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Going Loco

BLOG - A closer look at our collection of historic locomotives

With a collection of locomotives dating from Victorian times to the 1960s, there's plenty to discover.


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Going Underground, Going Underground...* Part 1

(A drawing of the original stations on the Metropolitan Railway)

And now for something completely different.** My right hand man on the Pendennis Castle Project, Harry Pettit, has a thing for trains that disappear down into holes in the Earth as well as an entirely understandable love of Castle class 4-6-0s. He’s helped me craft a two part blog on the strange link between the G.W.R., the London Underground and raw meat. Read on if you dare...


(A trial trip on the Metropolitan Railway at Edgware Road, 1862. And A drawing of the broad gauge Metropolitan class locomotives built in 1862.)

The Metropolitan Railway was the world’s first passenger carrying underground railway. The company came into being in November 1852 and construction commenced in 1860. Now, the strange thing about this from modern eyes at least is the fact that these lines were built as dual gauge. When first built, the GWR was built to broad gauge. This means that Brunel decided to space the tracks further apart (at 7 ft 0¼ in  than what we today regard as standard gauge (which is 4 ft 8½ in).*** This was done so that both the G.W.R. and the G.N.R. (Great Northern Railway which was built to standard gauge) could both run on the line which ran from Paddington to Farringdon.(A painting of a broad gauge train at Praed Street junction heading towards Paddington station. The line in the foreground is the westward extension towards Notting Hill Gate and Kensington.)

(Metropolitan class 2-4-0 No 3562 built in February 1894, fitted with large water tanks and condensing apparatus. After Metropolitan Railway electric locomotives took over the city services from Paddington in 1906 the condensing apparatus was removed and No 3562 worked on until she was withdrawn in 1949.)

On the 10th January 1863 the Metropolitan Railway opened using GWR broad gauge coaches hauled by Metropolitan Class tank locomotives. 22 of these locos were completed between June 1862 and October 1864, and having the staying power of a mayfly, were withdrawn between June 1871 and December 1877. Soon after however, operational disagreements caused the GWR stock to be withdrawn from the Met in August 1863. From then, standard gauge trains ran through to Moorgate Street. These were extended to Bishopsgate (Liverpool Street) in 1875 and Aldgate in 1894. Some G.W.R. engines continued to operate on other parts of what is now the underground - the famous standard gauge ‘Metro Class’ 2-4-0 tank engines began service in 1869 and ran services on what was to become the Circle line until its electrification in 1906.

So how does this link with our collection at Didcot? While the G.W.R. no longer operated on the underground, their coaches still did and the trains would arrive at Paddington’s Platform 15 or 16 to be connected to a Metropolitan loco and hauled off to trundle around on the underground. The earlier 4 and 6 wheel coaches used on this service were eventually replaced in the 1920s with the C sets. These were coaches designed to a slightly smaller than regular profile to fit through the tunnels. These became known as the ‘Main Line & City’ coaches and were arranged into sets that went as follows:

Brake Third**** - All Third - Composite***** - Composite - All Third - Brake Third.

There were 9 full sets of coaches - 8 for service and a spare. Most were built in 1920 and 1921, but two sets built in 1925 were articulated. This is where two coach bodies are coupled together permanently with just one 4 wheeled bogie underneath. The idea here being that it reduced rolling resistance. Less wheels there are, the easier it is to move. The idea is still around today - just look at many of the high speed trains in use on the continent like the French T.G.V. This was less useful when one coach had a mechanical problem. This meant that the whole set had to be removed from service until it was fixed where as a spare coach could be substituted in a normally coupled set. As a result, only one set had all 6 coach bodies fully articulated. There was then an attempt to mitigate the problem by building 4 half sets of 3 coaches. Swindon kind of lost interest in articulation after that.

(A Metropolitan Railway electric locomotive and rolling stock, showing the collector shoes under the brake van.) 

By the time these coaches appeared, the Metropolitan electric engines (like the famous preserved machine Sarah Siddons) had replaced steam on the Metropolitan services out of Paddington. This meant that the brake third coaches stock had electrical collector shoes on them that could pick up electricity from the two conductor rails on the underground. These were linked together and could be coupled to the electric locomotive. This prevented something called gapping. This is where an electric locomotive stops in a position where its collector shoes are not touching the conductor rails. This means no electricity, the engine can’t move and much embarrassment and delay occurs. Collector shoes at the other end of the train prevent this happening.(Southall station looking east in the 1908 to 1920 period. In the bay platform is a train of four-wheeled coaches and Metropolitan 2-4-0 tank engine No 1420, about to set off towards Paddington and the City. The first coach has the distinctive half-circle ventilators on the doors, a feature of reduced-height vehicles designed to go through the Metropolitan Railway tunnels. No 1420 was built in October 1878 and withdrawn in April 1936.)

In 1937 the through service stopped and the Hammersmith branch became the Hammersmith and City line. The ‘City Service’ via the Metropolitan Railway ceased in 1939 with the outbreak of WWII. This left the coaches at a loose end. They went on to less and less important duties. The two survivors - brake thirds No. 3755 & 3756 - found their way into preservation at Didcot via being press ganged into service on the Glyncorrwg Branch where they were used on Miners’ trains to transfer personnel to and from the pit. They were stripped out internally and fitted with propane powered lighting. Making them among the last gas lit coaches in service in the U.K.


(No 3755, one of the Main Line & City vehicles which replaced the 4-wheelers on the through services to Moorgate in the early 1920s. 3755 displays the Moorgate destination blind and is painted in the pseudo panelling livery with the steel panels lined out to match the mouldings of earlier wooden bodied coaches. The coach is 100 years old on 19 June this year. Crossrail, or Elizabeth Line, is due to start trial running later this year, but 3755 can proudly claim to have been taking commuters from the western London suburbs through to the City a century earlier!)

