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Going Loco - September 2020


Railmotor Requiem

If there’s one historic vehicle at Didcot that raises eyebrows and causes confusion it’s No. 93, the last surviving GWR Steam Railmotor. That name doesn’t help. Unless stood in front of the beast with all the sounds, sights and smells of steam, some people aren’t sure it’s not a diesel railcar. It also requires a fair bit of cross - turntable co-operation* being both a locomotive and a coach at the same time! Whatever it is, it is a unique beast in British preservation. So how did this type of vehicle come about and somewhat equally important: what happened to them all?

Picture the scene...

It’s 1847 and engineer James Samuel has had a really good idea, but one that will not come fruition in his lifetime. He is the engineer of the Eastern Counties Railway (situated in East Anglia). He has designed and built, with fellow engineer William Bridges Adams, a self propelled steam powered vehicle that has both its power source and its passenger compartment on the same chassis. The seating was just an open box at the back with a bench seat around its interior but still, it was a start.

Railmotor No 51 at Ebley Halt

The most notable (if late) adopter of the technology in the U.K. was our very own GWR. Their first 2 machines were completed in 1903 and there were a total of 99 GWR Railmotors in all. Nearly all were built at Swindon but a few were the products of outside contractors. The eventual design settled on for the vast majority was a single coach body that had a drivers cab at both ends. In one of those cab ends was a small 0-4-0 steam engine with a vertical boiler. While most locomotive boilers are a long horizontal barrel with the firebox at one end, a vertical boiler has is a simple cylinder shape on the outside. The innards are essentially in a stack configuration, the firebox at the bottom, then the ‘barrel’ with the tubes in and the water around them and then the smokebox at the top.

The power bogie of Railmotor No 93 during restoration at Didcot

So what was the appeal of the Railmotor design? The idea that a self contained vehicle, with low fuel consumption, that did not require turning at each end of the journey was doubtless quite an attractive one. It meant that the operations on lightly used branch lines could be much more cost effective. The pull out stairs used on the GWR vehicles meant that it was easy and cheap to set up additional stations without platforms and provide a very flexible service in both rural and urban areas. Well that was all sorted out then.

No 93 with compartment coach 3755 in tow at Didcot on 19 September 2020

Well, not really. As in all engineering, what the advantages give with one hand they take away with another. Simply servicing these hybrids was difficult. They needed the attentions of both the locomotive department with all the dirt of cleaning an ash pan, filling the coal bunker, and so on alongside the levels of cleanliness demanded by the passengers inside the coach section. Then we have the compromise of trying to fit a steam engine within the confines of a coach body. You have to make it so small that it lowers both the amount of pulling power and the amount of weight available for putting that power to the track. They were capable of pulling a single trailer coach but not much more. They actually made some of the small branch lines so efficient that more and more people wanted to use them. That got to a point whereby they became unable to pull the weight of the trains. Effectively victims of their own success...

The final big problem is one of failure. If a locomotive goes wrong, you get another one and hook it up to the train. If the Railmotor goes wrong, you have lost the whole train. They eventually became obsolete, and by the mid 1930s they had all been withdrawn. Many of them had their ‘locomotive’ removed and were converted into regular auto coaches, suffering the indignity of being pulled around by the auto working locomotives** that replaced them.

No 93 was able to return to some of the old haunts of Steam Railmotors and is seen at Coombe on the Looe Valley Line on 11/11/12 and on the Brentford Branch on 19/1014

Thankfully, this isn’t a true requiem - as we know, one of these converted railmotors slipped the scrap man’s net and survived by having a third existence as a workspace. This gave us at the GWS the opportunity to dream the impossible dream once again, eventually build a brand new power bogie and let it loose on the rails as was intended in 1908, as Railmotor No. 93. That’s a blog for another day. However, the basic idea of putting the power plant in the coach was a sound one. It was the more compact diesel and electric power plants that made it work. Just look over the fence of the modern railway - No. 93’s great, great grandchildren now rule the rails...

No 93 is scheduled to be in action on 26, 27, 30 Sept and 3, 10 and 17 October - book your tickets and come and travel aboard this remarkable survivor!

No 93 at the Old Oak Common open day in September 2017 alongside some of the direct descendants mentioned above (and a few indirect ones too!)

*The Didcot Carriage and Wagon Department are on the Oxford side of the turntable, the Loco Works is on the London side.

