Date   

Re: Where to isolate on large loops and wye

whmvd
 

Don,

One multi-axle pick-up truck isn't always enough. Not if a loco with two trucks is involved, because then the two trucks are electrically connected. A one-truck length will then leave both gaps bridged by one unit leading to the problematic outcome.

Wouter


On Fri, 26 Feb 2021 at 14:52, Don Vollrath <donevol43@...> wrote:
Gents, any good AR control unit will detect a short circuit that occurs on either (or both) rail as metal wheels connected together on multiple axles roll across and span the isolating gaps while exiting an AR section and enter into a fixed polarity section of track. So that causes the exiting AR section to align its polarity to be the same as the fixed polarity track. That part is done.

As that same multi-axle pickup rolls onto and spans the next isolating gaps (either rail or both) to enter a different AR controlled section of track there will be another connection to cause the next AR unit to align itself to the fixed polarity track.

So the minimum length of fixed polarity track separating two separately controlled  AR sections of track needs to be only as long as a milt-axle pickup truck. Think loco, or passenger car, or tender. It doesn’t even need to be used for that purpose as long as there is an electrical connection between axles and wheels on at least one side of the truck to be connected together. This is what will cause the entering AR controller to also align itself to the fixed polarity track.

A convenient choice may be a turnout located between the AR sections  with insulating joiners on all 6 rails and wired for fixed polarity. (Or As someone else has pointed out... am entire double crossover with all 8 rails isolated )

DonV





Re: Where to isolate on large loops and wye

Don Vollrath
 

Gents, any good AR control unit will detect a short circuit that occurs on either (or both) rail as metal wheels connected together on multiple axles roll across and span the isolating gaps while exiting an AR section and enter into a fixed polarity section of track. So that causes the exiting AR section to align its polarity to be the same as the fixed polarity track. That part is done.

As that same multi-axle pickup rolls onto and spans the next isolating gaps (either rail or both) to enter a different AR controlled section of track there will be another connection to cause the next AR unit to align itself to the fixed polarity track.

So the minimum length of fixed polarity track separating two separately controlled AR sections of track needs to be only as long as a milt-axle pickup truck. Think loco, or passenger car, or tender. It doesn’t even need to be used for that purpose as long as there is an electrical connection between axles and wheels on at least one side of the truck to be connected together. This is what will cause the entering AR controller to also align itself to the fixed polarity track.

A convenient choice may be a turnout located between the AR sections with insulating joiners on all 6 rails and wired for fixed polarity. (Or As someone else has pointed out... am entire double crossover with all 8 rails isolated )

DonV


Re: Where to isolate on large loops and wye

Blair
 

I concur with Allen.  As long as

- the normal section is truly longer than the longest single electrical entity crossing it (i.e. if you wired all pickups on two locos together to lengthen their electrical footprint for some reason, that would become your longest single entity), AND

- as long as both reversing sections are long enough to not have anything happening at their far boundaries simultaneously on the same train, and short enough that no other train is going to add confusion to the situation,

then a single separating section of track need not be train length, just longer than the longest single 'footprint'.  The reason is, either AR can align itself with the 'fixed' short zone without 'the sands shifting in the meantime', so they won't start that annoying flip-flop-flip that never ends, and all will be stable.  Neither case 1, nor case 2, below, suffices to begin the flip-flop behaviour.

A good example is the "hoary dogbone with middle crossover", where both loops are fed from separate reversers, and the crossover is wired 'straight'.  No problem.  Whether the crossover is aligned straight, or as an X, both reversers will behave.

Blair

On 2/25/2021 3:41 PM, emrldsky wrote:
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 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,

Re: advice concerning minimum length of fixed polarity track segment between AR segments:  I have not found any advice either.   

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


12 photos uploaded #photo-notice

w4dccqa@groups.io Notification <noreply@...>
 


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


Added Folder /HeljanWalthers Turntable #file-notice

w4dccqa@groups.io Notification <noreply@...>
 

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


Re: Where to isolate on large loops and wye

Steven Tobias
 

Thank you! very helpful. 


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




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