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‘Thunderer’ – Part Three.


MikeOxon

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Constructing the engine carriage, described in Part Two, went much more rapidly than I had expected, partly because of that brief spell of hot weather, which kept me indoors in our shady living room. An advantage of computer modelling is that I could sit in an armchair with my laptop, with no need to venture into my hot workroom. One problem of working this way is that I can get so engrossed in working out the details that my wife has difficulty extracting me, to suggest that it’s time to make a cup of tea!

 

3DmodelThunderer1.jpg.ce30728c82d1c3af976c7f92b207e02b.jpg
My model of Thunderer’s Engine Carriage

 

I have already mentioned some of the problems with modelling these very early engines, in that reliable information is hard to obtain and several misleading statements have been made over the intervening years. I suspect that, in the present case, there has been some confusion over the considerable difference between Harrison’s Patent drawings and the engine ‘Thunderer’ as it was actually built.  I have tried to stay as close as possible to Wood’s Plate XIII, because he says this was obtained from the builders of ‘Thunderer’.

 

In his text, Wood writes that Fig.8, “is a part of the boiler, which is, in every respect, the same as that shewn in Fig. 1, Plate XI.” I find this a very perplexing when I look at Plate XI, since it seems to bear very little resemblance to the fragment of the boiler shown in Plate XIII.

 

 

WoodPlateXIFig1.jpg.1cdb85f2651b4dc68faa0d4278fe077c.jpg

Wood Plate XI

 

In his text, Wood describes “… apparatus for generating the steam, .being placed upon one carriage, and the cylinders, and machinery, for propelling the engine, upon another carriage ; each of which is supported by four wheels” Every other reference I have seen, says 6 wheels. Since, I am aiming to be consistent, wherever possible, with Wood’s contemporary description, I have decided to see how the Boiler Carriage might look if running on four 6 foot diameter wheels.

 

NB: I’m now moving into a world of speculation...

 

In favour of Wood is his statement that “we have given a drawing of one, built by Messrs. Hawthorn of' Newcastle-upon-Tyne, for the Great Western railway”. This seems to give contemporary authority to what is shown on his Plate XIII.

 

That, though, has created another problem. Wood’s Plate XIII includes a drawing (Figure 8) of the front end of the boiler carriage, which appears to contradict many of the statements that have been subsequently been made about the appearance of ‘Thunderer’. I measured the dimensions (mm) off the scaled ‘canvas’ created from Plate XIII in ‘Fusion’, and then converted these into feet and inches on the prototype.

 

BoilerDims.jpg.c5a9035d7877d87a48631a46c89fc226.jpg

Wood (1838) Plate XIII Figure 8, with dimensions added

 

According to Colburn’s ‘Locomotive Engineering’ (1871) “The boiler was 44 inches in diameter, and contained I35 tubes l 5/8 inches in diameter and 8 feet 7 inches long, giving 516 square feet of surface. The fire box was of great size, the area of fire grate being 17 ½ square feet, while, by the introduction of a "midfeather" or intermediate water apace, the whole fire box heating surface was 108 ¼ square feet. … The chimney was 16 inches diameter.” This boiler diameter (inside) agrees very well with my own measurement from the ‘canvas’ so, perhaps increases confidence in the other dimensions quoted, including 6 foot diameter wheels.

 

Modelling the Boiler Carriage as described by Wood (1838)

 

I started by extruding a cylinder of 14.67mm diameter and 34.33mm length, to represent the boiler, with reference to Colburn’s figures. I then attached a smokebox to the front end of this boiler, produced by extruding from my ‘canvas’ of Plate XIII in Fusion. I assumed that the grate was approximately square so that, to achieve the quoted area of 17 ½ sq.ft., the length and width should be 16.73mm (in my chosen 4mm scale)

 

The boiler is thought to have had wooden cladding so I extruded a single plank in ‘Fusion’ and then used the ‘circular pattern’ tool to create a compete array of planks around the outer perimeter of my boiler tube. The results of this stage of modelling is shown below:

 

3Dboilerassy.jpg.b38aaa8f195a2b2c9215d790c93a3dcd.jpg

My 3D model of Thunderer’s boiler assembly

 

The height of the chimney and its flared top are speculative, as is the round-topped form of the firebox – I have based both of these features on contemporary practice. I have no idea how access was obtained to the smokebox for cleaning – with no cylinders below, a hatch at the bottom is one possibility.

