Signals: Stick relay....

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johnpenn74
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Signals: Stick relay....

Post by johnpenn74 »

Does anyone out there have a background in prototype railroad signals? Particularly, Absolute Permissive Block. I need some explanation on how the "stick" relay is wired in to maintain the voltage for the trailing section lights. Specifically, how does the whole circuit reset its self when the train(s) have clears all the blocks in the single track?

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Atkinson_Railroad
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Re: Signals: Stick relay....

Post by Atkinson_Railroad »

Ha Ha ; ) just mentioned Yahoo on another thread, and a better place to post such a question would be at the URL below. (An active group since 1999)

https://groups.yahoo.com/neo/groups/Rai ... aling/info

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Re: Signals: Stick relay....

Post by mspetersen »

There's a wealth of information here: http://www.rrsignalpix.com and i believe the guy who runs the site is full time RR signal tech and works on the ATT&NW.
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Atkinson_Railroad
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Re: Signals: Stick relay....

Post by Atkinson_Railroad »

Zach at Mark's suggestion of http://www.rrsignalpix.com/ is a participant at the Yahoo Group as well, so either way.

It's nice to see/read that signaling is on the minds of people lovin' the avocation.

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Re: Signals: Stick relay....

Post by Steggy »

johnpenn74 wrote:Does anyone out there have a background in prototype railroad signals? Particularly, Absolute Permissive Block. I need some explanation on how the "stick" relay is wired in to maintain the voltage for the trailing section lights. Specifically, how does the whole circuit reset its self when the train(s) have clears all the blocks in the single track?
I believe what you are referring to is a circuit in which a relay self-latches on its own contacts. Any electrical designer would know the circuit.

The latching occurs when the train passes the (absolute) headblock signal, at which time all opposing signals between the passing track endpoints are "tumbled" to STOP. As the train continues and passes each tumbled signal, the latched relay that put the signal at STOP is released by the track circuit relay of the block just entered and the signal returns to acting as a normal permissive signal. Split blocks are used between the passing track endpoints so the train's direction of travel is known. That logic is combined with the track circuit logic to determine when to clear the latch.

A detailed explanation on how it all works, as well as the circuitry, is really too involved to post here. Unfortunately, there isn't a lot on-line to read on the technical aspects of APB.
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Re: Signals: Stick relay....

Post by Mike Walsh »

mspetersen wrote:There's a wealth of information here: http://www.rrsignalpix.com and i believe the guy who runs the site is full time RR signal tech and works on the ATT&NW.
Zachary volunteers his time (and donates a lot of the signal/signal components) at the ATT&NW, and I have helped him install a few new control points as well. He does not do RR Signals for a living. Tis a fun activity. That being said, I can't help with stick logic... I just connect the red wire to this post, and the blue wire to this post, and occasionally cut the.. NO- not that one!
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Atkinson_Railroad
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Re: Signals: Stick relay....

Post by Atkinson_Railroad »

Agree with BigDumbDinosaur, a detailed explanation of Absolute Permissive Block Signaling is outside the scope of what can be explained here.
Googling "ABP", Absolute Permissive Block Signaling will keep you busy for quite a while.

From my signaling archives, here is the most abbreviated explanation I found related to [Stick Relay].
The scan is from "Railway Signaling" by Everett Edgar King, McGraw-Hill 1921.
Attachments
STICK RELAY.jpg
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Re: Signals: Stick relay....

Post by ccvstmr »

Slap switch signal systems work on this basic principle for protecting single track territories between passing tracks. At the head of the block, the 1st slap switch "latches" the circuit and provides protection at both ends of the single track block. At the other end, the 2nd slap switch "releases" the latch and signals at both ends of the single track go green or display "clear".

There are many types of physical switches that can be used for the slap switches. These include: push buttons, wand, whisker, rocker arm limit switches and more. The physical style doesn't matter as long as both NO (normally open) and NC (normally closed) contacts are available to make up the appropriate circuit.

