Now the DD35 chassis has been completed and the shell has been printed it is time to put them together. The prints arrived, along with some other parts I have been working on, in the usual big box from Shapeways. They were all in plastic bags and covered in the waxy residue left over from the 3D printing process which gave them a slimy feeling. Washing them in warm soapy water is the best way to remove the bulk of this residue but be careful not to have it too hot as there is a chance the plastic may warp. I also put the larger pieces directly under the tap, this seemed to blast a lot of it off. Once that was done the sliminess had gone from the parts which made them much nicer to handle. The next step was to cut the handrails from inside the shell without damaging either, this with done with a sharp craft knife. The blade ran along the inside of the shell and one by one the handrail posts popped off. Here are all the parts laid out ready to be test fitted.
The shell fitted perfectly sliding over the chassis and seated on the metal shelf. The lip all round the bottom of the shell overlapped the shelf concealing the shelf on the chassis, just as the DD40AX shell had done. There was a bit of tolerance allowing the shell to be positioned centrally on the chassis. The fuel tank then clipped into place with a positive click.
Comparing the DD35 next to a DD40AX, the walkways lined up perfectly. as did the height of the two shells.
After test fitting the shell on the chassis it was time to prepare the shell for painting. The parts, although having been cleaned in warm soapy water, still had a lot of the waxy residue in the grooves and details. If this residue is left on the model no paint will take to the plastic so it needs to be totally removed. A rubber cement solvent is a good way to do this but you have to be careful to find one that has no chemicals in it that will melt the FUD material. One suitable product is Bestine, which contains Heptane. Although this product cleans up FUD very well it is flammable and only seems to be available in the US. I prefer to use a product called Goo Gone; this is also a US product but it is not flammable or toxic and can be ordered online and shipped just about anywhere. (It is also great for cleaning wheels).
All the parts where put into a jar containing Goo Gone and left for 24 hours. A jar with a lid is best as the Goo Gone evaporates fast and you will want to keep the parts submerged for the process to work, and you can keep the Goo Gone in the jar to re-use the next time. On removal the parts were washed again in warm soapy water and lightly scrubbed with an old toothbrush to wash away all the remnants of the waxy material that the Goo Gone lifted off the parts. The parts will feel soft and flexible and they should begin to turn opaque with a yellow tint. It is not recommended to leave them submerged any longer than 24 hours as they will continue to get softer and may start to deteriorate. Once removed they will then need to be left to dry on paper towel for at least 24 hours. After this they should have turned totally white and become rigid and hard once again. The very last of the waxy residue will now have had a chemical reaction with the Goo Gone causing it to turn into powdery fuzz. This can be scraped off with a dry toothbrush. The main shell now looked like this.
The fans still had some fuzz left in them which was a little harder to get out and took a little more persistent scrubbing with the dry toothbrush.. This was also the first time I could see all the detail and I noticed things like some missing bolt detail which was traced back to an error in the 3D model.
There was also some rough patches on some of the doors which was also traced back to model errors.
Apart from the few small errors mentioned above, the first print was very good, and I was very impressed with the level of detail that came out. However, I have gone back to the original 3D drawing and ensured that future prints will not have these errors.
The shell was test fitted again just to ensure everything is okay, and it fitted just as well as before.
The shell and chassis was then handed back to Bob Norris for painting. The shell was sprayed with UP Harbor Mist Gray and UP Armor Yellow paints from Badger paints. The yellow was very thin and ended up being brush painted. In all this took five coats, but the detail showed up very well through the paint. The inside was also painted black to make the yellow color bolder.
The next step, once the paint had dried, was to add the decals for the red lining, numbers and lettering. Wet slide decals where used and these were then sealed with a coat of Testors Dullcoat (a clear matte overcoat) which stops the decals lifting off and removes any shininess from the decals and model. The last step was to add the handrails which had also been sprayed with UP Harbor Mist Gray. They were test fitted then super-glued into place.
And here it is. A DD35 in N Scale, it runs perfectly and pulls like a DD35! But as with all model railroads there is always more to do. To weather it Bob added some grime and dirt to make the loco look like it had been working hard so he could run it with his GE U50.
The time it took from receiving the first print from Shapeways to the finished product you see in the photo above was about a week. I have to thank Bob as his experience in painting and working on a different material whilst still achieving his usual high standard of finish meant we turned this project around a lot more quickly than if I had taken on this venture on my own. I’m very happy with the quality of the first model we’ve produced, and the next collaboration should be even better!