 

Wood’s Plate XIII shows what appears to be a safety valve behind the chimney. I have added a cover, modelled on Colburn’s drawing for this feature and I've also added a manhole cover on top of the firebox.

 

When it comes to the chassis, I have taken account of Wood’s statement that there were only 4 wheels and Plate XIII shows the front pair to have a diameter of 6 feet, the same as on the Engine carriage. I found, by experiment that an underframe with the same wheelbase as the Engine carriage would fit under this boiler, with an extension at the rear end to form a footplate. Plate XIII also shows the front part of a water tank suspended below the frame.

 

With these features in mind, I copied the framing and wheels from the Engine carriage and added the water tank between the frames. According to an article by Sekon in the Great Western Magazine, April 1910 “The boilers of these engines [Thunderer and Hurricane] were also peculiar, the firebox containing a partition dividing it into two independent sections with a door to each.”

 

In view of the large water tank below the boiler, it occurred to me that coal bunkers could also easily be accommodated an either side of the firebox, turning the vehicle into a self-contained tank engine. The division of the firebox into two separate sections adds plausibility to the idea of their having been two coal bunkers, one on either side of the footplate. Therefore, I have included this speculative feature into my model, as shown below:

 

3DmodelBoilerCarriage-annot.jpg.be540ec133656303bd57087c3f8edd60.jpg

 

This design diverges considerably from ‘received wisdom’. For example the RTCS Part Two states that “the carrying wheels were four of 4’ 6” and two of 4’ 0” diameter, but how these were arranged under the boiler is not clear.” This does not agree with the leading end of the boiler carriage as illustrated by Wood.

 

We know that ‘Thunderer’ was the first of two engines delivered to the GWR. The second, ‘Hurricane’ had not arrived when Wood was writing his book, so it is possible that some of the features recorded subsequently actually only applied to Hurricane. Hurricane’s engine carriage had a 2-2-2 wheel arrangement with 10 foot diameter driving wheels and no gearing This carriage must have been longer than that for Thunderer, in order to accommodate such large wheels and the motion connected to a central axle. It seems to me entirely plausible that a longer boiler carriage was attached to Hurricane’s longer engine carriage, also with six wheels. The central axle under the boiler would also have made it difficult to include such a large water tank, so a separate tender may have become necessary to carry coal and water. This would have led to the comments about the locomotive being a ‘train in itself’

 

Once I had brought together my two models of the Engine and Boiler carriages of ‘Thunderer’, it was clear that the arrangement I have devised leads to a more compact and purposeful looking locomotive than many later illustrations suggest. I appreciate that I am ignoring a lot of later ‘evidence’ but, without knowing the provenance of the various statements that have been made, I feel comfortable with my interpretation, unless further contemporary information is re-discovered.

 

3DThundererwithBoiler.jpg.e9352bf826cd22536b762309c856e6c7.jpg

My 3D model of ‘Thunderer’ as a two-part machine

 

I cannot ‘prove’ that my interpretation is correct but I believe that it is a plausible engineering solution, which conforms to Wood’s description and Figures:

 

Looking at my model and trying to construct a vision of the real engine in my mind, I can see why it made a strong impression on the GWR Directors of the time. In his diary, the Director George Gibbs wrote on 12th May 1838 that “Hammond came for me to Salt Hill with Harrison's engine: and I went backward and forward on it twice. .... Along the greatest part of the four miles the engine ran beautifully smooth and for some way we cleared sixty miles an hour."

 

A couple more views to finish my description of the construction of my model – I added some ‘safety rails’ at front and back:

 

3DThundererwithBoiler2.jpg.5350b2b978add2965d8e8fa1323a0ece.jpg

 

3DThundererwithBoiler3.jpg.4cbbf8d573574a60d5444a0e5b5137f9.jpg

 

‘Thunderer’ at Old Paddington

 

As an Addendum, I ‘cut and pasted’ my model of Thunderer, together with Vulcan, into my 3D model of Gooch’s round-house engine shed at Paddington.   A rare glimpse of early operations on the GWR!

 

ThundereratPaddington.jpg.fe4e26cd85477c286d3dbad81fd2b6a3.jpg

My model of Paddington Engine Shed ,with Thunderer and Vulcan

 

Having realised the possibilities, I imported a few more of my models of early Broad Gauge stock into my Paddington model, so that I could set up a scene of a train setting out from the Departure Platform for the terminus at Maidenhead.:

 

ThundereratPaddington3.jpg.3f9e2eda664967d968662e89f35ba1c1.jpg
Old Paddington in 1838, with a train setting out for Maidenhead

 

The above view is from the yard to the West of the old station, with Bishop’s Road bridge in the background. I have shown ‘Thunderer’ as a ‘stern wheeler’, which was probably a safer direction, placing that large revolving drum gear at the back.

