- [Log] Upgrading Kato N Scale P42 Amtrak Phase Vb Locomotive
- 06 Nov 2015 05:29:53 pm Permalink
- Last edited by KermMartian on 08 Sep 2016 12:45:21 pm; edited 3 times in total
My long-latent interest in trains and model trains has recently been rekindled, so I've been exploring the current state of N scale model trains. I frequently ride Amtrak's Vermonter between Burlington, VT and New York, NY, so I've been considering modeling that route. From New York, NY to New Haven, CT, a train of Amfleet I cars are pulled by Amtrak's newish ACS-64 electric locomotive; at New Haven, an erstwhile P42 "Genesis" diesel-electric locomotive takes over. Thus, I've started by purchasing an N scale P42 from Kato, as well as a Digitrax DCC decoder. Like everything else, model trains are digital these days, so digital controllers trackside and digital decoders inside locomotives are used to control trains. In fact, I've been working on a separate project called CalcDCC to control DCC-enabled model trains with a graphing calculator plus an Arduino. But I digress.
Having purchased my P42 and installed the DCC decoder, I discovered that it had LED headlights in the front and back for going forwards and reverse, respectively. However, the red tail lights at each end were colored plastic and did not light up, and the ditch lights at the front of the train only lit up with the front headlights. I figured it might be a fun way to exercise a few rudimentary EE skills and get a little experience with modeling to upgrade my N scale P42 with a few extra LEDs. Before I could do so, I had to install the DCC decoder in my P42. I was happy to discover that the SDN144K0a has a number of extra pads on the board for soldering wires for extra LEDs. The two photos below show the exterior of the P42 with the decoder board next to it (left) and the inside of the locomotive with the decoder installed, with the train's original non-DCC light board next to it (middle). Just for good measure, I had to take a picture of myself and my little P42 next to a real Amtrak P42 in Phase Vb paint. As always, click to enlarge.
Next, I needed to get myself some SMD LEDs. The white LEDs used in Digitrax's decoder are actually a yellowish-white, to emulate the color of incandescent headlights. Therefore, I purchased the following LEDs on Digikey:
- (Digikey #732-5659-1-ND) Size 1206 white LED, 3000K color temperature (41 cents each)
- (Digikey #754-1159-1-ND) Size 1206 red LEDs, slightly dimmer (52 cents each)
- (Digikey #1497-1149-1-ND) Size 1206 red LEDs, slightly brighter (77 cents each)
While I waited for the LEDs to arrive, I started to modify the brackets (hoods?) that Kato designed to hold light pipes at both ends of the P42. The top half of the locomotive is a shell with holes for light pipes, and two gray pieces of plastic that actually hold the light pipes. The bottom half is machined metal, including LEDs, electronics, motors, gears, and trucks. I popped the two gray plastic pieces out of the shell, and started figuring out how to modify them for additional lighting. The back part was easy: I simply drilled out tiny holes behind the shell's opening for the tail lights. The front part was similarly easy: I drilled out similar holes behind the openings for the front tail lights, and the ditch lights already had holes available.
The light pipes are more complicate. At the front of the train, a single clear plastic pipe splits the light from the front white LED to the main headlights, the number board with the locomotive's road number, and the two ditch lights. I cut two pieces out of this trident-shaped piece of clear plastic to turn it into three separate pieces, sanded the ends for better light transmission with incrementally finer grades of sandpaper, then used superglue to re-glue the ditch light pipes into place (first two photos below). I need to bend 0.75mm fiber optic cable to make another pair of light pipes for the front tail lights, and I have spent a great deal of time trying to make that happen. Future posts will add more details. For the back, I'm planning to use two light pipes to connect a single red LED on the right side of the locomotive to both rear tail lights (third photo below). The piece of fiber optic cabling in the photo is a temporary piece I was using to judge how far apart I need to make the bends in the fiber.
My next task was to find a way to fit three SMD LEDs along with associated current-limiting resistors and wires into the front of the locomotive. I originally planned to 3D print a bracket for this, but I discovered that the space was too small for what I had in mind. Therefore, I brainstormed alternatives, and decided to try to solder the SMD LEDs onto 6 pins of 0.1"-spaced male headers. The photos below show the results of that process. I had to use an Xacto knife and diagonal cutters to remove a small piece of the gray plastic hood on both sides to fit the 0.6"-wide section of header, but using tiny 1/8 Watt resistors and the 1206-size SMD LEDs I purchased, the whole light module fits snugly into place.
The work continues; I'll update this topic as it progresses, and I'll probably post news once the project is complete.