The story behind the Big Boy's design

This article is by the author MorningStrummer (Marti's Brick Models)

The design of the Big Boy:

By MorningStrummer (Marti's Brick Models)

The Inspiration (early 2000s):

As a child I was always obsessed with trains and steam engines. I have tried several times to build my own Lego steam locomotive. Eventually we got access to the internet where I found out about the Big Boy locomotive and fell in love with it immediately. I knew I had to build one. So I did, but as a 13-year-old who didn't have easy access to new stones, things really didn't look good. (I don't have any pictures of this first attempt)

When I was growing up, we also often went to a local model shop. There I found a Revell kit for the Big Boy which I bought and built. I still own the model today (a bit battered) and have often used it as a reference for designing my own Bog Boy models.

Start of draft (2011/2012):

Now that I'm older and have easier access to new building blocks, I decided to give another try at designing a Big Boy. This time, however, I took a completely different approach. I decided to take my time and buy parts as needed to eventually complete the locomotive.

Not only did I take my time, but I also decided that they MUST be able to run on standard curves and switches, mostly as I didn't want to buy retrofit track just to play with my train.
I started with the drive train, which should be completely self-contained so that no torque is transferred from the boiler to the drive wheels that could derail the locomotive. This meant that it had to be built entirely out of engineering blocks. In these early stages, I also determined the general shell shape I wanted to use, which was a basic hollow structure.

"Completion" of the first draft (2017/2018):

I said I'd take my time, right? It took about 6 to 7 years of building and building until I finally "finished" my Big Boy. Although it had some flaws in terms of its looks and shape, I was more than satisfied. That was a good thing, because that's when I decided to move out of my parents' house. This meant that building with Lego alongside my other hobbies would become too expensive. At that point I gave up my Lego hobby and put the model on display. Expecting that I wouldn't be touching Lego anytime soon.

Creation of building instructions (2018):

After it had been gathering dust for a while I had the brilliant idea of ​​sharing my Big Boy with the world, so I joined a Lego group on Facebook. I was hesitant at first, and only after about a month (and a slight rearrangement of the offer) did I dare to publish some photos. The response to this was amazingly positive, with several people asking me if I had building instructions for this and that they would be happy to pay for it if I had one. In this crazy situation I decided to get back into Lego and I jumped at the chance and taught myself how to make a building guide. I made a few changes while creating the building instructions, as there were some cases that could not be built without modifying the bricks. (Also, since I originally designed the Big Boy with my own drive rods, I had to design a 100% original drive rod system. This first guide was officially published on November 18, 2018 at ^th .

The 4014 update (2019):

After posting the instructions I was told that the REAL Big Boy number 4014 was almost fully restored and would be running under its own power again in May 2019. Of course, I had to use this opportunity to promote my design even more. So I took my Big Boy to my job site and started modifying the Big Boy again with the money I made from the instructions. This time I wanted to smooth the entire locomotive (no more lugs visible), redesign some details and parts of the cab, all based on my speculation of what the restored Big Boy would look like. The changes were pretty minor as you only need 178 additional parts.

Version 2 redesign (2019 to 2021):

After seeing several videos of the restored Big Boy, I once again decided to update my model. (This time I wanted to get the boiler into its proper shape, rebuild the design to be oil fired (just like the restored 4014) and update the locomotive colours. But that's just the start...

The moment I started taking things apart, I started to think of more and more things I wanted to change. It got to the point where I started completely redesigning the tender, boiler, cab, nose, firebox and most of the drive train. The only things that stayed the same are: the drive rods and the bell.

Once again I'm using my trusty Revell kit as a reference for my Lego model. In addition to that, I now have the luxury of using a ton of videos of the Big Boy to get an even better idea of ​​what she looks like.

The shape of the new boiler was achieved through the use of a hollow frame in the middle and a wedge structure at the front and rear. I was able to add bolts to all sides for easier assembly of the side, top and bottom panels.

Because of the different boiler size, I was also forced to redesign the cab and tender to be less wide while maintaining the original height and length.

Throughout the design process I experimented with different building techniques to achieve the final shapes. This means that some parts of the locomotive have been redesigned a dozen times, while other parts have been perfect from the start.

When I started the tender I took the opportunity to change the way the centipede axles work. Originally I had them firmly mounted to the tender but I didn't like how this looked when cornering. So I decided to make the centipede trucks a boogie, which also meant that any detailing had to either move with the wheels or stick out way too far on the sides. (Eventually I came up with a sliding construction where the details were attached section by section directly to the axle. When the tender is on a straight stretch the details look like one solid construction, but once it's on a curve you can see the sliding axles come to life.