They were finally withdrawn in 1965 and both Nos. 3755 and 3756 were purchased for preservation. They were initially delivered to Bridgnorth on the Severn Valley Railway and later moved to Didcot. No. 3756 is safely stored in essentially the same condition it was preserved in, awaiting restoration in the Carriage & Wagon Shed. No. 3755 however is fully restored and operational. Its non-corridor design with individual passenger compartments has been of great use in the Covid-19 situation. Social distancing train rides! When you think about it, these coaches and the service they were built for are very relevant to modern London. While their day ended in the 1930s, the idea was a good one - why do you think they have built Crossrail?

(Paddington suburban station being rebuilt in September 1933 to enable the new 61XX class 2-6-2T locomotives to use the platforms. On the left is platform 16, used by eastbound Hammersmith and City line underground trains. This track goes under the GWR Goods Offices, with the corner of that building supported by girders to allow the excavation. Platform 15 has a 61XX class loco standing next to it. Platform 14 is still at an early stage of rebuilding. On the right the electrified platform 13 was used by westbound electric trains. When the works were complete the GWR steam trains normally used platforms 14 and 15, but one electric train each day went through those platforms to keep the conductor rails clean. In 1967 the track approaches to Paddington station were remodelled and the physical connection between Western Region and London Underground tracks was removed. Now platforms 15 and 16 are exclusively for Underground trains and 13 and 14 for GWR trains.)

We will deal with the raw meat next time.

(3755 displaying a full complement of oil tail lamps.)

*With sincere apologies to The Jam...

**...and Monty Python.

***I’ve put a blog on this in the list of stuff we need to talk about.

****A coach with third class seating and a compartment for the guard & Luggage.

*****A coach equipped with both first and third class seating.




Actually, Totally Cool!*

2988 Rob Roy, showing the ATC shoe apparatus beneath the front buffer beam.

One of the things that the GWR prided itself on was a signalling system that was known as Automatic Train Control, or A.T.C. This was a quite remarkable feat of engineering in the predigital age. So, as you read this, remember that it was designed not that long after the 19th Century became the 20th. The system itself has to work in a manner that is known as ‘fail to safe’ or if something goes wrong, then everything stops. The system has two main parts on the engine. There is a box on the driver's side of the cab, most easily distinguished by the big brass bell on the top of it. This has a number of connections going in and out of it. More of which later...

The cab apparatus in No 6106 and the A.T.C. shoe fitted to No 7202 - this is easily visible because it is on the front of the loco, while most of the others at Didcot have theirs under the cab

6106's cab equipment is probably a unique survivor as it is the version with the shoe in or out indicator, for when the loco was running over the electrified lines into platforms 13 to 16 at Paddington. The 61XX and 97XX locos were fitted with these because of their regular trips over the electrified lines. The shoe was automatically lifted on the approach to the electrified lines, and lowered when they left them. The indication on the cab apparatus was a confirmation to the driver that it had taken place.

The other bit is more difficult to see and will be a second box with a metal shoe on a post sticking out of the bottom of it. This can be mounted in a range of different places, the most common being either at the front of the loco or under the cab. The early Castles for example had their shoe gear under the cab while the later ones had it at the front as built**. It's all the same equipment however and it does the same job. It just has to have the shoe mounted centrally between the rails and with the bottom of the shoe 2 ½” from the tops of the rails.

The third bit of this system isn’t attached to the engine at all and is in fact on the track, between the rails near the signal. This was a 44 foot long rail-like ramp that was made electrically live (had a current running through it) when the signal it was ‘attached’ to was clear. If the signal was at danger, it was electrically dead (no current). This is where the first fail to safe bit comes in. If the system is broken in any way - the ATC ramp for a signal isn’t working - it’s electrically dead, switched off. The system will therefore read it as at danger, no matter what the signal says. Failsafe No. 1.

So what does the two loco boxes do? Well, there is an electrical link between the two, via a battery that energises a pair of electromagnets in the box with the bell on it. These hold shut a valve that is linked to the vacuum brake system. The vacuum system also has a siren attached too. All the while the locomotive is going along and there are no signals, the battery keeps the valve shut. No battery voltage, the valve is open, the brakes cannot create a vacuum and the train is going nowhere. Failsafe No. 2!

Failsafe No. 3 is on the track side. There are two switches that both need to be turned on together in order for the ramp to be energised. There is a switch on the signal arm itself. Now, you may or may not know that G.W.R. Signals show they are clear by moving down. They are known as lower quadrant signals. The rear of the signal arm is a large metal casting so, in theory, it should counterbalance back to horizontal even if the wire snaps but there is the small chance that snow, ice, a fallen tree branch, or some other rogue element could force the end of the signal down, giving a false clear. As a result, the second switch was in the signal box and was only switched on by moving the lever for that signal to the clear position.


The ramp on the main demonstration line at Didcot - the ramp was originally on the main line at Didcot railway station.

A.T.C. ramp in everyday use. Southall station with 2-8-0 No 4708 hauling a goods train, which includes a crane, on the up relief line towards London. On the adjoining track, the down relief, the ATC ramp is visible. Photo taken by Mike Peart about 1962

When approaching a signal, the ramp lifts the shoe in the box under the engine by 1”. This operates a switch that disconnects the on-board battery from the system. This leaves the electromagnets holding the vacuum valve shut at the mercy of the ramp. If the signal is clear, then the electricity is supplied by the ramp and the current continues to flow to the electromagnets. The other thing this does is ring the bell. This gives the driver an audible confirmation that the road ahead is clear. If the shoe is lifted with the signal at danger, then there is no electricity going to the electromagnets and electromagnets without the electro bit aren’t very magnetic... This opens the vacuum system to the atmosphere. As the air rushes in to fill the vacuum, it goes through a siren and this gives an audible warning just before the brakes come on and stop the train.

On the side of the box in the cab is a little handle and this enables the driver to override the A.T.C. system if he needs to. It may sound a bit strange to want to override a perfectly good safety system but conceivably, there might be a situation whereby the train needs to stop but also needs to be removed from a position of danger. This handle enables this to happen. Now, as if this electro-mechanical system isn’t amazing enough, how about this? The system automatically turns itself off to save the battery charge! There is a small, vacuum operated switch on the circuit that is only turned on when there is a vacuum present in the system. No vacuum, the engine isn’t moving and therefore no need for the A.T.C. system to be on. Switch the system off and there is no current being drawn. Genius!

