Front Cluster

A close-up of the front cluster. I only applied a light coat of primer – the Tamiya Fine Surface Primer is more of a surfacer than a primer .. IMO .. meaning a lot less filler than a ‘normal’ primer. A very light sanding with fine sandpaper would help but honestly any defects you see are from the macro photography – normally viewing with your eyes you will not see any of this. The red angle .. that is to fit the angle of the locomotive hood. You can also see the wedge shape of the cluster itself.
Here’s a look at the backside. The biggest ‘problem’ will be to copy the angles and depth of the cluster body to fit nicely into a hood. Again, some light sanding is needed .. this is as it came from Shapeways with cleaning and a little primer without any sanding at all. The openings for the lights are more that large enough so a small LED could be inserted .. I think. I will be measuring to double-check that. If the holes are too small than fiber optics would surely work fine.
Some quick dimensions for the front cluster .. good enough to create a pocket in a hood.
A top and front view with dimensions in parallel format

Rear Cluster

What I said about primer and sanding applies to the rear cluster. You can see the round scar on the top left .. that is from where the sprue was attached .. again .. minor work to remove. Unlike the front cluster, the rear cluster is made to mound to the surface of the hood and not inset.
A look at the backside of the cluster. The red lines show the notch to fit over the angled nose of the hood. There is a matching angle at the top. Interestingly, the top of the bracket is proud of the top of the hood.
Here’s a look at the rear cluster from the front (left side) and rear (right side). The bit marked out in red again, evidently fits the angle on the nose of the loco.

Note:  That top red “V” is level with the top of the hood
Some rough dimensions – enough or “good nuff” to use for my 3D CAD work. The longest light cluster is approximately 6mm long. I show the depth of the “V” as 1.58mm .. that actually is a bit deeper as the vertical sides are on the same taper. I need to print a test hood at some point but need to figure out how to add that taper to it without causing other problems. More on that latter.
The same thing with parallel projection.

Hood Notch

I talked about modifying the curve for the top of the hood to match the curve on the U23B Exhaust Stack in the Atlas O scale section.

I notched the long hood for the rear cluster. This was a bit more involved than it might appear as there has to be walls on every side of the notch.

I punched holes for LEDs/wires for the lower lights .. not sure about the single top light.
… and here it is in place. Yes .. the placement vertically is correct. The flat ‘V’ is level with the top of the hood.

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