**There has been a previous blog on these fascinating machines - check it out!


1014 ‘County of Glamorgan’ - the TRUE story...

We are building a new County class locomotive. A replica of No. 1014 County of Glamorgan. The reason for the choice of this particular machine is the link between the Glamorgan area and the famous Barry Scrapyard from where so many locomotives were saved and where the material for this project came from. However, of course, it isn’t a County. It’s a Modified Hall with parts from an 8F boiler... * Ok, this isn’t news. It is in fact well known; there’s an update in today’s edition of Steam Railway magazine and before we press on we should really mention that the project needs funds for the next stage – you might like to pop a few coins into our virtual hat or read more about progress on the 1014 Project website.

But let’s have a look at the component parts and their history. The main frames of the replica are from a Modified Hall. The Counties and Modified Halls shared very similar frames or chassis. So why is the Modified Hall class called Modified?

The Modified Hall was exactly that – a Development of the original Hall class loco. While they both look pretty similar, under the skin there are a lot of changes. The biggest of which is the main frames. The engines that share their lineage from George Jackson Churchward’s Saint class engines that had two outside cylinders did not have the main frame side plates that go from the front of the locomotive to the rear of the cab. Instead the frames went from the rear of the cab up to the cylinder block. The cylinders are formed of two huge castings which have the cylinders, valves, exhaust steam passages and the saddle that the smokebox is attached to. They are in fact two of the same casting, bolted back to back. Clever stuff!

From the front of the cylinder block, what are known as extension frames go out to the front buffer beam. In a Modified Hall or County, the frames go from the front to the back and the two, much smaller cylinder castings are bolted to them on the outside. The other big change was in the bogie. In nearly all the 2 and 4 cylinder 4-6-0s to that point a derivative of the French De Glehn style of 4 wheeled truck which is based on narrow bar style frames. The Modified Halls and Counties both used a new plate framed design where 4 slabs of steel plate make up the frame that holds the two wheel sets.

The Modified Hall frames that are being used to build No. 1014 are from No 7927 Willington Hall. This was one of the last of the GWR designed tender locomotives ever to be built. 1950 saw not only the last batch of Halls but the last Castles rolling out of Swindon. They had comparatively short working lives, when you consider that these late Halls had around just 15 years in service. When you think that some of the Saint class engines had 50+ year service lives and even the earliest Halls were working for about 30 years, they were clearly thrown on the scrap heap long before their time.

Willington Hall was completed at Swindon Works in October 1950 as part of Lot No 376. She spent time serving from sheds at Reading, Old Oak Common (Paddington) and Cardiff before being finally assigned to Oxford for just a month before her withdrawal in December 1965. From there, she was put out for grass in the sunny seaside town of Barry. As one of the last locomotives to leave Barry, she was in a pretty poor state. She had been picked over for spares and was a pretty forlorn looking specimen despite her low mileage. However, in breaking her up, it allowed not just the new County to go ahead. The boiler is no use for a County but is good for a Grange class (the 3rd missing GWR 2 cylinder 4-6-0 design in preservation) and this gave a great impetus to get this project rolling too.

The boiler for the No 1014 project comes from a seemingly unlikely source. At the time the Counties were being designed, Swindon was heavily involved in war work. As well as maintaining the existing GWR fleet of locomotives, they were working on war material and producing new locomotives. Chosen as part of the war effort, the 8F class 2-8-0 heavy freight locomotive was already a proven winner.

It had been designed by one of Swindon’s best export products – Sir William Stanier. He had been subordinate to both Churchward and his successor Charles Benjamin Collett but had been ‘head hunted’ by the LMS railway to take over designing locomotives for them. The 8F was really his answer to the GWR’s 28XX class and it was a pretty good answer too! It had all the experience of both GWR and LMS practice and was an outstanding machine in its own right. It was chosen to be built in all the major locomotive works of the LMS, SR, GWR and LNER and by private contractors during WWII due to its efficiency, power and ‘go (pretty much) anywhere’ light loading on the track and size. An ideal machine for slogging vital goods trains up and down the nation. So much so that the design operated in war service and post war on the European continent and as far afield as Iraq, Iran and Turkey.

The GWR was building the 8Fs as well, turning out about 80 machines. When the then GWR chief locomotive designer, Fredrick William Hawksworth, was looking to design a new mixed traffic locomotive to meet the post-war challenges, but with an eye to making it easy to construct, he took a look at the boilers of the 8Fs then being made at Swindon. The boiler was very similar to Swindon practice, as you would expect from a previous practitioner, and the tooling was there to do it. The County version was made slightly longer in the barrel to fit the pre-existing Modified Hall type frame design and had a different pattern of internal stays to handle the increased boiler pressure (from the 8F’s 225 psi to initially 280 psi but later reduced to 250psi on the County) but it was still essentially an 8F boiler.

Our donor boiler was part of another of those last few residents of Barry Scrapyard. This time it was 8F No 8518. It was constructed at Doncaster locomotive works in 1944. The LNER called the class the O6 but she was not really that different to her 851 sisters. She never entered LNER stock to become an ‘official’ O6 and had the LMS number 8518 from the start. She left the LNER in 1947 and transferred to the LMS. Shortly after the nationalisation of the railways, 40,000 was added to her number and she became No 48518. She saw service at a range of different sheds and like many of her sisters, saw out an unglamorous career doing vital work.

She was withdrawn from Willesden Shed in June 1965 and as with Willington Hall, got to go on a long holiday to the seaside. Also like the Modified Hall, she was not in a great state by the end. Her remaining parts have ended up going to a whole host of different places. Her firebox has gone to the County Project and the boiler barrel has gone to help out another of her classmates, No 48173 on the Churnet Valley Railway. Many of her other parts have gone to other locomotives including the new build LMS Patriot Project which is replicating another lost class.

As sad as it is to see the end of the history of numbers. 48518 & 7927, their spirit will continue in the locomotives that benefit from their demise. It is a continuation of the tradition we talked about a few blogs back about the parts themselves having their own history. From the fiery ashes of their own demise, they will (sort of!) rise again like the mighty Phoenix of legend.

*Perhaps we should rename it Modified Modified Hall (8F) of Glamorgan? It might make the nameplates might be a bit long though...


The ‘Ten Year Ticket’

With 6023 ‘King Edward II’ about to steam for the last weekend of her ‘ten year ticket’, we look deeper at why steam locomotives once restored have to be taken out of service every ten years . . .

Boilers - there is a lot said about these vital parts of steam locomotive anatomy but the thing that often leads rise to questions about them is “why can you only use them for ten years?” Well, it’s a fairly easy answer - insurance certification. Well, that’s that sorted - see you next week.


That’s not enough?

Ok - pick up your oily rag, mug of tea and follow us once again and we will take another look beyond the workshop doors.

So - the rules say that you cannot operate a steam locomotive without the so called ‘ten year ticket’. Let’s get something straight. There is not in reality anything called a ten year ticket. The boiler inspectors will allow you, once you have overhauled your boiler, to operate your boiler for up to ten annual certificates. But we are getting ahead of ourselves here.

To gain that first year’s ticket, we need to convince the boiler inspector that the boiler is safe to operate. They will be an appointed engineer who inspects the boiler on behalf of the insurance company. In order to do this, we first remove our boiler from the engine, strip it right down so that there are no tubes, fittings and other parts attached and clean it to make inspection as easy as possible. The inspector will look over the condition of the metal, the fastenings (rivets in our case) and the stays (explained below). He will also ask us to commission a set of N.D.T. (Non-Destructive Testing) examinations.

There are certain areas that, despite the removal of all that can be easily removed, are inaccessible. This is mainly the space between the inner copper firebox and the outer steel firebox. This is the big box at the back of the boiler that we put the fire in. I know, right? The two metal skins are held fairly close together by a sort of double ended bolt thing called a stay and there are dozens of these all over the boiler. To inspect the inside of this water space as well as to find out how thick the metal is and if there are any internal or external cracks is done by two different methods.

The first is by ultrasonic testing. This is very similar to the test performed on a pregnant woman and her unborn baby except things are a little bit more powerful! This sends a pulse of ultrasound (sound waves above the usual 20 kilohertz of human hearing) through the metal. It is reflected on the other side and then picked up by a sensor. The trace that comes back on the little oscilloscope type screen can show the thickness of the metal by how far apart the two peaks are. The metal may have begun to lose thickness over the years due to corrosion so if the two peaks are too close, the metal may no longer be strong enough and will need replacing. Additional peaks are not welcome either as these can mean that there are other problems. This could be a defect in the metal or a crack. This also means replacing the metal panel.

