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Analog loop reversing relay

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Analog loop reversing relay
Posted by Dave K on Sunday, March 14, 2021 7:55 AM

Who makes a good relay for analog train operation?

 

Regards,

Dave K.

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Posted by Lastspikemike on Sunday, March 14, 2021 9:20 AM

I don't know about "good" but I use a plain old Atlas snap relay wired through the turnout switch to reverse polarity inside the loop as the turnout is thrown.  Works for DC quite nicely as long as you remember that it reverses polarity inside the loop. You need approaches to the loop exits at least as long as the longest locomotive consist you will run through the loop for this to work because you have to wait for the locomotive consist to clear the isolated section of the loop before throwing the turnout. Main polarity feeds these two sections of track between the turnout routes and the isolation points at each end of the reversing loop section. 

When the turnout is thrown on entry to the loop that snap relay matches polarity of the loop to main for that direction. Once the train is entirely in the loop the main polarity is reversed. When the locomotives leave the loop polarity section then polarity of that reversed section is reversed when the turnout is lined for the train to exit. This sets loop polarity for the next train entering.  Next train in traverses the loop in the opposite direction and polarity in the loop will be correct.

I could automate this with some sort of sensor and I expect I could automate this with a DCC style auto reversing relay board but I kind of like just driving the train. 

Alyth Yard

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Posted by Ian R. on Sunday, March 14, 2021 10:04 AM

A simple center-off, DPDT toggle switch does the trick nicely, changing the polarity in the loop just as Mike described.

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Posted by Lastspikemike on Sunday, March 14, 2021 1:52 PM

Ian R.

A simple center-off, DPDT toggle switch does the trick nicely, changing the polarity in the loop just as Mike described.

 

Yes, the Atlas snap relay is just such a switch, actually two SPDT in one which allows you to create the DPDT switch using the whole relay by cross wiring the four poles at the active end resulting in polarity reversal when the relay is energized. You run the track end to both sides of the "common terminals" and the powerpack end to the one set of active terminals, cross connecting these to the other set of active terminals. Atlas wiring book shows the schematic. I think the instruction sheet that comes in the box also explains this simple wiring.  

Alyth Yard

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Posted by ATLANTIC CENTRAL on Sunday, March 14, 2021 2:11 PM

With DC, if you plan to reverse the loop polarity, you need to stop the train, reverse the loop polarity, reverse the throtte polarity, then restart the train.

So yes, you can create a semi automatic situation where the turnout position controls the entry/exit polarity, but at some point while the train is in the loop, it has to stop and let the turnout be thrown and the throttle direction reversed for the other direction on the mainline.

Otherwise, when you throw the turnout, the train will change direction.

Sheldon

    

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Posted by Lastspikemike on Sunday, March 14, 2021 3:20 PM

ATLANTIC CENTRAL

With DC, if you plan to reverse the loop polarity, you need to stop the train, reverse the loop polarity, reverse the throtte polarity, then restart the train.

So yes, you can create a semi automatic situation where the turnout position controls the entry/exit polarity, but at some point while the train is in the loop, it has to stop and let the turnout be thrown and the throttle direction reversed for the other direction on the mainline.

Otherwise, when you throw the turnout, the train will change direction.

Sheldon

 

This turns out to be incorrect. Took me a little while to figure out.

The key aspect is to provide sections of main line powered track inside the actual geometric reversing loop long enough to hold the entire locomotive consist. This requires the reversing section to be shorter than might otherwise fit within a loop created by one turnout. For our back to back loops which basically have a long double isolated X  section  these main line powered sections are very long so there's practically no limit to train length, but for our one single turnout loop we sacrifice a little train length capacity to allow for these main line powered sections.

A section of track long enough to contain the locomotive consist just before the exit to the loop is all that is required. For a two way loop you need the same length of main line powered track at the other end of the reversing section. Each one of these sections forms  one of the two routes out of the turnout. 

