If you want to simplify your life:
"Reduced Tip Diameters:
Richmond Controls also offers the 3 mm and 5 mm LEDs with tips turned down to fit exactly into existing headlight holes. Only about the last 4 mm can be turned down, and the remainder (the base) remains at the full original diameter. For example, the upper headlight hole on a Kato N Scale PA1 is 0.108" in diameter, and the headlight holes in an Athearn HO Scale U33C are 1.5 mm. These LEDs eliminate any need to use fiber optics, and greatly simplify installations -- you just push them into the headlight holes in most cases."
http://www.richmondcontrols.com/
Jay
C-415 Build: https://imageshack.com/a/tShC/1
Other builds: https://imageshack.com/my/albums
If HO, I would go with the 3mm LEDs. The head of a 3mm LED fits just perfect inside a #32 (or 0.116" OD) drill bit hole.
Will, please reread my edited post above about lighting tubes. I edited it while you posted your response to my initial unedited post.
If your head light lens does NOT have a lighting tube, you can partially hand drill out the back of the lens to hold the 3mm LED (if long enough). Otherwise, you can remove the lens altogether and drill out the headlight shaft. A small amount of white glue can be used to secure the LED in place. If you ever need to change out the LED, a little water will reactivate the white glue and make removing it much easier.
As mentioned in the above post, I would consider smaller incandescents (e.g. grain 'o wheat) for your ditch lights. They really look more realistic and are more dynamic in on-off-on range.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
I am modeling HO, I guess I should use 3mm after all. I haven't placed the order for them yet. Thanks for the clarification.
Will
Will,
Is there any reason why you are going with 5mm LEDs for your headlights? I've found that 3mm LEDs work quite well and are the right size for my locomotives. Course, you may be using them for a larger scale. Are you modeling S- or O-scale? I model in HO.
Whichever scale you use: If your headlights come with lighting tubes (or plastic extensions off the rear of the headlight lens), use heat shrink around one end of the lighting tube and the other around the head of the LED. This helps to both secure the LED and focus the its directional light down the lighting tube and out the headlight lens. It also reduces that amount of extraneous "backlighting" of a cab.
One other point to raise. Although LEDs can be used for ditch lighting, incandescents will look more realistic, as they dim much better than LEDs. LEDs tend to dim to a certain point then immediately go dark.
I have some LEDs I would like to mount in a loco. There two 5mm for the front and rear headlights and two 3mm for the ditch lights. The loco is a P42. I was wondering what is the best way to mount these in the loco. Any photos posted would be greatly appreciated.
Thanks