MOC semaphores

[zephyr1934]

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I have finally had a chance to photograph my semaphores. First off the signal bridge is modified version of a design I first saw by Jeramy Spurgeon.

I have since seen this idea duplicated on several other layouts, but so far all of the examples I have seen have inactive signals. Sure, I had working LED signals, but then a few years back I started thinking about semaphores. There is just something nice about the changing position. So soon enough, I combined my semaphore idea with the signal bridge design.

The MOC is tucked away in a dark corner of my layout and my camera batteries were dying, so I couldn't get any good video, but I was able to piece together this animated gif to give you an idea of how they look when operating.

The mechanicals are fairly simple, a PF m-motor with a rubber band for a clutch. The one non-obvious feature is the two 1x1 plates just below the red and white semaphore arm. These are twisted ever so slightly to provide stopping points, the plate in back for the white and the plate in front for the red.

I use an RCX to run the whole signal tower with a simple "break beam" train detector consisting of a PF LED pair in the middle shining on two light sensors, one for each track. I used a technic half pin to keep the emitted light beam tightly focused and a 1x1 plate sized hole in front of the sensor to keep as much ambient light out as possible. Because the whole setup is in a dark corner, the light for the sensor looks a lot brighter in the photos than it would normally look, e.g., I had the semaphores at one show and some of my club members were puzzling over how it sensed the trains. Given normal light levels it was a lot harder to see the light used for the sensor. The RCX is tucked away in a snug shed along the tracks, with cables coming out for the sensors, light, and motors. The program isn't complicated, but it does have a few clever tricks worked in, e.g., at startup it samples the background light level and stores that for a reference (instead of using a hardcoded value). It then does a loop to check if beam a has broken (saving the result in a variable), then if beam b has broken (again saving the result), then checks to see if it needs to change the state of either semaphore (either due to a newly broken beam or timing out since the last detection). Then loops back. Since most of the action is confined to the conditional statements, the program can complete the loop quickly and sample both tracks with a fairly frequency. I should also mention that I do not actually cut power to the track, so these are just for show. It should be fairly simple to modify this set up to control a single block on one track.

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[Locomotive Annie]

Yes you can't beat the look of semaphore arms that actually move

That rubber band drive is really clever and I like the whole sturdy design of the signal bridge.

Anything involving electronics and logic systems is completely out of my league, though if I asked my computer science graduate daughter to explain it to me I'm sure she would and she would even draw up a schematic for me if I asked. However whenever I've had signaling systems before on other layouts I always did it with mechanical rodding, moveable contacts and ex-post office telephone exchange relays. Semaphore signals are on the 'to-do' list for the Kotanga Tramway, but I haven't got as far as devising how they might work yet.

[Hey Joe]

Very cool, thanks for sharing those with us.

What color scheme are those passenger cars, C & NW?

Wish Lego would do Jenks Blue but I'm not holding my breath for that!

Joe

[zephyr1934]

Thanks Locomotive Annie. Yes, it is neat to watch the semaphores do their job from across the room. Though the rubber band drive was has been around for a long time, probably to the early days of technic.

And thanks bjtpro, good eye. Yes, those are my CN&W cars, I rode on the prototypes a few times when I was young and they are still among my favorite MOCs. That's one of the things I really like about modeling in lego, if you like the train you can build the train without being at the whim of a manufacturer (okay, a scratch builder doesn't care about the manufacturer and we are still limited by the lego pallet, but I digress). Now as for Jenks Blue, isn't dark blue close enough? (I know I know, you can never get close enough, grin).

[Hey Joe]

Now as for Jenks Blue, isn't dark blue close enough? (I know I know, you can never get close enough, grin).

I dunno, MoPac fans are pretty serious about their shade of blue, ha ha.

I got into Lego while living here in China, I need to stop in a local LUG when I get back home and see what they're up to.

Those C & NW cars (and engine ) are nice, I've seen them before, probably on the cover of your magazine. Maybe the reason I like MoPac so much is I'll never forget a trip my Dad took me on probably just before the train was cancelled (the line I'm thinking of wasn't Amtracked); beautiful blue cars, coal black porters and waiters wearing white gloves. Hope that doesn't sound racist but it's so stereotypical it just sticks in my mind I guess.

Joe

[DaveBey]

That's really neat; thank you for sharing!

Have you modified it any since you originally built it in 2011?

Cheers from Claremore, Oklahoma USA!

Dave

[bricks n bolts]

Wow, very cool Zephyr! You've got a lot of heavy duty stuff totally hidden away. The bridge sections and the roof makes it look simpler than it is.

[zephyr1934]

That's really neat; thank you for sharing!

Have you modified it any since you originally built it in 2011?

Thanks DaveB, I've only made one modification and it was quite small. I originally had a 1x2x2 train window where the wall power goes into the RCX. But when I took it to a show the transformer there had a larger cord around the plug so I pulled the window.

Wow, very cool Zephyr! You've got a lot of heavy duty stuff totally hidden away. The bridge sections and the roof makes it look simpler than it is.

Thanks BnB. The bridge sections were pretty much Jeramy's idea, I just stuck the semaphores on them. The transformer box was a quick and dirty snot build (the door rail idea was inspired by some of my train cars). The head scratching came when I was trying to figure out the roof- I wanted something light. These wacky 6x6 tiles came in handy. As for my lego room, well, my wife is very understanding and the kids like the room, so it is easier to slowly accumulate this way. When we moved in to this house it took me a year to strike floor in the lego room, another year to get it shuffled around, and another two years before I got the semi-permanent loops of track down. Since I'm now using all of my straight track this means no more field trips to the living room for a while. I'm still working to get a couple of boxes sorted, then I might put the switching yard in.

[Hrw-Amen]

Very nice to see, I wish I had the knowledge and bits to put something like this together.

[Man with a hat]

Brilliant!

It is a really nice design with good looks. But that it actually works... Amazing.

Great idea of using the light sensor and the RCX.