The turnout also sets polarity in the reversing section to match train direction entering the loop.  The train proceeds into the loop and passes onto the reversing section proper. When the whole powered part of the train (which is the whole thing if you use metal wheels) is within the reversing section, I.e. has cleared the entry section of track powered by the mainline, you switch polarity of the main line,  as the locomotive consist clears the reversing loop onto the second section of main line included inside the loop only then do you throw the turnout which changes the polarity in the reversing section. The locomotives don't change direction and the trailing car wheels don't short out the isolating gaps.

It's all in the timing of the polarity changes. Should work fine for DCC in fact. I think for DCC the mainline sections aren't needed but I'm still thinking about that. DCC allows you to flip " polarity" inside the reversing loop whenever you like. The steel wheel effects from the trailing cars might be an issue though.

This all results from the Möbius Strip aspect of a reversing loop where one rail is always a continuation of the opposite rail. A reversing loop is made from one rail.  Magical in a way.

You never need to stop the train.

Alyth Yard

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Posted by ATLANTIC CENTRAL on Sunday, March 14, 2021 3:48 PM

Lastspikemike

 

 
ATLANTIC CENTRAL

With DC, if you plan to reverse the loop polarity, you need to stop the train, reverse the loop polarity, reverse the throtte polarity, then restart the train.

So yes, you can create a semi automatic situation where the turnout position controls the entry/exit polarity, but at some point while the train is in the loop, it has to stop and let the turnout be thrown and the throttle direction reversed for the other direction on the mainline.

Otherwise, when you throw the turnout, the train will change direction.

Sheldon

 

 

 

This turns out to be incorrect. Took me a little while to figure out.

The key aspect is to provide sections of main line powered track inside the actual geometric reversing loop long enough to hold the entire locomotive consist. This requires the reversing section to be shorter than might otherwise fit within a loop created by one turnout. For our back to back loops which basically have a long double isolated X  section  these main line powered sections are very long so there's practically no limit to train length, but for our one single turnout loop we sacrifice a little train length capacity to allow for these main line powered sections.

A section of track long enough to contain the locomotive consist just before the exit to the loop is all that is required. For a two way loop you need the same length of main line powered track at the other end of the reversing section. Each one of these sections forms  one of the two routes out of the turnout. 

The turnout also sets polarity in the reversing section to match train direction entering the loop.  The train proceeds into the loop and passes onto the reversing section proper. When the whole powered part of the train (which is the whole thing if you use metal wheels) is within the reversing section, I.e. has cleared the entry section of track powered by the mainline, you switch polarity of the main line,  as the locomotive consist clears the reversing loop onto the second section of main line included inside the loop only then do you throw the turnout which changes the polarity in the reversing section. The locomotives don't change direction and the trailing car wheels don't short out the isolating gaps.

It's all in the timing of the polarity changes. Should work fine for DCC in fact. I think for DCC the mainline sections aren't needed but I'm still thinking about that. DCC allows you to flip " polarity" inside the reversing loop whenever you like. The steel wheel effects from the trailing cars might be an issue though.

This all results from the Möbius Strip aspect of a reversing loop where one rail is always a continuation of the opposite rail. A reversing loop is made from one rail.  Magical in a way.

You never need to stop the train.

 

That is really the same thing with gaps in different places. You are still reversing the main and throwing the turnout in any case. And you failed to explain that little wrinkle of the mainline polarity extending into the loop to the OP, I bet that was not on his radar.

You are simply controlling the polarity of the reversing section with the turnout position ahead of the mainline reversing switch. Nothing new there. You then of course need a throttle location reverse switch to back up inside the reversing section.

And this is all great if you can see the train easily to know it has moved from the reverse section to the mainline fed section. Many great layouts I have operated on have hidden reverse loops and they easily work fine with two separate switches, using minimal detection or train locating methods.

For all that "timing" you are suggesting one might as well do it the conventional way and simply have separate reversing switches for the loops.