The really amazing thing about this is that as long as you position your ramps in the right place - far enough away from the relevant signals to allow a train at full line speed to stop - the driver can trust the system implicitly. And they did. They were won over by how simple and reliable it was. As a result, trains could keep moving at normal speeds where the system was fitted even in poor visibility.

This could prove terrifying for those not in the know. An old engineman's yarn*** went along the lines that a passenger train once had to be double headed**** with an L.N.E.R. (London & North Eastern Railway) locomotive behind a G.W.R. locomotive running on an A.T.C. equipped line. The majority of the L.N.E.R. did not have a comparable system and as the train plunged forth through dense fog at line speed, the crew of the L.N.E.R. loco became more and more terrified by the seemingly suicidal actions of the leading crew. Growing more and more nervous, the L.N.E.R. crew shut off steam and opened their brake valve, bringing the whole train to a juddering halt. The driver of the ‘foreign’ engine was incensed at the situation and went to the cab of the leading engine, ready to get some really good coarse to industrial grade Anglo Saxon flowing. He was put in his place however, when he was reminded by the G.W.R. driver (none too gently one imagines!) about what the A.T.C. system was and how well it worked...

True story or not, G.W.R. crews were right to be confident. Despite this being built firmly before the electronics age, this system kept G.W.R. travellers safe for decades. There was never an accident that was caused by the mechanical or electrical failure of the A.T.C. system. Later systems eventually replaced A.T.C. after the end of the steam era but it should still be admired as one of the unsung heroes of the rails. Its rugged simplicity and incredible ingenuity kept part of our nation moving quickly and safely. When we are able to reopen the Centre, you can discover more about the A.T.C. system in The Signalling Centre.

*Actually Totally Cool? A.T.C.? Get it? No? I’ll fetch my coat...

**For extra nerd points, on the Castles you can see where the shoe is by looking for an electrical conduit pipe running along the driver’s side running plate. No. 5051 has it to contain the wires that connect the shoe box to the cab box. No. 4079 doesn't as her shoe box was under the cab, so no need for wires going front to back!

***No verification, but it's a good tale!

****Two locos on the front of a train.

Dean Goods 0-6-0 No 2351 showing the ATC shoe under the front buffer beam 

FRIDAY 12 February

Working This Out Was A Real (Tractive) Effort!

The P2 class 2-8-2s had a relatively short life in their original form, being rebuilt as 4-6-2s by Gresley’s successor, Edward Thompson, in 1943. This reduced their tractive effort to 40,320lbf, still slightly ahead of the GWR’s Kings. They were classed A2/2. Thompson’s successor, A H Peppercorn, produced a development of the A2/2 class, the A2s introduced in 1947. They had a tractive effort of 40,430lbf which gave them the title of Britain's most powerful express passenger locomotives for the remainder of the steam era. This photograph is A2 No 60538 Velocity

So, I’ve frightened some in the past with a few impromptu science lessons, it’s about to get worse for some. Maths ahoy! It's not all that bad really - it’s one of those fantastic mathematical equations that is what might be referred to today as plug and play. You feed the numbers in and you get the information out that you wanted! So, what's this all about?


Southern Railway Lord Nelson class No 857 Lord Howe, a member of the Lord Nelson class which took the tractive effort prize from the GWR, at 33,510lbf when introduced in 1926

You will often find that in many publications and websites, that the power of a steam locomotive is described with a strange figure which is known as ‘Tractive Effort’ or T.E. What is stranger is that it is usually presented as a measurement in lb or imperial pounds or more accurately lbf which is pound of force. We will work in imperial measures here if that’s ok - much easier with the old school beasts we work with! Basically, it’s the pushing or pulling force that a locomotive can exert. It is WAY more complicated than that - there are such things as starting tractive effort, maximum tractive effort, continuous tractive effort and so on but as always we will simplify this down to a more layman’s perspective.

The Erie Railroad in the USA employed and “triplex” locomotives including 2-8-8-8-2 Matt H Shay (built 1914) with the driving force spread over three sets of wheels. The locomotive was reputed to be capable of hauling 650 freight cars!

This isn’t a fool proof measure of the strength of a locomotive. This gives you the fact that it can certainly start a train with close to this tractive effort. If you take the example of the steam locomotive that had the highest tractive effort in history, the picture becomes less clear. This was a 6 cylinder 2-8-8-8-2 monster that had a tractive effort of 199,560lbf! Great you all say! 50 coach passenger trains, here we come! Well, no. The issue was that the cylinders of the ‘Triplex’ were so big that it could empty all the steam out of the boiler if you were to open the regulator all the way and go past 5mph. So that amazing tractive effort was practically useless. Tractive effort is a reasonable measure of a locomotive but there are a lot of other factors to consider when we think about how practical a steam locomotive is.

4073 Caerphilly Castle, which claimed to be the most powerful express passenger locomotive in Britain with a tractive effort of 31,625lbf when introduced in 1923. This photograph was taken during 4073s stay at Didcot in the 1990s, between leaving the Science Museum in London and being installed in the Steam Museum at Swindon

As you might know from our Pendennis Castle updates, there was a bit of a controversy about tractive effort that ended in a set of trials in 1925 involving No. 4079 herself. I won’t spoil that further here. This talk of tractive effort of passenger locomotives became something of a P.R. point of honour and the Castles (31,625lbf.) were beaten by the Southern Railway in 1926 when they introduced the Lord Nelson class in 1926 with a tractive effort of 33,510lbf. The GWR decided fight back and introduce the King Class at 40,285lbf. in 1927.


