
transferred from one track system to another, float requirements must be
determined and the running gear reconstructed as required to fit the new track
Transition Curve (Inside or Control Curve). This transition curve
is a series of compounding circular arcs, in which change of degree of curve
is uniform and directly proportional to the flexible curve length. The first
20 feet of curvature of all transition curves is identical.
Gage Reduction. Although the actual reduction for a given radius
may be computed precisely, the gradual reduction between tangent gage and
reduced gage is an approximation.
Switch Curve (Inside or Control Curve). The first 20 feet of the
transition curve, which is the switch curve, is an arc of constant radius of
300 feet. All switch curves, being identical, permit the standard switch to
be inserted at the point of tangency of any curve design in accordance with
these criteria, at any time (See Figure 7).
Switch Alignment. Although the body of the switch may project a
few inches beyond the sharp edge of the switch curve, the switch alignment
will match precisely any designed flexible transition. Switching from curved
track shall not be used unless the radius of the curve is greater than 300
feet and the turnout is to the outside of the curve, that is, not the center
of the curve.
Main Circular Curve (Inner). This curve is an arc of constant
radius located between the beginning and ending transition curves (See Figure
General Requirement. The general practice is to make an arbitrary
choice of Rmin, assuming Rmin and RC to be approximately equal. The curve which
results from this choice of Rmin must fit available space and other field
conditions, and must not cause the available float of any crane using the
track to be exceeded. Upon satisfying these conditions, Rc should normally be
in the range: