MIL-HDBK-1005/6

RC = Rmin + 3.00 ft.

Unless extreme space limitations dictate otherwise, it is desirable that

neither Rmin nor Rc be less than 80 feet.

3.7.2

Selection of Radius. The following are suggested methods for

selecting Rmin and Rc for use in the design procedure, Table 1.

a) For a symmetrical curve with ) = 180E (i.e. parallel tangents

forming a "horse-shoe" curve), a first approximation of Rmin should be:

Rmin = 0.93M

The radius of the main circular curve is:

RC =

M - YC

cos 2

b) For 90E < ) < 180E, a recommended first approximation of Rmin

would be a value equal to one half the distance from PC to PT.

Note: The choice of Rmin in this case is strictly an approximation.

A certain

amount of trial and error is involved in the final choice of Rmin.

c) For ) < 90E, it is recommended that the first trial should be

based upon historical data of a similar curve if available. Otherwise,

estimate and refine by trial and error.

), M, YC and 2 = (See Table 4).

3.8

Complete Curve Combination. A complete curve combination consists

of a minimum of two switch curves and two abutting transition curves, or a

maximum of two switch curves and two transition curves, separated by one main

circular curve (See Figure 7).

Transition Curve. When the main intersection angle ( ) ) is 90

3.8.1

degrees or less, the curve may be made transitional throughout. When the

curves are transitional throughout, the inner transition curves abut, but the

outer transition curves are separated by a tangent of 2t length.

Tangent Length. Tangent length between curves of opposite

3.8.2

direction shall be at least equal to the equivalent length of the crane.

Under no circumstances shall the commonly called

3.9

Reverse Curve.

"reverse curve" be used.

Transition Curve (Outside). This curve is a series of compounding

3.10

circular arcs which are not concentric with the corresponding arcs of the

inside transition curve. The first 20 feet of curvature of all transition

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