6000 King George V flying the flag for Britain at the Baltimore & Ohio Railroad's Fair of the Iron Horse in 1927. The King class regained the most powerful express passenger locomotive crown for the GWR with 40,285lbf but interestingly TE wasn't amongst the dimensions listed on this postcard of the era


The Princess Royal class 4-6-2s, designed by ex-Swindon man William Stanier for the LMS, equalled the tractive effort of the GWR’s King class when introduced in 1933, having identical cylinder dimensions, boiler pressure and driving wheel diameter. This photograph by R A Panting shows 46201 Princess Elizabeth ready to depart from Euston on 30 May 1953. The locomotive is now preserved

This settled the deal for a while until the LMS built the Princess  Royal class 4-6-2s in 1933 with identical dimensions to the King class of cylinder diameter and stroke, boiler pressure and driving wheel diameter. Therefore identical tractive effort of 40,285lbf. Quickly after that, the LNER built the P2 Class 2-8-2s which topped out at 43,462lbf. These locos were rebuilt into less than successful 4-6-2s during WWII but the new build P2 No. 2007 Prince of Wales will return this class to reality and slightly increase its tractive effort to 43,684lbf. For U.K. steam at least it will probably remain a record for a long time to come.

The LNER’s P2 class 2-8-2s, designed by Nigel Gresley, took the accolade of Britain’s most powerful express passenger locomotives when introduced in 1934, with tractive effort of 43,462lbf. This photograph was taken of No 2001 Cock O’The North at New Barnet by Charles Gordon Stuart in 1934. Charles left a generous bequest to the Great Western Trust which enabled the Charles Gordon Stuart annexe to the museum and archive at Didcot Railway Centre to be built

The engineers that designed any steam engine will have given the locomotive several characteristics that will determine its eventual tractive effort. The variables we are going to work with to give us a very reasonable approximation of a given loco's tractive effort. These are as follows:

t = the tractive effort in pounds of force or lbf.

What we want to know!

d = The diameter of the piston in inches (“).

The bigger the area of the piston, the more area the pressure of the steam has to push on.

s = the stroke (distance the piston travels in the cylinder in either direction) in inches (“).

The longer distance that the piston has to travel then the more the steam can expand. This allows more of its energy to be exerted on the piston before it’s exhausted up the chimney.

p = the working pressure of the boiler in pounds per square inch (psi).

The higher the psi of the boiler, the more energy the steam has in it when it gets to the cylinders.

w = the diameter of the driving wheels in inches (“).

If a loco has large wheels it can get up to higher speeds - one revolution of the wheels moves the engine a long way forward - but it pays a price for doing so. A large wheel is difficult to get turning. A smaller wheel had less resistance to being turned and more of the energy of the engine can go to pulling the train. It will however limit your top speed because the pistons can only go backwards and forwards so fast before things begin to break! This is why express passenger engines have big wheels, mixed traffic (passenger and freight) engines have middle sized wheels and freight and shunting engines have small wheels. Their wheel size is ‘tuned’ to their job.

The Coronation class 4-6-2s introduced by the LMS in 1937 were an enlargement of the Princess Royal class, but with their larger 6ft 9in diameter driving wheels their tractive effort was lower, at 40,000lbf exactly. This photograph, by F R Hebron, shows 46240 City of Coventry enjoying the attention of a large cleaning gang

We also use something called a constant. This is to do with the efficiency. No matter how good we are, forces such as friction, losses in heat energy as the steam moves around and so on will always bite into the numbers. If we didn’t use a constant, we would get the theoretical maximum output of the engine but there is no way it could ever achieve it. You can try to disobey a lot of laws but the ones set down by physics are pretty tough to break... American and British engineers used a constant of 0.85 so, when we do the last bit of the equation we get 85% of the total theoretical output. Here's how to do it for a two cylinder locomotive.

Hmmmm - let’s translate that into bite size chunks shall we?

Step 1: multiply the diameter of the piston (d) by itself.

Step 2: multiply the piston stroke (s) by the working pressure of the boiler (p).

Step 3: multiply together your answers from Step 1 and Step 2.

Step 4: divide your answer from Step 3 by the wheel diameter (w).

Step 5: multiply your answer to Step 4 by 0.85

Step 6: If your engine has 2 cylinders, go directly to Step 7. If it has 3 cylinders multiply your answer to Step 5 by 1.5 and if it has 4 cylinders, multiply your answer to Step 5 by 2. It is rare for steam locos to have more than 4 cylinders in the U.K.

Step 7: round your answer to something reasonable if you need to, then pat yourself on your back and look smug. You just calculated your first tractive effort!

As with all maths lessons, let’s do a worked example using No. 2999 Lady of Legend as our example. The things we need to know about her are:

d = 18.5” diameter pistons**

s = 30” piston stroke

p = 225 psi boiler pressure

w = 80.5” diameter driving wheels*

The Saint Class is a 2 cylinder design.

It will help you to write it all down as I have above. So the tractive effort of Lady of Legend is:

Step 1: 18.5 x 18.5 = 342.25

Step 2: 30 x 225 = 6,750

Step 3: 342.25 x 6,750 = 2,310,187.5

Step 4: 2,310,187.5

80.5. = 28,697.98136645963

Step 5: 28,697.98136645963 x 0.85 = 24,393.28416149068lbf.

Step 6: Ignore this step as a Saint Class has 2 cylinders. Go directly to Step 7.

Step 7: let’s round that to a more easily digested 24,393lbf. The published figure for a Saint** is usually quoted as about 24,395lbf. You may engage smug mode.***

The great thing about this is that you can pick up the required data for doing this calculation (and the published answer so you can see if you got it right!) on line for the vast majority of steam locomotives the world over. It is interesting to run the figures and see exactly why a King has a higher tractive effort than a Castle or why a Hall has a lower tractive effort than a 28XX 2-8-0, despite having the same size boiler. It’s a great little glimpse into the world of steam locomotive designers.

Well, what are you waiting for? Off you go and try it out...

Tell us how you got on!


*You might need to convert this figure from feet and inches to inches. For non steam mechanics, non Americans or those just not used to the old ways, there are 12 inches in one foot. A Saint has 6’ 8 1/2” driving wheels. So, 12 x 6 is 72. Then add the 8 1/2” and you get 80.5”. Remember to convert your fractions to decimals!

