Bowser turntable shorts when turned 180 degrees

No. Track polarity does not matter.

Are you using a Dallee Electronics indexer (#1700)?

Can you explain what you're using and how it's hooked up? Pictures might be helpful. Please give us more specific information.

2 rail or 3 rail?

Three rail.  I am not using an indexer.  I got the Ross upgrade kit for the turntable drive.  The power to the main track and and to the track on the turntable come off the same bus lines.  I am using alligator clips temporarily to get power to the turntable track.  I don't have any stub tracks set up yet.  As you can see in the photo below the gap in the pit rails is well to the right of the turntable bridge.  With the turntable in its current position in the photo I can run a locomotive on or off the turntable without problems.  When the turntable is rotated 180 degrees it will then short out if I try to run a locomotive on or off the turntable.  If I reverse the alligator clips with the turntable rotated 180 degrees the engine will run on and off the turntable without problems.   

Is it possible that the power (center Rail) is shorting to ground by touching the brass pit side wall at some point when you rotate it? I think the power comes up through the senter of the table, and the ground comes thru the pit rail, is that correct?  I don't recall how I connected mine.

I am puzzled.  My turntable rail is not split.  Ground I feed thru turntable rail, and hot through shaft.  What is purpose of the split?

So while it's true that you don't really have polarity characteristics with AC, Hot and Common, I think in this case it explains why you're shorting out.....   Assuming you are using both halves of the pit rail independently from each other, one half for AC hot, and the other half for AC common...  then when you rotate 180 degrees, your center rail on the turntable bridge is now common, and the outer rail(s) are AC hot....  Problem is this same reversal of the AC wiring has not occurred on the fixed track that you're running the loco onto..  So the first outer wheel to bridge the gap is connecting AC hot to AC common, direct short

I chose to do what Rich did, which is to run the AC hot up the center shaft of the turntable, and use both 1/2's of the pit rail to conduct the AC common...  works really well.    I don't have a good photo of it, but I attached a 4" x 4" metal plate to the bottom of the drive disk around the shaft mount, then ran an arm with some sprung brass to contact the metal plate.  The arm is hinged on one side, and pulled up with a tension spring on the other end to keep the "contact" point between the brass wiper and the metal plate making good electrical connection.  This assembly carries my AC hot up the shaft without issues.  

Chris your explanation makes sense as when I spin the turntable 180 degrees and then reverse the alligator clips supplying power to the track it works okay.  Is there another option besides running the AC hot up the center shaft and using both 1/2s of the pit rail as common.  Is there a automatic polarity reversing switch for AC like there is for DC on HO scale layouts?

Neal    

Chris A explained the problem precisely.  The result is similar to what occurs when your block power transformers are not in phase....I.e. The locomotive wheel creates a short.

I offer a somewhat different solution illustrated in the photos.  Please excuse the "rough" paint and weathering, but I needed to resolve the electrical issue before proceeding.  

In this case, both running rails serve as the common, just like the remainder of the railroad and the roundhouse trackage.  The CENTER RAIL on the turntable bridge is HOT, but fed from above via the brass pole and (currently bare) copper wire to the metal arch.  Yes, Erector set....but brass in the future, along with different wiring.

The hot feed was soldered to the arch and  to the CENTER RAIL.  The  entire turntable now operates reliably, enabling a  hostler to be plenty busy during operating sessions.  We have 6-10 operators running a dozen manifest freights (with waybills) plus passenger trains and extras during a session.  This terminal is now a functional busy spot--FINALLY!

Chris A posted some photos a couple of years ago

Makes sense to use the center post for hot

Also, you could email Big_Boy_4005 - Elliot has one in his Dream/Nightmare layout.

Good looking engine facility Don. I like how you solved the problem. Pretty cool.

Carl,  thanks for finding the photos of my own Bowser turntable fix for me.....   Feeling pretty lame this AM, that another OGR member had to find my photos for me.....  Went looking on my hard drive for them last night, but I have too many photos and folders, and forgot that I had posted them earler...   Anyway, thanks very much.    Chris A

Carl:

Thank you for finding Chris's post from back in 2015.

Neal

Here's a photo of the underside of the turntable and the mounting bracket.  Any suggestions on how to get the AC hot to the center shaft?  Can I run the AC hot to the screw that tightens on the shaft or would it be better to take the mounting bracket off and drill in to the shaft and attach the AC hot directly to the shaft?