How to draw a digital Big Boy locomotive. Step by Step

Trains Illustrator Rick Johnson highlights the methods and computer-based tools he used to draw the world's largest currently operating steam locomotive
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Rick Johnson; Trains staff
“We’ve done a diesel and an electric; now we need to do a cutaway of a steam locomotive.”

Those words from a retired Kalmbach Media vice president sent a bit of a shiver down my spine as well as sparked a challenge I found irresistible. I’d love to do it, but it’s substantially more complex than either the SD40-2 I drew for the September 1997 issue of Trains or the GG1 cutaway I drew for the Summer 2009 issue of Classic Trains.

But, we knew Big Boy 4-8-8-4 No. 4014 was on the Road to Restoration, and surely needed a worthy drawing for our coverage.

Here's how I went about drawing a version of the famous locomotive, digitally.
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Rick Johnson; Trains staff
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Rick Johnson; Trains staff
All of these drawings were done in Adobe Illustrator, with the transparency and blending done in Photoshop, using a pretty old-school approach of projecting top, front, and side views to corresponding axonometric planes and assembling the pieces.

The steam locomotive posed more of a challenge, though, in that its components couldn’t be “snapped” to a floor plan or built up like blocks. The spatial relationships of the pieces had to be correct, but positioning them wouldn’t be nearly as straightforward. In addition, there is simply a lot more parts to show in a steam locomotive.
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Trains staff
When Trains editor Jim Wrinn was planning the June 2019 special issue on Union Pacific’s Big Boy, he brought up the possibility of a 3D cutaway of the 4014.

Gulp.

Any steam locomotive would be a tall order, but the Big Boy is about as intense as a steam locomotive can get. And once the project gets started, there’s really no opting out.

The project began in August 2018, to be done in an on-and-off fashion between work on issues of Trains, Model Railroader, and other Kalmbach publications. The primary references for my drawing were a scanned image of an actual blueprint of the Big Boy as well as a drawing by E.W. Bearman in Kalmbach Books’ Steam Locomotives Cyclopedia — Volume I compiled by Linn Westcott. Kalmbach’s David P. Morgan Library had a good variety of photos of Big Boys, as well as William W. Kratville’s 1972 book “Big Boy” which contained a lot of photos of the locomotives under construction.

A 1941 Locomotive Cyclopedia provided details on components such as superheaters and stokers. With some oversight by John Bush and Robert Lettenberger, I was in a good position to draw the Big Boy.

Using the CADtools plugin from Hot Door Software, I sized the scanned images to my drawing scale of 3/16-inch equals 1 foot and began tracing. CADtools can project flat art to axonometric planes, but the challenge with this drawing was in correctly positioning the pieces. I’ve also been writing plugins for Adobe Illustrator since Adobe first added support for that in 1993, and one of my recent projects was a specialized tool for projecting flat orthographic art into its correct position in a 3D axonometric view by first marking corresponding points in the top, front, and side views.
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Rick Johnson
For a drawing of these proportions, I determined that tilt and turn settings of 30-degrees/30-degrees would work well. It would make sense to start with the frame and work my way out from there, but what’s fun about that? I wanted to see some cooler stuff early on so I drew the front set of drivers, carefully tracing from one of the scanned images.
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Rick Johnson
I projected this to the “left” plane and began its conversion to a 3D look.
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Rick Johnson
The scanned images were projected to their respective axonometric planes and assembled so that their section lines corresponded. I used my plugin to offset the wheels one half of the scale 4-feet, 8 1/2-inch-wheel gauge along the correct axis angle, then added depth and shading to the wheels.

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Rick Johnson
Now on to the front cylinders. I drew half of the cylinder from the Steam Cyclopedia’s half section view, then reflected across the center line, visible here as the colored reference line.
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Rick Johnson
I projected this to the front view at its correct position in the axonometric area. The brown line you see here is again the vertical center line at the boiler’s front edge. I extruded the casting to its scale length and added some detail and shading.
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Rick Johnson
Next I added the frame and compressor equipment in front of the cylinder casting. If you’ve worked in Adobe Illustrator, you’ve probably guessed that I place different assemblies on different layers and sub-layers.
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Rick Johnson
I didn’t have a top view of the locomotive itself (only of the tender), so I worked out the geometry of the point of the pilot based on what information I had in the other views.
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Rick Johnson
Let’s fast-forward a bit to something resembling a completed locomotive.
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Rick Johnson
None of my photos, of course, were taken from just this angle.

Sometimes the drawings showed “almost” enough detail for some areas and other plans were down to the fastener level. It was like working with computer technical support, where the information given was very accurate, but not very helpful.

Fortunately, Kalmbach is located a couple of hours away from Green Bay, Wis., so I took a trip to the National Railroad Museum. There I could take notes and reference photos of the Union Pacific 4-8-8-4 No. 4017 on display there, which was incredibly helpful. For example, the organic shape of the single center front exhaust pipe was one of the day’s best takeaways, along with the swiveling fitting at the front cylinder.
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Image of file drawing of a Union Pacific Big Boy locomotive
We wanted to show some interior parts, so for these I referred to the scanned blueprints. Here’s an overview of drawing the fire bricks in the fire box. I imported a general arrangement blueprint into Illustrator and sized it to my 3/16-inch working scale so all of the pieces would (or at least should) fit.
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Rick Johnson
Here are my drawings of the section, top, and side views of the bricks and arches.
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Rick Johnson
Next I drew a wireframe of the inside and outside of the firebox, added the fire brick and circulators, and drew break lines for the cutaway. The red and blue lines are simply there as guides.
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Rick Johnson
In the same way, I added the flues, dry pipe, superheater, exhaust ports, and stacks.
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Rick Johnson
We’d need some indication of a cab interior, so I added that as well.
Eventually, all of the pieces I needed to show were done. Here’s what it looks like in wireframe mode. What a mess! This is one of the reasons it helps to break things down into meaningful layers. The finished illustration would grow to 68 top-level layers to keep everything separated in order from back to front.
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Rick Johnson
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Rick Johnson
Next I exported everything to a Photoshop file to add softer touches like shading and transparency to achieve the phantom views.

This view of the firebox interior with painted coal and fire is a combination of 16 layers, although the final view includes more intermediate layers and vignetting with layer masks. The final Photoshop file contains well over 100 layers.
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Rick Johnson
In the final composite, many of the interior areas actually float above the locomotive’s exterior, masked and vignetted to give the impression of a see-through boiler. Other floating details include the stoker’s auger, the throttle lever, and a few people for scale.

The ballast and shadows under the locomotive are placed on lower layers below the rails. In any illustration like this, there are always areas where one has to make a compromise between what to show and what not to so that the reader gets as much useful information as possible, and in a way that everything one sees makes sense.
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Rick Johnson
This is one of my favorite areas in that it shows the steam delivery pipe splitting outside of the smoke box to supply both the front and rear cylinders.

The front platform is translucent to show how the front pipe is jointed in three places to allow the front to swing side to side, and how the single exhaust pipe runs back from the center of the front cylinder casting while the rear exhaust pipes join in a tee. At the left of this image is the phantomed tongue of the front frame section, which was added to show the point where the locomotive is articulated.
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Rick Johnson
There’s so much to see in this massive locomotive that one could easily spend years drawing it all. It’s been a real pleasure having the opportunity to work on it!
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