Technical Matters

Merchant Navy Double Action Piston Animated graphic to show the piston and cylinder on a rebuilt Bulleid Merchant Navy Pacific Leading Driving Wheel Centre Driving Wheel Trailing Driving Wheel Coupling Rod Connecting Rod Cylinder Cross Head Piston Rod Piston Head Slide Bars

The basic principles of steam engines are quite simple. Water is heated in the boiler to produce steam, and the pressure of this steam acts on pistons in cylinders to provide motion. However, the more that you look into the workings of steam locomotives, such as Clan Line, the more complex they become. This complexity is added to by the need to make them compatible with the modern railway.

This section of the website is intended to give a brief introduction to some of the important parts of our engine, and the way that they work. It is designed for the layman who has an interest in the technicalities of steam locomotives, but it does not pretend to be an authoritative treatise on the subject.

Oliver Vaughan Snell Bulleid included lots of innovations when he designed the Merchant Navy class of steam locomotives. He also carried these forward into his light pacifics – the West Country and Battle Of Britain classes.

Air Brakes

How we added air braking

The Basics

A brief introduction to the way Clan Line works

The Braking System

How Clan Line’s steam-, vacuum- and air-braking systems work

Boiler Washout

Why and how we washout Clan Line’s boiler


What the injectors do, and how they do it

Safety Valves

How our safety valves work, and how we set them


How tyres are fitted to the wheels


Why our wheels are different to most locos

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