18/03/2026
From SVR News:
The freshly repainted 813 hasn’t yet appeared in public, primarily because a couple of mechanical jobs need to be completed at Bridgnorth.
The first of these requires the trailing wheelset to be lowered using the wheel-drop within the works to enable some packing pieces to be installed in the springing arrangement.
This will lift the loco fractionally at the rear end, because it is running a little low now that it has settled down following the major works to the framing previously completed beneath the cab and bunker.
The second job on 813 is the machining and fitting of a new regulator valve of a modified design. It sometimes occurs to me that readers of these notes may have minimal understanding of some of the locomotive terminology used – so I’ll try to briefly explain the workings of a steam locomotive regulator.
The regulator is the valve which the driver uses to control the flow of steam from the boiler to the cylinders. It can be closed completely, such as when the loco is stationary, coasting or being brought to a halt, or it can be opened in varying amounts, as required, by the driver. Regulators on locomotives used on the SVR normally have two openings in the valve mechanism. These are usually termed ‘first valve’ and ‘second valve’ or sometimes ‘pilot valve’ and ‘main valve or ‘big valve’.
Typically, on the SVR, ‘first valve’ is used for starting away from a standstill and initially getting the train on the move. On some of our larger locomotives, depending on the weight of the train, ‘first valve’ is sufficient to operate the train, even when climbing our gradients. With heavy trains or on our smaller locomotives it is necessary to move the regulator handle further to use ‘second valve’.
To those riding on the train the use of ‘second valve’ is usually noticeable by a sudden increase in the noise from the chimney, and hopefully a noticeable acceleration, as its opening gives an increase in the amount of steam being admitted to the cylinders.
For decades, the regulator on 813 has been difficult for drivers to finely adjust. ‘First valve’ allowed just a small volume of steam to the cylinders, enough to get the train away, but not sufficient for accelerating to normal speed, especially when climbing a gradient. The use of ‘second valve’ however usually resulted in a cacophony of noise from the chimney and considerable use of steam.
The modifications currently being completed will, we hope, enable drivers to more routinely manage the loco and avoid the previous all-or-nothing performance!
SVR Bridgnorth Engineering Dept