**The early saints had 18” cylinders, the later ones had 18.5” cylinders. Our one has the older outside style but the later inside diameter. Make sure you look up the right figure!

***One for the Red Dwarf fans out there - you know who you are...



Wonderful Winter Wagons Part 4 - It’s Go Go on the MOGO but No Go on the ASMO*

So, in the fourth and final chunk of wagon goodness for now we will take a look at the covered road vehicle wagons we have in the fleet. These are offshoots of the standard 4 wheeled covered van design but with a few evolutionary adaptations to their specialised purpose. The GWR was transporting road vehicles ever since its inception and the carriage of (horse) carriages was commonplace.

A royal luggage train at Acton on 21 June 1897, hauled by No 3040 'Empress of India' - note the horse-drawn carriage amongst the items being conveyed.

The later specially built vehicles all lived under the same index letter - G. The open wagons (which we have 2 different examples of**) really deserve a blog of their own but suffice to say that the types included HYDRAs, LORIOTs, SERPENTs and, MAYFLYs. Ironically, the MAYFLYs were converted from old brake vans in 1919 and were all scrapped by 1940. Talk about living up to your name...

There were also the BOCARs. These beasts were truly freight carrying in that their sole job was to move completed car bodies from one factory to another. These operated between Oxford and the Midlands and were sort of an outlier being based on long flat bogie trucks originally but later using converted coach chassis. These were provided with numerous tie down points to prevent the car bodies moving and getting damaged and then a framework that supported a large canvas cover that went over the top.

The reason for the specialist covered vans was due to the increasing road vehicle ownership in the U.K. In 1920 there were about 20,000 cars in private hands. In 1915 there were just 101,000 lorries and vans. By the 1930s that had become 1,000,000 cars and 350,000 commercial vehicles. While this rise in ownership was detrimental to the business of carrying passengers and freight, the GWR were smart enough to realise that moving the vehicles themselves were a potential source of revenue.

A train of ASMOs loaded with cars at Morris Cowley, headed for the Scottish Motor Show in Glasgow in 1930, with Aberdare class 2-6-0 No 2653 in charge

The first of these covered road vehicle vans was introduced in 1925 and eventually ran to three main types. In ascending size these were the MOGO, DAMO and ASMO. The sizes were as follows:

MOGO = 20’ 6” (6.111 metres) long

DAMO B = 23’ (7.01 metres) long

DAMO A = 32’ 5” (9.881 metres) long

ASMO = 36’ 4” (11.074 metres) long. 

The ASMO train at Morris Cowley loaded for the Scottish Motor Show at Glasgow in 1938, with Dean Goods No 2383 in charge

They all were built to essentially the same 4 wheel design. They had an inside frame body with a small pair of double doors in each side. The interior was completely open and had a series of tie down points and chocks on the floor to secure the vehicle. Both ends have a pair of large doors and a fold down section that forms a ‘bridge’ over the buffers. The wagon could be pushed up to a loading ramp and road vehicles driven straight in or out. The wagons were fitted with vacuum braking systems and were capable of running in both fast freight and passenger trains.

The GWS ASMO at Abingdon station on 23 May 1970 when the GWS had a weekend display there. Somehow the team managed to fit three Austin 7s (owned by Kevin McCormack, GWS secretary at the time) in the ASMO, although it is only designed to take two cars!

The one failing with the design was that in most cases, there were just the two doors on each end of the wagons. The doors were too big to open if the wagons were coupled together. This meant that each wagon could only be loaded or unloaded one at a time. If you had to load 10 wagons, a locomotive would have to move each of them to the loading ramp in turn. This was time consuming and labour intensive. In later versions the end doors were hinged in the middle, just like a modern bi-fold door. This meant that ALL the doors in the train could be opened at once while still coupled together and the road vehicles driven through the train without uncoupling them. Something still done on today’s car carrying wagons.


The GWS exhibition train returning from Wallingford Carnival on 20 June 1970. The ASMO is the fourth vehicle behind the two steam locos, 1466 and 6106. The train is hauled by D6343, one of the North British class 22 diesel-hydraulics. The head code OP03 suggests its day job is a station pilot at Paddington, hauling empty coaching stock to and from the station. As an aside, the class 22s were 50% longer and heavier than the 57xx pannier tanks they replaced on the station pilot duties, and the panniers had been cheaper to build and more reliable - but that's probably for another blog!

There are preserved examples of all three of these wagons. However, if you want to see a DAMO, you have to go to our friends at the South Devon Railway to see it. They have just (at the time of writing) begun the restoration of DAMO B No. 42223. This is the sole survivor of the type. MOGOs, are fairly common in preservation and our version was built in 1936 to diagram G.31. No. 105742 is fully restored and is capable of being used in our display freight trains. The sole surviving ASMO is also ours but it’s definitely on the to do list...

Our ASMO had a starring role in Thank You Comrades, a television play broadcast on BBC One on 19 December 1978. The play dealt with the film industry in the early days of the Soviet Union. A train was sent around the country to show propaganda films to the peasantry, with the ASMO taking on the role for the filming at Didcot

116954 was one of 80 similar vehicles built in 1930 to diagram G26. ASMOs would have been be a common sight around Didcot as they were used for both MG at Abingdon and Morris at Cowley. As it stands, it is unrestored, being stripped down with the wood panelling removed. It was started some time ago but other projects have sadly overtaken it. No doubt it will get done. It is currently not on public view, being safely contained in our carriage shed, awaiting its turn in the works.

Restored MOGO 105742 at Didcot

On the outside, the only clue to these vehicles’ fascinating history and their connection to the 40,000,000 cars that now inhabit our roads are the large end doors. If you didn’t know that then it’s just another van! It is remarkable however that despite the fact that a great deal of the freight that once went on the railways is now on the roads (and we are arguably worse off because of it...), cars are still being transported by rail and still go through the junction at Didcot. When you next visit, keep an eye out for the gigantic light blue articulated sets that occasionally trundle past on the main line. That’s one of the amazing things that Didcot does like almost nowhere else, while you look at our preserved vehicles, outside the fence their modern equivalents are ‘displayed’ as well. A historical juxtaposition like no other.

