Re: Where to isolate on large loops and wye

wirefordcc

Hi Mike,

I thought about the usual scenarios.  The usual problem is the train exiting a reversing section while another portion of the same train enters it at the far end.  This causes one of the train to want to flip the auto reversing one way while the other end is trying to get it to go the other way.  Both ends of the reversing section are competing with itself and causes a short.

Now let's think about 2 separate auto reversing sections separated by a fixed polarity section, say 18" long.  A train with lighted passenger cars, leaving reversing section #1, enters the fixed polarity section of track.  If need be, the auto reverser #1 switches and all is well.  It travels through the fixed polarity section, that let's assume is the length of a Big Boy.  The train then enters reversing section #2.  If need be the #2 auto reverser switches.  #1 is still fine and stays put.  In this situation, #1 and #2 are not competing with each other.

Any other thoughts anyone?

Allan

Re: Where to isolate on large loops and wye

emrldsky

On 2/25/2021 1:02 PM, wirefordcc wrote:
Does anyone have a scenario you think I need to think about that might be a problem?
Hi Allen,
Two instances come to mind, although I do not know how common they might be.
1. A long passenger train with all lighted cars, and
2 A freight train with helpers in the middle and at the end.
In these situations I would imagine the fixed polarity track to be shorter than the train length, possibly a lot shorter, so the front end would be in one reversing section, the middle in the fixed polarity section, and the end of the train in the other reversing section.
I can see some home layouts, especially those in small spaces, where the fixed polarity track would be small for space reasons because the reversing sections need most of the space for the loop radius to be big enough to make the turns with the longer cars.

Peace,
Mike G.

Re: Where to isolate on large loops and wye

wirefordcc

Hi Bill,

I thought about situations where modelers might have two reversing sections controlled by automatic reversing circuits with a fixed polarity section between them.  I couldn't think of a problem if the fixed polarity section was only as long as a single locomotive (your longest locomotive or powered passenger car).

Does anyone have a scenario you think I need to think about that might be a problem?

Allan Gartner
Wiring for DCC

Re: Where to isolate on large loops and wye

wirefordcc

Hi Bill,

Thanks for the column ideas.  Keep 'em coming!

To answer that question, I need to think on that some more.  For sure, making a fixed polarity section as long as your longest powered train would be adequate.  But let me think about that some more.  If that isn't necessary, I'm sure that would benefit some modelers.

Allan

Re: Where to isolate on large loops and wye

D B

Wouter,

Allen,

Maybe a subject for a follow-up article?

Bill D
N&W Steam Only

On Feb 25, 2021, at 9:47 AM, whmvd <vandoornw@...> wrote:

Hi Don,

That 'short' piece of track linking to AR sections does raise the question 'how long at least?' immediately. My first thought is that it should be at least as long as the maximum (outer) distance between axles that pick up current on the longest individual piece of rolling stock - but I could easily be wrong, and it gets even more complicated with staggered pick-ups. Is there any guidance on this somewhere? If so, I've not found it.

Wouter

On Thu, 25 Feb 2021 at 14:25, Don Vollrath <donevol43@...> wrote:
Good description of AR, Bill.
Some may argue with the need to have the AR section longer than the train only to get caught later with problems when using lighted passenger cars or a lighted caboose or a following helper loco.
If two AR sections abut one another there can be a never ending cycle of both AR controllers detecting a phase mismatch and flipping the polarity only to find a mismatch again and repeating the cycle. A simple fix is to provide a short section of track between them wired at a fixed polarity.

DonV

Re: Where to isolate on large loops and wye

whmvd

Hi Don,

That 'short' piece of track linking to AR sections does raise the question 'how long at least?' immediately. My first thought is that it should be at least as long as the maximum (outer) distance between axles that pick up current on the longest individual piece of rolling stock - but I could easily be wrong, and it gets even more complicated with staggered pick-ups. Is there any guidance on this somewhere? If so, I've not found it.

Wouter

On Thu, 25 Feb 2021 at 14:25, Don Vollrath <donevol43@...> wrote:
Good description of AR, Bill.
Some may argue with the need to have the AR section longer than the train only to get caught later with problems when using lighted passenger cars or a lighted caboose or a following helper loco.
If two AR sections abut one another there can be a never ending cycle of both AR controllers detecting a phase mismatch and flipping the polarity only to find a mismatch again and repeating the cycle. A simple fix is to provide a short section of track between them wired at a fixed polarity.

DonV

Re: Wiring Up a Manual Turntable?

