One of the other areas of the Atlas shell that could use improvement involved the cooling system details, including the fan and grille on the front of the loco as well as the radiator cores and corresponding grille at top front area of the hood. The stock Atlas shell is rendered with closed shutters at the front of the loco, and a boxy representation of the radiator cores that is wrong in shape and completely devoid of any of the detail or character of the prototype. Combined with etched metal grilles that are a touch heavy and generally inaccurate, and the overall effect is fairly underwhelming.
In addition to improving the radiator details, I wanted to represent a Southern Pacific prototype, which is well known for utilizing unusual lighting packages on the nose and above the cab, and for the high mounted numberboard housing above the windshields on the front of the cab. Lastly, I wanted to improve the sand filler hatches, adding depth and detail, and revise some of the sheet metal around the nose area.
The following images are copyrighted as noted, and used here for reference only. The first picture illustrates the original as-delivered light package. The second pic shows the revised arrangement later in life, with two of the lights removed and the class lights blanked out, which is what I will be modeling. The last photo shows the numberboard housing.
First up are the radiator cores. The goal here was to capture as much of the detail as possible, including the nuts and bolts, headers, core frames, core mesh, and so on. One trick is to first decide which type of radiator core to model. Cores can have different frame styles, different mounting tabs, and different stiffening ribs on the sides. There are also three sizes of cores, in effect 1X, 2X, and 3X lengths. The radiator core compartment is the length of three small cores, plus the headers. Cores can be found in combinations, per side, of 3 short cores, 1 short and 1 medium core combined, or 1 single full length core. Often the two sides will have different core arrangements. It all depends on what the original unit was delivered with, and what components were used during shoppings. This really is a situation where proto photos of a specific unit would be useful, but they frequently aren't available. At some point, one must simply bite the bullet and choose a style. Again, the following photos are for reference only.
3 short cores:
1 short and 1 medium core:
1 full length core:
The best part is that I can find examples of SP locos with all three conditions. I went with the 1X+2X version for this model. Of course, I had to go ahead and do 3d cad for all three combinations, so I can always use a different style on a different model.
One of the other goals with the radiator core model was to have a screen representing the core mesh that would allow for sound to escape the shell. The idea is mount a shelf inside the shell, from nose to just in front of the cab, above the motor. The front part of the shelf would hold a Tang Band speaker facing upward, to fire through the radiator "screen". The back part of the shelf will hold a Loksound decoder. The original inspiration for this speaker arrangement came from a Bob Sobol post on the
Appalachian & Ohio crew forum (a very nice O scale layout out in Colorado). Bob was going to use speaker fabric to hide the speaker on an Atlas sw8/9 model. I was concerned that after painting and weathering, the fabric might stiffen up and not be so "accoustically transparent". I plan to instead use an etched metal screen, ideally with an appropriate grid sizing to mimic the core mesh, and either paint it or blacken for color. In the photos to follow the test screen is from a Plano Models HO scale hopper walkway. I will go with the smallest commercially available mesh I can find, or have a piece custom etched.
In the last three photos, you can see the slots in the end to slide a piece of .008" mesh into the radiator frames. The narrow slots below are for tabs on the end closure piece to fit into. The mesh as shown is just a test, but I would definitely like for it to have smaller openings. The goal is to mask the speaker below, and I'm not sure that would happen as it stands. If I can't get something more suitable, I will consider layering a second piece of mesh below this one, ideally with the members offset so they obscure more of what is below.
A picture of the original Atlas part can be found back on page 2, post #38, of this thread. As with the bogie sideframes, there's no comparison between the two versions.