Set them correctly to enter the loop, reverse the main while the train is in the loop, throw the turnout and exit the loop, all easily done in the time it takes and normal train to travel around any usable sized reverse loop.

But since I don't have time to draw a bunch of diagrams today, or this week, once again I will leave you to it.

And, for what it is worth, my layout is full of X sections. They are used at every mainline interlocking to eliminate unnecessary blocks.

Sheldon

    

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Posted by Dave K on Tuesday, March 16, 2021 8:02 AM

Gents:

I am researching an Alastranz turnback relay with an infrared sensor.  I would prefer an automated process but it starting to get complicated.

Dave

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Posted by Dave K on Tuesday, March 16, 2021 8:15 AM

I meant to say Azatrax.  I am going to try the Atlas switch method first.

 

Thanks to all.

 

Dave

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Posted by Chuck S on Tuesday, March 16, 2021 8:31 AM

Curious why you want an "analog" or manual reverse loop switch.  I have enough problems avoiding running thru closed turnouts to risk having to throw a toggle switch every time one of my trains enters the reverse loop.  I plan to install the Azatrax IR detector to handle one turnout at my "yard" that I constantly forget to throw after the train leaves. 

Plug-n-Play Digitrax AR1 and NCE AR10 reversers handle reverse loops perfectly with no intervention.  Two wires to the reverse loop tracks, nothing exotic, no sensors needed, etc.  Just run the trains.  I've used both. 

-- Chuck

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Posted by ATLANTIC CENTRAL on Tuesday, March 16, 2021 8:44 AM

Chuck S

Curious why you want an "analog" or manual reverse loop switch.  I have enough problems avoiding running thru closed turnouts to risk having to throw a toggle switch every time one of my trains enters the reverse loop.  I plan to install the Azatrax IR detector to handle one turnout at my "yard" that I constantly forget to throw after the train leaves. 

Plug-n-Play Digitrax AR1 and NCE AR10 reversers handle reverse loops perfectly with no intervention.  Two wires to the reverse loop tracks, nothing exotic, no sensors needed, etc.  Just run the trains.  I've used both. 

-- Chuck

 

Because the original poster is running DC, not DCC, so a DCC auto reverser will not work.

That is what he meant by "analog train operation", his trains are "analog", not digital.

Sheldon

    

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Posted by Chuck S on Wednesday, March 17, 2021 7:02 AM

Thanks, and sorry for posting bad information.  I was under the impression the autoreversers would work on either DC or DCC but it ain't so!  Embarrassed  DCC is so simple I forgot some folks like to or at least have to throw dozens of switches to run a couple of trains. Back into trains a couple of years ago and DC was never a consideration.

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Posted by ATLANTIC CENTRAL on Wednesday, March 17, 2021 8:48 AM

Chuck S

Thanks, and sorry for posting bad information.  I was under the impression the autoreversers would work on either DC or DCC but it ain't so!  Embarrassed  DCC is so simple I forgot some folks like to or at least have to throw dozens of switches to run a couple of trains. Back into trains a couple of years ago and DC was never a consideration.

 

Chuck, I understand why you like DCC, and I have lots of experience using DCC. But I am building a new layout, 1500 sq ft, 450' double track mainline, 8-10 operators in play, staging for 30 trains, 40-50 car train lengths, and it will be DC.

And guess what? There will not be one block toggle.

There will be walk around operation with radio throttles, detection, signaling, CTC, ATC (if you run a red single your train stops), one button turnout route control.

As a guest operator on my layout you would likely push less buttons than on a similar DCC layout.

For more info look for my thread about my track plan.

In fact. You might be surprised at the percentage of modelers in HO and N with moderately large layouts who still use DC. Every casual survey we have taken on here, some fairly recent, puts DC use still at 40-45% and not likely to change.