After the hardware, there is one ever present danger. Someone can design/build the most simplistic or elaborate control arrangement. But that signal system is only as good as the people using it. The human interaction element. Hopefully, engineers realize their action is needed at both ends of the blocks to assure protection for themselves, their train and other rail traffic. Carl B.
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Atkinson_Railroad
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Re: Signals: Stick relay....

Post by Atkinson_Railroad »

Here is additional material related to the OP's original question described by an actual manufacturer of "the relay".
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MAGNETIC STICK RELAY.JPG
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Re: Signals: Stick relay....

Post by Atkinson_Railroad »

Flip flopped APB "ABP" in earlier reply. Oops ; )

Abbreviation should be A P B.

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Re: Signals: Stick relay....

Post by Steggy »

Atkinson_Railroad wrote:Here is additional material related to the OP's original question described by an actual manufacturer of "the relay".
The illustrated relay is a remanent magnetism latching relay, which is latched by the application of a short pulse of direct current to the coil. Once so latched, the relay will indefinitely remain in that state, even if removed from the system and transported to another location. There are two designs in common use: single and dual coil. In the single coil unit, the relay is released with a short DC pulse of the opposite polarity on the coil. In the dual coil design, there is one coil for latching the relay and another to release it.

I don't recommend the use of these types of relays in riding scale ABS. The fact that a latching relay retains state indefinitely means that if the signal system is powered down while the relay is latched and then later powered up, a possible undefined sequence of operation may occur. Using one of the relay's contacts to electrically latch it avoids this sort of problem, as it will always start in a known state at power on.
Atkinson_Railroad wrote:From my signaling archives, here is the most abbreviated explanation I found related to [Stick Relay].
The scan is from "Railway Signaling" by Everett Edgar King, McGraw-Hill 1921.
http://www.chaski.org/homemachinist/dow ... &mode=view
In the above illustration, the "front contact" refers to a normally open contact that is closed when a relay is actuated. A "back contact" is a normally closed contact that is opened when the relay is actuated. Railway signal engineering uses some terms that are alien to electrical engineers and technicians who don't work with signals.
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Re: Signals: Stick relay....

Post by ccvstmr »

Not all persons participating in this forum have been indoctrinated to real railroad practices. Big D Dino...worked for a company that supported the railroad industry. I have several years of working for Amtrak after school. If there's one thing you can say about railroad hardware...it's usually overbuilt. Has to be for the various environments the equipment is exposed to...and continue to operate with the highest degree of reliability.

Several years ago I was able to get into a Class 1 railroad training facility. Training personnel is imperative to keep a railroad moving. Thought I'd share some photos from the switch and signal "training lab"...

In the next photo, you'll see the "business end" of a turnout. Yes, there is a set of switching points on the floor in the lab. Students have an opportunity to see/understand the switch hardware they'd see in the field.
xIMG_6091.jpg
In the next photo, here's the signal relay hardware used for section of single track, passing sidings and turnouts. Single line track diagram overhead. Relay hardware mounted on the main panel...as students would encounter in a relay cabinet in the field. And then there's some G gauge track on the working surface on which they can simulate a passing train.
xIMG_6092.JPG
Here's another such work station.
xIMG_6093.JPG
As in all cases in these labs, once the students have become familiar with the signalling rules, the controls and train operations...the instructor will purposely "bug" the systems. Students then have to come in an troubleshoot...and return their little section of railroad to full working condition.

The training center contained other labs. These included grade crossing stands, locomotive simulators, crane operation simulators for cranes and boom trucks. In another part of the facility, there were locomotive brake stand hardware training stations, a display for various kinds of wheel defects...there might have been a section for rail defects as well.

No doubt, it was an interesting visit. If you EVER get the offer to see such a place, don't pass up that kind of opportunity. Will give you a new perspective for the real railroading some of us try to recreate and model. Carl B.
Life is like a sewer...what you get out of it depends on what you put into it!
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