Atlas O scale U23B Cab

This was my starting point to design my own cab. Andrew Gillette supplied me with the cab so I could then design everything around that cab and the SD40-2 chassis. While Andrew wanted the more modern SD40-2 cab I like the idea of first generation diesels and created what I call a GP7-ish cab .. something that visually resembles a GP7 cab but is made to the basic dimensions of the Atlas U23B cab.

From this cab I could get the width, length and overall height. Things like the door latches, hinges, recessed lines for the doors, windows and such could be used as a guide for my own design. Note the tabs at the bottom of the cab for snapping into the HO shell. While I successful re-created them for my cab and they worked initially in the end I decided to discard them since the 3D resin copies are a lot weaker and broke off easily. I will have to come up with an alternate way to mount the cab.

I re-created the cab in Sketchup. This was for Andrew since he liked the cab .. well .. he DID purchase it after all. The important dimensions are shown which I would use to make my own cab design .. length, width and height.

GP7-ish Cab

My cab is quite a bit simpler than the U23B cab .. but that’s what I wanted. I added a opening at the top of the cab .. just .. because I could.

Yeah. I call it a GP7-ish cab as I like the early covered wagon look


Version 1 Print 1

Honestly .. If I wanted to I could use this .. it would just take some work … but I see it more like a learning process and this is part of that

I printed this at 30°. The part of the roof that is ripply and wavy was the higher part of the model nearest the build plate. There are some minor flaws on the vertical surfaces .. my guess right now is that supports are needed on the back side .. possibly the front.

This is looking at the same wall .. but I spun it a bit so the light would highlight the face better. That ‘floater’ is possibly a bit of support that broke off during the printing.

The ripple on the surface barely shows .. it could be filled with some careful use of filler. I think that just because it is hard to see in the photo shows how minor it is. Again .. I think this is from the print not being supported behind that front surface and that adding supports would fix that problem .. probably.

This is a view from the other side. I manually added the supports on this side .. you can just see where they attached to the roof. This part was the lowest part of the roof in the 30° print angle and came out very nice .. my guess is that there was little strain on the print at this point. You can just see the far side of the roof where it is rippled .. this was the point that most of the weight of the print pulled on (again .. a guess)
Finally a look from the other end of the cab opposite the first photo showing the rippling and wavy surface of the cab. This again, is mostly due to not using enough supports.The worse part of this sort of slow progression of correcting printing errors is I am using up my resin. Not complaining about the use or cost so much as that resupply has become an issue.


FAILURE!! Big time.

Looking at the first print I thought that angling the model at 30° might not be necessary. It seems that the biggest reason to do that is to lower the suction created when printing a flat surface. Since the base of the walls is really thin I thought that it might make sense to print the cab without that angle/tilt.

In that I was successful and printed the cab vertically. I still had some surface artifacts where I identified that it needed supports (this ‘supports needed’ is ‘after the fact’ .. not identified until looking at the prints just recently)

The failure came when I went to cure the model. This cab is what I call the “High-Hood” version which has openings at both ends for said ‘High-Hoods’ which results in a hinging effect and the cab developed a “bowlegged” stance. I thought to fix this during curing buy bowing some cardboard in the opening .. which was a major mistake resulting in the cab distorting during the cure. I also managed to break the model trying to correct that but that is really secondary. Ahh. Now what?

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