John White

Jerry
I just uploaded several files with some instructions for powering the Heljan/Walthers 90 ft turntable plus some others of the turntable. I have mine powered with the wipers as shown. Although my turntable goes back to 1970's or 80's & it works fine. Contact me if you need too. Hope it helps.
John

The following photos have been uploaded to the Heljan/Walhers 90' Turntable vintage album of the w4dccqa@groups.io group.

By: John White <jtw37@...>

Re: Where to isolate on large loops and wye

Don Vollrath

Good description of AR, Bill.
Some may argue with the need to have the AR section longer than the train only to get caught later with problems when using lighted passenger cars or a lighted caboose or a following helper loco.
If two AR sections abut one another there can be a never ending cycle of both AR controllers detecting a phase mismatch and flipping the polarity only to find a mismatch again and repeating the cycle. A simple fix is to provide a short section of track between them wired at a fixed polarity.

DonV

John White <jtw37@...> added folder /HeljanWalthers Turntable

Re: Where to isolate on large loops and wye

Steven Tobias

On Wed, Feb 24, 2021 at 12:08 PM D B <1932mgj2@...> wrote:
Steven Tobias,

AR refers to “auto reverse” — either a segment of track controlled by an AR device or the device itself, which automatically senses the incidence of a short circuit as the conductive wheels of an engine or car pass over the “gap” between two segments of track of opposing phase/polarity.  The device automatically switches the phase/polarity of the reversing segment of track to match that of the non-reversing segment, averting the short before it can trip the circuit breaker.

Bill D
N&W Steam Only

On Feb 24, 2021, at 1:14 AM, Steven Tobias <srtobias29@...> wrote:

﻿
sorry - what does AR stand for.

Thanks,

Steven Tobias

On Thu, Feb 18, 2021 at 8:24 AM Don Vollrath <donevol43@...> wrote:
Yes you can attach the output wires of an AR until to more than one place within the AR section of track. May help bypass misc poor rail connections, etc. Just make sure you have a consistent rail polarity.

DonV

Re: Where to isolate on large loops and wye

D B

Steven Tobias,

AR refers to “auto reverse” — either a segment of track controlled by an AR device or the device itself, which automatically senses the incidence of a short circuit as the conductive wheels of an engine or car pass over the “gap” between two segments of track of opposing phase/polarity.  The device automatically switches the phase/polarity of the reversing segment of track to match that of the non-reversing segment, averting the short before it can trip the circuit breaker.

Bill D
N&W Steam Only

On Feb 24, 2021, at 1:14 AM, Steven Tobias <srtobias29@...> wrote:

﻿
sorry - what does AR stand for.

Thanks,

Steven Tobias

On Thu, Feb 18, 2021 at 8:24 AM Don Vollrath <donevol43@...> wrote:
Yes you can attach the output wires of an AR until to more than one place within the AR section of track. May help bypass misc poor rail connections, etc. Just make sure you have a consistent rail polarity.

DonV

Re: Wiring Up a Manual Turntable?

wirefordcc

Hi Bill,

My next column in Model Railroader, which should arrive in everyone's mail box in the next couple of days, is on reversing.  I think I addressed your issues there and will also be adding content to my website as a result.

I find it a real challenge to fit things into two pages of the magazine.  So my website will continue to provide any additional details I need to discuss.

Thanks and keep those ideas coming!

Allan

Re: Wiring Up a Manual Turntable?

Steve Hubbard

On my Bowser 130’ Turntable I used the ring rail for one bridge conductor and the bridge shaft for the other conductor.  The shaft utilizes a 5/16”’ thick X  ¼ ID X ½” OD brass setscrew collar and a commutator style wiper.  Then I used an NCE decoder to drive the Turntable motor.  A DCC specialty’s AR for polarity control.  I would refrain from using a pair of wires that will be twisted CW and CCW as eventually they will break and to keep track of when to reverse direction will be a PITA and will get old quick, just sayin..

Sent from Mail for Windows 10

Re: Wiring Up a Manual Turntable?

Dave Emery

I wonder if it’s easier to explain reversing loops first, or turntables first?

dave

Re: Wiring Up a Manual Turntable?