Version 2 building instructions (2021):

Once again it was time to create a building guide. At this point I was fed up with the simplicity offered by standard Lego instructions and some MOC instructions. (It's my fault too) So once again I took inspiration from my Revell model, or more specifically the instructions used in model making (Revell, Tamiya, Trumpeter, etc.) and re-imagined how they do instructions work.

Before I fully immersed myself in this concept, I put an example online to get outside input. After that feedback, I made some changes and felt confident enough to make the entire guide this way.

This version 2 guide was officially released and published on October 8, 2021: ^th .

Version 2 in production (2021):

Knowing that this new Big Boy model, just like Version 1, would be copied by other manufacturers and sold as a kit, I decided it would be a good idea to get ahead of them. So while creating the building instructions I approached several manufacturers and was contacted by Lesdiy/Lightake/Letbricks to put my version 2 Big Boy into production. Eventually I came to an agreement with Lesdiy/Lightake/Letbricks and they were able to launch the (currently) final model.

This is how the Big Boy works:

A steam locomotive is a complicated machine in itself. Now imagine taking two steam locomotives instead of one and putting them together... Then you have the Big Boy. When many people see a steam locomotive they are most likely impressed by everything that goes on inside the locomotive, but few know the inner workings and workings. In order to build an accurate looking model, it is very useful to do some research so you know what you are building.

Explanation of the different components:

1. The bell serves as a warning when approaching a level crossing, train station or when driving slowly.
2. The used vapor from the cylinders (19) returns to the smoke box. The steam pipes are not connected directly to the chimney (3), resulting in the steam drawing a vacuum through the firebox (21), drawing hot air through the boiler and heating the water.
3. The Big Boy has a double chimney, one for the front drive wheels and one for the rear drive wheels.
4. The whistle is used as a means of communication between locomotives and railway workers. Different sequences all have different meanings.
5. Sand is used to increase friction between the wheels and rails. This is stored in one or more sand domes above the boiler and, if necessary, the sand is blown to the wheels with the help of steam and pipes. The Big Boy has 2 domes, one for the front drive wheels and one for the rear.
6. The steam dome is the highest point in the boiler. This is where the steam is extracted to prevent water from entering the steam lines and cylinders.
7. When the pressure in the boiler gets too high, these spring-loaded valves open, releasing some of the pressure.
8. Sand is used to increase friction between the wheels and rails. This is stored in one or more sand domes above the boiler and, if necessary, the sand is blown to the wheels with the help of steam and pipes. The Big Boy has 2 domes, one for the front drive wheels and one for the rear.
9. The Big Boy is equipped with 2 dynamos that supply the entire train with electricity.
10. A steam tower is a valve manifold that takes the steam from the boiler and distributes it to all the auxiliary functions of the locomotive. Think of the alternator, water pump, compressor, etc.
11. The entire locomotive is controlled in the driver's cab, normally a locomotive is operated by 2 people. The engineer is responsible for running the locomotive, the stoker takes care of the boiler (fire/pressure/water level etc.) and helps the engineer monitor the signals.
12. This is the part of the tender where the fuel is stored. The current Big Boy stores oil here, but when these locomotives (and many other locomotives) were built, this is where the coal was.
13. This is the water supply/storage for the locomotive.
14. Various auxiliary functions are mounted on the front of the locomotive. The radiators for cooling parts of the locomotive are also installed here.
15. The steering wheels guide the locomotive in curves/switches, without them the danger of derailing increases dramatically.
16. These are the tubes that bring the high pressure vapor to the piston/barrels (19) and return the spent vapor back to the smoke chamber (2).
17. The Big Boy uses Walschaerts valve gears as they are known for their high efficiency.
18. Inside the boiler there are many pipes and wires that lead from the firebox(21) to the smokebox(2). The heat generated in the firebox is conducted through these tubes into the smokebox, where it heats the water that surrounds it. There are also some superheaters fitted to the front of the locomotive, which dry and heat the steam going to the cylinders, increasing the pressure even further.
19. The pistons are a small switch at the top driven by the valve trains(17) and their main function is to direct the vapor to the correct side of the cylinders. The cylinders then use the high-pressure steam to power the locomotive.
20. These are the wheels driven by the cylinders (19). The Big Boy has 2 sets of 8 drive wheels driven by 4 pistons/cylinders. A hidden feature of these axles (on the real locomotive) is their ability to slide left to right within the frame, which aids the locomotive in negotiating curves and switches.
21. The firebox is another essential part of locomotive operation. Here the fuel (oil or coal) is burned to heat the water.
22. The caster wheels carry the weight of the locomotive.
23. A key feature of the later Union Pacific tenders is their set of 5 axles. These axles are mounted directly to the tender and not to an undercarriage as in previous designs. These axes can turn by sliding from left to right.