I originally posted this info on the Atlas forum several years ago. The post is still there in the archive, but the photo hosting website decided to cancel their free accounts, so all the images were missing. Here is a copy of that post with photos hosted elsewhere.
I recently decided to finally install a decoder in my Shay. My goal was to install it without any body modifications and to also improve the illumination of its headlights. By chance there was a recent thread about Atlas possibly reissuing this wonderful jewel of a locomotive so this information is quite apropos.
I think that this is the best steam locomotive Atlas has ever produced! Its level of detail rivals brass models and that is explained by the fact that Ajin of Korea made these locos for Atlas. They are die cast metal locomotives with add-on lost wax brass castings. They have a *HUGE* motor with well-made precision worms and gears which explains why they perform so well and why they have excellent slow (more like "crawl") speed. Their fully articulated and animated drive shafts, universals and connecting rods are all fascinating to watch as the loco moves down the track. All of that for a price closer to a plastic model than to brass model! I sure hope that Atlas does re-run them.
Sorry for gushing, but I really like these little Shay I was able to squeeze a Digitrax DZ125 decoder inside the body shell. While similar installs were posted on other forums I think that mine is different enough to be documented on its own.
I measured loco's internal cavities and I determined that I could build a brass "shelf" for the decoder above the rear drive worm. The shelf itself is made of 0.015" brass. Its shape resembles squared off letter "U" with the bottom of the "U" pointing to the rear. Top of the worm is inside of the "U". Unfortunately I didn't take photo of the shelf before I assembled everything. The ends of the "U" are fastened to loco's frame with 2 000-120 screws.
This photo shows holes in the frame drilled and tapped for 000-120 screws. This is bottom of the frame with the plastic insulator removed for drilling. Since I was going to modify the frame fully disassembled the model.
I also decided to improve the headlights using white surface mounted 0603 LEDs and 0.040" fiber optics directing the light into headlight housings. I etched my own tiny circuit boards to hold the LEDs and their current limiting resistors while keeping them insulated from the metal frame.
Here is the DZ125 decoder with the wires removed (I'll be using different wires). Next to the decoder are front and rear circuit boards I made and surface-mount 1K ohm resistors and white LEDs (the yellow components). A 1/64" resolution ruler is in the photo for size reference.
This photo shows the decoder, circuit boards with the LEDs and resistors soldered onto it. Also shown are original headlight lenses (short clear pieces) and two 0.040" plastic fiber optics. Fiber optics were bent while heated and softened over soldering iron's tip. Then I trimmed and polished the short ends. The long end is still not trimmed to its final size or polished. For polishing I use a 4-sided disposable fingernail file available in beauty shops. Those have 3 grits plus a polishing end. They do a great job polishing plastic fiber optic ends.
Here is the front LED board glued to the frame using 5 minute epoxy. I also cut grooves into the frame (using a Dremel with a cutoff wheel) into the frame to route the LED wires so that they do not get pinched between the frame and body. The wires I used are very fine wire I normally use on my 1:24 scale model cars to simulate electrical wiring. They are sold by
http://www.protechmodelparts.com . It actually is a real insulated wire which comes in very handy in situations with limited space. The wire was then sealed into the groove with 5 minutes epoxy.
Here is the DCC decoder installed and wired. There is a 0.005" styrene insulator between the brass shelf and decoder. This photo shows how the worm sits inside the open "U" brass shelf. I used 30ga. solid-copper wire wrapping wire for the track and motor hookups because is is easy to solder and it retains its shape. Since wire is routed so close to moving parts it needs to stay in place.
Next 2 photos show overall photos of the mechanism after the decoder was installed.
A close-up of the rear LED board and of the decoder. This photo also clearly shows the 0.005" white plastic insulator under the decoder. Both insulator and the decoder are attached using 5 minute epoxy.
This photo shows front fiber optic glued in in its final position with the LED end also polished. The piece of white styrene is just a spacer to position the fiber optic directly over the corresponding LED. I had to enlarge the hole leading to the headlight in order to accommodate the fiber optic. I also painted the inside of the headlight with white paint. The original headlight lenses had to be shortened (cut off) and polished after shortening them. Everything was glued using 5 minute epoxy. The epoxy does not adhere to the fiber optic very well so I used enough epoxy to go around the strand of fiber optic. It is not going anywhere now! I took a yellow sharpie to tint the end of fiber optic to make the headlight glow look less bluish. The black line drawn along the fiber optic was a reference I used while gluing the fiber optic. That gave me reference to properly aim the end of that fiber inside the headlight housing.
Same procedure was used on the rear headlight.
Here is the final photo with the oil bunker removed to show how the decoder clears top of the body.
That's it! Now I have a digitally controlled great little loco! It took some extra effort but it was worth it!
EDIT: Photobucket fix