Sheldon

    

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Posted by Dave K on Saturday, March 20, 2021 7:59 AM

How do I operate the snap switch?  In other words the left and right buttons as the train approaches the reversing loop, in the loop, and exiting the loop?

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Posted by Lastspikemike on Saturday, March 20, 2021 8:27 AM

Dave K

How do I operate the snap switch?  In other words the left and right buttons as the train approaches the reversing loop, in the loop, and exiting the loop?

 

Assuming DC power. Assuming the activation circuit for the snap relay is wired to the turnout switch. Your reference to left and right buttons implies to me that you have an Atlas turnout switch (the one with the blue button). The snap relay has no buttons.

Set the turnout for the desired train direction into the loop. That should match the polarity of the reversing section to that of the main. If it does not then reverse the polarity of the contacts at the actuating side of the snap relay ( there are three wires, black is common, reverse the red and the green). 

Once the entire train is within the reversing loop select the opposite direction (polarity) for the main line. Do not line the turnout yet. As the locomotives leave and completely clear the reversing loop and fully enter onto the main line which now has matching polarity you then line the turnout. This then also conveniently reverses the polarity within the reversing loop ready to accept the next train entering from the opposing direction.  If the next train is to enter in the same direction as the first train then you must re-line the turnout back to the desired direction which will again match the polarity.  

Alyth Yard

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Posted by SeeYou190 on Saturday, March 20, 2021 10:41 AM

Dave K
Who makes a good relay for analog train operation?

Dave K
I am researching an Alastranz turnback relay with an infrared sensor.  I would prefer an automated process but it starting to get complicated.

Dave K
How do I operate the snap switch?  In other words the left and right buttons as the train approaches the reversing loop, in the loop, and exiting the loop?

Hello Dave.

I am trying to figure out your question, and filter out the noise in the responses.

It sounds like you have a turn-back reverse loop at the end of your run, and you want to turn the train around in the loop, without stopping, and return on the same track.

You want control of this reverse loop to be simple and preferably automatic.

Is this correct? If not, can you explain your goals a bit more?

Are you comfortable bulding a DC control system for this, or do you need to use something off the shelf?

Is it OK to have a complicated system as long as control is simple, or would you prefer to build something simple and have it a bit more fiddly to control?

I can help, I have done such a thing on real layouts, but I need to understand exactly what your goals are.

Let me know. I am here to help.

I will check back in a few hours when I have time this evening.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Dave K on Sunday, March 21, 2021 7:31 AM

Kevin,

 

You are correct. A smple turn back using DC analog power.  I am using Atlas snap switched to accomplish the reveres polarity control.

 

Dave

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Posted by ATLANTIC CENTRAL on Sunday, March 21, 2021 9:38 AM

Dave K

Kevin,

 

You are correct. A smple turn back using DC analog power.  I am using Atlas snap switched to accomplish the reveres polarity control.

 

Dave

 

Dave, Why is it important to you to try an automate the reverse loop function?

Good DC practice suggests that the reverse switch positon for the mainline should refect the "EAST - WEST" direction of travel, so even with some semi automation of the loop you will need to throw the mainline reverse switch.

I use DC, very complex DC with detection, signals, one button route control, CTC, walk around radio throttles - and I avoid reverse loops as much as possible.

I'm getting ready to start on this basement filling layout - there will only be two reverse loop situations - neither is part of the mainline:

 

I would be interested to see you track plan and offer my thoughts on a total wiring solution.

Sheldon 

    

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Posted by SeeYou190 on Sunday, March 21, 2021 10:46 AM

Dave K
You are correct. A smple turn back using DC analog power.  I am using Atlas snap switched to accomplish the reveres polarity control.

Which do you prefer?

1) Simpled to install, but not as simple to use.

2) More involved to build, but simple to use.

Also, I never use Atlas wiring components. I prefer full size toggle switches.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Dave K on Monday, March 22, 2021 4:12 PM

I have wired the Atlas switches as required.  Purchased two.  The center slide position shoul be off, yet my center position on both is showin power out?  The down position is off.  Are these faulty switches?