The second test method is magnetic particle testing. This uses a fluid with metallic particles that glow under specific wavelengths of light suspended in it. The fluid is painted on and then a strong electromagnet is placed against the metal of the boiler and turned on. The metallic particles are drawn into any cracks and show up when the light is passed over them. Given their findings and those of the NDT exams, a report is drawn up by the inspector and they will point out all the defects that they want to see repaired. We then enter a phase of discussion whereby we agree on the best possible repair methods for each defect. This could be as simple as replacing a rivet or as complex as large sections of metal being replaced.

The repairs are then undertaken and the work is periodically examined as the inspector sees fit. The key thing is that all of the work is properly recorded and that all the materials that we use in them are certificated as being of the required quality. That means that we can trace the history of that material and any parts made from it from it right back to the time the material itself was made. It is of a known standard and therefore can be guaranteed as fit for purpose.

Any welding that is done on the boiler is undertaken by a coded welder. This is a welder that has been trained to and is continually assessed to be able to produce welds of a very high quality. This is mandatory for work on boilers. Technology has moved on as well so that the more expensive copper inner firebox can be welded too. This is dependent upon the grade of copper used but Swindon-built GWR boilers of the 20th century like the majority of ours seem to be compatible.

Once that’s all sorted, the boiler is reassembled. All new drawn tubes (a tube made out from a single piece of metal rather than one having a join down the side) are fitted and any last repairs and sealing using the caulking gun are undertaken. Once the boiler is pressure tight, the first test it undergoes is the hydraulic test. This is where the boiler is pumped up to 1.5 times is maximum working pressure. It then has to hold this pressure for a given time. This is done with cold water rather than steam because, if there is an undetected flaw and something goes wrong you tend to just get wet rather than have high pressure steam loose about the workshop.

This is quite stressful for the boiler. A cold hydraulic is in some ways the ultimate test. When a boiler is steamed it get hot (obvious or what?!) and the advantage there is that the metal expands and fits together even tighter. Without the heat, you lose this advantage and you then rely on the workmanship of the boilersmiths alone! Having passed that test in the presence and to the satisfaction of the inspector, the boiler will then undergo an out of the frames (not in the engine) steam test. We light a fire in the boiler and bring it up to working pressure. This is particularly important as there is a great deal of the lower firebox that you cannot see when the boiler is mounted on the loco. This will then be witnessed by the inspector and all being well, they pass it for replacement in the frames. The engine is then reassembled and a final ‘in frames’ steam test is witnessed by the inspector. Given a pass here, the boiler is then insured to run for one year.

At the end of that year, the boiler is drained of water, and the boiler inspector will return and have a good look around as much as possible and then the boiler will be refilled and steam tested for the inspector to witness again. All being well, another annual certificate is issued.

And so on up to ten years.

Sometimes, depending upon the condition of the boiler, a short extension might be granted at the end but it’s usually at the ten year mark that the boiler has to come out again and you then go right to the top of this blog post and start all over again.

Currently there are 7 projects on the go within the workshops, so the plan is finish several of those before taking 6023 to pieces to start her next overhaul. Also, as next year is our 60th Anniversary and the restoration of the King is undoubtedly one of the major achievements of the past six decades, we want to keep her on display and an integral part of our celebrations.

Given that we are now starting from the top, I seem to remember that we had a cup of tea with us when we went into the works. Would you put the kettle on please? Lots of work to do...


Lubrication? We Are At A Total Loss...

No, not a discussion about tea. Although, it has to be said that very little would actually get done in the works or in the loco cabs if this vital human lubricant dried up... let’s instead talk about the way we get oil to prevent our historic machines from wearing out. There are two types of oils that we use in our locomotives.* A thinner general lubricating oil and a thicker, gloopy steam oil. We will indulge our sweet tooth while we describe these lubricants. Go into your kitchen and get out (if you have them) a pot of maple syrup and a pot of traditional Golden Syrup. The thinner oil flows pretty much like a maple syrup. Take your golden syrup, open the can, move it about and imagine that the contents is a sort of greenish colour. That’s what the steam oil looks and moves like. It’s really easy to tell the difference and really important NOT to get them mixed up...**

The ‘golden syrup’ steam oil is special and has a very important job to do. The regular ‘maple syrup’ lubricating oil is fine at temperatures and in environments outside those where you encounter live steam. You see this being used for bearings on wheels, motion and the like. In the high heat environment found inside the regulator, valves and cylinders however, the lubricating oil would break down, become much thinner and would provide none of the much needed lubrication in these key areas. What the steam oil does is that in being far thicker to start with, it has much further to go to break down to the point where it becomes useless. In the hostile live steam and even superheated steam, the oil is still doing its job even though it’s not as viscous as it was when it started the day!

