Wiring a turntable

[Anonymous]

Need help in wiring my turntable, so when turned 360 degrees, the locos don't short out, coming off the bridge. Or is there some electronic device such as an auotomatic reversing unit that I can use. Any suggestions would be helpful.
Thank-you very much.
Ed

[Sperandeo]

Hi Ed,

If you use DCC you can use one of the DCC automatic reversing circuits to reverse polarity on your turntable. Or if you use a programmable controller such as the one made by New York Railway Supply, the control circuitry includes an automatic reversing option.

The first thing I'd look at, though, is how you're getting current to the turntable rails. There are a couple of ways to wire them so that the rail polarity is automatically reversed by the movement of the table.

One is to use a split pit rail with wipers under each end of the bridge to pick up power. The other is to build a simple commutator into the turntable shaft with brushes mounted under the turntable pit. Both methods are shown in my book, "Easy Model Railroad Wiring," published by Kalmbach. In the second edition see pages 43 and 44.

When using either of those methods with command control, you want to make sure there are dead sections in the pit rail or on the commutator where the changeover occurs. This will prevent a passing short every time the turntable changes ends. In electrical-switch terminology, you want to have "break-before-make" action.

Good luck,

Andy Sperandeo
MODEL RAILROADER Magazine

[BR60103]

Ed:
Andy's covered the field pretty well. If you really can't get it wired through the pit rails, you could put in a standard dpdt reversing switch. Then put something on the turntable bridge at one end (a control cabin or a different handrail arrangement or maybe your road's herald) and set it up so the handle on your reversing switch points at the different end. It'll be a bit more confusing if you have a full set of tracks going off all the way around.
If you have dead sections in the pit rail, make sure they don't line up with roundhouse tracks, because the locos won't run on/off the turntable at those points.
David