 

Dave 

K.

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Posted by ATLANTIC CENTRAL on Monday, March 22, 2021 6:49 PM

Dave K

I have wired the Atlas switches as required.  Purchased two.  The center slide position shoul be off, yet my center position on both is showin power out?  The down position is off.  Are these faulty switches?

 

Dave 

K.

 

Well Dave, without a wiring diagram showing what you have done, it is hard to say.

Sheldon

    

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Posted by Lastspikemike on Monday, March 22, 2021 7:52 PM

The Atlas turnout switches are constant contact when you press down regardless of where the switch button is. There's no dead centre position. The pressing down of the button against a spring is what makes the contact. The blue button slides to the left or to the right and is off when the button has no downward pressure on it  

Only if you have a live connection without your finger on the button do you have a fault. This is a well known failure mode for Atlas turnout switches.

Common power is the black wire to the center terminal. Left is red and right is green (although that is arbitrary). If you slide the button over then no contact is made. You press the button to make contact. As far as I know there is no dead spot in the centre of the button movement range, although technically there must be at least a small gap.  

Atlas snap relays also have no center off position. The slide switch (tiny black button in the slot) can be moved by hand but when triggered electrically it has two "on positions" and no off. 

If no photos then post the Atlas part numbers. We have the wiring diagrams. 

Alyth Yard

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Posted by SeeYou190 on Monday, March 22, 2021 9:21 PM

Dave,

Before this discussion swirls any further down, can you please provide a track plan, wiring diagram, and any pictures?

You can email them to me if you want to.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Dave K on Tuesday, March 23, 2021 8:20 AM

Kevin,

 

I will do that.  I am not sine powere turnout switches but snap switches for turnback control.

 

Dave

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Posted by Lastspikemike on Tuesday, March 23, 2021 8:27 AM

Snap relays are powered by momentary on/off switches like turnout motor switches. Indeed, those Atlas snap relays are just turnout motors with specialized innards.

Track power is connected to the side terminals. The "to track" side is usually the single terminal in the middle of the side of the relay. The four terminals on the sides towards the end of the relay opposite the three AC terminals are used for the reversing of polarity from the DC terminals on the power pack. You can do it the other way (direction of current) if you prefer. These terminals route DC power from the powerpack to the track whenever the throttle is above zero. The only interruption is through the polarity reversal effected at the four terminal end by wiring in a pair of crossover wires. Those crossover wires create a DPDT switch operated by a solenoid relay. The same crossover wires are inside or underneath a standard DPDT switch. However, the Atlas snap relay has no center off position. Well, it does but only if you center the slide pin manually. 

The three end terminals are connected INDIRECTLY to the AC power on the power pack. These MUST NOT be connected directly to the power pack terminals. You can ask me how I found this out but I won't answer. It wasn't me that done it but I was a bit slow figuring out who did. 

You can operate these snap relays with your finger just moving the slide pin but then it's not operating as an electrical relay but as a manually operated DPDT with a powered option should you choose to wire up the AC part.  

To operate the snap relay remotely you need another switch to control AC power to those three end terminals, ensuring only a momentary blip of AC  power activates the solenoids. That AC power is normally off and must be. The most convenient control switch is the Atlas turnout switch which has two AC power terminals on each end (or side depending on your perspective) and the same three control terminals at the bottom edge as the snap relay does. AC goes into the side terminals and exits through the (usually) black center terminal wire returning through the green or red terminal wire (usual but entirely arbitrary wire colours) depending on whether the turnout switch button is to the left or to the right when pressed. The turnout switch is normally off due to springs under the button.

In your application you cannot wire AC power direct to the snap relay, it will melt the solenoid windings and the plastic housing in about 3 minutes. The solenoid will be destroyed in less time than that.

