My First Steam Special

I travelled on my first steam special back in 1960 when scheduled steam was still around. In that year, the city of Stoke-on-Trent was celebrating its Jubilee. A railway exhibition was held in the North Western Yard at Stoke from the 11th to 24th May. British Rail organised an excursion from Birmingham New Street to Stoke allowing a visit to the exhibition. The preserved Midland Compound, 1000, was rostered for the trip. I arranged a Brake Van Permit (in those far-off days, such things were possible) because I hoped to make some sound recordings on the trip. Permission to travel in the end of the leading brake-composite would, I thought, position me next to the engine and allow me to make some decent recordings.

When I arrived at Birmingham New Street, the special train was already waiting with 1000 at the head, resplendent in its Midland crimson livery. There were also a large number of rather excited railway enthusiasts milling about the platforms. I don't think the term 'anorak' had been coined then but I remember that I wan't very impressed with their behaviour. We set off Northbound, past the busy No. 5 signal box and into New Street North Tunnel. The tunnel was always smoke-filled with water dripping from the roof and the driver had to proceed cautiously to maintain traction up the bank. He made a fair job of it and picked up speed as we passed the signal boxes at Shepcote Lane, Monument Lane and Harbourne Junction. We must have turned right at Winson Green Junction, to take the Soho Road Line to Perry Barr where we joined the original Grand Junction Line. At Bescot we turned right again, for Pleck Junction and Walsall. Leaving Walsall, there's another climb through Park Street Tunnel up to Ryecroft Junction. Passing Walsall Shed, 1000 gave a whistle in salute to the assorted locomotives. A driver travelling 'on the cushions' joined me in the brake end. He was 1000's regular driver but had handled over the locomotive to local men with the appropriate route knowledge. I thought the train was running quite well, but the driver shook his head. "They don't know how to make her 'compound'". However, by the time the train had reached East Cannock Junction, the regular driver looked a bit happier. "That's better" he said, nodding his head in approval. We flew towards Rugeley, where we joined the Trent Valley Line until Colwich, turning right there onto the line for Stone and then Stoke. All too soon, we were running into the down platform at Stoke-on-Trent.

A short walk took me to the Technical College where a number of railway exhibits had been arranged. I remember being impressed by the preserved 'Knotty' (North Staffordshire Railway) 0-6-2 tank engine but I've forgotten what else was on display. Later on, I returned to the station where our return train was waiting. I presume the 'Compound' had been onto Stoke shed for turning and 'fettling' for the return journey whilst the passengers had been enjoying the exhibition. Once again, I established myself in the leading guard's van, immediately behind the locomotive.

We retraced our route as far as Stone, where we turned right onto the Stafford line, running at reduced speed through the sharply-curved platforms past the attractive and distinctive station buildings. We made good speed until Norton Bridge's distant signal, which remained obstinately 'on', despite impatient whistling from the driver. It was just becoming dark as we crawled to a standstill at the home signal protecting the junction with the four-track main line between Stafford and Crewe. The red glow from the firebox lit up the surrounding area. For a while, all was quiet - the usual hisses and 'clinks' from the locomotive and the sound of conversation on the footplate, then the sound of an approaching train and a 'Rebuilt Scot' passed on the Up Fast, working hard, with the following coaches spilling yellow light onto the ballast. Soon, there was a 'clank' from our signal as we 'got the road' and our driver made a cautious start, drawing his train around the curve and onto the Up Fast. Local whistle codes were authorised at Norton Bridge so that drivers of up train could signal their requirements at Stafford - the signalman at Norton Bridge could telephone ahead to Stafford so that the correct arrangements could be made. As we moved towards the signal box, our driver gave the whistle for 'Train not stopping at Stafford requiring the Stour Valley Line' - two long and a 'crow' (I think). What an evocative sound!

We had an uneventful trip to Stafford, where we slowed first to get onto the Slow lines then to get onto the Goods Lines. We clanked past Stafford No. 5 Box, the adjacent Motive Power Depot, the signal box on the Goods lines and made our way to Stafford No.1 where the Stour Valley line to Wolverhampton diverges to the right. Once clear of Stafford, speed picked up again and it was not long before we were passing Bushbury Shed and Bushbury No. 1 signal box. Once over the viaduct, we were soon making our station stop at Wolverhampton, where I left the train. The special then continued back to Birmingham New Street.

It was years before I saw '1000' again, sadly, 'stuffed and mounted' in the National Railway Museum at York. And the sound recordings? I'm sorry to say that, at present, they're missing. If I can find them, and if they're still playable, I'll do what I can to preserve them.

Locomotive Regulators (part 1)

The other week, I was asked by one of my young friends to explain what I meant in saying "The regulator's 'gagged' in Second Valve". I'm afraid a little lecture is required.

In this country, it's usually called the 'regulator', in America it's invariably the 'throttle' but all steam locomotives have a valve, controlled by the driver (alright, 'engineer' in America) which controls the flow of steam from the boiler to the cylinders. This isn't an on-off valve but is adjustable by the driver to provide the appropriate effort.