 

The following train comprises a Luggage Truck , a closed 2nd-class carriage, a Posting Carriage , and a 4-wheel 1st class carriage [to be described]. The scene also includes Vulcan on the other platform line and a horse box being loaded from the end of the carriage road.

 

In the foreground in another closed 2nd, waiting to be assembled into a train.  In the background, the tunnels under the bridge can be seen, These were for goods trains to reach the goods depot which was on the other side of the bridge.

 

This is, of course, only a static ‘diorama’ but I suggest that it would make a splendid broad gauge scenario for @Annie to create as a 'Trainz' model.

 

Mike

Edited by MikeOxon
typos

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I have just read back through the "Thunderer" build. Given that the primary sources are vague I do think that your interpretation is very realistic, it brings to life an engine about which I knew very little. 

 

Although I model 50 years or so later I am involved with restoration of historic buildings from the 1850s. There are times when no real evidence is available, you just have to think how a joiner, stonemason or blacksmith of that period would have tackled the job given the resources available to them. I think that your interpretations do reflect the methods and skills of the period, probably as accurate as it gets. 

 

I can see what the original design was trying to achieve. Big long stroke engine engine geared down to give speed. By all accounts it did at the expense of any decent tractive effort.  I'd agree, how was the smokebox cleaned? How much steam blew out of the flexible couplings? Why was backlash an issue? the reverser must have been really wobbly at that distance. Such is early locomotive design. 

 

Fascinating stuff, and very enjoyable. 

 

 

 

 

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Mikkel

Posted (edited)

I can only agree with Dave.

 

Out of interest: The visualisation is a very pedagogical tool for understanding how it all worked (also for yourself, I imagine). Is it possible with this or other software to take it one step further by working with the colouring, texture etc as one would a physical model? I.e. adding weathering and so on, seeking to enhance realism. The last photos above of the engine at Paddington are extremely interesting for getting a feel for "how it was", but also clearly a computer image.

 

I am not expecting you do to it - you have enough on your plate with this work. Just wondering what current software allows and how hard it is. Perhaps very time consuming at present, but with AI maybe soon just a click of a button?

 

Edited by Mikkel
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11 hours ago, Dave John said:

I have just read back through the "Thunderer" build. Given that the primary sources are vague I do think that your interpretation is very realistic, it brings to life an engine about which I knew very little.

I'm pleased to know that you approved of my text.  I had to do a lot of reading and then a lot of thinking before I felt ready to start creating a plausible model.  It was a tough decision to go with Wood's Plate XIII, when every other (later) source reported something quite different.  The actual build was also quite a challenge and I found it best to print the individual parts first and then to juggle them around until I found a 'fit' - a sort of 3D jigsaw.

 

Like you, I try to get into the mind-set of the period and frequently marvel at what they managed to achieve with very basic tools and materials.  Many construction methods were taken from earlier times, like lots of tapered wedges to hold everything together!

 

I shall wait and see what some of the Broad Gauge Society members, many of whom have done far more research then I have, make of it!

 

Mike

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2 hours ago, Mikkel said:

Is it possible with this or other software to take it one step further by working with the colouring, texture etc

I feel that I have only touched the hem of the capabilities of 'Fusion ' software.  I have seen some remarkably realistic scenes created by others  The 'hobbyist' version that I use omits many of the more advanced capabilities.  I believe that the full package allows for moveable joints and simulation.  I don;t know what methods the train simulator software packages use - I am always amused by @Annie writing about 'magical incantations'.

 

It is only recently that I discovered how to assemble several models into a 'scene', so I'm taking it step by step.  The main thing is that I'm enjoying the learning process.

 

Mike

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4 hours ago, Mikkel said:

The last photos above of the engine at Paddington are extremely interesting for getting a feel for "how it was", but also clearly a computer image.

Unfortunately,  Amy wasn't around in 1838 so I had to look to other method for creating a 'painterly' appearance 🙂  The image below was produced by Mediachance DAP software:

 

DAPThundereratPaddington3.jpg.ac82203f0047411c1d6b83ebb37dd6da.jpg

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Thank you, it's fascinating.

 

I don't recall you mentioning where the driving controls are situated. I sort of assumed they were on the engine carriage, and that this would lead, but I see you have the boiler carriage leading in your pictures of the locomotive on a train. Or perhaps it would work either way.

