I wasn't quite sure when I was going to start this project, but having solved some mechanism issues, with a day or so of vacation, cool weather, and fiddling with the 3D modeling software, and well, here we are When I first started in this nice hobby, I ended buying a KATO VIA rail passenger car set off eBay - the blue ones. Just seems like the right thing to buy at the time, but turns out it's completely wrong for the era I'm making my layout. My layout isn't prototypical, so in my world, a museum saved two of these coaches from being scrapped and runs then for tourists. Why not eh? So what locomotive to run this little train? I absolutely wanted a high hood nose locomotive, even if it doesn't fit my modern era, and it just so happens that RS-18s have actually pulled these blue coaches in the past! But there are no RS-18s in n-scale. Or well, there might have been once upon a time, one or two companies that produced shells that were used on Atlas RS-11 mechanisms. Now since I do own a 3D resin printer, and it's on my TODO list to make a locomotive shell, seems everything was in place to try this out! So first step, was to locate and buy an Atlas RS-11 - in this case, I lucked out and found a recent run of the model - a Toledo, Peoria and Western model that was last released in 2015 - DCC even! It took some time getting up here to Canada, and had a bit of trouble getting it running, but it now works absolutely great. So this will be my first locomotive shell that I 3D print, and well, in the past, my biggest projects so far have been an HO cattle car, and and the n-scale gondolas that where the subject of a previous thread on this sub-forum So what exactly do I model? Well, this proved to be a really easy choice. I live in the province of Quebec, and have visited Exporail, a local(ish) rail museum. There they have an RS-18, in Canadian National Railways colours. Not only that, but I found a website, Trainiax, run by someone here in Quebec that appears to make line drawings of locomotives as a hobby, and he's produced such a drawing for the Exporail's RS-18! (image linked from http://www.railpictures.ca/?attachment_id=34896) (image by Trainiax - http://trainiax.net/medim-mlw-rs18.php) Armed with a bunch of drawings, a bunch of detail photos of pretty much every angle of the real locomotive, and more than a little hope, I launched Fusion 360 and started drawing! Baby steps, I need a replacement shell for the mechanism. That's where it all starts. Well, with no prior experience in this sort of thing, I figure that's likely my first step. I used the existing Atlas shell for the two most important measurements, the inner shell width and length. Everything will have to build from that, because anything smaller will just not fit the mechanism. In terms of the side view, I used Trainiax's drawings. I cannot be certain that his measurements are 100% correct, but I have to draw a line somewhere (no pun intended), so for all intents and purposes, I will consider his drawings as perfect and not look back. Head on and rear views of the locomotive, including dimensions are a problem though. Trainiax's drawings are strictly side view. So for those, I used the Atlas shell to determine the width of the hood and the sill. So where did this get me? I started modeling exactly to the drawing, only making adjustments where necessary. For example, strictly speaking, the sill is thicker than in the drawing, but I don't have much of a choice if I want it to fit the mechanism (the Atlas sill is almost twice the thickness of the drawings - understandable considering we don't have all the under body details). Now, the point was to just make a box that would fit the mechanism. I just wanted to get the basic shape that would fit perfectly on the Atlas frame, and then see where to go with details. But as it is for my projects, I got carried away and did the hood curves and cab The question you're probably not asking, but I will answer anyway - with only side views, how did I come up with the "correct" curves?? Well, I had to cheat, but I think I got it right. I looked online and found low quality head-on drawings of RS-11 and RS-18s paint schemes. The curvature on the hood and cab seemed to match, so I used the best one, added it to Fusion 360 and then did my best to match the same curve. Trainiax also does imply the curves on his side drawings, to which I did my best to match the model... Now, I don't want to leave you all with just a bunch of drawings, did I get anywhere with this??? Yes! I did print a basic shell, and it mostly fits. In terms of width and length, the shell fits very snugly right over the frame, and the deck/sill covers the metal tabs on the bottom of the Atlas frame. Now there are some improvements to be made for sure. First, the shell bulges out on both sides, and it took me a bit of time to figure out why. Looking at the frame, see that there are two dimples on each side? on the Atlas shell, these key into dimples in the inside of the shell. I'll need to do that too. I also printed the model flat, mostly as an experiment in supports (blades/skirts to reduce warping). While a mild success in some ways, it caused the expected problems in others (suction issues, and still a bit of warping post curing). Still, the basic shape is there! I still will revisit the curvature of the cab, it seems to be flatter than expected on top. Also, the curve of the hood where it changes from vertical to mostly horizontal doesn't look quite right compared to photos - too sharp. I'm also wondering if I should try to print this in two pieces - hood + deck, or keep it in the single part seen here. This is where my lack of experience is showing. I still need to measure the height of the hood from the rails. In terms of the drawing (deck to top of hood), it's correct. But the lightbulb "bottoms" out in the short hood section causing the DCC board to bend a bit. The Atlas shell has a slightly taller hood. I'm fully aware that sometimes you just have to make sacrifices to realism to fit the scale. Anyway, this has been waaay too long already. Very sorry for the long post, I do tend to ramble on I hope you like - like my previous Gondola build, this is going to be a journey into 3D printing with a newbie, warts and all!