A search for pictures and
A search for pictures and videos on the Internet started the project. While doing this I found that the locomotive was a rebuilt SD40-2 and that the train was developed and built by Relco in Iowa. I contemplated asking for information from the builder but companies these days are not very receptive no giving information to modelers. I continued with my search for information but figured I could at least start work on the locomotive.
I figured that the best was to approach this was to start with and Athearn SD40-2 drive, I have a lot of old Blue Box components but no SD40-2 frame. I guess you could say I am somewhat cheap as I didn’t feel like getting the updated frame from Athearn nor did I find anything on Ebay that I wanted as the base for the project.
As I had an Athearn SD40-2 that I had weathered I didn’t what to sacrifice it so my alternative was to reverse engineer the frame and print it. Taking measurements using calipers I created the frame in 3D minus the fuel tank. As the frame is longer than my printers print area, I cut the frame in half in the slicing software. My intent here was to join the halves of the frame together using the fuel tank as the splice
I have heard that a problem with a lot of models is that the fuel tank contour is not correct. I happened to find a drawing of the end of a EMD tank on the Internet and used it to create the fuel tank. I’ll explain how I scaled the drawing later in the article.
The photo below shows the three parts of the frame prior to assembly and detailing. This is actually the second go around as the Blue Box trucks I had were not in good condition so I ordered another set. I had to add a #50 hole in the bolsters to accommodate the new trucks and re-print the frame.
The frame was assembled using 2-56 machine screws through the bottom of the fuel tank the bonded together with a 50-50 mixture of MEK and Acetone. I have found that this mixture seems to work best on object produced with ABS printer filament.
As the model has no walkways, I added .080 strips around the motor well so that I could attach the air reservoirs. This is one of those things I should have designed into the frame but just didn’t think of it at the time.
With the frame assembled and fuel tank detail added the frame was ready for priming and painting. I primed the frame with a rattle can primer then painted it and the truck sideframes with Tru-Color UP harbor Mist.
Since the plastic frame was an unproven concept, I decided to add the motor and trucks to the frame and test it with a bench power supply to make sure everything work to my satisfaction before adding the decoder.
The motor mount was an adaption of the Athearn Genesis mount. As you can see, I added supports so that the moto would sit slightly higher than the screws used to join the frame pieces.
My intent was to use double sided tape to hold the mount in place. That didn’t would well so I used a bit of Gorilla contact adhesive. Even when cured a sharp force will break the mount free if I ever have to change the motor.
I finished the drive train with a set of A-Line Hex drive shafts. Looks like an Athearn frame, doesn’t it?
With the frame completed I turned my attention to the body of the locomotive. My original thought was to take measurements from a SD40-2 drawing but the remembered how I had created an Indian Head sign for a motel project.
I think the following is a great way to scale a project if you can find photos that are as close to straight on as possible. I brought an image of the locomotive into Adobe Illustrator and then saved the file as an AutoCAD DXF file. The CAD Software I use to create my models can import DXF and I placed the picture in the lowest layer. All you need now is one measurement. I my case I had a measurement of the SD40-2 over the end sills. Placing points on the end sills in the picture I set the units between these points to the SD40-2 length scaling to the actual distance. Now I had the change this to scaling for HO gauge. Since an actual inch in HO scale is 7.25 feet. I create a line in the CAD drawing that was 7.25 feet long. I selected the end points of this line and set the units to 1 inch. I now had an image that I could take measurements from using the dimension feature of the CAD software. No rulers!
Now it can take quite some time to draw a locomotive body in 3D. Now that I am retired, I have the time and the wife says it keeps me out of the bars. I believe the body took around 50-60 hours to create. I was going to print the body on my own printer just as I did with the frame. However, I ran into issues with printing something this large. The filament printer tended to misalign layers at times which resulted in noticeable ridges in the body. Also, I had issues with warping of the edges.
After several test prints, I came to the realization I would have to have Shapeways do the printing for me. To make the design work a bit easier I decided to not draw the rooftop details and grilles. Instead, I would use Canon parts to do the finishing. So, armed with my drawing I submitted it to Shapeways for printing.
The body itself didn’t require a lot of work when I got it from Shapeways other than adding the detail parts. One of the issues I had was with the headlights as I had them cast in place. The issue was really, “how are you going to paint these”. Since the headlights were cast and they were aluminum color on the locomotive it would be near impossible to paint. I ended up using Nelson Beaudry’s method and drilled out the headlights with a 3/32 bit. Instead of brass tubing, I will use Aluminum tubing after the body is painted, that way I don’t have to paint it.
A problem with using a plastic frame is weight. I weighed one of the Kato SD40-2s that I had and found that it came out just over 16oz. My model was about 8oz lighter. Since the locomotive has a cowl type body, I was able to add 4.5oz of weight by attaching 1/4oz wheel weights to the sides of the body. This brought the weight to 12.5 oz. Although slightly less than the Kato model this should give it enough pulling power for my 5 car work train.
I use TCS WOW Sound decoders in all my motive power. I find that the audio assist feature makes it easy to set up the decoders and having all the same decodes means I only have to learn on set up procedure. The LEDs I used are Micro Litz Wired Leads Pure White SMD 0603 leds from Amazon and a cemented to the ends of the Aluminum tubes then inserted in the body The picture below shows how I wired the leds to the decoders motherboard using micro connectors so I can remove the body if needed.
Now All I need to do is add glazing to the windows and attach the couplers before some exterior detailing. The couples will hold the body in place on the frame.
Most of the locomotives on my layout are “working models” like the Scale Trains “operator” series, therefor the detailing was kept to a minimum. The only details added were the horn, MU hoses, steps and handrails. I wanted to add the cut levers but could not find any is stock.
The photos below shows the completed locomotive. All to the decals were produced using a laser printer and some white toner.
Actually didn't notice that the back to fans were cocked, correct this after the photo was taken.
The next update will deal with the well cars that hold the used ties. Just waiting on Shapeways to deliver them.
Happy Railroading
Greg
