Midland Railway Centre, located north of Derby in the Midlands, has 3.5 miles of line which reopened part of the complicated mining lines around there, between Hammersmith and Ironville (there is no station, just a terminus).
Though line is not long, there are a lot of displays including a museum at Swanwick Junction. Here, railway preservation and museum come together. There are also a loco shed and works at Swanwick Junction.
 
 

The notable engine in this railway is BR 5MT class No.73129 with British Caprotti Poppet Valve. Duke of Gloucester No.71000 is the only other one with poppet valve operational in Britain, possibly in the world, so there is no other place to drive such a precious engine.

The driving course includes brief instruction on safety and a short tour of the museum and shed, driving two turns each with light engine and with coaches. As with driving courses at the other railways, the participant is paired with another participant, and they drive and fire the engine in turn. A certificate is presented at the end of the course.
The cost is 225 pounds for steam, 195 pounds for diesel, but the author took a special course organized to gather the costs of restoration of No.73129, which costs 300 pounds.

While a slide valve controls the admission and exhaust of steam by a D-shaped valve or piston valve, a poppet valve does it with a mushroom-shaped valve as in an internal combustion engine. Although long lap and long travel were widely adopted to optimise slide valve results all over the world, poppet valves can control valve timing much better.
Valve timing control with British Caprotti poppet valves depends on the cam profile of rotary cams, driven by rotation of driving wheels through a shaft and bevel gearbox. The motion of cams is transfered to the valves through rollers and rocking levers, and cutoff is adjusted by phase shift of the cams. The valve returns not springs but by steam pressure under the valve cages. The valves fall into cages whilst the regulator valve is closed, making a path between both sides of the piston. Two valves, one for admission and the other for exhaust, are fitted at each end of the cylinders, so in total eight valves are fitted for one two-cylinder engine.

When driving an engine with British Caprotti Poppet Valve:
・The reverser must be placed full gear position when reversing the direction.
・The regulator must be shut off on coasting (hence the notice on the regulator handle).
Note the pressure gauge which indicates the pressure in the valve cage to lift the valve.
On the platform you can see as the engine moves that the valves spring up immediately the regulator valve is opened, then the admission and exhaust valves are pushed down respectively from the motion of rocking levers driven by the cam profile. This is rarely seen worldwide.

This is the only place where not only you can see an operational engine with British Caprotti poppet valves, but also you can drive it.
 
 

For more details about Midland Railway Center and driving course, please take a look at the following site.

Midland Railway Center
 
 

(The information about this page is as of September 2005)
 
 

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