The online magazine on the history and operation of vintage scale model trains in American OO gauge

Sunday, July 3, 2016

A 3D printed SD24 in American OO

A few months ago I posted about my nearly finished 3D printed SW7 models (which are also seen below, with some revisions to the paint scheme). Those were not the only 3D printed bodies I had though, the other being a SD24.

Big picture, at a distance certainly, this model looks great, it is very effective, and do click on the photo for a good view. When you look at it closely in person, however, the surface is rough and the details somewhat heavy, and it can probably only be successfully lettered for some roads. But I get ahead of myself.

The model itself, credit Jack Bartman for getting the ball rolling. The design was scaled up for him from an N scale model by a Shapeways designer. Sensing that some details might be rough, Jack had a few things taken off, specifically the roof fans and the big vents. The ones you see are HO parts that have been added to the body.

Looking at it, the drive looks good and runs well, and I think one probably would not notice without prompting that the trucks are under scale and the fuel tank is too large. They are from an Athearn HO SD40-2 model, blue box era with plastic side frames. I have by now modified quite a few of these drives for 19MM gauge, with this article describing the basics of the conversion. In this case, the frame only needs slight modification (I cut the ends off) to make for a frame and drive that works well.

To connect the drive to the body I decided the best option was to cut down the original Athearn body to fit inside the SD24 shell, as seen in the final photo. It sat a little too low so styrene shims hold the body at the correct height. The bottom edge of the original Athearn body is just visible but not really, as it is black and disappears under the 3D body.

Couplers were added and connected to wood pads on the body (that had been glued on with super glue). As with the SW7 models I painted it with PolyScale Pullman green paint (see this article for notes on painting 3D printed models) and added decals. The “Quincy Route” decals were added to the SW7 models and to this one. I added a bit of weight to the body as well.

Looping back to the paint scheme, the road is a freelanced road I last built models for in high school. I had the “Quincy Route” decals on hand (Champ decals purchased back then) and it seemed like a good time to use them. My goal with the scheme was to get the look of a 1970s/80s shortline, and I am happy with the result. I drew on Penn Central specifically though to just paint part of the hand rails a lighter color -- the original SW7 scheme I used had more white on the railings but it only emphasized that they were heavy, they have been modified into this revised scheme.

Speaking of the Penn Central, I think their scheme would work well on this model as would PRR, as the schemes are dark (which hides the detail issues) and don't have a lot of lettering. Any complicated scheme would be a nightmare if not impossible to do on this specific model, as the paint actually soaks into the “Strong & Flexible” material of the 3D printing. If it were produced in the FUD material it would paint better and look sharper but the cost is a good bit higher. So that is one to weigh out based on what you want it to look like and your actual budget.

To close I thank Jack again for getting the ball rolling. American OO has entered a new era with 3D printing. As noted in my first article on the Shapeways products, I purchased three FUD Diesel cabs and have three more diesels underway to use them, a dummy GE U23B and two powered SD40 prototypes. Maybe they will be finished this summer? More on them when they are further along, but this article gives a quick look at the start of the SD40 project.

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