Semaphores explained?

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PRR5406
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Semaphores explained?

Post by PRR5406 » Thu Jul 13, 2017 8:49 am

I've asked about constructing and operating semaphore signals on this board in the past, but here goes:

I've started to receive the Marlin P. Jones catalogs, and get their email ads several times a week. They are presently selling stepper motors with screw motion extensions. That is, has the motor turns, a rod turns with a tracked piece of plastic which follows, traveling up or down the rod. This seems like a good beginning to build an electronically actuated semaphore signal (at least to me).

What I don't understand is how to build a semaphore so it drops the blade as a train passes, then raises to the caution position, and eventually returns to upright. Does this require micro circuitry, an Arduino controller, and/or more complicated systems? Is there a simplified system I can build, but have totally overlooked?

Suggestions? Discussion?

Dick
"Always stopping my train, and risking my ankles, with American made, New Balance sneakers."

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NP317
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Re: Semaphores explained?

Post by NP317 » Thu Jul 13, 2017 9:04 am

I would expect that the same circuitry required to operate three lights (green, yellow, red) would be needed to position the semaphore arm.
Also, circuitry is required to change the light instruction to motor position equivalent.
~RN

Mike Walsh
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Re: Semaphores explained?

Post by Mike Walsh » Thu Jul 13, 2017 1:02 pm

Also you want the signal to be failsafe. Lose power, it should revert to stop indication.

I am working on something -- waiting on parts.

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Re: Semaphores explained?

Post by mspetersen » Thu Jul 20, 2017 5:54 pm

Might try here: http://www.rrsignalpix.com/documents.php Lots of Signal related material.
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VO4454
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Re: Semaphores explained?

Post by VO4454 » Fri Jul 21, 2017 12:10 am

Very nice and informative link. Thank you Mark.

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Atkinson_Railroad
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Re: Semaphores explained?

Post by Atkinson_Railroad » Sun Jul 30, 2017 11:07 pm

Dick;

Building a functioning, realistic semaphore model requires a knowledge base of multiple skill sets and disciplines.
It helps first to be obsessed with the idea of making such a device… and maybe being on the fringe of [crazy].
Choose your model signaling objectives as they best fit you, and go for it.

John
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DS2944.jpg
LED Retrofit / Rebuilt Upper Quadrant Three Position Semaphore

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PRR5406
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Re: Semaphores explained?

Post by PRR5406 » Mon Jul 31, 2017 8:47 am

John: I have the crazy part covered, so step one is completed. You are absolutely right about the complexity.
What I've been thinking about is a stepper motor attached to a lead screw on a threaded rod. One might be able to get a lever action to move between upright, middle, and horizontal. That's the simple part. What I don't understand is how to regulate that transition. That's where "crazy" comes in. For somebody who has worked in electronics, I'm certain it could be figured in a matter of minutes.
I'm betting a simple, affordable product would sell like crazy. <----Note, this word reappears!
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Re: Semaphores explained?

Post by ccvstmr » Mon Jul 31, 2017 9:44 am

Dick...there are most likely many ways to get from where you're at...to where you want to go. One such solution might include a motor with a disk or motor driving a disk. Attach a push rod from the disk to the semaphore blade...and machine some indents on the perimeter of the disk for limit switch positioning. Semaphores typically run through the same cycle all the time...clear, stop, approach. Therefore, the motor always turns in the same direction, stopping at the appropriate position based on track occupancy.

Borrowed such a design (motor driven disk) from a club member when it was time to "ruggedize" his electric switch motor. The motor driven cam had two sets of indents: 1st set was for motor control that allowed the motor turn a half rev and stop, each time the switch position pushbutton was pressed. The 2nd set was for the switch position signal indication. Make sense? Carl B.
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Atkinson_Railroad
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Re: Semaphores explained?

Post by Atkinson_Railroad » Tue Aug 01, 2017 4:44 am

A semaphore could be viewed as a robotic arm. You might consider picking up a book on robotics to gain further ideas that can be helpful.
Gordon McComb’s “Robot Builder’s Bonanza” is one that comes to mind and there are obviously others published.
Thinking back, I wish I had explored more options using model aircraft servos to drive the signal’s arm.
Your lead screw idea is one I pursued for a while and eventually abandoned for reasons I’d have to go back to my notes to remember the decision factors. (It may have been physical space restraints, or too many required parts. I just don’t recall.)