P.S. It would be interesting for your blogger to know if this little off topic diversion into the wagon fleet was interesting to our readers - please let us know if another dive into the wagon box would be appreciated! We have a load of coaches too...

* Alliteration for the nation?

**We have HYDRA D No. 42193 and LORIOT L No. 42271 but these are a bit too close to the CROCODILEs for inclusion this time round. They are on the blog list...



Wonderful Winter Wagons Part 3: More Ribbit than Rivet?*


Well, after our look at the POLLEN Es last week, I felt we needed to have a look at a type of wagon that was central to the operation of freight workings on the GWR. The brake van - otherwise known to them as TOADs. We have no less that 4** of the beasts at Didcot ranging in build dates from 1900 to 1950. Why do we have so many of these vehicles and why were they so important?

We need to take a look at the operation of freight trains in the steam era. Amazingly, as late as the early 1970s, many of the freight vehicles on the U.K. rail network had no continuous brake. A continuous braked train has either vacuum or air operated brakes on every vehicle in the train and that brake is operated by the driver in the cab. Put the brakes on in the cab and the braking effect is the same all down the train. If the train separates, all the brakes come on and stops the train. A large proportion of U.K. freight vehicles of the era only had a hand brake for when it was parked. That means that if it was a fully unfitted train - and that could be well over 1,000 tons of train - the only brakes were in the locomotive. Yikes...

GW 16 ton Toad brakevan No 35856

The brake van was a response to this situation. On the earliest railways, train lengths were limited by the braking force of the locomotives but tramways had already found the solution. They added a vehicle at the end of the train that had a handbrake fitted to it. This solved a number of problems. Firstly, if the train broke - the coupling between two wagons came undone or snapped - each resultant portion of the train had a person on board and a brake to stop it. Particularly important if the train snapped going uphill. A runaway train of wagons going the wrong way down a hill with no way of stopping it would have some, let’s say, undesirable outcomes...

Secondly, having a set of eyes at the rear of the train meant that there was someone to keep watch. Any accidents or incidents had someone there to help deal with them. If something was wrong with the train the guard could send a signal with a red lamp to the crew of the locomotive, signallers or other railway staff and get the train stopped.

The GWS exhibition train returning from a visit to Wallingford Carnival in June 1970. 68684 at the rear doing its job

Thirdly, the action of a steam locomotive sometimes causes a backwards and forwards surging action - particularly when working hard. This surging action causes the loose couplings between the wagons to go repeatedly slack and then tight. This could cause the couplings to fail. In this situation, the guard would make the brakes on the TOAD drag very slightly. This kept the couplings taught and prevented the snatching action. Even with all these extra precautions, unfitted trains were still limited to 25mph.

The veranda of Toad 68684 showing the handbrake and sandboxes

Let's have a look at a typical TOAD. The first thing to note is the veranda. This is where the handbrake is. There is another control lever, duplicated on the front wall of the enclosed section, that operates the sanders. These drop sand onto the track in order to improve the grip of the wheels in greasy conditions. This veranda was originally fully open to the elements without even a roof in the earliest versions but later on, the GWR at least tried to keep the weather off the guard.

There are a number of lamp irons all round the TOAD. This is so that the all essential red tail lamp can be hung on them. This denotes to signallers that the whole train has gone through their section. If the train snaps, and part of it is left in the section, there will be no tail lamp and the signaller will know to prevent other trains using that section until the errant vehicles have been rescued. Somewhat perversely, the enclosed section carried the guard’s equipment, the log book and a stove to keep it warm. There must have been many the cold winter night when the poor guard was on the veranda with a roaring fire in the enclosed section of the TOAD and they had to stay at the brake handle... The bit you can’t see is that between the frames is a large box and this is filled with scrap metal or concrete. This is what provided the weight to give the TOAD its braking force.

Toad 68684 at Didcot Railway Centre's ‘Oxford Road’ platform - January 2021

All the TOADs had wagon diagram codes*** beginning with AA, there being more wagon codes than there are letters in the alphabet! Our earliest is No. 56400 which was built in 1900 to diagram AA.3. It was built with a ballast weight of 14 tons and was later upgraded to 16 tons to improve its stopping power. No. 68684 was built in 1924 as a 20 ton brake van to diagram AA.15. No. 17447 - the only unrestored vehicle in this list - was one of 100 built to diagram AA.21 in 1940 as part of the war effort. This one is actually a TOAD A which means that it is fitted with a vacuum brake system as well as the handbrake. This enabled it to run in fully fitted goods trains with a continuous brake that were allowed to run at much higher speeds than the unfitted variety. This would be really great to get restored one day as its vacuum brake would allow us to offer rides to visitors on a freight train. One for the future.

Our final TOAD is the most recent. No. 950592 and was built at Swindon in 1950 by British Railways (B.R.) as a 20 ton brake van to diagram AA23 - almost the last of the breed. GWR TOADs were not popular in B.R. as their exposed working conditions but despite this they hung on in many odd corners of the network for many decades. The increase in use of freight vehicles with continuous brakes eventually saw the end of all brake vans in the U.K. Now, there’s just the tail lamp there to remind us. You can see from our collection that the design was pretty much a constant throughout the GWR era. It became a classic design and is instantly recognisable. Although there were a few variants****, it was pretty much the same wine in different size bottles. Although, it has to be said, I’m not sure that I want to know what TOAD wine tastes like...

Toad 17447 awaits restoration - note the flexible pipe on the buffer beam for the vacuum brakes

*Nearly all frogs and toads don't go ribbit. The reason we all think frogs do? The only species that do go ribbit are the frogs that live around the area that includes a certain part of Los Angeles. It's called Hollywood...

**We technically have 5, but 1902 TOAD AA2 No. 56867 was rebuilt into Signal & Telegraph Department Mess Van No. 263 in 1952 and is preserved as such.

