Turntable Wiring, Need Help

[Geohan]

Thank you both. I guess I was hoping for some magic that just isn't there.

[selector]

So, you have a choice of manually changing the bridge rails' polarity or using an electronic one available from retailers..there are several makes. If you want to go the handraulic method, use a douple-pole/double throw switch (DPDT), and wire the approach rails to one set of the posts making sure to keep their polarities all matched to the correct posts, and then wire the bridge trails to the other two posts on the DPDT. You can keep track of the bridge rail's polarity by noting which end of the bridge is meeting the train, the controller's shack end or the free end. You can correlate that to the switch by noting which direction of throw is necessary (forwar/back or left/right, depending on how you mount the switch) to the end that is meeting the approach.

Note that you will get the loco onto the bridge, but unless you consider the polarity of the exits, such as into roundhouse stalls, you could still get a short when the loco attempts to leave the bridge. So, before you let it do that, you might have to rethrow the DPDT...but you'll figure that out soon enough.

[MisterBeasley]

No, that's the way it is. Think of a single track coming in to the turntable. If you are running either DC or DCC, when you run an engine on to the turntable the polarity of the rails must match as the engine passes from the track to the table. For the sake of argument, let's say that the track on the right side of the engine is positive, both on the incoming track and on the table. Now, if you rotate the turntable 180 degrees, you will notice that the rail on the right side of the engine now mates up with the incoming rail on the other side. If the turntable hadn't reversed the polarity for you, the engine would cause a short circuit as you moved back off the turntable.

[Geohan]

I have an Atlas turntable with three lead tracks coming to it. Each lead track position is labeled "A" or "B". When an end of the turntable track passes from an "A" to "B", or vice versa, the polarity reverses. Is there a way to prevent this?

Thanks for any help, Geohan