There are a huge number of lubricating oil pots on a steam loco and they all distribute their oil in different ways. Some of the oil pots look like you expect. Either a cylindrical or rectilinear shape with a method of filling them at the top. Some have little metal flaps on them but the vast majority are filled up by removing a cork. Take a closer look at the corks. You will find that there is a circle shape on the top. This is a piece of bamboo that goes right through the middle of the cork, top to bottom. Why? This is to slowly let air into the oil pot. If it wasn’t there, the oil would only flow out until a vacuum was created in the top of the pot.


There are other types of oil pot still. There is always a big, solid looking cylindrical one somewhere on a GWR engine. It is most often found on the driver’s side (the left side as you look at the front of a GWR engine) running plate and this one is deliberately sealed as it is the one that lubricates the vacuum pump. Some are built into the part that they serve. The ones in the connecting and coupling rods and the cross heads that support the trailing end of the piston rods are the easiest ones to spot.

Getting the oil to where it is needed can take several different methods. Splash lubrication is where there is a tube sticking up through the middle of the oil pot. Screwed into the end of this is a thing that looks a bit like a broken off tap (the thread creating tool not the method of delivering water!) This is called a restrictor and as the part is moved up and down - such as the side rods - the oil is splashed around in the pot. Only some of it escapes down the tube past the restrictor. The bearing merely sips at the oil rather than swigging it! If the pot is stationary, a worsted trimming is provided. These are little loops of a special wool that are bound together with fine wire. The bit with the wire is pushed into the tube in the middle of the pot and the ‘tails’ of worsted drape down into the oil reservoir. The worsted acts like a sponge, soaking up the oil and delivering it down the tube to get to the bearing surface.

When you get to the bearing, there can be a number of different ways of spreading the oil around. Some just have small holes with grooves cut into the bearing surface radiating away from it, down which the oil flows. Larger bearings or journals (the spinning bit that is in the bearing) can have either a pad of worsted wool - the sprung examples that live under the axle bearings are a particularly impressive example - or felt pads. some of the larger of these felt pads are in the aforementioned cross heads and wipe oil along the surface of the slide bars they travel up and down.

The steam oil needs something a little more potent to deliver it as it doesn’t flow easily. There are two solutions on the locomotives in the collection at Didcot. The first is the wonderfully titled hydrostatic displacement lubricator. These really deserve a look at in their own blog as they are one of those ‘really clever’ bits of steam locomotive engineering. Suffice to say that they work by floating the oil on water in a big brass container which is in the cab. It uses the water at boiler pressure to force the oil from there all the way along pipes to the front end where it is atomised into the steam flow.

When some of the GWR fleet started to get larger super heaters of 3 or 4 row designs, it was decided to supply oil via a mechanical pump that was driven by the motion. The Kings (like our own No. 6023 ‘King Edward II’), Castles that had high superheat boilers fitted (like Vintage Trains’ No. 7027 ‘Clun Castle’) and later Modified Halls were fitted with this system as are a few of the non-GWR designed locos in our fleet. This is a large black box on the driver’s side running plate with lots of pipes coming out of it.

So what’s the title about? Clearly we know at least a bit about lubricating steam engines! Well, this is the final thing about oil in steam engines. It’s not like a car that you (hopefully!) check periodically and top up as required. No, a steam engine has to have all of its oil pots filled up at the start of every day that you operate it. This is because the oil will continue to flow no matter what. There isn’t a ‘switch’ as such to turn it on and off. This means that all the oil all leaks out eventually. This is called a ‘total loss’ system. So, every time you see a steam engine running, spare a thought for the driver - oiling up is his responsibility. He clambered all over, through, under and around that morning, making sure his iron horse could easily stretch its mechanical muscles. If it was a big 4 cylinder engine like a King or a Castle, he had over 100 oil pots to fill...

*Us steam engine types have heard tell of some mysterious type of locomotive that actually burns oil in a enclosed box thing with pistons going up and down inside of it, completely out of sight. No coal being burnt at all. We think this unnatural and we don’t think it will catch on.

**It is also of massive importance also not to mistake either lubricating or steam oil for maple or golden syrup. Do not expect the oils to compliment your food or either syrup to be an effective lubricant. You have been warned.


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