*** See Wonderful Winter Wagons Part 1 for an explanation.

**** Including some 6 wheeled versions, ballast plough versions and special ‘Road Vans’ that had goods carrying space on board.



Wonderful Winter Wagons Part 2: A Case of Hay Fever?

So, we had a snappy look at the GWR CROCODILEs* last time and we managed to get off the river bank without losing an appendage. This time however we are going to get horticultural. We are going to look at perhaps the strangest of the preserved wagon fleet at Didcot - the POLLENs. Whereas all the other freight vehicles at Didcot are wagons in the sense that you can clearly see that there is an obvious place for the load to go, there is just a big turntable on the top of the POLLENs. They aren't ‘wagons’ in the traditional sense.

The POLLENs were designed for moving outsize loads. Really long, awkward and occasionally quite heavy loads. The idea is that instead of putting the load in these wagons, you put them on top of them. It’s probably best to think of these a ‘temporary bogie coach’. Bogies are any wheeled truck that goes under a vehicle to carry weight. Some of our locomotives have them. For example, No. 2999 ‘Lady of Legend’ has a 4 wheeled truck up front to carry the cylinders & smokebox and to help guide the front of the loco into curves. This is a bogie. The majority of the passenger coaches in our collection are bogie coaches. They have a main body, suspended between two 4 or 6 wheeled bogies. This allows the body of the coach to be long and yet still be able to go around corners. If you just fixed the wheels at each end of the body, you would be lucky to get it to go up and down anything but dead straight track without falling off!

In the POLLENs, the load does the same job as the coach body. The load is strapped to the turntables at each end and this allows the POLLEN to turn underneath it like a bogie. Temporary bogie coach! When empty, there is a link bar that connects the two vehicles together in a similar way as how a large locomotive is connected to its tender. There were two basic designs. A two wagon set which are as described above and then there were 4 wagon sets that spread the load between two bridge sections connecting two of the wagon turntables together. This increases the load capacity but is more complicated to set up.

Coupling and buffers which splits the unit in two

The first of the POLLENs date way back into the earliest days of the GWR, being built before the 1870s although these were not known as POLLENs at this stage. They were built to the old GWR broad gauge and could even be used to transport standard gauge vehicles on broad gauge track. The first true POLLENs (the code name came later) were built in the mid 1880s. Due to their specialised nature, there were never more than about 30 individual wagons constructed. They all had Diagram codes** that started with the letter A. There were several rebuilds of these sets too. Typically these rebuilds meant taking the 4 wagon sets and converting them into 2 two wagon pairs. This involved pairing the two outer wagons that had the buffers and couplings on and then putting removable buffers and couplings on the inner pair so they can be used separately if needed.

Fixed links between two 6-wheel units

Our set are known as the POLLEN Es and they were built originally under diagram A6 in 1904. They were built as a result of the Royal Navy’s development of the Dreadnought type of warships. These vessels were huge beasts with steam turbine propulsion, thick armour and most importantly for us, an all ‘big gun’ armament policy. The main guns on the original HMS Dreadnought could fire a 12” (304.8mm) shell that weighed 850lbs (385.6kg) at a speed of 2,700 feet per second (823 meters per second) a distance of 25,000 yards (22,860 metres). That’s just over 14 miles. As you can imagine, these were fairly sizeable bits of equipment. Well over 50 tons. Guns only got bigger from here for a while as the technology developed. There are even a few pictures of the POLLEN Es carrying guns 62 feet long and weighing over 100 tons.

The POLLEN with a naval gun barrel on it

POLLEN E was a 4 wagon set that was made up of Nos. 84997, 84998, 84999 and 85000. They were provided with two bridge structures that linked the pairs at each end together with a cradle on top. Each cradle accepted either the barrel or the breach (loading end) of these enormous guns. Until the building of the CROCODILE L**, the POLLEN Es were the highest capacity wagons on the GWR’s books.

A frame from Sherlock Holmes: A Game of Shadows, filmed at Didcot in 2010. They show the POLLENs in the background while Holmes (right) and Watson (middle) shoot it out with Moriarty's soldiers

The POLLEN Es were rebuilt from a 4 wagon set to 2 twin wagon sets with removable buffers being fitted to Nos. 48998 and 48999 in 1930. This gave each wagon a maximum load of 30 tons meaning long loads of up to 60 tons per pair were possible. The inner pair were given the new diagram number of A9 and the outer wagons were the given diagram number A10.

And that's how they stayed.

For a LONG time...

They were so useful that they kept being used, seeing the end of the GWR in 1948 and continuing through nationalisation. So good at their job were they that they finally ended their careers as late as 1993 when their historical significance was recognised. That means that they were in service for nearly 90 years. A quite remarkable record.*** They were made part of the National Railway Museum's Collection but it was felt that their inclusion in the displays at Didcot gave them the most appropriate final resting place. They are fittingly displayed with the upper works of a footbridge on top of them, just outside the Railmotor shed. So, when you next visit, take 5 minutes to see these hidden gems of the collection.

One of the 6-wheel units

Or maybe that should be hidden blooms?

*I am SO sorry about the quality of this ‘joke’. I will go sit in the corner and have a long, hard think about what I've done...

**See Wonderful Winter Wagons Part 1 for an explanation.

***At this point they were certainly one of one of if not THE oldest serving freight vehicles on the network. We are working on breaking that record however. Our chaired sleeper wagon No. 100682, later renumbered to No. 91200, was built in 1939 and is still main line registered being used for bringing large items into the railway centre. 82 years and counting...


Wonderful Winter Wagons Part 1: Into the Swamp...

Welcome back and we hope that you all had the very best festive season given the current circumstances. As a bit of an aside, I thought I’d take a left turn at Albuquerque and shine a light on a few of the less glamorous but by no means less historically important wagon fleet that we have here at Didcot. The first thing to say is that we have to talk about the names as this gets a little bit weird.

