Fastrack Switch Lamp

Synopsis
I was in a Hangout talking to Josh and he asked about designing some Switch Lamps for his Fastrack switches. With the Switch Stand removed he had a small pad with a .090″ hole. I told him I could see what I could do and this is the result.
LED
I had previously found a bi-color … Red/Green SMD Pre-Wired 0603 LED on eBay. I thought these might work (emphasis on might). The link is good at the time I am typing this .. 10PCS 0603 1615 Pre-soldered Bi-Color Red Green Light Pre Wired SMD LED Diodes – 10 pcs for $10.99 with free shiipping is a pretty good deal IMO.

These are SMD LEDs so the viewing angle is 120° unlike the more common ‘mushroom’ shape so that might affect how well they work. Donno.

>What caught my attention was 1) they are bi-colored – and that is what some model railroaders wanted for signals and 2) they were SMD .. so small(ish) in size. The smallest I found were these 0603 LEDs. If you look at the diagram to the left (click to enlarge) you will see that it shows as 1.5 mm across the soldering pads. That is fine for the Anode connections but if you look at the photo above you see that the Cathode (black wire) runs down the side of the LED package. I *guesstamate* that adds another .50 mm so it will need approximately a 2 mm hole.
The Lamp Design
When working on something small like this to be 3D printed we have to take into account the material used to print the model and the capabilities of the printer itself. I used FD (Frosted Detail) plastic for this – it being the one that provides the best detail from Shapeways and passes light. The biggest constraint is what Shapeways calls ‘Wall thickness” which is 0.3 mm .. which I never use. Every time I have tried to use that suggested minium I get the models kicked back for thin walls. I have found that using a 0.4 mm minimum works fine so that is what I go with. The Switch Lamp itself is nothing more than a cylinder with other shapes that resemble the top of full-size lamps and four projections that resemble lenses. I use the term ‘resemble’ here because the model is so small we have to get ‘close’ while keeping within the constraints for the material and printer.

A lot of searching for dimensions came up blank so I found a photo that showed a man next to a switch lamp and I *guesstamated* (love that word) that around 12″ across the width of the lenses would not be that far off. The Lionel Fastrack switch that Josh has with the switch stand removed has a .090″ hole that can be used to mount the lamp and pass through wiring. With that I went to work.

The lamp
Like I said, I just whipped out the model really quick since all I had to go on were photos .. and thy vary so widely in shape that anything I came up with pretty much would work. Keep in mind that (and Yes .. I repeat myself) shapes have to fall within the guidelines for printing FD plastics. The width of 7.35mm across the face of the lenses comes out to about 13.8″. The 3.045m is around .120″ so the lamp will fit nicely into a 1/8″ hole.

This is then the solid model. Next step was to hollow it out.

With LED
.. aaaannndddd .. this is how it should work. Plenty of room to slide the LED up into the lamp, plenty of room from the wires to run to wherever.

.. and .. how well will it work? Donno. The LED has a 120° viewing angle so I assume it will have to face toward the operator. The FD .. either FUD or FXD is translucent .. not clear .. but HO and O scale light globes make a nice white glow with a warm white SMD LED. In this case everything but the lens should be painted so the light will shine through the lenses. Hopefully. How well this will work .. ummmm .. donno. Guess we will see when we see.

Cleaning
I can pretty much guarantee that there will be wax left inside the models. During processing of FUD/FXD it involves a series of steps (this is taken from a video .. think I have the steps right . or nearly so):

  1. Putting parts in a freezer to make it easier to separate pieces
  2. Putting the parts into an oven. This melts the wax (mostly). If you think about it .. the opening required for hollow parts has to be pointing down or the melted wax won’t drain .. that is my assumption at least
  3. Putting the parts into a hot oil ultrasonic bath to remove remaining wax
  4. Putting the parts into a detergent water ultrasonic bath to remove any oil

With all of that you will still get parts with wax in hollow spaces. I can almost *guarantee* this will be so with the lamps. That requires additional cleaning – more so in this case as we would like the lamps as clean as possible inside so the LED has a chance to shine through the plastic ‘lens’.

This is some information I have gathered on cleaning Frosted Detail plastics .. some of which I have used. Note that using Simple Green has risen to the top of my list. I also have an Ultra Sonic cleaner .. and am thinking of trying to combine the two and use the Simple Green as the agent in the Ultra Sonic bath and see how that works.

Cleaning Frosted Detail Plastics