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Third rail arcing circuit


Sasquatch
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There are plenty of southern electric layouts being built at the moment and the old grey cells have been keeping me awake thinking about how to reproduce this.

No doubt it has been done before.

 

The best I can come up with involves reed switches under the ballast and magnets under the bogies. A capacitor discharge unit to power small bright white LED circuits triggered by the reed switches.

 

On DCC the LEDs could no doubt  be mounted on the train and triggered by a command. I know nothing about DCC so feel free to correct me. 

 

Anyone got any better ideas or knowledge on the subject?

 

Shaun.

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Shaun, you are correct about the DCC idea. I did this with a Hornby/Lima hybrid class 73. I mounted two blue LEDs just above the bogie at the non-motored end. They were connected, via appropriate resistors, to the ESU LokSound decoder auxilliary output. Bryan, of Howes, had pre-programmed the flashes to functions 10 and 11 but it is not that difficult to program these on other decoders with suitable auxilliary outputs.

I do need to paint the outer edges of the LEDs where they project below the floor line (obvious in the video below but not so obvious when viewed from higher up) but other than that, I would deem them a success.

th_HowesClass73wihFlash_zpsd5493e8c.jpg

Edited by SRman
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There are plenty of southern electric layouts being built at the moment and the old grey cells have been keeping me awake thinking about how to reproduce this.

No doubt it has been done before.

 

The best I can come up with involves reed switches under the ballast and magnets under the bogies. A capacitor discharge unit to power small bright white LED circuits triggered by the reed switches.

 

On DCC the LEDs could no doubt  be mounted on the train and triggered by a command. I know nothing about DCC so feel free to correct me. 

 

Anyone got any better ideas or knowledge on the subject?

 

Shaun.

Hi Sasquatch

 

I don't model southern but was sorting through a bunch of old Railway Modeller magazines literally 30 minutes before reading your post and 'lo and behold' there is a three page article by John Wass in the October 2011 edition entitled 'Electric Arc; how to simulate the conductor rail flash on third rail systems!

 

I pull out all the articles I want to keep and then use a thermal binder to archive my 'greatest hits' neatly together; I'm afraid I wasn't going to keep that article..  I can send it to you if you like?

 

Dave

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Sasquatch, I can heartily recommend the MERG pocket money flash unit. It's cheap and can be activated by means of a Reed switch, LDR detector or manually using a push button. It's cheap and allows for building without the "What happens if I screw it up" worry of commercial circuits.

 

It can be set up as either a welder simulator, lighthouse flash unit, fluorescent tube firing or an Arc from a third rail/ catenary.

 

Andy.

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I have to admit a preference for the camera flash methods... Lord & Butler (I think) were offering a DCC-fitted Bachmann 2EPB with LED arc wired as a decoder function. I saw one demoed, and the tiny LED just didn't have anything like the right intensity. Judge Dread's Meopham East Junction layout has by far the best flash effect I've ever seen and the method is something I plan to shamelessly copy on a future project.

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Shaun, you are correct about the DCC idea. I did this with a Hornby/Lima hybrid class 73. I mounted two blue LEDs just above the bogie at the non-motored end. They were connected, via appropriate resistors, to the ESU LokSound decoder auxilliary output. Bryan, of Howes, had pre-programmed the flashes to functions 10 and 11 but it is not that difficult to program these on other decoders with suitable auxilliary outputs.

 

I do need to paint the outer edges of the LEDs where they project below the floor line (obvious in the video below but not so obvious when viewed from higher up) but other than that, I would deem them a success.

 

th_HowesClass73wihFlash_zpsd5493e8c.jpg

All interesting stuff.  I wonder if you can trigger it so it arcs when the shoe leaves a ramp end.  I liked the noise the arc made.

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I've done my own:

 

attachicon.gifelectric_flash.jpeg

Very simple, isn't it? Capacitor C is loaded through switch S1 to 12 V DC. If you add a diode in the feed you can use AC too. Switch S1 is mechanically operated by (the shoe of) the train. It must have a very distinctly defined switch-over moment, a microswitch with lever will do best (it's what I've used anyway). If the switch is operated the capacitor empties its charge into the led, giving a short, bright spark. You can increase the intensity and time of this spark by increasing the size of the capacitor. Don't over-do it though, 22 uF is probably too much already.

 

HTH!

That's the kind of thing I was on about! Simple.

 

I think Dutch Master has the answer to your question Bigbeeline. That'll look fab on Falmer!

