Designing a Model Live Steam Train

This project began after a visit to the London Museum of Water and Steam, where I was fascinated by the steam engines on display. Inspired, I started researching how steam engines work. Steam trains were first invented in the early 19th century, with George Stephenson’s Locomotion No. 1 in 1825 marking one of the earliest successful designs. My live steam train design is based on engines from the Victorian era, reflecting the style and engineering of that time.

I saw this as an exciting opportunity — not only to enter a competition and test my 3D design skills, but also to push myself to learn new techniques and real engineering concepts along the way.

Although I haven't built the steam engine yet due to time and cost constraints, the design process alone has taught me a huge amount — from thermodynamics and pressure systems to mechanical design and problem-solving.

Below, I will explain how I went about designing my live steam engine.

The first thing I do before starting any project is research what I’m working on. For this steam engine, I watched countless YouTube videos, looked at examples of steam engines that other people had built, and read articles explaining how steam systems work — from boiler pressure to piston movement. I also explored diagrams and technical drawings to better understand how each component fits and functions together. This helped me figure out what kind of design would be realistic for me to create, and what challenges I might face.

Below are some of my favorite resources that helped me the most during the design process:

1. HOME | Wigwag
2. Steam Engine - How Does It Work
3. Animated Engines - Steam Locomotive
4. Index

Something I always like to do before starting a project is lay out exactly what I want to achieve. For this steam engine, I set myself a few clear goals:

1. It had to be small
2. It had to be made from metal
3. It had to actually work using live steam
4. It had to look good (for obvious reasons)
5. It had to be relatively simple to build
6. I also wanted to learn something new throughout the process

Having these goals from the very start helped guide all of my design decisions.

Before jumping into it, I did some quick sketches and 3D models to figure out the look I wanted. I decided on a small Victorian-era shunting engine — simple and realistic for me to design.

At first, I thought about using a double-acting steam engine like the ones in real locomotives, but it seemed too complex. So instead, I went with two oscillating engines — they’re much simpler, even if they sacrifice some efficiency. I also chose my boiler size to give myself a scale to work off.

To help me understand how the engine would work, I also modelled a small oscillating steam engine separately. This gave me a better sense of how the moving parts fit together and how it would all function in the final design.

Then I decided I was ready to move on to CAD. I used Fusion 360 for the entire project, as it had all the features I needed for modelling and assembling the parts properly.

All of the pictures I added here are from after the design was finished as I did not screenshot my progress as I went along. In the next steps, I’ll go through how I designed each part and put everything together.

I like to have something solid as a base when I model, so I started by designing the frame. I planned to make it from 2 mm mild steel — at first, I thought that was quite thin, but I later found out it’s actually really thick and strong. So strong, in fact, that it can’t be bent easily, which was a bit of a problem since my original design relied on bending parts of the frame into shape. That meant I had to rethink the whole structure and redesign it to work with flat pieces instead — which is what you can see in the picture.

The wheels are aluminum with the back wheels having brass inserts instead of bearings. When modeling the wheels I realised I would have to build my own custom track for the train.

The engine uses steam pressure to move pistons back and forth inside the cylinders. In my design, I’m using two oscillating steam engines — these have cylinders that rock or “oscillate” as the piston moves, which helps control the steam flow in and out. The pistons connect to the wheels via rods, so as the steam pushes the pistons, it turns the wheels and makes the train move. If you want to see an animation of this have a look at step 3.

The boiler is where water is heated to create steam. In my design, it’s a small cylinder, 50 mm wide and 120 mm long, made from 1.6mm copper that can (hopefully) safely handle the pressure. When the water inside heats up, it turns into steam, which then flows through pipes to power the engines. The boiler needs to maintain enough pressure to keep the steam moving and drive the pistons effectively. It also has a firebox where steam and smoke is exhausted.

The piping in the model isn’t fully finished yet — as you can probably tell — but it still looks good in the render. More importantly, it helps me figure out where holes need to go and gives me useful reference points when building it.

The water tanks are mainly there to improve the look of the model by covering up piping and making everything appear more complete. That said, they’re not just for show — they’re silver soldered, so they’re fully watertight and could actually hold water if needed.

The burner is a gel fuel burner as solid fuel is banned in the uk. It sits underneath the boiler and covers about half its length. It’s designed to provide a steady flame directly under the boiler to heat the water and produce steam. It’s compact, easy to refill, and fits neatly into the frame with 3 bolts. It is made out of 1mm mild steel that is bent (see picture).

The cab is made from 1mm thick brass sheet, which is bent into shape and then joined together using silver solder.

Safety is absolutely critical when working with steam engines. Steam pressure can build up quickly and, if not properly managed, can cause serious injury or damage. The open flames from the burner add another level of risk, so it’s important to take safety seriously and never cut corners—even if following all the precautions can sometimes feel a bit boring or slow.

While the pressure gauge and release valve aren’t included in the current design yet, I plan to add them to keep a close eye on the steam pressure and make sure it stays under control.

I’m 13 years old, and this project has been one of the most challenging and rewarding things I’ve done so far. Even though I haven’t built it yet, I’ve learned a huge amount about steam engines, mechanical design, and CAD modelling. I’m really proud of the final design, but I’m holding off on sharing the files for now because I want to build it first and figure out any design flaws that can’t be spotted on a computer. However, if you’re up for the challenge and want to try building it yourself, just message me and I’d be happy to send the files.

There’s a lot more behind each part of the design, but hopefully this gives a clear overview of the process and what I’ve learned along the way. If you have any questions, feel free to ask! Big thanks to my DT teachers for their help and advice throughout — I definitely couldn’t have done it without them!