Note that the Atlas turnout switch handles only momentary AC power, there are no DC connections. The snap relay (the "relay" aspect) uses the same momentary AC power in the same way as the turnout switch to activate the same double coil solenoid slide. The side mounted Atlas turnout motors even have the same slide pin in the slot enabling easy manual operation. The difference is the snap relay operated so as to switch DC constant power from one application to another. Reversing frog polarity is a common use as is powering a siding on and off (since Atlas makes no power routing turnouts). DC power is always connected through one set of snap relay terminals or the other. Two separate DC circuits can be controlled with one snap relay as long as both benefit from the same power polarity. For reversing loops the snap relay uses all six DC terminals for one function. Always transfers DC power, only momentarily powered by AC. 

PS to Sheldon's point I orient my snap relays so that the manual slide pin is oriented to track polarity as indicated by the main line direction switch. That reminds me to switch the main polarity after the train fully enters the loop. A glance shows me that the main and reversing loop are the same polarity at that time. Once the main polarity is reversed the position of the slide pin no longer matches the position of the main polarity switch. The East West orientation Sheldon refers to. Once the locomotives leave the reversing loop I trigger the snap relay and the pin then lines up with the main.

Alyth Yard

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Posted by Dave K on Tuesday, March 23, 2021 10:38 AM

The problem involves the turnback polarity control and reversal.  It has nothing to do with the turnouts as they are all manual.  I've included some pictures of my layout (work in progress) emphasising the turn back with the bridge in the middle.  plastic gap joiners installed at the beginning and end of the turnback.  Feeder in the middle.  The issue is how to reverse polarity using the Atlas snap switches. I am trying to send pictures.

Dave

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Posted by Dave K on Tuesday, March 23, 2021 11:00 AM

I sent you an email plus pictures.

 

Dave

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Posted by Mark R. on Tuesday, March 23, 2021 11:20 AM

I once created a DC reverse loop controller that was so simple, I'm surprised I've never seen it in print. The only downside is that the train had to go through the loop in the same direction, but in my case, both loops were hidden, so it was a non-issue ....

All I used was a single bridge rectifier. The main track power was connected to the two AC terminals and the loop power was connected to the + and - terminals. Once in the loop, the train would continue moving forward regardless of which direction the reversing switch was thrown.

All you had to remember was that the train must enter the right leg of the loop turnout (for example). Once the engines were in the loop, the direction switch is thrown allowing the engines to leave the loop without stopping.

Three downsides (which were negligeable to me) - 1. train can only travel in one direction around the loop. 2. you cannot change direction in the loop. 3. There is a 1.5 volt drop in track power IN the loop, which is barely noticeable at track speed.

Mark.

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

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Posted by SeeYou190 on Tuesday, March 23, 2021 11:53 AM

Dave K
I sent you an email plus pictures.

Here are Dave's Pictures:

There are two crossovers in an oval.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by ATLANTIC CENTRAL on Tuesday, March 23, 2021 12:00 PM

Mark R.

I once created a DC reverse loop controller that was so simple, I'm surprised I've never seen it in print. The only downside is that the train had to go through the loop in the same direction, but in my case, both loops were hidden, so it was a non-issue ....

All I used was a single bridge rectifier. The main track power was connected to the two AC terminals and the loop power was connected to the + and - terminals. Once in the loop, the train would continue moving forward regardless of which direction the reversing switch was thrown.

All you had to remember was that the train must enter the right leg of the loop turnout (for example). Once the engines were in the loop, the direction switch is thrown allowing the engines to leave the loop without stopping.

Three downsides (which were negligeable to me) - 1. train can only travel in one direction around the loop. 2. you cannot change direction in the loop. 3. There is a 1.5 volt drop in track power IN the loop, which is barely noticeable at track speed.

Mark.

 

I have seen it in print and seen it in use before, works well if you can except those limitations.

I would have to dig thru a few old books that are currently packed up to find who published it.

Sheldon

    

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