The April, 1982 issue of Mainline Modeler featured a description of a lead screw mechanism with illustrations operating a double arm lower quadrant style semaphore. So, that type of arrangement has indeed been utilized.

In the past, I’ve also used the electric solenoid route, but people seeing a signal operate one year at N.A.M.E.S. in Wyandotte using that set-up said it reminded them of an old Lionel semaphore. (And we couldn’t have that ; )

The semaphore photo attached has been shown here at this forum before when I was trying to track down the gentlemen who constructed it sometime in the late 1980’s (maybe early 90’s). I don’t know what kind of mechanism operated the signal arm.

Using the terms “simple”, and “affordable” in describing a 1-1/2” scale semaphore is a tough objective to achieve given the installation restraints of where one can be safely placed in service without being tampered with by overzealous souls. Hence the reason most outdoor wayside signals built or offered today continue to utilize parts and pieces found at Home Depot, or the local hardware store. The hobby has come a long way though from the days of the immaculate looking steam engine running down the line followed up by a piece of plywood mounted to a set of trucks.

Enjoying the discussion,

John
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MVC-008F.jpg
Permissive Semaphore. Builder unknown.

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ccvstmr
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Re: Semaphores explained?

Post by ccvstmr » Tue Aug 01, 2017 7:55 am

PRR...thought I'd stop and ask you a couple questions...

1) are you looking to model an "upper quadrant" semaphore as Atkinson RR posted in his recent photo...or a "lower quadrant" semaphore. Believe UQ semaphores were used most often in the US. Doesn't matter as you're still looking for a 3-position control system.

2) you didn't specify a preference for electric-mechanical actuation or other. Your locations says Maine. A 3 position control system could be configured using pneumatics. Two air cylinders attached to each other would yield: both extended, both retracted, one extended-one retracted. If there was an objection to the air cylinder "snap action"...a flow control valve could be incorporated to slow down the cylinder movement.

Just trying to determine what you're looking for an offer alternate control schemes. A motor-driven screw can be used...but have to wonder about the cleanliness of the environment to insure trouble-free operation. As you can see...there's lots of ways to get from Pt. A to Pt. B. Carl B.
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PRR5406
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Re: Semaphores explained?

Post by PRR5406 » Tue Aug 01, 2017 8:36 am

This is a good discussion, and I'm glad you guys with far more tech/mech experience are choosing to get involved! So first, "thank you"!

I have been thinking of an electrical system over pneumatic. I kind of like the cycling motor with stop-caution-go upper quad blade. Running a 12 volt current to a motor seems like it fits most home or club RR's. The parts that got me thinking about this once more, appeared in the Marlin P. Jones catalog, which, if you've not familiar with them, is the Harbor Freight of electronics.

A stepper motor, a lead screw, and a lever with a push-rod as the moving component, seem to want to congregate in my mind. Once it's drawn out on paper, I think putting the parts together in a plastic or metal box/cabinet would be the artistic part. It has to be functional, then pretty.

To me, semaphores always seemed a more positive way to signal a train, using both position and lighting. I guess they went out due to improvements in electrical cab signaling and maintaining the mechanical aspect.
"Always stopping my train, and risking my ankles, with American made, New Balance sneakers."

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Re: Semaphores explained?

Post by SCBryan » Tue Aug 01, 2017 11:40 am

I would like to chime in on the obsessive and crazy portion of this thread. A number of years ago, I went to an estate auction and bought some Erie semaphores from a scrap dealer there. The control boxes weren't there so I came up with a quick and dirty way to mechanize mine. I poured a concrete base, hollow in the middle, and mounted the semaphore to that. The center operating pipe was cut off at the base so I fitted an old bottle jack under the pipe. I had an old garage door opener that I attached to the driving portion of the jack through a flexible coupling. Unfortunately, the drive only allowed enough travel to go from permissive to restrictive and not all the way to stop. It was still cool watching it cycle back and forth while sitting in the back yard. I had it on a ten minute timer so it wasn't in constant motion. Unfortunately, mice got into the wiringand chewed everything up. I am working on something a little more substantial but it is going to take a while.

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