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I believe Express Models do a 3rd rail arcing kit, which contains an LED and some kind of motion sensor. I've got it stored in the back of my mind for my Poole layout but I've not yet got round to ordering one to see what they're like or how they work.

 

Mark

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Thanks for such a great response folks! :fan: :fan: :fan: :fan:

After studying this topic some things have come to light, for instance. Flashes only occur when the pick up shoe leaves the third rail. Camera flashes are brighter than LEDs. Bright Blue LEDs give a better effect. Diesel locos wont cause an arc. There is a simple circuit!

 

It is my opinion that reed switches between the sleepers triggered by magnets placed under electric stock at just the critical point would be the best option. Despite Some advantages DCC might have, I think the arcing should be something that is not controlled by the push of a button but that which occurs as per prototype.

 

I'd go with the simplicity of Dutch Masters circuit.

Edited by Sasquatch
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For normal use, I only push the button near rail breaks such as over pointwork.

 

The reed switches and magnets are a good idea but for the sound of the arc, you need a recording on a short loop and something to play it with a small speaker (part and parcel of the DCC sound decoder installation).

 

You could also do the flash in reverse, installing the circuit and reed switch in the locomotive/unit, with the magnets under the track. That way the flashes follow the locomotive rather than being in one static spot.

 

There are many possibilities, depending on how simple or complex you wish to make it, and several useful suggestions here. Perhaps a little experimentation is called for to find which method suits you the best (and I'm not suggesting you should equip every electric locomotive and unit with expensive sound decoders just to get the effect with sound and flash!!).

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For normal use, I only push the button near rail breaks such as over pointwork.

 

The reed switches and magnets are a good idea but for the sound of the arc, you need a recording on a short loop and something to play it with a small speaker (part and parcel of the DCC sound decoder installation).

 

You could also do the flash in reverse, installing the circuit and reed switch in the locomotive/unit, with the magnets under the track. That way the flashes follow the locomotive rather than being in one static spot.

 

There are many possibilities, depending on how simple or complex you wish to make it, and several useful suggestions here. Perhaps a little experimentation is called for to find which method suits you the best (and I'm not suggesting you should equip every electric locomotive and unit with expensive sound decoders just to get the effect with sound and flash!!).

One problem mounting the switches on the train is that when using Kadee couplings the magnets in the track would uncouple stock and the stock uncoupler magnets would cause an unwanted flash!

I still like the capacitor discharge unit idea. That way one circuit could control all the flashes on a layout and it could be linked to a single sound circuit via a relay.( on a smaller layout )

On a DCC layout could the magnets/reed switches be set up to command the flash? Or is that too advanced. I'm not DCC, so am totally in the dark here!!     

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I've done a (short: 31 sec.) video, operating a test circuit I'd built before, but it's too big for uploading it on RMweb. And I'm not really interested in going through the hassle of signing up at youtube or whatever other (never-free) video service. I can make it into a torrent and provide a link, if you'd really, really like to see it, but it's 64MB and my upload speed is only 6-7 kB/s  :sorry:

 

Let me know if you want to see it :)

You have done more than enough for this thread already as far as I'm concerned mate!!!

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Some observations about where, when and how flashes occur on the Southern's third rail system. The comment about flashes only being generated at third rail ends is not strictly true. My observations have showed that the rail in question could sink in places caused by the sleeper ends becoming rotten. The original shoes were kept in contact by their own weight as they were only supported by links at their front and rear resulting them bouncing as they left a section of depressed conductor rail. That fact I have used to my advantage by allowing me to place the flash gun I use away from conductor rail ends if under baseboard obstructions demand it. In fact I tend to place the outlet between two tracks and trigger the flash by two reed switches, one on each track, allowing the effect to be available to trains in both directions. That brings me to the reed switch it'self. I discovered that the system would fail on earlier models and the fault was traced to the switch's contacts becoming stuck together. The back EMF was presumed to be so great that the switches could not handle it and so I added a relay into the circuit and that still seems to be working after some ten years now. Incidentally there is an added bonus in the shape of the sound of the relays operating sounds to me just like the clatter of the shoe striking the conductor rail ramp.

post-276-0-31595500-1394800031.jpg

My main reason for using a flash as opposed to a twinkle is to provide an effect which can be observed at a distance and does not demand that the observer be concentrating on a particular spot at a particular time. "Blink and you miss it!"  

post-276-0-19988500-1394800374.jpg

You will see here that in fact the flash is not even on the third rail side but after 17 exhibitions no-one has commented on that! As an aside it took several attempts to catch this effect by Steve.

As always I hope this helps.     

Edited by Judge Dread
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