I recently installed DCC decoders and LED lights (front and rear) into a pair of Walthers GP9Ms. These locos have a clear plastic ‘spine’ on which the window glazing, number boards and headlights are all molded. Unfortunately as the thread title suggests, my cabs glow like jackolanterns on Halloween night.
Does anyone have a suggestion to elimate this problem? I thought about covering the spine with electrical tape, but that’d likely come off after a while.
I second the idea of painting, but I don’t think it need be black - a good coat or two of acrylic paint, flat colors such as dark green, light grey, or light blue should work - perhaps a light grey (say) first, and then a black second coat - this way the light grey would be visible through the cab window and look like an average prototype cab interior (this thread on a different board has some images of cab interiors - some links are dead, but enough still work to give you ideas of interior cab color)., and the black portion (invisiable to the viewer) does ensure no light leakage.
Yes, they do light up, don’t they? [:O] Does the green BNSF locomotive exhibit the same qualities?
O’Ghoul, I’m not exactly sure what you mean by “spine”. Are you talking about a light pipe of some kind? Also, are these Walthers “Trainline” or train set quality locomotives? From the video, it appears that the LED is located in the rear of the cab?
One thing you can might be able to do is to insert the LED inside of a piece of styrene tubing (painted black) and glue it to the backside of the front headlight lens, inside the cab. This will 1) help focus the beam of the LED out through the lens and 2) drastically minimize the light leakage into the cab.
Here is a pic of a rear headlight tube that I installed inside a cab of a Walthers SW1 last year:
It’s worked very well so far and the tutorial for making one can be found on this page. You can just adapt it for your locomotive. FYI: The LED is press fit into the styrene tubing. Should I need to replace the LED at some point, all I have to do is to gently pull it out of the tubing with a pair of tweezers or needle-nose pliers.
Now just paint the exposed part of the LED flat black and there should be NO light leakage. The paint will act as glue to hold the LED in but should be easy enough to pop free if it ever needs to be changed (which it shouldn’t, the LED shoudl outlive your grandchildren).
On other locos where there were plastic light pipes, I’ve attached he LED with heat shrink tube, which covers the sides of the LEDs so there is no light leakage. An alternative is to use a glue liek Faller Expert Cement to glue the LED to the light pipe, supposedly this cement makes a very smooth surface at the joint to allow the light to pass from the LED intot he light pipe. Then paint the exposed sides of the LED and even the light pipe with an opaque color. Flat black is the usual suggestion because if it’s visible throught he cab windows, it will disappear, but as mentioned, any opaque color will work to keep the light from shining out where you don’t want it.
It may be just the sensitivity of the camera, but the light looks awfully bright. Have you tried using a larger resistor to dim down the LED?
I would get rid of the whole “light pipe” thing and just mount the headlight at the appropriate spot at the end of the shell. The cabs of these engines don’t have details, so there’s not point in lighting them up from the inside.
Thanks for the replies everyone. It is indeed a light pipe. The factory mounting location for the light is actually at the back of the cab. In the BNSF loco, I actually did put white heat shrink tubing on the LED, however I did not cover the domed tip. This may be why the BNSF can glows yellow and the BN cab (with no heat shrink) glows more natural.
The camera does make the lights look brighter, but they are considerably brighter than my Atlas and P2K Geeps with factory DCC and LEDS. I am pretty sure I used 1k, 1/4w resistors front and rear.
I could paint the light pipe with no problem, then cover the “joint” between the LED and light pipe with electrical tape, but I wonder if the windows might still glow, since the light pipe, windows, headlight and number boards are a one piece casting.
If this doesn’t work, I’d like to get rid of the light pipe all together. The problem is that the piece is really, really well glued into the cab. Any suggestions other than a dremel (because I have no idea where mine has gotten to)?
Since it is a light pipe, that makes the solution easier. The main issue is the white heat shrink. In order to drastically reduce the light leakage, your heat shrink ought to be black. (Remove the shell and see whether the white heat shrink glows when the front headlight is on.) I like to shrink the heat shrink around both the LED and light tube.