Jerry Breon

I am also to the point where I need to select a wiring method for my Diamond Scale 120' HO turntable. I use NCE DCC and will include a DCC reverser of some description (likely a DCC Specialties OnGuard AR) for the turntable bridge track. I'm not sure that I want to rely on the ring rail for power conductivity and certainly don't want to get into the delicacy of conducting power thru the overhead arch structure. My installation is further complicated by a NYRS PTC actuator motor connected to the base of the rotating turntable bridge shaft so wires to the bridge rails will need to enter thru the side of the rotating shaft. My wiring options seem to be fabricating dual insulated wipers located on the shaft just above the NYRS motor and sending two wires up thru the drilled out shaft to the bridge rails OR foregoing the wipers and just sending two wires up thru the drilled out shaft and looping enough flexible slack beneath the turntable to allow the wires to wind up with rotation in one direction and unwind with rotation in the opposite direction. This would by far be the most simple and conductively reliable method, and I may give it a try before moving on with the more complicated wiper design. I would add that I am a lone operator and therefor can easily monitor the wind up status of the bridge wiring beneath the turntable.
Does anyone have any experience with or thoughts on this plan?
Thanks,
Jerry Breon
Mooresville, NC

Re: Where to isolate on large loops and wye

Steven Tobias

Thanks

On Wed, Feb 24, 2021 at 4:12 AM whmvd <vandoornw@...> wrote:
Steven: AutoReverser.
Wouter

On Wed, 24 Feb 2021 at 06:14, Steven Tobias <srtobias29@...> wrote:
sorry - what does AR stand for.

Thanks,

Steven Tobias

On Thu, Feb 18, 2021 at 8:24 AM Don Vollrath <donevol43@...> wrote:
Yes you can attach the output wires of an AR until to more than one place within the AR section of track. May help bypass misc poor rail connections, etc. Just make sure you have a consistent rail polarity.

DonV

Re: Wiring Up a Manual Turntable?

D B

Allen,

When you discuss reversing phase/polarity segments and use of auto-reverse devices in an article, I suggest you discuss WHY a reversing segment must be longer than one’s longest train. Not too long ago I was a total newbie, and often saw that rule recited (including in universally respected websites). But I didn’t see a cogent (and non-technical) explanation for that rule, or similarly, a clear and concise explanation why two reversing segments cannot be connected to one another.

I figured out the reasons underlying both those rules after giving the issue considerable thought (because frankly I did not intuitively understand “why”). In retrospect my failure to understand was influenced by my (mistaken) “forward-looking” focus on how an AR device switched phase/polarity of the reversing segment as the front wheels of the engine passed from the reversing segment to the non-reversing “mainline.” Coming from the world of DC, I was amazed at the prospect of auto-reversing and simply failed to consider what was going on at the rear of the train as the phase/polarity of the reversing segment switched based on what was happening at the front of the train.

Once I began to look “both ways,” and to consider both front and rear consequences of a change in phase/polarity, the underlying rationale for both rules came into sharp focus. That in turn led to an understanding of the relationship of the AR segment to the segments to which it is directly connected and an appreciation of why two reversing segments cannot be directly connected to one another.

Bill D
N&W Steam Only

On Feb 22, 2021, at 9:10 AM, wirefordcc <bigboy@wiringfordcc.com> wrote:

﻿Hi Dave,

I should have said, keep those ideas coming! The one scary thing I worry about is running out of ideas for my column. I scan my Q&A forum, as well as some of the other forums for ideas. So far, so good.

Thanks!

Allan Gartner

-----Original Message-----
From: w4dccqa@groups.io <w4dccqa@groups.io> On Behalf Of Dave Emery via groups.io
Sent: Sunday, February 21, 2021 2:57 PM
To: w4dccqa@groups.io
Subject: Re: [w4dccqa] Wiring Up a Manual Turntable?

Alan, I think ‘wiring a turntable for DCC’ would make a great MR column.

dave

Re: Where to isolate on large loops and wye

whmvd

Steven: AutoReverser.
Wouter

On Wed, 24 Feb 2021 at 06:14, Steven Tobias <srtobias29@...> wrote:
sorry - what does AR stand for.

Thanks,

Steven Tobias

On Thu, Feb 18, 2021 at 8:24 AM Don Vollrath <donevol43@...> wrote:
Yes you can attach the output wires of an AR until to more than one place within the AR section of track. May help bypass misc poor rail connections, etc. Just make sure you have a consistent rail polarity.

DonV

Re: Where to isolate on large loops and wye

Steven Tobias

sorry - what does AR stand for.

Thanks,

Steven Tobias

On Thu, Feb 18, 2021 at 8:24 AM Don Vollrath <donevol43@...> wrote:
Yes you can attach the output wires of an AR until to more than one place within the AR section of track. May help bypass misc poor rail connections, etc. Just make sure you have a consistent rail polarity.

DonV

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