SelectingTurnouts

[NewRRer]

What factors are involved in selecting appropriate turnouts to use? For instance when would a #4 be preferable to a #5 or #6 or even a WYE?

[Doneldon]

New-

The selection of turnouts is a function of the sharpness of the turnout and the needs of your rolling stock and motive power. Let's discuss these in turn.

The numbering of turnouts expresses the ratio of the distance the turnout moves left or right of the straight leg of the turnout compared to the length of track it needs to move that much. Thus, a number eight turnout needs twice as much track length to deviate a given distance from the through (straight) track as does a number four turnout. And therefore a number eight has a significantly less severe change in the track direction than a number four, with the number six offering an intermediate degree of sharpness. Twelve inches to the foot railroads use much, much longer and more gentle turnouts than what we use on our models but the principle is the same: The higher the number the gentler the change and the easier for trains to negotiate the turnout, and conversely. That is, turnouts with lower numbers are sharper and trickier for longer locomotives and cars. The numbers do not have to be even, by the way; it's just that most manufacturers find it cost effective yet responsive to customers' needs not to produce turnouts of every possible degree of divergence. Neither are turnouts restricted to whole numbers.

Some turnouts don't carry numbers but are identified merely as left or right turnout or switch. These differ from true turnouts in that their diverging track is curved rather than straight. It's counterintuitive but numbered turnouts, with their straight legs, tend to be easier for trains to follow than curved switches. And then there is the wye turnout. This special turnout has tracks which diverge for both legs, making the track separation twice as fast without increasing the sharpness of the change. There are other specialty turnouts which only rarely appear on model railroads (i.e., a gantlet turnout or a double slip switch) to which the same numbering system applies.

The second aspect of turnout choice, the needs of locomotives and rolling stock, is probably already obvious: Longer wheelbases on our models need more gentle turnouts for reliable operation. Because of that, many modelers set specifications for their layouts such as requiring that mainline tracks have at least number eight or six turnouts but yards can use sharper turnouts, say number four or five.

I hope this is helpful. Welcome to model railroading and this board. Please visit us often and share your progress.
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