the valve gear

Of course, the valves that control the steam distribution into the cylinders must also be controlled to allow for speed changes and direction of travel. This is the valve gear and many weird and wonderful types have been developed over the years. 

Stephenson's valve gear

The most common valve gear has been Stephenson which can be mounted inside or outside the frames.

A control from the cab is also required to reverse the motion. This is called the reversing lever (or screw) which also can adjust how much steam is let into the cylinder (cut off).


Walschaerts valve gear

More modern locomotives use Walschaerts gear.

1 Eccentric Crank (Return Crank)
2 Eccentric Rod
3 Reach Rod
4 Lifting Link
5 Lifting Arm
6 Reverse Arm & Shaft
7 Link (Expansion Link)
8 Radius Bar
9 Crosshead Arm (Drop Link)
10 Valve Stem Guide
11 Union Link (Anchor Link)
12 Combination Lever
13 Valve Stem


The animation below shows how to locomotive is reversed.


Joy valve gear

Our Lynton and Barnstaple Manning Wardle locomotives have the much rarer Joy valve gear.