When Snowdon Mountain Railway approached us about flaws in the axles of their historic Locomotive No. 5, we knew we were facing a unique and complex challenge. Routine safety inspections by the client had uncovered surface flaws, and further testing revealed internal issues that made repair impossible. As a long-standing partner of the heritage railway, we were determined to deliver a solution that not only met their technical needs but also respected the locomotive’s historical significance.
About The Customer And Project
Snowdon Mountain Railway, established in the mountains of North Wales in 1896, is a historic narrow-gauge railway that climbs to the summit of Mount Snowdon, Wales’s highest peak. Spanning 4.7 miles with gradients as steep as 1 in 5.5, it relies on a unique rack-and-pinion system to navigate the challenging terrain. Combining its role as a working transport system and a heritage attraction, the railway offers visitors a journey through breathtakingly beautiful landscapes while preserving a remarkable piece of Victorian engineering.
A tricky feat of remote-terrain engineering in any era, the Snowdon Mountain Railway was a masterpiece considering the technologies available to engineers and project planners in the late 19th Century without any of the communication or software tools taken for granted by modern engineers.
Locomotive No. 5, or Moel Siabod, has been a part of Snowdon Mountain Railway since its opening, making it 129 years old this year (2025). Built by Swiss Locomotive and Machine Works (SLM), it features a rack-and-pinion system designed to tackle the steep gradients of the railway. Despite its venerable age, this remarkable piece of Victorian railway engineering continues to operate, offering passengers an authentic heritage experience. For us, preserving this legacy was as important as solving the technical problem.
How We Helped
Initially, we were tasked with repairing the axles. However, after conducting ultrasonic and non-destructive testing (NDT) in our Liverpool-based Mechanical Workshop, we discovered that the flaws were too extensive for repair. We proposed an alternative: manufacturing entirely new axles from solid steel billets, using modern machining techniques while maintaining the original design’s dimensional integrity.
Here’s How We Approached It:
- Material analysis: We brought in a specialist to perform Positive Material Identification (PMI) testing, which allowed us to determine the exact chemical composition of the original steel.
- 3D scanning: Using advanced laser scanning, we created precise models and engineering drawings of the worn components.
- Precision manufacturing: Each axle started as a 4-tonne solid steel billet. Our team machined away three-quarters of the material to achieve the exact specifications, using our extensive range of lathes, milling machines, and borers.
“This is exactly the kind of work we’re set up for,” said Bernard Darlington, our Managing Director. “It’s low-volume, high-skill, and requires demanding tolerances. We’re not producing hundreds of parts, we’re solving one very specific problem.”
Training The Next Generation Of Heritage Engineers
The project wasn’t just a matter of solving a technical challenge. It was also an opportunity for RJW to invest in the future of engineering. Our apprentices played a key role, working under the supervision of senior machinists. They were involved in every stage of the process, from hand-finishing to operating large-scale equipment.
“It’s not every day that a trainee gets to work on components for a century-old steam engine,” Bernard added. “But it’s a brilliant example of how we pass skills on in a live engineering environment.”
Outcomes
We delivered the new axles on schedule and within budget, supporting the ongoing rebuild of Locomotive No. 5 and helping to ensure Snowdon Mountain Railway’s summer timetable could continue without disruption. Seeing the locomotive back in action will be incredibly rewarding, knowing we played a part in preserving a piece of locomotive history.
The project has strengthened our partnership with Snowdon Mountain Railway, and we’re already in early discussions about future collaborations, including the potential construction of a new locomotive, continuing the role of the heritage railway in the living tradition of British railway engineering.
What The Customer Said:
“It’s been a big week for our No. 5 steam loco, with the arrival of its brand-new axles – a remarkable engineering achievement delivered by our partners at Rewinds & J. Windsor & Sons Limited. This work reflects our ongoing commitment to preserving and maintaining our historic fleet, ensuring our locomotives remain operational for future generations.”
— Kristian Johnson, General Manager, Snowdon Mountain Railway
Find Out More
If you’d like to learn more about this restoration project, or discuss how RJW’s specialist engineering expertise can support your own heritage machinery or infrastructure, please contact our team. With decades of experience and a proven track record in complex restorations, we’re here to provide practical, informed support at every stage.
