BNSF,
From the diagram you posted, you definitely have a reverse polarity issue as you can see in the diagram that follows. I always find it useful to color the rails because any mismatch of colors between the rails on adjoining pieces or sections of track will immediately show a reverse polarity situation.
That "wye" that you refer to causes a reverse polarity situation at the point where the two legs of the wye meet the turntable track. This reverse polarity situation occurs because the turntable track will cause a mismatch of polarities when engines attempt to cross the gap between the turntable track and one of the wye legs depending on how the turntable track is wired.
In my diagram, the right leg of the wye is mismatched to the turntable track if the turntable is rotated counter clockwise. If the turntable is rotated clock wise, the left leg of the wye will be mismatched to the turntable track.
As already mentioned by others, if the turntable has a built in reverse polarity unit, no external auto-reversing unit is required. The reverse polarity situation will be taken care of automatically by the operation of the turntable. However, if the turntable does not have a built in reverse polarity unit, then an external auto-reversing unit must be provided, or at least an external switch that can reverse polarity when thrown.
Hope this helps.
Rich
Alton Junction
The Atlas TT has a built-in auto reverse circuit. If wired from the track next to the hand crank(that square blob), the power will be aligned with the left lead. Note that there is an 'A' engraved into the plastic on that lead. If you rotate the TT counter-clockwise to the right lead, you will have a polarity mis-match since there is an engraved 'A' on that lead as well. By rotating the entire TT assembly counter-clockwise, so that the 'B' is on the left lead, and a 'A' is on the right lead, you may be able to get rid of the problem without using a DPDT reversing toggle(DC) or a DCC auto-reversing unit. Read the direction that are packed with the Atlas TT, and experiment. The Walthers RTR powered TT's also have a built-in auto-reverse with an 'A' & 'B' side that is similar. Many other TT's do not have this built in and you will need a DPDT or DCC auto-reverser to handle the 'sort of' wye that this configuration creates.
BTW, I used an Atlas TT 'underneath' my old Walther 'kit' 90' TT to provide positive indexing and make up for the rather poor plastic bearings/out of round pit provide in the 'kit'. All of this was replaced about 3-4 years ago with a Walthers RTR 90' TT - Much better(and quiet to boot).
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Unless the Y leads to another track.
Springfield PA
As long as you have the turntable in the layout, I see no need at all for the "Y" -- all this is doing is duplicating the function of the turntable.
In this case the Y isn't a reverse loop but as someone noted earlier the Turntable could be if the track is powered while it rotates.
Let me see if I underestand this:
You have two spurs off one track that meet at a turntable. If that's the case, the turntable is a reversing section (not a reverse loop since the geometry of a loop is pretty specific and that's not the case here.) Note that the turntable is a reversing section whether the two tracks are opposed (as you describe) or parallel, because it can be rotated to turn a locomotive (or whatever*) end for end.
If the two tracks joined into a single track at a turnout to form a single tail track where a locomotive entering either track would end up with its front coupler against the end-of-track bumper, that's a wye - and the tail track is a reversing section.
Why the, "Or whatever*?" I have a turntable that will never turn a locomotive! It's used to turn the business/inspection car, and those cars which have to be unloaded from a specific side that are oriented in the wrong direction. A locomotive might run straight across it to get to the head end of a unit coal train from the engine service track, but won't be turned - the management wants the crown sheet on the downhill end when the loco hits the 4% grade out of town.
Chuck (Modeling mountainous Central Japan in September, 1964)
Take two colored pencils (e.g., red and blue) and trace over the rails on the track plan. That way you can visualize the reverse loop if there is one where one color rail connects to the other color.
The only other issue is whether or not the turntable has a reverse polarity mechanism built into it.
As the last post noted, try posting a pic or diagram.
Otherwise a Y is usually a reverse loop. The way to check is to follow one of the rails. If it can somehow come in contact with the other rail through turnouts or any other way, then you have a reverse loop.
without a pitcure, best guess is "probably".
to post a picture, upload it to photobucket/railimages/etc, then use the "forum code" (on photobucket, it's "IMG CODE") link and paste it right in the body. If you don't have a forum/image code version of the link, you have 2 options:
1. take the "direct link" and copy/paste it into [ img] [ /img] tags (spaces added by me so the tag shows up)
2. take the "direct link" and copy/paste it into the "Insert media" tool (looks like a film strip).
-Dan
Builder of Bowser steam! Railimages Site