May 3, 2016 LED Marker Lights

I decided to attempt to make my own LED illuminated Marker Lamps.  I'm going with Cal-Scale Lost Wax detail castings because they are more accurate to scale than any of the other manufacturers.

The Cal-Scale markers are solid brass castings so step one is to drill them out to except a light source.

I'll begin drilling out the casting using a #60 drill bit (0.040").  To prevent breaking the drill bit I use a slow speed Craftsman 4 volt drill.  When working with the tiny drill bits it's mandatory to use a quality chuck to hold the bits for perfect centering.

I use a mini vice to hold small stuff for drilling, mounting the casting as close to the jaws will prevent the soft brass casting from bending from the pressure of drilling.

First I will drill straight through the casting using a #60 drill, actually drilling half way then finish up from the opposite side.  Once that hole is done the next step is the remaining hole on top of the casting.  I slowly increase the size of the holes so as not to ding the fragile casting.  Next I enlarge all three holes with a #58 drill.  With all three holes done the last step with drilling is to enlarge the hole that will become the rear and mounting side with a #53 drill to 1.5 mm.

Here the casting is complete, two 1 mm holes for the red and green lenses.

I've done pretty good at modifying the Cal-Scale markers for lights, I've only dinged one and that was my first attempt, this one will be my 17th pair.  I have equipped 16 articulated locomotives with working marker lights. 

Now it's time to go into the LED portion of this post.

I've been using 1 mm 1½ volt micro bulbs in my Cal-Scale Markers, the bulbs measure between 1 and 1.3 mm in diameter and will easily slide inside the casting above.  Not so with LEDs.

The smallest normal LED I've found is a Top Hat or Stovepipe 1.8 mm.  They are much too large but I came up with a way to reduce the diameter to 1.3 mm rather easily.

I used a short piece (1") of 1/16" K&S brass tubing (0.062") with a 0.010" wall thickness leaving the ID at 0.044", slightly larger than 1.3 mm.  Using my Atlas Snap Saw I roughed up one end of the brass tube to resemble saw teeth.  I insert the tube in a mini-chuck tooth end out.  Again using my slow speed Craftsman 4 volt drill I use the tube as a reverse drill cutting away the outside of the LED leaving the center at slightly under 1.4 mm.

The LED is now small enough to slip into the brass casting.

As you can see the fit is very good and the Marker Lamp is ready to install.  This one will go on one of my Southern Pacific Cabooses.  I will use Crafter's Glass Stain to form the lenses.

It looks sloppy but it will clean up nicely.  This will have to come apart to install, I'll clean it up before I install it in a caboose.

This is a completed LED powered Cal-Scale Marker lamp.  For this picture I have a 10 K resister in series operating from my 12 volt bench power supply.  The LED is drawing 1 ma. and that is sufficient light for a marker lamp. 


Now on to another project.