# Using Fiber Optics for Locomotive Lighting



## KisNap (Aug 4, 2014)

Hi Everyone,

I thought I'd share my most recent project with you in which I used 1/2 mm fiber optics to route light from the rear of my n scale locomotive light to create red marker lights in the front of the locomotive when it's going in reverse. Using this method allows me to achieve the effect without having to wire LEDs to the DCC PC board.

Not shown here is how i had to do a little milling at the front of the locomotive to create a channel to run the wires in to allow the shell to close all the way.

Here you can see the piece of styrene I glued to the decoder which has 2 channels to hold the cables in place ensuring they're lined up with the rear LED.












I used a soldering iron to create a permanent bend in the fiber optic wire. To do this you just hold the wire close to the soldering iron and let the heat and gravity bend the wire as it softens. I made sure the cable would line up with the LED before I used caulk to hold it in place.











Here you can see how the light is transmitted to the opposite end of the cables despite the bend I created.












I drilled 2 holes in the light blocking plastic piece in the front of the locomotive to hold the cables in place and help it get directed towards the front.











These next two pictures show the fiber optics fed through the holes I drilled in the front of the locomotive and the light being transmitted. The second photo shows my test of using Microscale Kristal Klear mixed with red food coloring to create a red lens over the end of the cables.





















Next I trimmed the cables flush with the shell and re-applied the Krystal Klear & red food coloring to create the red lenses. Now when my train is in push mode you'll see the red marker lights just like the prototype.


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## Lemonhawk (Sep 24, 2013)

I thought you dropped you ice cream sandwich on the decoder board


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## gunrunnerjohn (Nov 10, 2010)

Nice job with the fiber optics. I haven't run anything that far, nice to know they work that well. :thumbsup:


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## DougL (Feb 2, 2016)

beautiful work. The 1/2 mm wire looks huge in N scale.


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## Cycleops (Dec 6, 2014)

Nice work. Just shows what can be done with a bit of thought.


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## jlc41 (Feb 16, 2016)

Genius, nice bit of modeling.


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## KisNap (Aug 4, 2014)

Thanks. I thought it was a good minimal mess solution. Currently doing it to my second NJ Transit locomotive I kit bashed, a GP40PH-2. Size is definitely a major issue when working in N scale. I had to apply about 80 1mm x 1mm decals for the passenger cars I made. That's pretty frustrating when working with custom made decals.


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## Lemonhawk (Sep 24, 2013)

Is there much light leakage in the cab, do the light pipes keep if well contained?


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## KisNap (Aug 4, 2014)

There's really no leakage in the cable. The light bounces around inside the cable and doesn't exit the cable until it reaches the end. If you look at the last picture you can see that the two cables are not visible even in the low light condition.


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## Fire21 (Mar 9, 2014)

Do I understand correctly that the styrene piece you show in the first photo covers the taillight and keeps it from ever showing as a "headlight", that it only powers the red indicator lights??


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## KisNap (Aug 4, 2014)

No. The LED is actually underneath the board. The styrene is just on top of an area of the PC board where there happens to be no exposed electronics and helps to hold the fiber optics in position. The rear lights still light when the locomotive is in reverse. The first picture is a little dark so here's an explanation of that picture.


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## KisNap (Aug 4, 2014)

I can't say I've ever really paid attention to the rear light on the loco before when it's in push mode, but it makes sense that it might not be on since the cab car has the light. If that's the case then you could always paint over the light on the inside of the shell so it doesn't transmit light. Hm... something to think about.


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## RonthePirate (Sep 9, 2015)

Have to say, the loco looks like a giant bug with feelers before you trimmed those cables!

All kidding aside, that's a great approach to adding lights.
And the possibilities are endless.
Depending on how small you can get the cables, there are few limits as to how small you can make lighting.
And that brings lights down closer to scale.


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## Lemonhawk (Sep 24, 2013)

This leads to more experiments! Like if you made 45 deg cuts and stuck them together could you achieve a 90 deg angle. Or can you make a splitter by inserting a wedge shaped piece in-line. I'm thinking true fiberoptic pipes may not allow this. Maybe that's the difference between coherent and non-coherent light pipes.


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## RonthePirate (Sep 9, 2015)

Lemonhawk said:


> This leads to more experiments! Like if you made 45 deg cuts and stuck them together could you achieve a 90 deg angle. Or can you make a splitter by inserting a wedge shaped piece in-line. I'm thinking true fiberoptic pipes may not allow this. Maybe that's the difference between coherent and non-coherent light pipes.


I will say that if it were possible to make 90 deg bends by cutting 45's, you would have to be 100% accurate piecing them together.
Otherwise, the light would leak from the sides.

And do they have a special adhesive so as to not lose any light?
Seems you would lose some at every glued joint.


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## KisNap (Aug 4, 2014)

While it's not an exact sharp 90 degree turn you can use heat to heat the fiber optic and it can bend to any angle with minimal light loss. The further you go with the cable the more light loss, but it's minimal, however when putting two wires together the chances of getting them to line up perfectly and not having an adhesive in between them is probably zero which means you could lose a good amount at that intersection. You'd be better off running multiple lines to the light source rather than trying to splice it.

One other problem is that when you cut the line, you aren't going to get a 100% flat clean cut. There will at the very least be microscopic ridges that will prevent it from being a smooth surface.


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## /6 matt (Jul 7, 2015)

That's really cool. Question is where do you get the fiber optics?


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## KisNap (Aug 4, 2014)

I happened to get mine at the store below. The price on the unjacketed cable is shown at the price per foot. So if you want 10 feet you would just add the item to the cart 10 times.

An example is the .5mm cable at $0.08/ft. So 10 feet is $0.80. Cost effective enough? Always buy a lot more than you need to help justify the shipping which is $3.00 on 10 feet of .5mm. $3.00 isn't a lot, but it is over 3 times the price of the cable.

http://shop.fiberopticproducts.com/index.php?route=product/category&path=96_112

If you do a Google search for "unjacketed fiber optic" I'm sure you'd get hundreds of stores selling it.

One nice thing to note is that you can get the cable colored so if you only wanted red lights you could always get the red cables and have it end with the red light. My only caution to this is that you'd probably be able to see the cable easier inside the model and it may be too bright. My cables are red because I put 2 applications of Krystal Klear that was tinted with red food coloring so it dimmed it down to a more realistic level.


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## Patrick1544 (Apr 27, 2013)

Your use of fiber optics is a great idea. I can envision many uses around the layout for them.


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## santafealltheway (Nov 27, 2012)

How did you attatch the fibre tube to the led? Is it glued?

I just wanted to share this method just in case.

Drill a hole the size of the fibre tube in an LED like this. Just don't drill too far.

Then you can just slip the tube inside the bulb.


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## gunrunnerjohn (Nov 10, 2010)

I like that idea, it makes it easy to connect them If you had three or four fine strands, you could also drill a slightly larger hole and just bundle them.

Another tip is to grind or file a small flat right on the top of the LED, gives you a flat surface to start drilling on.


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## KisNap (Aug 4, 2014)

I thought of that too, but the LEDs I work with in N and Z scale are too small to do that. I solved this in my z scale layout by gluing the led to a piece of styrene where I drilled a hole and fed the led through the hole so it made direct contact with the LED straight-on.

The LED is on the top and glued to the styrene and on the other side is 2 fiber optic cables being fed directly to the LED. This was the method I used when I made the flashing lights for my Z scale police car. I used caulk to hold everything in place which is what that white glue is.


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## gunrunnerjohn (Nov 10, 2010)

That works.


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