In early locomotives, the valve gear could be set only to 'forwards' or 'backwards', so the regulator was the only means of adjusting the power output of the locomotive. There were two common types of regulator - plug and butterfly. Both types were operating by rotating a shaft connected between the regulator valve inside the boiler and a lever attached to the shaft outside the boiler, positioned on the boiler backhead and accessible to the driver. The shaft was provided with a gland where it passed through the outer firebox. Keeping this gland steamtight with the available materials was always a problem.

In the plug-type regulator, the end of the shaft inside the boiler would be provided with a coned plug arranged to be a good fit in the open end of the main steam pipe when the regulator was closed, preventing steam entering the main steam pipe. The regulator handle was then constrained by the quadrant, shaped as a section of a helix. When the handle was moved, the regulator rod turned and was also drawn back by the shape of the quadrant, with the result that the coned plug was withdrawn from the orifice of the main steam pipe, allowing steam to enter the pipe. This design was widely used by the Grand Junction Railway and a picture of the regulator quadrant of 'Lion' should help to clarify matters.

View of Lion's regulator from above. The regulator handle is in the closed position, extending to the right. As the lever is pushed to the left, the quadrant causes the regulator rod to be drawn back, opening the plug valve.

In the butterfly regulator, the regulator rod merely turned a two-lobed valve across the port face of the main steam pipe which was provided with two wedge-shaped steam ports. With the regulator closed, the valve lobes covered the steam ports, preventing steam from entering the main steam pipe. As the regulator was turned, the steam ports would be progressively uncovered, allowing steam to flow.

Illustration of a typical dome-mounted vertical slide-valve regulator

As boiler pressures and output power increased, the widely-used slide valve regulator was developed, often mounted vertically in the steam dome, as shown above. The main steam pipe terminates in a casting provided with a vertical, machined port-face provided with two more-or-less rectangular steam ports. Two flat valves lie over the port face, one on top of the other. Guides are provided which allow the two valves to move up and down independently. The outer valve (the 'pilot' or 'first' valve) connects via a link to a crank at the end of the regulator rod, so that moving the regulator handle pushes the valve up and down. The inner valve (the 'main' or 'second' valve) is also connected to the link but via a slot, such that, on progressively opening the regulator, the first valve is the first to move and the second valve only moves once the first valve is open. A series of ports in the two valves are arranged so that a moderate amount of steam is allowed to flow as the first valve is opened: once the main valve starts to open, a much larger port opening is achieved. This two-stage arrangement is intended to give the driver more accurate control over the flow of steam.

In this type of slide-valve regulator, the pressure of steam in the boiler is pressing the both main and pilot valves against the port face, preventing steam from leaking into the main steam pipe when the regulator is closed. But this pressure also makes it hard for the driver to move the regulator, as the pressure prevents either valve from sliding. Novices are frequently surprised at the effort required to initially open the first port. Once steam is flowing, the resistance will be somewhat reduced, but the required effort is still significant. After the pilot valve is fully open, further movement of the regulator handle will start to open the larger, main valve and considerable force may be required. Some locomotives are provided with two regulator handles to operate the regulator rod. This is partly for the convenience of the driver, for instance when shunting, partly so that the driver and fireman can co-operate in opening the main valve.

As boiler pressures continued to increase and larger locomotives appeared, the problem of adjusting the regulator became greater. In his larger locomotives, Churchward produced an excellent design of slide valve regulator, using horizontal valves fitted in the smokebox. Perhaps most importantly, he also provided an oil line from the sight feed lubricator directly to the regulator valve. Despite claims made by other designers, the only engines I've worked on which could be said to have "fingertip control" of the regulator were Great Western designs.

So, how about closing a regulator? Even in first valve, the flowing steam tends to interfere with getting the valve to slide closed. The regulator usually needs to be smartly brought against the stop to ensure complete closure. If second valve was open, the problem is increased. It's particularly difficult if second valve was only partly open as it then very hard to get both valves back to their proper, closed position. What usually happens is that the steam is cut off, but with the pilot valve slightly displaced from its normal, closed position. This is detectable from the cab, as the regulator handle may be reluctant to sit hard against the 'Shut' stop on the quadrant, because the misplaced second valve pushes against the regulator linkage and prevents the regulator rod from being moved to the correct, closed position. When the regulator is next re-opened, second valve is immediately partly open and an unexpectedly large steam flow may be obtained. This can be dangerous, for instance, whilst shunting, which is why it is so important for all drivers to have a thorough understanding of their machines. Once a regulator is partly open on second valve, the only reliable technique for full closure is to briefly open the regulator to the fully open position ('putting the handle in the roof') and then very smartly bring it to the fully closed position. After this treatment, when the regulator is re-opened it will open on the pilot valve.

There's more about Regulators in part 2.
(Only took me 9 years to complete part 2 which is why the blog is called 'occasional').

[Link to part 2 added: 11-Sep-2016]