Wiring Turntable track for DCC

[bp020897]

Is an auto reversing module a must to prevent a DCC equiped locomotive, on my turntable track, from shorting when reversed and moving off the table into a roundhouse or back toward the mainline? Could I get by with a switch (SPST or ?) and manually reverse polarity? I am feeling electrically challenged.

It would be nice to save a few bucks if possible. I have a Lenz DCC system for my 4'x9' layout and recently installed a Wathers 90' turntable, which feeds into a roundhouse, located on a peninsula attached to the layout.

I was looking at the auto reverse module sold by Tony's Trains for $40 and the Lenz LK100.

Any suggestions would be appreciated.

Bob

[Anonymous]

No matter if you have DCC or conventional DC, when you reverse the direction of the rails, you reverse polarity (DC) or phase (AC). You can use a double pole double throw switch if you have a good memory and attention span. Otherwise, life is much easier using an automatic reverser. MRC make them and you can find them at Micro-Mark for around $30.
Or you can use of the reversing circuit on your booster, if equiped, and it's not being used for a reverse loop, wye or other trackage that requires reversing track polarity.

[olequa]

You don't need a good memory to remember which way to throw the switch. Probably one end of the turntable has a cab. Mark the switch as 'Cab' in one position and blank in the other. Match the switch position to the cab position.

You just have to remember to throw the switch whenever you rotate the turntable.

[MisterBeasley]

The Atlas turntable does the reversing for you, so no additional circuitry is needed. Does anyone with a Walther's 90-footer know whether a reverser is needed? I think most turntables do require some sort of reverser (either automatic or manual) but there are some that don't. Hopefully, the instructions will provide wiring diagrams.

[tomikawaTT]

If the turntable powers the bridge rails through either the carrying wheels or a wiper riding on the 2-part ring rail at the two ends, the track on the table reverses itself and no further attention is required. DCC will suffer a momentary interruption, no effect at all on DC.

If the bridge rails are powered through slip rings that don't automatically reverse the rails, then a reverse switch or autoreverser is necessary.

Chuck

[UNIONPACIFIC4018]

I use a digitrax reversing module.
One rail on the bridge is fed through the wheels on the bridge
the other rail is fed from a small wire run up the bridge arch.
the pit rail is fed to the module and a bare wire with a tiny loop in the end goes from the bridge arch to a brass pole that extends below the subroadbed with a wire from it to the module. Runs like a champ and is pretty cool knowing you are supplying power to the bridge arch like the prototype.

[selector]

QUOTE: Originally posted by MisterBeasley

Does anyone with a Walther's 90-footer know whether a reverser is needed? I think most turntables do require some sort of reverser (either automatic or manual) but there are some that don't. Hopefully, the instructions will provide wiring diagrams.

Yes, it does. And yes, the instructions are fairly straightforward. What is not straightforward is getting the thing installed and operating reliably, if my experience and those of a few others on this forum are any indication. When you are ready to assemble it, let me know, and I will talk you through some handy fixes that placed mine in the 90% solution range.

-Crandell

[bp020897]

Thanks for the help this forum is great. I am leaning toward installing a DPDT switch.

I have the 90' Wathers kit turntable and their DC motor to drive it. I installed the dual wipers on the drive shaft for track power hook-up and have operated it. A switch or auto reverser is needed as a loco produces a short after being turned around and trying to exit .

The drive motor is powered by an old DC train transformer I have which allows me to dial down the voltage when lining up the turntable with other track.

[Anonymous]

I think the response that you have to change the track polarity either manually with a switch or automatically with a reverser pretty much covered your question. But some replies indicated that there is some construction obstacles that you might want to consider.

I also have the Walters 90 footer and when I put mine together a couple of years ago I received excellent advice about some problems to be aware of and solutions that individuals devised so your 90 footer will run well. I made a number of those changes and I am satisfied with it's operation. Ask the forum members and you will get good advice.

One problem that I recognized by watching a friends turntable was the speed of rotation. A 12v motor will spin it around like a merry go round. In other words way to fast. I didn't know what speed that it should turn I just knew that 12v was way to fast. If you consider that the first turn table were moved by hand the sure wouldn't go around very fast. When the TT's were later electrified the motors would have had to been geared down be cause they needed torque not speed. Locos were getting ever heavier.

The whole speed thing was solved for me when I stopped by a small tourist railroad. They have a turn table and I was able to time the revolution required to make the turn. When I got home I tried a couple of thing and settled on 5 volts. Works good and isn't as noisy.

Another thing that helped me was that the turn table operator overshoot his stopping place and had to reverse the power to get it lined up properly. I do it pretty often my self.

[richhotrain]

Before recently installing a fully indexed "auto reverse" Walthers 130' turntable, I had a 90' version that I operated manually with a DPDT switch to reverse polarity. I soldered a bi-polar LED to the DPDT switch which lighted green for normal polarity and red for reverse polarity. Could also wire a signal to the DPDT to show green or red for normal or reverse polarity.

[blarger]

QUOTE: Another thing that helped me was that the turn table operator overshoot his stopping place and had to reverse the power to get it lined up properly. I do it pretty often my self.

I installed a DPDT momentary contact , center-off switch wired as a reverse switch to opearte the TT motor. This makes it easy to reverse the TT direction when overshooting.

I really like the idea of labeling the TT track reversing switch indicating the cab end of the TT bridge.

[Anonymous]

I have used both methods. It depends on the budget. Also, prototype tables rotate pretty fast. Got to keep em rolling.

[Anonymous]

In the back pages of the last Model Railroad Planning are diagrams for setting the ring rail gaps for dcc. I`d start there. I like the suggestion on wirring the decoder into the bridge!
LATER!