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2 hours ago, Jeremy Cumberland said:

I don't recall you mentioning where the driving controls are situated.

There's no hard evidence that I have found.  There's no indication of any controls on the Engine carriage in Wood's Plate XIII, while his Plate XI, said to be similar 'in every respect' shows a regulator on the backhead of the firebox. 

 

I find it hard to see how my version of the engine could have been driven from the Engine carriage, in view of all that whirling machinery.  The primitive reversing gear could only be operated when the engine was stationary and the levers for this operation could easily be placed where they could be reached from the sides. 

 

The thought that it might have run footplate-first only came to me when I assembled that Paddington scene.  I doubt whether this engine could have been turned complete on the small turntables of the day and I find it hard to imagine that the two carriages were separated at each terminus, with all the difficulties associated with making the joints steam-tight again.  I assume, therefore  that it was not turned for the return trip from Maidenhead.

 

The simple answer is that I don't know!

 

Mike

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An interesting read and a fascinating machine.  Would it have worked if the gearing was different, or would it have failed anyway as there is no weight over the driving wheels?

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2 hours ago, ChrisN said:

Would it have worked if the gearing was different, or would it have failed anyway as there is no weight over the driving wheels

This manufacturer made a brave attempt to meet Brunel's weight and piston speed requirements.  In doing so, other more practical considerations were ignored. 

 

Maintenance seems to have been a huge problem, although it was used for a year or so after its initial service for various draughting experiments including using a centrifugal blower, said to resemble a large snail, arranged to blow air into the ashpan. The lack of adhesion weight meant it could only pull very light trains over level ground.  With more development, it could have become something like a Beyer Garratt but the necessary technology was not there in 1837

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On 06/07/2024 at 19:48, MikeOxon said:

The primitive reversing gear could only be operated when the engine was stationary and the levers for this operation could easily be placed where they could be reached from the sides.

Thank you for your reply.

 

I'm pretty new to learning about slip eccentrics in full size locomotives, but my understanding is that slip eccentrics of the type you describe (they are free to rotate 180 degrees on the crankshaft, having end stops but no locking mechanism), have to be set by moving the crankshaft half a turn or more in the required direction. When the locomotive is stationary, the gabs are disengaged. The locomotive then needs to be driven for at least half a crankshaft revolution in the correct direction using the manual valve levers, and then the gabs can be re-engaged, by which time the locomotive is moving. Do you think the four levers would have been carried back to the firebox end of the boiler carriage?

 

This seems rather primitive for 1838, when you compare it with Planet (1830), which used a locking mechanism for the two eccentric positions, which meant that the locomotive could be put in reverse while it was still moving forward (slowly), without any need to disengage the gabs or manually work the valves, and steam could then be applied to bring the train to a halt, and I would have expected technology to have moved on since then. What did other contemporary Great Western locomotives have?

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On 06/07/2024 at 13:55, MikeOxon said:

Unfortunately,  Amy wasn't around in 1838 so I had to look to other method for creating a 'painterly' appearance 🙂  The image below was produced by Mediachance DAP software:

 

DAPThundereratPaddington3.jpg.ac82203f0047411c1d6b83ebb37dd6da.jpg

 

That's lovely. Adds a lot of atmosphere to the image. Like model photos, a slight fuzziness can sometimes aid realism.

 

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14 hours ago, Jeremy Cumberland said:

This seems rather primitive for 1838, when you compare it with Planet (1830),

I agree.  I can only assume that this very simple system was applied because the gear was so accessible.  By that time, most engines had four eccentrics, based on variation of Stephenson's Patentee.  This included the Stars and the Fireflies, both of which I have modelled .  Sharp Roberts used the system I describe in modelling Eagle.

 

Gooch introduced his 'Link' motion in 1843 and this was applied to all new builds from the Swindon Works after 1846.  It was retro-fitted to many earlier engines as they came through the works.

 

GoochLinkMotion.jpg.20fc2095cc5fd188db2d273bd2fe635c.jpg

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7 hours ago, Mikkel said:

 

That's lovely. Adds a lot of atmosphere to the image. Like model photos, a slight fuzziness can sometimes aid realism.

 

Thank you, Mikkel.  I know you have the DAP software.  When making railway images, I often find it is a good idea to paste the DAP image over the original, in a photo editor, and then adjust the transparency of the upper layer until I judge that a suitable amount of detail shows through the painterly version.

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