And you do NOT want to cover the dome of the LED. LEDs are very directional in their beam so this would severely reduce the amount of light coming out the front headlight lens. You want to concentrate the light through the lens.
Lastly, a small amount of glow inside the cab is fine. If you want to eliminate light leakage inside the cab altogether, you can paint the backside of the LED with black paint.
The problem with heat shrinking the light pipe is that it’s molded with the window glazing and number boards. It’s all one piece and “generously” glued into the cab.
Ive thought of using an Xacto to cut the light pipe from the glass, then painting it, being sure to get paint into the newly created cut. That would separate it from the glass and still retain the functionality of it being a light pipe, right?
If you mean slice along the sides fo the light pipe, yes, the ligth pipe would still do its thign exactly as before, but no side light could get out to the rest of the windows. If that’s actually what’s happening - look carefulyl before cutting anything, it could be they are modled together but weren;t actualyl shot as a single piece. If there’s a visible line where the window glazing parts meet the light pipe for the lights, there should be minimal if any transmission fromt eh light pipe to the side glass. Light normally stays inside a light pipe, unless there are scratches on the surface. It’s a rather interesting phenomenon, but we can use it to our advantage. SO check before cutting, otherwise, if it truly is one monolithic piece of plastic, cuttign and painting as you suggest your block any light from the pipe getting to the side windows, and unless you break the pipe portion, it would not do anything to the headlights.
Yes, I have seen things done that way - usually two slightly different plastics so injectign the second oen doesn’t melt the piece that’s already there. This will be very obvious by visible lines in the piece. If that’s not there, then they did the side glass plus light pipe all as one big piece, in which case your cutting idea would probably work.
If your light pipe is feeding your number boards as well as the headlight I would modify it as Randy has suggested. If you take it out you will lose the illumination in the number boards.
The entire window glazing assembly isn’t glued in, but melted in. The horns’ mounting tabs are melted through the cab roof and into the window glazing.
The number boards aren’t part of the light pipe. They’re flat and flush, like the windshield.
The glazing isn’t mounted flush on the BNSF GP9M, so the light pipe actually is slightly visible in the windshield opening.
I painted over the light pipe with flat black. This immediately cut the number boards to a dim glow, and tremendously dimmed the cab. I then layered over this with black electrical tape, but this is already coming off.
The paint + tape seems to do the trick pretty well; I just need to figure out how to get it to actually stick. Any ideas or alternative materials? I think the area that needs covered the most is where the LED meets the light pipe.
Perhaps instead of the electrical tape you could glue some black craft paper in its place. Aleene’s “Tacky Glue” is cheap and would likely do the job.
Since the light pipe does not feed the number boards, you could do away with it and put the headlight LED right behind the lense with suitable light blockage. If you want to properly illuminate your number boards you could mount separate LEDs behind each board. SMD (Surface Mount Device) LEDs and resistors take very little space. To make the light even across the number boards you could use pieces of the light pipe to make diffusers the size of the number boards and attach the SMD LEDs to the back of them. If you leave a little bit of the light not blocked, either from the headlight or the number boards, you can get cab lighting as well.
With the way that the light pipe is molded into the window glazing and then melted into place in the cab, I’m not sure how I’ll be able to remove it without damaging the window glazing, if not the cab itself.
Im thinking of pulling all of the electrical tape out and replacing it with Kaptop tape… then painting that black. I also have liquid electrical tape. I just need to find a more precise brush than what comes attached to the jar lid.
Should it come down to it, what’s a good way to replace the window glazing?
Initially, I would have suggested the same as Mr B, and place the LEDs directly into the light openings, but with some other issues you have, this may be a place to use fiber optics. The LED can be placed in the shrink tube along w/ the needed no. of fiber optics. You can hot glue the small plastic fiber optic lengths to the shell routing to the headlight openings. Bulb and tube positioning in the shell would be the only critical work.