Given the myriad of different GWR freight carrying vehicles, simply specifying a 12 ton wagon wouldn’t be precise enough and if you were trying to send what you wanted over a telegraph then asking for “one of those twelve ton wagons, you know - the ones that have the special holders for the things on them” is a bit long winded. Something had to be done.

One of Didcot's lesser-known Toads - the magnificent 7¼ inch model in the Great Western Trust museum

The GWR used telegraphic code names. The most famous of these is that all the brake vans they used were called TOADs. Indeed the GWR brake van in the Thomas stories was called ‘Toad’ for exactly that reason. There were MACAWs, MICAs, MINKs, HYDRAs, POLLENs and even MONSTERs! The one we will look at today will be a river dweller that has quite the presence. Take care as we go hunting for CROCODILEs...

While the type was locked down with the code names, there were individual versions within that group of wagons and these were differentiated by the addition of a letter. For example, there were CROCODILE Bs, CROCODILE Gs and so on. The final bit of identification used was the drawing used to build the wagon itself. They started with a code letter - all the CROCODILE diagrams started with a ‘C’- and then a number to tie it down to a batch.

Crocodile F 41934 at Didcot

The logical thing to assume was therefore that a C1 CROCODILE was older than a C4 but, as with much in life, it’s not that simple! Various reallocations of the codes as wagons were withdrawn and scrapped mean that a whole lot of shifting around took place. If trying to track the history of a specific wagon - you have been warned...*

The CROCODILEs evolved into a wide range of different designs. They were originally designated as boiler trucks but this was later updated to boiler trollies. Although this was their function on the books, their design with strong construction and a depressed centre section to get the load as far down as possible to clear the loading gauge meant that they were highly adaptable. They were known to carry anything from large sections of structures, enormous castings, machine parts, naval buoys and even statues.

A trainload of Admiralty buoys loaded onto Crocodile Gs. These had been manufactured in Chepstow and were taken as an out-of-gauge load to Newport Docks in the 1930s

Our CROCODILE is specifically a CROCODILE F built in 1909 to diagram No. C12. It was numbered No. 41934 as part of lot 549. There were 12 of this particular batch manufactured and it is well worth us taking a look at this strange vehicle. It weighed 18 tons 10 cwt. and although it is over 52 feet long, it has quite a small load carrying capacity of just 25 tons. Some of the CROCODILEs were real heavyweights with a single vehicle that was constructed to move enormous electrical Transformers and the like called the CROCODILE L being able to bench press up to 120 tons.

No. 41934 has some interesting constructional details. Not least of which is that a lot of the internal structure of the wagon is made from a whole heap of reused broad gauge era rail. When you think about it, the abolition of the broad gauge in the late 19th century must have left a huge amount of this good quality steel ripe for reuse for an ever cost conscious private enterprise. It makes sense. Who said recycling was a new thing?

This is all very well but at the end of the day, how interesting can a boiler trolley actually be? Well, this CROCODILE’s tale has a strange twist to it. The GWR Index of Wagon Diagrams has survived and has been published* so if we scroll down to the entry for the C12 CROCODILEs, we see this historical gem:

CROCODILE F 41933-42/50/1 [the numbers allocated to the vehicles] Delete 41934/51 in 1941 Lost in France; Reinstate 41934 in 1945 (12 then 10 then 11)

A Crocodile G converted at Swindon to carry a naval gun in 1940. Its role as a gun carrier was short-lived as the threat of invasion receded and the vehicle was returned to the GWR in 1942

What’s this all about? Well, as you are all aware, the Second World War didn’t start so well for the allies. The initial German Blitzkrieg or ‘lightning war’ conquered all before it. The British sent an expeditionary force to the continent with dozens of pieces of large military equipment. These needed to be transported to the battlefronts and a large number of rail vehicles were pressed into service to do this. Nos. 41934 and 41951 were just two of these conscripts to the cause. When France was overrun by the Germans in just 6 weeks in May 1940, the miracle of planning and determination that was Operation Dynamo extracted thousands of allied soldiers off the beaches of Dunkirk to fight another day. The heavy equipment however was left behind. It is clear from the document that by 1941, the GWR has declared the two CROCODILEs as missing in action and didn’t expect to get them back.

Remarkably, No. 41934 had been pressed into service in occupied France by the German Army. Come the Operation Overlord / D-Day Invasion of the 6th of June 1944, the wagon soon changed hands again, this time being pressed into service with the invading American 5th Army as part of the allied effort to liberate Europe. Even more amazingly, someone in the GWR must have got wind of this and said something along the lines of “please sir, if you have finished with our wagon, we’d really rather like it back...” No. 41934 returned to the UK in 1945 and eventually found its way into traffic, through nationalisation and into the collection at Didcot. The fate of its compatriot, No. 41951, is unknown to this day. In the chaos that was WWII Europe, that our CROCODILE survived at all is frankly amazing in itself.

41934 is still used for the purpose for which it was designed - here the boiler of Pendennis Castle is steamed for the first time after overhaul while accommodated on the Crocodile boiler wagon

So, what do we at Didcot do with our ex prisoner of war? Well, we do exactly what the GWR did with it. We use it as a boiler trolley. It was very recently host to the boiler of No. 4079 Pendennis Castle during its test program and will no doubt go on to serve in this capacity for many years to come. It’s a very ‘Didcot’ kind of pure preservation. Preserved by the very act of continuing to do the thing that it was designed for. The best kind of preservation in our opinion frankly! Remember, as the as the Australian gentleman who was associated with crocodiles in that movie said: “That’s not a knife - THIS is a knife!”. Well, we at Didcot can confidently say “That’s not a historic CROCODILE - THIS is a historic CROCODILE!”

* THE book on GWR wagons was written and has been updated several times by A. G. Atkins, W. Beard and R. Tourret and is called simply “GWR Goods Wagons”. It is published as a mighty combined volume by O.P.C. (ISBN 978-0-86093-657-2). Your blogger’s copy is somewhat careworn being present at the construction of a growing fleet of 4mm scale replicas but is still going strong. Wholeheartedly recommended.



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