3D printing an O scale box car

I first met Ryan Tamburrino on Facebook as he asked me a weathering question. The discussion moved to B&O box cars and then he mentioned printing his own. In O scale. Here’s Ryan with some of the details.

It all started in May 2022, when, after a few discussions with George Podas about creating 3D printed Baltimore & Ohio prototype truck sideframes. He nicely nudged me multiple times to consider designing a B&O M-27F boxcar in O scale.

This car’s Tatum mansard roof is uniquely B&O, and they were never commercially made for O scale. Since we are both modeling B&O in the 1950’s, he thought this would be a good addition to both of our rosters.

I got to work with basic dimensions and a blank screen in Fusion 360. With the aid of incredible friends and research with the B&O Railroad Historical Society, I was able to obtain hi-resolution photos to extrapolate other dimensions and features.

M-27b used for the model prototype

Prototype notes from Jim Mischke

B&O M-27a class cars were built in 1926 as the latest, greatest boxcar for automobiles. The cars featured six-foot wide double-doors and a nine-foot inside height. They were taller than the eight-foot inside height B&O M-26 subclasses or PRR X29.

B-end detail of the M-27a and M-27f class box cars showing the unique roofline

Confronted with other taller boxcars equipped with Evans Auto Loaders, B&O rebuilt 501 M-27a into M-27b class cars during 1933-36. Unique Tatum XLT roofs were installed for room to stow Evans Auto Loader ramps when not in use. The Evans ramps allowed automobiles to be loaded into a tilted position, with room for four autos instead of two or three.

M-27f used for the model prototype

About 1939, B&O withdrew many X-27b from automobile service and placed them in grain service. The left doors were welded shut and the Evans equipment was removed. These modified cars became the M-27f class. In due course, the second door was replaced with a steel panel and the door opening reduced to a single six-foot door.

Design and print

The biggest challenge for creating this car in O scale was printing it. I was using Rich-Opto ABS-like resin and had tried printing in sections on an Anycubic Mono X printer. However, no matter how I oriented the car, I was unable to both hide the support insertions and prevent edge warping on a long span. I needed to try to print the car as one piece, but the build plate of the Mono X could not accommodate a car of this size.

Along came a new release over the summer, the Anycubic M3 Max printer. With a build plate size of 13-inches, this car would fit in its entirety. Above is an O scale model emerging from the printing resin. The photo is overexposed so the model and supports can be seen. The body was printed as one complete piece. Each detail part was separately designed, printed, and attached. Each car has over 50 individual printed parts from 22 drawings.  

All parts are 3D printed except for the brass strip for the running board, Precision Scale AB brake kit, Kadee 740 coupler shanks, P&D air hose, and InterMountain 33-inch wheelsets.

The Fusion360 files can also be resized. I printed an HO scale version as seen beside the O scale print above.

This is the design file as prepared for the printer.


Assembly of the model was uneventful and assembled as any good kit would. Care had to be taken with the resin grabs and other fragile detail parts, but fortunately all worked out ok!

Paint is Krylon Professional red oxide primer, followed up with Ace Hardware gloss coat prior to pinwashing and decaling. The Krylon and Ace colors were from rattle cans and they sprayed smoothly. Both Krylon Pro and ACE clear gloss have a very high flow and fine mist.   

I created the lettering artwork from prototype photos of B&O 295332 and 382481 in Adobe Illustrator. The decal set was printed by Highball Graphics. Chalk mark decals for the M-27B are from Protocraft, and I had drawn the chalk marks on the M-27F with Prismacolor pencils.

For both cars, weathering was done in layers of Testors Dullcote followed by raw umber pin wash, Pan Pastels, and Prismacolor pencils.

The oxidized panels on the M-27f were done with sponged oils.

I couldn’t have moved these O scale projects forward without some help. Huge shout out again to George Podus for the impetus to do this.

Thanks to Sarah Griessenböck, for her work designing the doors and locking mechanism!

Thanks to to John Haney for review and critique.

I also thank Bruce Griffin, Eric Hansmann, Jim Mischke, and the B&O Railroad Historical Society for help with research and documentation. The encouragement and inspiration from all these modelers and historians sparked my work to move these models forward.

Wow. 3D printed O scale freight cars. My mind will never be the same. Thank you, Ryan, for sharing your photos and notes on these amazing projects.

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25 thoughts on “3D printing an O scale box car

  1. Mr. Hodina,

    Will kits for your beautiful and unusual O-scale B&O M-27F 3D-printed boxcars be made available from you for us hungry O-scalers?

    Best regards,
    Gary Patrik

    1. Gary, the blog post on 3D printing an O scale B&O box car was not intended as a product announcement. It was a piece to inform and inspire as many modelers are now going the 3D printing route for specialty detail parts and models. – Eric H.

  2. Excellent work. Makes me very hopeful for getting some more models of SP NG cars in Sn3. I actually really like some of the print artifacts in the car sides. In natural light it really looks like the car sides are sheet metal. Very well done

  3. For anyone who might arrange to produce kits for this unusual car I would be interested in having one.

  4. Very nice. The paint looks great / thanks for the tip on Krylon

    Unique protypes / models like this one are what makes modeling the 30’s through the 50’s so satisfying

    Thanks for sharing

    (If someone wants to print some of these in O Scale – it looks like there would be some interest 🙂 )

  5. Fantastic is all I can say — makes some of us in S scale very hopeful. I am seeing the supports touching in the middle of blank panels – very smart! Also noting the relative lack of supports, perhaps due to the relatively thicker wall sections in O scale than smaller scales? Thank you for sharing in this well written post.

    1. The internal has thousands of supports! Externally there aren’t too many because the only significant overhangs are on the door rails and end caps of the roof

  6. Thanks for the kind words. I did forget to mention…I have not found a source to print these commercially, but will provide a zip file with all the STLs for anyone to print on their own for their personal use.

    It was drawn 1:1 for O scale, so you will need to adjust the scale accordingly (55% for HO, etc) in your slicer prior to printing.

    To get a link to the zip file you can email mr at ryantamburrino@gmail.com

    1. Thanks mine! However I’m just having fun with the hobby so not offering them for commercial sale. See my comment below though for how to get a kit to print for yourself!

  7. I too would be interested in an HO scale version should they become available. Your results look spectacular!

    Mark Rossiter

    1. Greg. Krylon pro primer is the most matte paint I’ve ever seen. I can’t tell the difference between that and the airbrush.

  8. Very nicely done, Ryan!! I’d love to hear a bit more about the resin you used for this project.

    1. I got it on Amazon. Around $30/L. It’s nice because it has some give and isn’t super brittle like other resins. I wish it was water washable because its pretty nasty on the skin but it does print well! It’s my go to (so far) for 90% of train projects.

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